--
-- MobDebug -- Lua remote debugger
-- Copyright 2011-15 Paul Kulchenko
-- Based on RemDebug 1.0 Copyright Kepler Project 2005
--

-- use loaded modules or load explicitly on those systems that require that
local require = require
local io = io or require "io"
local table = table or require "table"
local string = string or require "string"
local coroutine = coroutine or require "coroutine"
local debug = require "debug"
-- protect require "os" as it may fail on embedded systems without os module
local os = os or (function(module)
    local ok, res = pcall(require, module)
    return ok and res or nil
end)("os")

local mobdebug = {
    _NAME = "mobdebug",
    _VERSION = "0.641",
    _COPYRIGHT = "Paul Kulchenko",
    _DESCRIPTION = "Mobile Remote Debugger for the Lua programming language",
    port = os and os.getenv and tonumber((os.getenv("MOBDEBUG_PORT"))) or 8172,
    checkcount = 200,
    yieldtimeout = 0.02, -- yield timeout (s)
    connecttimeout = 2, -- connect timeout (s)
}

local HOOKMASK = "lcr"
local error = error
local getfenv = getfenv
local setfenv = setfenv
local loadstring = loadstring or load -- "load" replaced "loadstring" in Lua 5.2
local pairs = pairs
local setmetatable = setmetatable
local tonumber = tonumber
local unpack = table.unpack or unpack
local rawget = rawget
local gsub, sub, find = string.gsub, string.sub, string.find

-- if strict.lua is used, then need to avoid referencing some global
-- variables, as they can be undefined;
-- use rawget to avoid complaints from strict.lua at run-time.
-- it's safe to do the initialization here as all these variables
-- should get defined values (if any) before the debugging starts.
-- there is also global 'wx' variable, which is checked as part of
-- the debug loop as 'wx' can be loaded at any time during debugging.
local genv = _G or _ENV
local jit = rawget(genv, "jit")
local MOAICoroutine = rawget(genv, "MOAICoroutine")

-- ngx_lua debugging requires a special handling as its coroutine.*
-- methods use a different mechanism that doesn't allow resume calls
-- from debug hook handlers.
-- Instead, the "original" coroutine.* methods are used.
-- `rawget` needs to be used to protect against `strict` checks, but
-- ngx_lua hides those in a metatable, so need to use that.
local metagindex = getmetatable(genv) and getmetatable(genv).__index
local ngx = type(metagindex) == "table" and metagindex.rawget and metagindex:rawget("ngx") or nil
local corocreate = ngx and coroutine._create or coroutine.create
local cororesume = ngx and coroutine._resume or coroutine.resume
local coroyield = ngx and coroutine._yield or coroutine.yield
local corostatus = ngx and coroutine._status or coroutine.status
local corowrap = coroutine.wrap

if not setfenv then -- Lua 5.2+
    -- based on http://lua-users.org/lists/lua-l/2010-06/msg00314.html
    -- this assumes f is a function
    local function findenv(f)
        local level = 1
        repeat
            local name, value = debug.getupvalue(f, level)
            if name == '_ENV' then return level, value end
            level = level + 1
        until name == nil
        return nil end
    getfenv = function (f) return(select(2, findenv(f)) or _G) end
    setfenv = function (f, t)
        local level = findenv(f)
        if level then debug.setupvalue(f, level, t) end
        return f end
end

-- check for OS and convert file names to lower case on windows
-- (its file system is case insensitive, but case preserving), as setting a
-- breakpoint on x:\Foo.lua will not work if the file was loaded as X:\foo.lua.
-- OSX and Windows behave the same way (case insensitive, but case preserving).
-- OSX can be configured to be case-sensitive, so check for that. This doesn't
-- handle the case of different partitions having different case-sensitivity.
local win = os and os.getenv and (os.getenv('WINDIR') or (os.getenv('OS') or ''):match('[Ww]indows')) and true or false
local mac = not win and (os and os.getenv and os.getenv('DYLD_LIBRARY_PATH') or not io.open("/proc")) and true or false
local iscasepreserving = win or (mac and io.open('/library') ~= nil)

-- turn jit off based on Mike Pall's comment in this discussion:
-- http://www.freelists.org/post/luajit/Debug-hooks-and-JIT,2
-- "You need to turn it off at the start if you plan to receive
-- reliable hook calls at any later point in time."
if jit and jit.off then jit.off() end

local socket = require "socket"
local coro_debugger
local coro_debugee
local coroutines = {}; setmetatable(coroutines, {__mode = "k"}) -- "weak" keys
local events = { BREAK = 1, WATCH = 2, RESTART = 3, STACK = 4 }
local breakpoints = {}
local watches = {}
local lastsource
local lastfile
local watchescnt = 0
local abort -- default value is nil; this is used in start/loop distinction
local seen_hook = false
local checkcount = 0
local step_into = false
local step_over = false
local step_level = 0
local stack_level = 0
local server
local buf
local outputs = {}
local iobase = {print = print}
local basedir = ""
local deferror = "execution aborted at default debugee"
local debugee = function ()
    local a = 1
    for _ = 1, 10 do a = a + 1 end
    error(deferror)
end
local function q(s) return string.gsub(s, '([%(%)%.%%%+%-%*%?%[%^%$%]])','%%%1') end

local serpent = (function() ---- include Serpent module for serialization
    local n, v = "serpent", 0.285 -- (C) 2012-15 Paul Kulchenko; MIT License
    local c, d = "Paul Kulchenko", "Lua serializer and pretty printer"
    local snum = {[tostring(1/0)]='1/0 --[[math.huge]]',[tostring(-1/0)]='-1/0 --[[-math.huge]]',[tostring(0/0)]='0/0'}
    local badtype = {thread = true, userdata = true, cdata = true}
    local getmetatable = debug and debug.getmetatable or getmetatable
    local keyword, globals, G = {}, {}, (_G or _ENV)
    for _,k in ipairs({'and', 'break', 'do', 'else', 'elseif', 'end', 'false',
        'for', 'function', 'goto', 'if', 'in', 'local', 'nil', 'not', 'or', 'repeat',
        'return', 'then', 'true', 'until', 'while'}) do keyword[k] = true end
    for k,v in pairs(G) do globals[v] = k end -- build func to name mapping
    for _,g in ipairs({'coroutine', 'debug', 'io', 'math', 'string', 'table', 'os'}) do
        for k,v in pairs(type(G[g]) == 'table' and G[g] or {}) do globals[v] = g..'.'..k end end

