--[[
MIT License

Copyright (c) 2015 2dengine LLC

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

]]
local clock = os.clock

--- The "profile" module controls when to start or stop collecting data and can be used to generate reports.
-- @module profile
-- @alias profile
local profile = {}

-- function labels
local _labeled = {}
-- function definitions
local _defined = {}
-- time of last call
local _tcalled = {}
-- total execution time
local _telapsed = {}
-- number of calls
local _ncalls = {}
-- list of internal profiler functions
local _internal = {}

--- This is an internal function.
-- @tparam string event Event type
-- @tparam number line Line number
-- @tparam[opt] table info Debug info table
function profile.hooker(event, line, info)
  info = info or debug.getinfo(2, "fnS")
  local f = info.func
  -- ignore the profiler itself
  if _internal[f] or info.what ~= "Lua" then
    return
  end
  -- get the function name if available
  if info.name then
    _labeled[f] = info.name
  end
  -- find the line definition
  if not _defined[f] then
    _defined[f] = info.short_src .. ":" .. info.linedefined
    _ncalls[f] = 0
    _telapsed[f] = 0
  end
  if _tcalled[f] then
    local dt = clock() - _tcalled[f]
    _telapsed[f] = _telapsed[f] + dt
    _tcalled[f] = nil
  end
  if event == "tail call" then
    local prev = debug.getinfo(3, "fnS")
    profile.hooker("return", line, prev)
    profile.hooker("call", line, info)
  elseif event == "call" then
    _tcalled[f] = clock()
  else
    _ncalls[f] = _ncalls[f] + 1
  end
end

--- Sets a clock function to be used by the profiler.
-- @tparam function func Clock function that returns a number
function profile.setclock(f)
  assert(type(f) == "function", "clock must be a function")
  clock = f
end

--- Starts collecting data.
function profile.start()
  if rawget(_G, "jit") then
    jit.off()
    jit.flush()
  end
  debug.sethook(profile.hooker, "cr")
end

--- Stops collecting data.
function profile.stop()
  debug.sethook()
  for f in pairs(_tcalled) do
    local dt = clock() - _tcalled[f]
    _telapsed[f] = _telapsed[f] + dt
    _tcalled[f] = nil
  end
  -- merge closures
  local lookup = {}
  for f, d in pairs(_defined) do
    local id = (_labeled[f] or "?") .. d
    local f2 = lookup[id]
    if f2 then
      _ncalls[f2] = _ncalls[f2] + (_ncalls[f] or 0)
      _telapsed[f2] = _telapsed[f2] + (_telapsed[f] or 0)
      _defined[f], _labeled[f] = nil, nil
      _ncalls[f], _telapsed[f] = nil, nil
    else
      lookup[id] = f
    end
  end
  collectgarbage("collect")
end

--- Resets all collected data.
function profile.reset()
  for f in pairs(_ncalls) do
    _ncalls[f] = 0
  end
  for f in pairs(_telapsed) do
    _telapsed[f] = 0
  end
  for f in pairs(_tcalled) do
    _tcalled[f] = nil
  end
  collectgarbage("collect")
end

--- This is an internal function.
-- @tparam function a First function
-- @tparam function b Second function
-- @treturn boolean True if "a" should rank higher than "b"
function profile.comp(a, b)
  local dt = _telapsed[b] - _telapsed[a]
  if dt == 0 then
    return _ncalls[b] < _ncalls[a]
  end
  return dt < 0
end

--- Generates a report of functions that have been called since the profile was started.
-- Returns the report as a numeric table of rows containing the rank, function label, number of calls, total execution time and source code line number.
-- @tparam[opt] number limit Maximum number of rows
-- @treturn table Table of rows
function profile.query(limit)
  local t = {}
  for f, n in pairs(_ncalls) do
    if n > 0 then
      t[#t + 1] = f
    end
  end
  table.sort(t, profile.comp)
  if limit then
    while #t > limit do
      table.remove(t)
    end
  end
  for i, f in ipairs(t) do
    local dt = 0
    if _tcalled[f] then
      dt = clock() - _tcalled[f]
    end
    t[i] = { i, _labeled[f] or "?", _ncalls[f], _telapsed[f] + dt, _defined[f] }
  end
  return t
end

local cols = { 3, 29, 11, 24, 32 }

--- Generates a text report of functions that have been called since the profile was started.
-- Returns the report as a string that can be printed to the console.
-- @tparam[opt] number limit Maximum number of rows
-- @treturn string Text-based profiling report
function profile.report(n)
  local out = {}
  local report = profile.query(n)
  for i, row in ipairs(report) do
    for j = 1, 5 do
      local s = row[j]
      local l2 = cols[j]
      s = tostring(s)
      local l1 = s:len()
      if l1 < l2 then
        s = s .. (" "):rep(l2 - l1)
      elseif l1 > l2 then
        s = s:sub(l1 - l2 + 1, l1)
      end
      row[j] = s
    end
    out[i] = table.concat(row, " | ")
  end

  local row =
    " +-----+-------------------------------+-------------+--------------------------+----------------------------------+ \n"
  local col =
    " | #   | Function                      | Calls       | Time                     | Code                             | \n"
  local sz = row .. col .. row
  if #out > 0 then
    sz = sz .. " | " .. table.concat(out, " | \n | ") .. " | \n"
  end
  return "\n" .. sz .. row
end

-- store all internal profiler functions
for _, v in pairs(profile) do
  if type(v) == "function" then
    _internal[v] = true
  end
end

return profile