    local function s(t, opts)
        local name, indent, fatal, maxnum = opts.name, opts.indent, opts.fatal, opts.maxnum
        local sparse, custom, huge = opts.sparse, opts.custom, not opts.nohuge
        local space, maxl = (opts.compact and '' or ' '), (opts.maxlevel or math.huge)
        local iname, comm = '_'..(name or ''), opts.comment and (tonumber(opts.comment) or math.huge)
        local numformat = opts.numformat or "%.17g"
        local seen, sref, syms, symn = {}, {'local '..iname..'={}'}, {}, 0
        local function gensym(val) return '_'..(tostring(tostring(val)):gsub("[^%w]",""):gsub("(%d%w+)",
            -- tostring(val) is needed because __tostring may return a non-string value
            function(s) if not syms[s] then symn = symn+1; syms[s] = symn end return tostring(syms[s]) end)) end
        local function safestr(s) return type(s) == "number" and tostring(huge and snum[tostring(s)] or numformat:format(s))
                or type(s) ~= "string" and tostring(s) -- escape NEWLINE/010 and EOF/026
                or ("%q"):format(s):gsub("\010","n"):gsub("\026","\\026") end
        local function comment(s,l) return comm and (l or 0) < comm and ' --[['..select(2, pcall(tostring, s))..']]' or '' end
        local function globerr(s,l) return globals[s] and globals[s]..comment(s,l) or not fatal
                and safestr(select(2, pcall(tostring, s))) or error("Can't serialize "..tostring(s)) end
        local function safename(path, name) -- generates foo.bar, foo[3], or foo['b a r']
            local n = name == nil and '' or name
            local plain = type(n) == "string" and n:match("^[%l%u_][%w_]*$") and not keyword[n]
            local safe = plain and n or '['..safestr(n)..']'
            return (path or '')..(plain and path and '.' or '')..safe, safe end
        local alphanumsort = type(opts.sortkeys) == 'function' and opts.sortkeys or function(k, o, n) -- k=keys, o=originaltable, n=padding
            local maxn, to = tonumber(n) or 12, {number = 'a', string = 'b'}
            local function padnum(d) return ("%0"..tostring(maxn).."d"):format(tonumber(d)) end
            table.sort(k, function(a,b)
                -- sort numeric keys first: k[key] is not nil for numerical keys
                return (k[a] ~= nil and 0 or to[type(a)] or 'z')..(tostring(a):gsub("%d+",padnum))
                        < (k[b] ~= nil and 0 or to[type(b)] or 'z')..(tostring(b):gsub("%d+",padnum)) end) end
        local function val2str(t, name, indent, insref, path, plainindex, level)
            local ttype, level, mt = type(t), (level or 0), getmetatable(t)
            local spath, sname = safename(path, name)
            local tag = plainindex and
                    ((type(name) == "number") and '' or name..space..'='..space) or
                    (name ~= nil and sname..space..'='..space or '')
            if seen[t] then -- already seen this element
                sref[#sref+1] = spath..space..'='..space..seen[t]
                return tag..'nil'..comment('ref', level) end
            -- protect from those cases where __tostring may fail
            if type(mt) == 'table' and pcall(function() return mt.__tostring and mt.__tostring(t) end)
                    and (mt.__serialize or mt.__tostring) then -- knows how to serialize itself
                seen[t] = insref or spath
                if mt.__serialize then t = mt.__serialize(t) else t = tostring(t) end
                ttype = type(t) end -- new value falls through to be serialized
            if ttype == "table" then
                if level >= maxl then return tag..'{}'..comment('max', level) end
                seen[t] = insref or spath
                if next(t) == nil then return tag..'{}'..comment(t, level) end -- table empty
                local maxn, o, out = math.min(#t, maxnum or #t), {}, {}
                for key = 1, maxn do o[key] = key end
                if not maxnum or #o < maxnum then
                    local n = #o -- n = n + 1; o[n] is much faster than o[#o+1] on large tables
                    for key in pairs(t) do if o[key] ~= key then n = n + 1; o[n] = key end end end
                if maxnum and #o > maxnum then o[maxnum+1] = nil end
                if opts.sortkeys and #o > maxn then alphanumsort(o, t, opts.sortkeys) end
                local sparse = sparse and #o > maxn -- disable sparsness if only numeric keys (shorter output)
                for n, key in ipairs(o) do
                    local value, ktype, plainindex = t[key], type(key), n <= maxn and not sparse
                    if opts.valignore and opts.valignore[value] -- skip ignored values; do nothing
                            or opts.keyallow and not opts.keyallow[key]
                            or opts.keyignore and opts.keyignore[key]
                            or opts.valtypeignore and opts.valtypeignore[type(value)] -- skipping ignored value types
                            or sparse and value == nil then -- skipping nils; do nothing
                    elseif ktype == 'table' or ktype == 'function' or badtype[ktype] then
                        if not seen[key] and not globals[key] then
                            sref[#sref+1] = 'placeholder'
                            local sname = safename(iname, gensym(key)) -- iname is table for local variables
                            sref[#sref] = val2str(key,sname,indent,sname,iname,true) end
                        sref[#sref+1] = 'placeholder'
                        local path = seen[t]..'['..tostring(seen[key] or globals[key] or gensym(key))..']'
                        sref[#sref] = path..space..'='..space..tostring(seen[value] or val2str(value,nil,indent,path))
                    else
                        out[#out+1] = val2str(value,key,indent,insref,seen[t],plainindex,level+1)
                    end
                end
                local prefix = string.rep(indent or '', level)
                local head = indent and '{\n'..prefix..indent or '{'
                local body = table.concat(out, ','..(indent and '\n'..prefix..indent or space))
                local tail = indent and "\n"..prefix..'}' or '}'
                return (custom and custom(tag,head,body,tail) or tag..head..body..tail)..comment(t, level)
            elseif badtype[ttype] then
                seen[t] = insref or spath
                return tag..globerr(t, level)
            elseif ttype == 'function' then
                seen[t] = insref or spath
                local ok, res = pcall(string.dump, t)
                local func = ok and ((opts.nocode and "function() --[[..skipped..]] end" or
                        "((loadstring or load)("..safestr(res)..",'@serialized'))")..comment(t, level))
                return tag..(func or globerr(t, level))
            else return tag..safestr(t) end -- handle all other types
        end
        local sepr = indent and "\n" or ";"..space
        local body = val2str(t, name, indent) -- this call also populates sref
        local tail = #sref>1 and table.concat(sref, sepr)..sepr or ''
        local warn = opts.comment and #sref>1 and space.."--[[incomplete output with shared/self-references skipped]]" or ''
        return not name and body..warn or "do local "..body..sepr..tail.."return "..name..sepr.."end"
    end

    local function deserialize(data, opts)
        local env = (opts and opts.safe == false) and G
                or setmetatable({}, {
            __index = function(t,k) return t end,
            __call = function(t,...) error("cannot call functions") end
        })
        local f, res = (loadstring or load)('return '..data, nil, nil, env)
        if not f then f, res = (loadstring or load)(data, nil, nil, env) end
        if not f then return f, res end
        if setfenv then setfenv(f, env) end
        return pcall(f)
    end

    local function merge(a, b) if b then for k,v in pairs(b) do a[k] = v end end; return a; end
    return { _NAME = n, _COPYRIGHT = c, _DESCRIPTION = d, _VERSION = v, serialize = s,
        load = deserialize,
        dump = function(a, opts) return s(a, merge({name = '_', compact = true, sparse = true}, opts)) end,
        line = function(a, opts) return s(a, merge({sortkeys = true, comment = true}, opts)) end,
        block = function(a, opts) return s(a, merge({indent = '  ', sortkeys = true, comment = true}, opts)) end }
end)() ---- end of Serpent module

mobdebug.line = serpent.line
mobdebug.dump = serpent.dump
mobdebug.linemap = nil
mobdebug.loadstring = loadstring

local function removebasedir(path, basedir)
    if iscasepreserving then
        -- check if the lowercased path matches the basedir
        -- if so, return substring of the original path (to not lowercase it)
        return path:lower():find('^'..q(basedir:lower()))
                and path:sub(#basedir+1) or path
    else
        return string.gsub(path, '^'..q(basedir), '')
    end
end

local function stack(start)
    local function vars(f)
        local func = debug.getinfo(f, "f").func
        local i = 1
        local locals = {}
        -- get locals
        while true do
            local name, value = debug.getlocal(f, i)
            if not name then break end
            if string.sub(name, 1, 1) ~= '(' then locals[name] = {value, tostring(value)} end
            i = i + 1
        end
        -- get varargs (these use negative indices)
        i = 1
        while true do
            local name, value = debug.getlocal(f, -i)
            -- `not name` should be enough, but LuaJIT 2.0.0 incorrectly reports `(*temporary)` names here
            if not name or name ~= "(*vararg)" then break end
            locals[name:gsub("%)$"," "..i..")")] = {value, tostring(value)}
            i = i + 1
        end
        -- get upvalues
        i = 1
        local ups = {}
        while func do -- check for func as it may be nil for tail calls
            local name, value = debug.getupvalue(func, i)
            if not name then break end
            ups[name] = {value, tostring(value)}
            i = i + 1
        end
        return locals, ups
    end

    local stack = {}
    local linemap = mobdebug.linemap
    for i = (start or 0), 100 do
        local source = debug.getinfo(i, "Snl")
        if not source then break end

        local src = source.source
        if src:find("@") == 1 then
            src = src:sub(2):gsub("\\", "/")
            if src:find("%./") == 1 then src = src:sub(3) end
        end

        table.insert(stack, { -- remove basedir from source
            {source.name, removebasedir(src, basedir),
                linemap and linemap(source.linedefined, source.source) or source.linedefined,
                linemap and linemap(source.currentline, source.source) or source.currentline,
                source.what, source.namewhat, source.short_src},
            vars(i+1)})
        if source.what == 'main' then break end
    end
    return stack
end

local function set_breakpoint(file, line)
    if file == '-' and lastfile then file = lastfile
    elseif iscasepreserving then file = string.lower(file) end
    if not breakpoints[line] then breakpoints[line] = {} end
    breakpoints[line][file] = true
end

local function remove_breakpoint(file, line)
    if file == '-' and lastfile then file = lastfile
    elseif file == '*' and line == 0 then breakpoints = {}
    elseif iscasepreserving then file = string.lower(file) end
    if breakpoints[line] then breakpoints[line][file] = nil end
end

local function has_breakpoint(file, line)
    return breakpoints[line]
            and breakpoints[line][iscasepreserving and string.lower(file) or file]
end

local function restore_vars(vars)
    if type(vars) ~= 'table' then return end

    -- locals need to be processed in the reverse order, starting from
    -- the inner block out, to make sure that the localized variables
    -- are correctly updated with only the closest variable with
    -- the same name being changed
    -- first loop find how many local variables there is, while
    -- the second loop processes them from i to 1
    local i = 1
    while true do
        local name = debug.getlocal(3, i)
        if not name then break end
        i = i + 1
    end
    i = i - 1
    local written_vars = {}
    while i > 0 do
        local name = debug.getlocal(3, i)
        if not written_vars[name] then
            if string.sub(name, 1, 1) ~= '(' then
                debug.setlocal(3, i, rawget(vars, name))
            end
            written_vars[name] = true
        end
        i = i - 1
    end

    i = 1
    local func = debug.getinfo(3, "f").func
    while true do
        local name = debug.getupvalue(func, i)
        if not name then break end
        if not written_vars[name] then
            if string.sub(name, 1, 1) ~= '(' then
                debug.setupvalue(func, i, rawget(vars, name))
            end
            written_vars[name] = true
        end
        i = i + 1
    end
end

local function capture_vars(level)
    local vars = {}
    local func = debug.getinfo(level or 3, "f").func
    local i = 1
    while true do
        local name, value = debug.getupvalue(func, i)
        if not name then break end
        if string.sub(name, 1, 1) ~= '(' then vars[name] = value end
        i = i + 1
    end
    i = 1
    while true do
        local name, value = debug.getlocal(level or 3, i)
        if not name then break end
        if string.sub(name, 1, 1) ~= '(' then vars[name] = value end
        i = i + 1
    end
    -- returned 'vars' table plays a dual role: (1) it captures local values
    -- and upvalues to be restored later (in case they are modified in "eval"),
    -- and (2) it provides an environment for evaluated chunks.
    -- getfenv(func) is needed to provide proper environment for functions,
    -- including access to globals, but this causes vars[name] to fail in
    -- restore_vars on local variables or upvalues with `nil` values when
    -- 'strict' is in effect. To avoid this `rawget` is used in restore_vars.
    setmetatable(vars, { __index = getfenv(func), __newindex = getfenv(func) })
    return vars
end

local function stack_depth(start_depth)
    for i = start_depth, 0, -1 do
        if debug.getinfo(i, "l") then return i+1 end
    end
    return start_depth
end

local function is_safe(stack_level)
    -- the stack grows up: 0 is getinfo, 1 is is_safe, 2 is debug_hook, 3 is user function
    if stack_level == 3 then return true end
    for i = 3, stack_level do
        -- return if it is not safe to abort
        local info = debug.getinfo(i, "S")
        if not info then return true end
        if info.what == "C" then return false end
    end
    return true
end

local function in_debugger()
    local this = debug.getinfo(1, "S").source
    -- only need to check few frames as mobdebug frames should be close
    for i = 3, 7 do
        local info = debug.getinfo(i, "S")
        if not info then return false end
        if info.source == this then return true end
    end
    return false
end

local function is_pending(peer)
    -- if there is something already in the buffer, skip check
    if not buf and checkcount >= mobdebug.checkcount then
        peer:settimeout(0) -- non-blocking
        buf = peer:receive(1)
        peer:settimeout() -- back to blocking
        checkcount = 0
    end
    return buf
end

local function readnext(peer, num)
    peer:settimeout(0) -- non-blocking
    local res, err, partial = peer:receive(num)
    peer:settimeout() -- back to blocking
    return res or partial or '', err
end

local function handle_breakpoint(peer)
    -- check if the buffer has the beginning of SETB/DELB command;
    -- this is to avoid reading the entire line for commands that
    -- don't need to be handled here.
    if not buf or not (buf:sub(1,1) == 'S' or buf:sub(1,1) == 'D') then return end

    -- check second character to avoid reading STEP or other S* and D* commands
    if #buf == 1 then buf = buf .. readnext(peer, 1) end
    if buf:sub(2,2) ~= 'E' then return end

    -- need to read few more characters
    buf = buf .. readnext(peer, 5-#buf)
    if buf ~= 'SETB ' and buf ~= 'DELB ' then return end

    local res, _, partial = peer:receive() -- get the rest of the line; blocking
    if not res then
        if partial then buf = buf .. partial end
        return
    end

    local _, _, cmd, file, line = (buf..res):find("^([A-Z]+)%s+(.-)%s+(%d+)%s*$")
    if cmd == 'SETB' then set_breakpoint(file, tonumber(line))
    elseif cmd == 'DELB' then remove_breakpoint(file, tonumber(line))
    else
        -- this looks like a breakpoint command, but something went wrong;
        -- return here to let the "normal" processing to handle,
        -- although this is likely to not go well.
        return
    end

    buf = nil
end

local function normalize_path(file)
    local n
    repeat
        file, n = file:gsub("/+%.?/+","/") -- remove all `//` and `/./` references
    until n == 0
    -- collapse all up-dir references: this will clobber UNC prefix (\\?\)
    -- and disk on Windows when there are too many up-dir references: `D:\foo\..\..\bar`;
    -- handle the case of multiple up-dir references: `foo/bar/baz/../../../more`;
    -- only remove one at a time as otherwise `../../` could be removed;
    repeat
        file, n = file:gsub("[^/]+/%.%./", "", 1)
    until n == 0
    -- there may still be a leading up-dir reference left (as `/../` or `../`); remove it
    return (file:gsub("%.%./", "", 1))
end

local function debug_hook(event, line)
    -- (1) LuaJIT needs special treatment. Because debug_hook is set for
    -- *all* coroutines, and not just the one being debugged as in regular Lua
    -- (http://lua-users.org/lists/lua-l/2011-06/msg00513.html),
    -- need to avoid debugging mobdebug's own code as LuaJIT doesn't
    -- always correctly generate call/return hook events (there are more
    -- calls than returns, which breaks stack depth calculation and
    -- 'step' and 'step over' commands stop working; possibly because
    -- 'tail return' events are not generated by LuaJIT).
    -- the next line checks if the debugger is run under LuaJIT and if
    -- one of debugger methods is present in the stack, it simply returns.
    if jit then
        -- when luajit is compiled with LUAJIT_ENABLE_LUA52COMPAT,
        -- coroutine.running() returns non-nil for the main thread.
        local coro, main = coroutine.running()
        if not coro or main then coro = 'main' end
        local disabled = coroutines[coro] == false
                or coroutines[coro] == nil and coro ~= (coro_debugee or 'main')
        if coro_debugee and disabled or not coro_debugee and (disabled or in_debugger())
        then return end
    end

    -- (2) check if abort has been requested and it's safe to abort
    if abort and is_safe(stack_level) then error(abort) end

    -- (3) also check if this debug hook has not been visited for any reason.
    -- this check is needed to avoid stepping in too early
    -- (for example, when coroutine.resume() is executed inside start()).
    if not seen_hook and in_debugger() then return end

    if event == "call" then
        stack_level = stack_level + 1
    elseif event == "return" or event == "tail return" then
        stack_level = stack_level - 1
    elseif event == "line" then
        if mobdebug.linemap then
            local ok, mappedline = pcall(mobdebug.linemap, line, debug.getinfo(2, "S").source)
            if ok then line = mappedline end
            if not line then return end
        end

        -- may need to fall through because of the following:
        -- (1) step_into
        -- (2) step_over and stack_level <= step_level (need stack_level)
        -- (3) breakpoint; check for line first as it's known; then for file
        -- (4) socket call (only do every Xth check)
        -- (5) at least one watch is registered
        if not (
        step_into or step_over or breakpoints[line] or watchescnt > 0
                or is_pending(server)
        ) then checkcount = checkcount + 1; return end

        checkcount = mobdebug.checkcount -- force check on the next command

        -- this is needed to check if the stack got shorter or longer.
        -- unfortunately counting call/return calls is not reliable.
        -- the discrepancy may happen when "pcall(load, '')" call is made
        -- or when "error()" is called in a function.
        -- in either case there are more "call" than "return" events reported.
        -- this validation is done for every "line" event, but should be "cheap"
        -- as it checks for the stack to get shorter (or longer by one call).
        -- start from one level higher just in case we need to grow the stack.
        -- this may happen after coroutine.resume call to a function that doesn't
        -- have any other instructions to execute. it triggers three returns:
        -- "return, tail return, return", which needs to be accounted for.
        stack_level = stack_depth(stack_level+1)

        local caller = debug.getinfo(2, "S")

        -- grab the filename and fix it if needed
        local file = lastfile
        if (lastsource ~= caller.source) then
            file, lastsource = caller.source, caller.source
            -- technically, users can supply names that may not use '@',
            -- for example when they call loadstring('...', 'filename.lua').
            -- Unfortunately, there is no reliable/quick way to figure out
            -- what is the filename and what is the source code.
            -- If the name doesn't start with `@`, assume it's a file name if it's all on one line.
            if find(file, "^@") or not find(file, "[\r\n]") then
                file = gsub(gsub(file, "^@", ""), "\\", "/")
                -- normalize paths that may include up-dir or same-dir references
                -- if the path starts from the up-dir or reference,
                -- prepend `basedir` to generate absolute path to keep breakpoints working.
                -- ignore qualified relative path (`D:../`) and UNC paths (`\\?\`)
                if find(file, "^%.%./") then file = basedir..file end
                if find(file, "/%.%.?/") then file = normalize_path(file) end
                -- need this conversion to be applied to relative and absolute
                -- file names as you may write "require 'Foo'" to
                -- load "foo.lua" (on a case insensitive file system) and breakpoints
                -- set on foo.lua will not work if not converted to the same case.
                if iscasepreserving then file = string.lower(file) end
                if find(file, "^%./") then file = sub(file, 3)
                else file = gsub(file, "^"..q(basedir), "") end
                -- some file systems allow newlines in file names; remove these.
                file = gsub(file, "\n", ' ')
            else
                file = mobdebug.line(file)
            end

            -- set to true if we got here; this only needs to be done once per
            -- session, so do it here to at least avoid setting it for every line.
            seen_hook = true
            lastfile = file
        end

        if is_pending(server) then handle_breakpoint(server) end

        local vars, status, res
        if (watchescnt > 0) then
            vars = capture_vars()
            for index, value in pairs(watches) do
                setfenv(value, vars)
                local ok, fired = pcall(value)
                if ok and fired then
                    status, res = cororesume(coro_debugger, events.WATCH, vars, file, line, index)
                    break -- any one watch is enough; don't check multiple times
                end
            end
        end

        -- need to get into the "regular" debug handler, but only if there was
        -- no watch that was fired. If there was a watch, handle its result.
        local getin = (status == nil) and
                (step_into
                        -- when coroutine.running() return `nil` (main thread in Lua 5.1),
                        -- step_over will equal 'main', so need to check for that explicitly.
                        or (step_over and step_over == (coroutine.running() or 'main') and stack_level <= step_level)
                        or has_breakpoint(file, line)
                        or is_pending(server))

        if getin then
            vars = vars or capture_vars()
            step_into = false
            step_over = false
            status, res = cororesume(coro_debugger, events.BREAK, vars, file, line)
        end

        -- handle 'stack' command that provides stack() information to the debugger
        if status and res == 'stack' then
            while status and res == 'stack' do
                -- resume with the stack trace and variables
                if vars then restore_vars(vars) end -- restore vars so they are reflected in stack values
                -- this may fail if __tostring method fails at run-time
                local ok, snapshot = pcall(stack, 4)
                status, res = cororesume(coro_debugger, ok and events.STACK or events.BREAK, snapshot, file, line)
            end
        end

        -- need to recheck once more as resume after 'stack' command may
        -- return something else (for example, 'exit'), which needs to be handled
        if status and res and res ~= 'stack' then
            if not abort and res == "exit" then mobdebug.onexit(1, true); return end
            if not abort and res == "done" then mobdebug.done(); return end
            abort = res
            -- only abort if safe; if not, there is another (earlier) check inside
            -- debug_hook, which will abort execution at the first safe opportunity
            if is_safe(stack_level) then error(abort) end
        elseif not status and res then
            error(res, 2) -- report any other (internal) errors back to the application
        end

        if vars then restore_vars(vars) end

        -- last command requested Step Over/Out; store the current thread
        if step_over == true then step_over = coroutine.running() or 'main' end
    end
end

local function stringify_results(status, ...)
    if not status then return status, ... end -- on error report as it

    local t = {...}
    for i,v in pairs(t) do -- stringify each of the returned values
        local ok, res = pcall(mobdebug.line, v, {nocode = true, comment = 1})
        t[i] = ok and res or ("%q"):format(res):gsub("\010","n"):gsub("\026","\\026")
    end
    -- stringify table with all returned values
    -- this is done to allow each returned value to be used (serialized or not)
    -- intependently and to preserve "original" comments
    return pcall(mobdebug.dump, t, {sparse = false})
end

local function isrunning()
    return coro_debugger and (corostatus(coro_debugger) == 'suspended' or corostatus(coro_debugger) == 'running')
end

-- this is a function that removes all hooks and closes the socket to
-- report back to the controller that the debugging is done.
-- the script that called `done` can still continue.
local function done()
    if not (isrunning() and server) then return end

    if not jit then
        for co, debugged in pairs(coroutines) do
            if debugged then debug.sethook(co) end
        end
    end

    debug.sethook()
    server:close()

    coro_debugger = nil -- to make sure isrunning() returns `false`
    seen_hook = nil -- to make sure that the next start() call works
    abort = nil -- to make sure that callback calls use proper "abort" value
end

local function debugger_loop(sev, svars, sfile, sline)
    local command
    local app, osname
    local eval_env = svars or {}
    local function emptyWatch () return false end
    local loaded = {}
    for k in pairs(package.loaded) do loaded[k] = true end

    while true do
        local line, err
        local wx = rawget(genv, "wx") -- use rawread to make strict.lua happy
        if (wx or mobdebug.yield) and server.settimeout then server:settimeout(mobdebug.yieldtimeout) end
        while true do
            line, err = server:receive()
            if not line and err == "timeout" then
                -- yield for wx GUI applications if possible to avoid "busyness"
                app = app or (wx and wx.wxGetApp and wx.wxGetApp())
                if app then
                    local win = app:GetTopWindow()
                    local inloop = app:IsMainLoopRunning()
                    osname = osname or wx.wxPlatformInfo.Get():GetOperatingSystemFamilyName()
                    if win and not inloop then
                        -- process messages in a regular way
                        -- and exit as soon as the event loop is idle
                        if osname == 'Unix' then wx.wxTimer(app):Start(10, true) end
                        local exitLoop = function()
                            win:Disconnect(wx.wxID_ANY, wx.wxID_ANY, wx.wxEVT_IDLE)
                            win:Disconnect(wx.wxID_ANY, wx.wxID_ANY, wx.wxEVT_TIMER)
                            app:ExitMainLoop()
                        end
                        win:Connect(wx.wxEVT_IDLE, exitLoop)
                        win:Connect(wx.wxEVT_TIMER, exitLoop)
                        app:MainLoop()
                    end
                elseif mobdebug.yield then mobdebug.yield()
                end
            elseif not line and err == "closed" then
                error("Debugger connection closed", 0)
            else
                -- if there is something in the pending buffer, prepend it to the line
                if buf then line = buf .. line; buf = nil end
                break
            end
        end
        if server.settimeout then server:settimeout() end -- back to blocking
        command = string.sub(line, string.find(line, "^[A-Z]+"))
        if command == "SETB" then
            local _, _, _, file, line = string.find(line, "^([A-Z]+)%s+(.-)%s+(%d+)%s*$")
            if file and line then
                set_breakpoint(file, tonumber(line))
                server:send("200 OK\n")
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "DELB" then
            local _, _, _, file, line = string.find(line, "^([A-Z]+)%s+(.-)%s+(%d+)%s*$")
            if file and line then
                remove_breakpoint(file, tonumber(line))
                server:send("200 OK\n")
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "EXEC" then
            local _, _, chunk = string.find(line, "^[A-Z]+%s+(.+)$")
            if chunk then
                local func, res = mobdebug.loadstring(chunk)
                local status
                if func then
                    setfenv(func, eval_env)
                    status, res = stringify_results(pcall(func))
                end
                if status then
                    if mobdebug.onscratch then mobdebug.onscratch(res) end
                    server:send("200 OK " .. tostring(#res) .. "\n")
                    server:send(res)
                else
                    -- fix error if not set (for example, when loadstring is not present)
                    if not res then res = "Unknown error" end
                    server:send("401 Error in Expression " .. tostring(#res) .. "\n")
                    server:send(res)
                end
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "LOAD" then
            local _, _, size, name = string.find(line, "^[A-Z]+%s+(%d+)%s+(%S.-)%s*$")
            size = tonumber(size)

            if abort == nil then -- no LOAD/RELOAD allowed inside start()
                if size > 0 then server:receive(size) end
                if sfile and sline then
                    server:send("201 Started " .. sfile .. " " .. tostring(sline) .. "\n")
                else
                    server:send("200 OK 0\n")
                end
            else
                -- reset environment to allow required modules to load again
                -- remove those packages that weren't loaded when debugger started
                for k in pairs(package.loaded) do
                    if not loaded[k] then package.loaded[k] = nil end
                end

                if size == 0 and name == '-' then -- RELOAD the current script being debugged
                    server:send("200 OK 0\n")
                    coroyield("load")
                else
                    -- receiving 0 bytes blocks (at least in luasocket 2.0.2), so skip reading
                    local chunk = size == 0 and "" or server:receive(size)
                    if chunk then -- LOAD a new script for debugging
                        local func, res = mobdebug.loadstring(chunk, "@"..name)
                        if func then
                            server:send("200 OK 0\n")
                            debugee = func
                            coroyield("load")
                        else
                            server:send("401 Error in Expression " .. tostring(#res) .. "\n")
                            server:send(res)
                        end
                    else
                        server:send("400 Bad Request\n")
                    end
                end
            end
        elseif command == "SETW" then
            local _, _, exp = string.find(line, "^[A-Z]+%s+(.+)%s*$")
            if exp then
                local func, res = mobdebug.loadstring("return(" .. exp .. ")")
                if func then
                    watchescnt = watchescnt + 1
                    local newidx = #watches + 1
                    watches[newidx] = func
                    server:send("200 OK " .. tostring(newidx) .. "\n")
                else
                    server:send("401 Error in Expression " .. tostring(#res) .. "\n")
                    server:send(res)
                end
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "DELW" then
            local _, _, index = string.find(line, "^[A-Z]+%s+(%d+)%s*$")
            index = tonumber(index)
            if index > 0 and index <= #watches then
                watchescnt = watchescnt - (watches[index] ~= emptyWatch and 1 or 0)
                watches[index] = emptyWatch
                server:send("200 OK\n")
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "RUN" then
            server:send("200 OK\n")

            local ev, vars, file, line, idx_watch = coroyield()
            eval_env = vars
            if ev == events.BREAK then
                server:send("202 Paused " .. file .. " " .. tostring(line) .. "\n")
            elseif ev == events.WATCH then
                server:send("203 Paused " .. file .. " " .. tostring(line) .. " " .. tostring(idx_watch) .. "\n")
            elseif ev == events.RESTART then
                -- nothing to do
            else
                server:send("401 Error in Execution " .. tostring(#file) .. "\n")
                server:send(file)
            end
        elseif command == "STEP" then
            server:send("200 OK\n")
            step_into = true

            local ev, vars, file, line, idx_watch = coroyield()
            eval_env = vars
            if ev == events.BREAK then
                server:send("202 Paused " .. file .. " " .. tostring(line) .. "\n")
            elseif ev == events.WATCH then
                server:send("203 Paused " .. file .. " " .. tostring(line) .. " " .. tostring(idx_watch) .. "\n")
            elseif ev == events.RESTART then
                -- nothing to do
            else
                server:send("401 Error in Execution " .. tostring(#file) .. "\n")
                server:send(file)
            end
        elseif command == "OVER" or command == "OUT" then
            server:send("200 OK\n")
            step_over = true

            -- OVER and OUT are very similar except for
            -- the stack level value at which to stop
            if command == "OUT" then step_level = stack_level - 1
            else step_level = stack_level end

            local ev, vars, file, line, idx_watch = coroyield()
            eval_env = vars
            if ev == events.BREAK then
                server:send("202 Paused " .. file .. " " .. tostring(line) .. "\n")
            elseif ev == events.WATCH then
                server:send("203 Paused " .. file .. " " .. tostring(line) .. " " .. tostring(idx_watch) .. "\n")
            elseif ev == events.RESTART then
                -- nothing to do
            else
                server:send("401 Error in Execution " .. tostring(#file) .. "\n")
                server:send(file)
            end
        elseif command == "BASEDIR" then
            local _, _, dir = string.find(line, "^[A-Z]+%s+(.+)%s*$")
            if dir then
                basedir = iscasepreserving and string.lower(dir) or dir
                -- reset cached source as it may change with basedir
                lastsource = nil
                server:send("200 OK\n")
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "SUSPEND" then
            -- do nothing; it already fulfilled its role
        elseif command == "DONE" then
            coroyield("done")
            return -- done with all the debugging
        elseif command == "STACK" then
            -- first check if we can execute the stack command
            -- as it requires yielding back to debug_hook it cannot be executed
            -- if we have not seen the hook yet as happens after start().
            -- in this case we simply return an empty result
            local vars, ev = {}
            if seen_hook then
                ev, vars = coroyield("stack")
            end
            if ev and ev ~= events.STACK then
                server:send("401 Error in Execution " .. tostring(#vars) .. "\n")
                server:send(vars)
            else
                local ok, res = pcall(mobdebug.dump, vars, {nocode = true, sparse = false})
                if ok then
                    server:send("200 OK " .. tostring(res) .. "\n")
                else
                    server:send("401 Error in Execution " .. tostring(#res) .. "\n")
                    server:send(res)
                end
            end
        elseif command == "OUTPUT" then
            local _, _, stream, mode = string.find(line, "^[A-Z]+%s+(%w+)%s+([dcr])%s*$")
            if stream and mode and stream == "stdout" then
                -- assign "print" in the global environment
                local default = mode == 'd'
                genv.print = default and iobase.print or corowrap(function()
                    -- wrapping into coroutine.wrap protects this function from
                    -- being stepped through in the debugger.
                    -- don't use vararg (...) as it adds a reference for its values,
                    -- which may affect how they are garbage collected
                    while true do
                        local tbl = {coroutine.yield()}
                        if mode == 'c' then iobase.print(unpack(tbl)) end
                        for n = 1, #tbl do
                            tbl[n] = select(2, pcall(mobdebug.line, tbl[n], {nocode = true, comment = false})) end
                        local file = table.concat(tbl, "\t").."\n"
                        server:send("204 Output " .. stream .. " " .. tostring(#file) .. "\n" .. file)
                    end
                end)
                if not default then genv.print() end -- "fake" print to start printing loop
                server:send("200 OK\n")
            else
                server:send("400 Bad Request\n")
            end
        elseif command == "EXIT" then
            server:send("200 OK\n")
            coroyield("exit")
        else
            server:send("400 Bad Request\n")
        end
    end
end

local function output(stream, data)
    if server then return server:send("204 Output "..stream.." "..tostring(#data).."\n"..data) end
end

local function connect(controller_host, controller_port)
    local sock, err = socket.tcp()
    if not sock then return nil, err end

    if sock.settimeout then sock:settimeout(mobdebug.connecttimeout) end
    local res, err = sock:connect(controller_host, tostring(controller_port))
    if sock.settimeout then sock:settimeout() end

    if not res then return nil, err end
    return sock
end

local lasthost, lastport

-- Starts a debug session by connecting to a controller
local function start(controller_host, controller_port)
    -- only one debugging session can be run (as there is only one debug hook)
    if isrunning() then return end

    lasthost = controller_host or lasthost
    lastport = controller_port or lastport

    controller_host = lasthost or "localhost"
    controller_port = lastport or mobdebug.port

    local err
    server, err = mobdebug.connect(controller_host, controller_port)
    if server then
        -- correct stack depth which already has some calls on it
        -- so it doesn't go into negative when those calls return
        -- as this breaks subsequence checks in stack_depth().
        -- start from 16th frame, which is sufficiently large for this check.
        stack_level = stack_depth(16)

        -- provide our own traceback function to report the error remotely
        do
            local dtraceback = debug.traceback
            debug.traceback = function (...)
                if select('#', ...) >= 1 then
                    local err, lvl = ...
                    if err and type(err) ~= 'thread' then
                        local trace = dtraceback(err, (lvl or 2)+1)
                        if genv.print == iobase.print then -- no remote redirect
                            return trace
                        else
                            genv.print(trace) -- report the error remotely
                            return -- don't report locally to avoid double reporting
                        end
                    end
                end
                -- direct call to debug.traceback: return the original.
                -- debug.traceback(nil, level) doesn't work in Lua 5.1
                -- (http://lua-users.org/lists/lua-l/2011-06/msg00574.html), so
                -- simply remove first frame from the stack trace
                return (dtraceback(...):gsub("(stack traceback:\n)[^\n]*\n", "%1"))
            end
        end
        coro_debugger = corocreate(debugger_loop)
        debug.sethook(debug_hook, HOOKMASK)
        seen_hook = nil -- reset in case the last start() call was refused
        step_into = true -- start with step command
        return true
    else
        print(("Could not connect to %s:%s: %s")
        :format(controller_host, controller_port, err or "unknown error"))
    end
end

local function controller(controller_host, controller_port, scratchpad)
    -- only one debugging session can be run (as there is only one debug hook)
    if isrunning() then return end

    lasthost = controller_host or lasthost
    lastport = controller_port or lastport

    controller_host = lasthost or "localhost"
    controller_port = lastport or mobdebug.port

    local exitonerror = not scratchpad
    local err
    server, err = mobdebug.connect(controller_host, controller_port)
    if server then
        local function report(trace, err)
            local msg = err .. "\n" .. trace
            server:send("401 Error in Execution " .. tostring(#msg) .. "\n")
            server:send(msg)
            return err
        end

        seen_hook = true -- allow to accept all commands
        coro_debugger = corocreate(debugger_loop)

        while true do
            step_into = true -- start with step command
            abort = false -- reset abort flag from the previous loop
            if scratchpad then checkcount = mobdebug.checkcount end -- force suspend right away

            coro_debugee = corocreate(debugee)
            debug.sethook(coro_debugee, debug_hook, HOOKMASK)
            local status, err = cororesume(coro_debugee, unpack(arg or {}))

            -- was there an error or is the script done?
            -- 'abort' state is allowed here; ignore it
            if abort then
                if tostring(abort) == 'exit' then break end
            else
                if status then -- normal execution is done
                    break
                elseif err and not string.find(tostring(err), deferror) then
                    -- report the error back
                    -- err is not necessarily a string, so convert to string to report
                    report(debug.traceback(coro_debugee), tostring(err))
                    if exitonerror then break end
                    -- check if the debugging is done (coro_debugger is nil)
                    if not coro_debugger then break end
                    -- resume once more to clear the response the debugger wants to send
                    -- need to use capture_vars(2) as three would be the level of
                    -- the caller for controller(), but because of the tail call,
                    -- the caller may not exist;
                    -- This is not entirely safe as the user may see the local
                    -- variable from console, but they will be reset anyway.
                    -- This functionality is used when scratchpad is paused to
                    -- gain access to remote console to modify global variables.
                    local status, err = cororesume(coro_debugger, events.RESTART, capture_vars(2))
                    if not status or status and err == "exit" then break end
                end
            end
        end
    else
        print(("Could not connect to %s:%s: %s")
        :format(controller_host, controller_port, err or "unknown error"))
        return false
    end
    return true
end

local function scratchpad(controller_host, controller_port)
    return controller(controller_host, controller_port, true)
end

local function loop(controller_host, controller_port)
    return controller(controller_host, controller_port, false)
end

local function on()
    if not (isrunning() and server) then return end

    -- main is set to true under Lua5.2 for the "main" chunk.
    -- Lua5.1 returns co as `nil` in that case.
    local co, main = coroutine.running()
    if main then co = nil end
    if co then
        coroutines[co] = true
        debug.sethook(co, debug_hook, HOOKMASK)
    else
        if jit then coroutines.main = true end
        debug.sethook(debug_hook, HOOKMASK)
    end
end

local function off()
    if not (isrunning() and server) then return end

    -- main is set to true under Lua5.2 for the "main" chunk.
    -- Lua5.1 returns co as `nil` in that case.
    local co, main = coroutine.running()
    if main then co = nil end

    -- don't remove coroutine hook under LuaJIT as there is only one (global) hook
    if co then
        coroutines[co] = false
        if not jit then debug.sethook(co) end
    else
        if jit then coroutines.main = false end
        if not jit then debug.sethook() end
    end

    -- check if there is any thread that is still being debugged under LuaJIT;
    -- if not, turn the debugging off
    if jit then
        local remove = true
        for _, debugged in pairs(coroutines) do
            if debugged then remove = false; break end
        end
        if remove then debug.sethook() end
    end
end

-- Handles server debugging commands
local function handle(params, client, options)
    -- when `options.verbose` is not provided, use normal `print`; verbose output can be
    -- disabled (`options.verbose == false`) or redirected (`options.verbose == function()...end`)
    local verbose = not options or options.verbose ~= nil and options.verbose
    local print = verbose and (type(verbose) == "function" and verbose or print) or function() end
    local file, line, watch_idx
    local _, _, command = string.find(params, "^([a-z]+)")
    if command == "run" or command == "step" or command == "out"
            or command == "over" or command == "exit" then
        client:send(string.upper(command) .. "\n")
        client:receive() -- this should consume the first '200 OK' response
        while true do
            local done = true
            local breakpoint = client:receive()
            if not breakpoint then
                print("Program finished")
                return nil, nil, false
            end
            local _, _, status = string.find(breakpoint, "^(%d+)")
            if status == "200" then
                -- don't need to do anything
            elseif status == "202" then
                _, _, file, line = string.find(breakpoint, "^202 Paused%s+(.-)%s+(%d+)%s*$")
                if file and line then
                    print("Paused at file " .. file .. " line " .. line)
                end
            elseif status == "203" then
                _, _, file, line, watch_idx = string.find(breakpoint, "^203 Paused%s+(.-)%s+(%d+)%s+(%d+)%s*$")
                if file and line and watch_idx then
                    print("Paused at file " .. file .. " line " .. line .. " (watch expression " .. watch_idx .. ": [" .. watches[watch_idx] .. "])")
                end
            elseif status == "204" then
                local _, _, stream, size = string.find(breakpoint, "^204 Output (%w+) (%d+)$")
                if stream and size then
                    local size = tonumber(size)
                    local msg = size > 0 and client:receive(size) or ""
                    print(msg)
                    if outputs[stream] then outputs[stream](msg) end
                    -- this was just the output, so go back reading the response
                    done = false
                end
            elseif status == "401" then
                local _, _, size = string.find(breakpoint, "^401 Error in Execution (%d+)$")
                if size then
                    local msg = client:receive(tonumber(size))
                    print("Error in remote application: " .. msg)
                    return nil, nil, msg
                end
            else
                print("Unknown error")
                return nil, nil, "Debugger error: unexpected response '" .. breakpoint .. "'"
            end
            if done then break end
        end
    elseif command == "done" then
        client:send(string.upper(command) .. "\n")
        -- no response is expected
    elseif command == "setb" or command == "asetb" then
        _, _, _, file, line = string.find(params, "^([a-z]+)%s+(.-)%s+(%d+)%s*$")
        if file and line then
            -- if this is a file name, and not a file source
            if not file:find('^".*"$') then
                file = string.gsub(file, "\\", "/") -- convert slash
                file = removebasedir(file, basedir)
            end
            client:send("SETB " .. file .. " " .. line .. "\n")
            if command == "asetb" or client:receive() == "200 OK" then
                set_breakpoint(file, line)
            else
                print("Error: breakpoint not inserted")
            end
        else
            print("Invalid command")
        end
    elseif command == "setw" then
        local _, _, exp = string.find(params, "^[a-z]+%s+(.+)$")
        if exp then
            client:send("SETW " .. exp .. "\n")
            local answer = client:receive()
            local _, _, watch_idx = string.find(answer, "^200 OK (%d+)%s*$")
            if watch_idx then
                watches[watch_idx] = exp
                print("Inserted watch exp no. " .. watch_idx)
            else
                local _, _, size = string.find(answer, "^401 Error in Expression (%d+)$")
                if size then
                    local err = client:receive(tonumber(size)):gsub(".-:%d+:%s*","")
                    print("Error: watch expression not set: " .. err)
                else
                    print("Error: watch expression not set")
                end
            end
        else
            print("Invalid command")
        end
    elseif command == "delb" or command == "adelb" then
        _, _, _, file, line = string.find(params, "^([a-z]+)%s+(.-)%s+(%d+)%s*$")
        if file and line then
            -- if this is a file name, and not a file source
            if not file:find('^".*"$') then
                file = string.gsub(file, "\\", "/") -- convert slash
                file = removebasedir(file, basedir)
            end
            client:send("DELB " .. file .. " " .. line .. "\n")
            if command == "adelb" or client:receive() == "200 OK" then
                remove_breakpoint(file, line)
            else
                print("Error: breakpoint not removed")
            end
        else
            print("Invalid command")
        end
    elseif command == "delallb" then
        local file, line = "*", 0
        client:send("DELB " .. file .. " " .. tostring(line) .. "\n")
        if client:receive() == "200 OK" then
            remove_breakpoint(file, line)
        else
            print("Error: all breakpoints not removed")
        end
    elseif command == "delw" then
        local _, _, index = string.find(params, "^[a-z]+%s+(%d+)%s*$")
        if index then
            client:send("DELW " .. index .. "\n")
            if client:receive() == "200 OK" then
                watches[index] = nil
            else
                print("Error: watch expression not removed")
            end
        else
            print("Invalid command")
        end
    elseif command == "delallw" then
        for index, exp in pairs(watches) do
            client:send("DELW " .. index .. "\n")
            if client:receive() == "200 OK" then
                watches[index] = nil
            else
                print("Error: watch expression at index " .. index .. " [" .. exp .. "] not removed")
            end
        end
    elseif command == "eval" or command == "exec"
            or command == "load" or command == "loadstring"
            or command == "reload" then
        local _, _, exp = string.find(params, "^[a-z]+%s+(.+)$")
        if exp or (command == "reload") then
            if command == "eval" or command == "exec" then
                exp = (exp:gsub("%-%-%[(=*)%[.-%]%1%]", "") -- remove comments
                :gsub("%-%-.-\n", " ") -- remove line comments
                :gsub("\n", " ")) -- convert new lines
                if command == "eval" then exp = "return " .. exp end
                client:send("EXEC " .. exp .. "\n")
            elseif command == "reload" then
                client:send("LOAD 0 -\n")
            elseif command == "loadstring" then
                local _, _, _, file, lines = string.find(exp, "^([\"'])(.-)%1%s+(.+)")
                if not file then
                    _, _, file, lines = string.find(exp, "^(%S+)%s+(.+)")
                end
                client:send("LOAD " .. tostring(#lines) .. " " .. file .. "\n")
                client:send(lines)
            else
                local file = io.open(exp, "r")
                if not file and pcall(require, "winapi") then
                    -- if file is not open and winapi is there, try with a short path;
                    -- this may be needed for unicode paths on windows
                    winapi.set_encoding(winapi.CP_UTF8)
                    local shortp = winapi.short_path(exp)
                    file = shortp and io.open(shortp, "r")
                end
                if not file then return nil, nil, "Cannot open file " .. exp end
                -- read the file and remove the shebang line as it causes a compilation error
                local lines = file:read("*all"):gsub("^#!.-\n", "\n")
                file:close()

                local file = string.gsub(exp, "\\", "/") -- convert slash
                file = removebasedir(file, basedir)
                client:send("LOAD " .. tostring(#lines) .. " " .. file .. "\n")
                if #lines > 0 then client:send(lines) end
            end
            while true do
                local params, err = client:receive()
                if not params then
                    return nil, nil, "Debugger connection " .. (err or "error")
                end
                local done = true
                local _, _, status, len = string.find(params, "^(%d+).-%s+(%d+)%s*$")
                if status == "200" then
                    len = tonumber(len)
                    if len > 0 then
                        local status, res
                        local str = client:receive(len)
                        -- handle serialized table with results
                        local func, err = loadstring(str)
                        if func then
                            status, res = pcall(func)
                            if not status then err = res
                            elseif type(res) ~= "table" then
                                err = "received "..type(res).." instead of expected 'table'"
                            end
                        end
                        if err then
                            print("Error in processing results: " .. err)
                            return nil, nil, "Error in processing results: " .. err
                        end
                        print(unpack(res))
                        return res[1], res
                    end
                elseif status == "201" then
                    _, _, file, line = string.find(params, "^201 Started%s+(.-)%s+(%d+)%s*$")
                elseif status == "202" or params == "200 OK" then
                    -- do nothing; this only happens when RE/LOAD command gets the response
                    -- that was for the original command that was aborted
                elseif status == "204" then
                    local _, _, stream, size = string.find(params, "^204 Output (%w+) (%d+)$")
                    if stream and size then
                        local size = tonumber(size)
                        local msg = size > 0 and client:receive(size) or ""
                        print(msg)
                        if outputs[stream] then outputs[stream](msg) end
                        -- this was just the output, so go back reading the response
                        done = false
                    end
                elseif status == "401" then
                    len = tonumber(len)
                    local res = client:receive(len)
                    print("Error in expression: " .. res)
                    return nil, nil, res
                else
                    print("Unknown error")
                    return nil, nil, "Debugger error: unexpected response after EXEC/LOAD '" .. params .. "'"
                end
                if done then break end
            end
        else
            print("Invalid command")
        end
    elseif command == "listb" then
        for l, v in pairs(breakpoints) do
            for f in pairs(v) do
                print(f .. ": " .. l)
            end
        end
    elseif command == "listw" then
        for i, v in pairs(watches) do
            print("Watch exp. " .. i .. ": " .. v)
        end
    elseif command == "suspend" then
        client:send("SUSPEND\n")
    elseif command == "stack" then
        client:send("STACK\n")
        local resp = client:receive()
        local _, _, status, res = string.find(resp, "^(%d+)%s+%w+%s+(.+)%s*$")
        if status == "200" then
            local func, err = loadstring(res)
            if func == nil then
                print("Error in stack information: " .. err)
                return nil, nil, err
            end
            local ok, stack = pcall(func)
            if not ok then
                print("Error in stack information: " .. stack)
                return nil, nil, stack
            end
            for _,frame in ipairs(stack) do
                print(mobdebug.line(frame[1], {comment = false}))
            end
            return stack
        elseif status == "401" then
            local _, _, len = string.find(resp, "%s+(%d+)%s*$")
            len = tonumber(len)
            local res = len > 0 and client:receive(len) or "Invalid stack information."
            print("Error in expression: " .. res)
            return nil, nil, res
        else
            print("Unknown error")
            return nil, nil, "Debugger error: unexpected response after STACK"
        end
    elseif command == "output" then
        local _, _, stream, mode = string.find(params, "^[a-z]+%s+(%w+)%s+([dcr])%s*$")
        if stream and mode then
            client:send("OUTPUT "..stream.." "..mode.."\n")
            local resp, err = client:receive()
            if not resp then
                print("Unknown error: "..err)
                return nil, nil, "Debugger connection error: "..err
            end
            local _, _, status = string.find(resp, "^(%d+)%s+%w+%s*$")
            if status == "200" then
                print("Stream "..stream.." redirected")
                outputs[stream] = type(options) == 'table' and options.handler or nil
                -- the client knows when she is doing, so install the handler
            elseif type(options) == 'table' and options.handler then
                outputs[stream] = options.handler
            else
                print("Unknown error")
                return nil, nil, "Debugger error: can't redirect "..stream
            end
        else
            print("Invalid command")
        end
    elseif command == "basedir" then
        local _, _, dir = string.find(params, "^[a-z]+%s+(.+)$")
        if dir then
            dir = string.gsub(dir, "\\", "/") -- convert slash
            if not string.find(dir, "/$") then dir = dir .. "/" end

            local remdir = dir:match("\t(.+)")
            if remdir then dir = dir:gsub("/?\t.+", "/") end
            basedir = dir

            client:send("BASEDIR "..(remdir or dir).."\n")
            local resp, err = client:receive()
            if not resp then
                print("Unknown error: "..err)
                return nil, nil, "Debugger connection error: "..err
            end
            local _, _, status = string.find(resp, "^(%d+)%s+%w+%s*$")
            if status == "200" then
                print("New base directory is " .. basedir)
            else
                print("Unknown error")
                return nil, nil, "Debugger error: unexpected response after BASEDIR"
            end
        else
            print(basedir)
        end
    elseif command == "help" then
        print("setb <file> <line>    -- sets a breakpoint")
        print("delb <file> <line>    -- removes a breakpoint")
        print("delallb               -- removes all breakpoints")
        print("setw <exp>            -- adds a new watch expression")
        print("delw <index>          -- removes the watch expression at index")
        print("delallw               -- removes all watch expressions")
        print("run                   -- runs until next breakpoint")
        print("step                  -- runs until next line, stepping into function calls")
        print("over                  -- runs until next line, stepping over function calls")
        print("out                   -- runs until line after returning from current function")
        print("listb                 -- lists breakpoints")
        print("listw                 -- lists watch expressions")
        print("eval <exp>            -- evaluates expression on the current context and returns its value")
        print("exec <stmt>           -- executes statement on the current context")
        print("load <file>           -- loads a local file for debugging")
        print("reload                -- restarts the current debugging session")
        print("stack                 -- reports stack trace")
        print("output stdout <d|c|r> -- capture and redirect io stream (default|copy|redirect)")
        print("basedir [<path>]      -- sets the base path of the remote application, or shows the current one")
        print("done                  -- stops the debugger and continues application execution")
        print("exit                  -- exits debugger and the application")
    else
        local _, _, spaces = string.find(params, "^(%s*)$")
        if spaces then
            return nil, nil, "Empty command"
        else
            print("Invalid command")
            return nil, nil, "Invalid command"
        end
    end
    return file, line
end

-- Starts debugging server
local function listen(host, port)
    host = host or "*"
    port = port or mobdebug.port

    local socket = require "socket"

    print("Lua Remote Debugger")
    print("Run the program you wish to debug")

    local server = socket.bind(host, port)
    local client = server:accept()

    client:send("STEP\n")
    client:receive()

    local breakpoint = client:receive()
    local _, _, file, line = string.find(breakpoint, "^202 Paused%s+(.-)%s+(%d+)%s*$")
    if file and line then
        print("Paused at file " .. file )
        print("Type 'help' for commands")
    else
        local _, _, size = string.find(breakpoint, "^401 Error in Execution (%d+)%s*$")
        if size then
            print("Error in remote application: ")
            print(client:receive(size))
        end
    end

    while true do
        io.write("> ")
        local file, line, err = handle(io.read("*line"), client)
        if not file and err == false then break end -- completed debugging
    end

    client:close()
end

local cocreate
local function coro()
    if cocreate then return end -- only set once
    cocreate = cocreate or coroutine.create
    coroutine.create = function(f, ...)
        return cocreate(function(...)
            mobdebug.on()
            return f(...)
        end, ...)
    end
end

local moconew
local function moai()
    if moconew then return end -- only set once
    moconew = moconew or (MOAICoroutine and MOAICoroutine.new)
    if not moconew then return end
    MOAICoroutine.new = function(...)
        local thread = moconew(...)
        -- need to support both thread.run and getmetatable(thread).run, which
        -- was used in earlier MOAI versions
        local mt = thread.run and thread or getmetatable(thread)
        local patched = mt.run
        mt.run = function(self, f, ...)
            return patched(self,  function(...)
                mobdebug.on()
                return f(...)
            end, ...)
        end
        return thread
    end
end

-- make public functions available
mobdebug.setbreakpoint = set_breakpoint
mobdebug.removebreakpoint = remove_breakpoint
mobdebug.listen = listen
mobdebug.loop = loop
mobdebug.scratchpad = scratchpad
mobdebug.handle = handle
mobdebug.connect = connect
mobdebug.start = start
mobdebug.on = on
mobdebug.off = off
mobdebug.moai = moai
mobdebug.coro = coro
mobdebug.done = done
mobdebug.pause = function() step_into = true end
mobdebug.yield = nil -- callback
mobdebug.output = output
mobdebug.onexit = os and os.exit or done
mobdebug.onscratch = nil -- callback
mobdebug.basedir = function(b) if b then basedir = b end return basedir end

return mobdebug