-----------------------------------------------------------------------------
-- URI parsing, composition and relative URL resolution
-- LuaSocket toolkit.
-- Author: Diego Nehab
-----------------------------------------------------------------------------

-- Made some modifications to the original code (mostly formatting)

-----------------------------------------------------------------------------
-- Declare module
-----------------------------------------------------------------------------
local string = require("string")
local base = _G
local table = require("table")

local _M = {
	_NAME = "luanode.__private_url",
	_PACKAGE = "luanode."
}

-----------------------------------------------------------------------------
-- Encodes a string into its escaped hexadecimal representation
-- Input
--   s: binary string to be encoded
-- Returns
--   escaped representation of string binary
-----------------------------------------------------------------------------
function _M.escape(s)
	return (string.gsub(s, "([^A-Za-z0-9_])", function(c)
		return string.format("%%%02x", string.byte(c))
	end))
end

-----------------------------------------------------------------------------
-- Protects a path segment, to prevent it from interfering with the
-- url parsing.
-- Input
--   s: binary string to be encoded
-- Returns
--   escaped representation of string binary
-----------------------------------------------------------------------------
local function make_set(t)
	local s = {}
	for i,v in base.ipairs(t) do
		s[t[i]] = 1
	end
	return s
end

-- these are allowed withing a path segment, along with alphanum
-- other characters must be escaped
local segment_set = make_set {
	"-", "_", ".", "!", "~", "*", "'", "(",
	")", ":", "@", "&", "=", "+", "$", ",",
}

local function protect_segment(s)
	return string.gsub(s, "([^A-Za-z0-9_])", function (c)
		if segment_set[c] then return c
		else return string.format("%%%02x", string.byte(c)) end
	end)
end

-----------------------------------------------------------------------------
-- Encodes a string into its escaped hexadecimal representation
-- Input
--   s: binary string to be encoded
-- Returns
--   escaped representation of string binary
-----------------------------------------------------------------------------
function _M.unescape(s)
	return (string.gsub(s, "%%(%x%x)", function(hex)
		return string.char(base.tonumber(hex, 16))
	end))
end

-----------------------------------------------------------------------------
-- Builds a path from a base path and a relative path
-- Input
--   base_path
--   relative_path
-- Returns
--   corresponding absolute path
-----------------------------------------------------------------------------
local function absolute_path(base_path, relative_path)
	if string.sub(relative_path, 1, 1) == "/" then return relative_path end
	local path = string.gsub(base_path, "[^/]*$", "")
	path = path .. relative_path
	path = string.gsub(path, "([^/]*%./)", function (s)
		if s ~= "./" then return s else return "" end
	end)
	path = string.gsub(path, "/%.$", "/")
	local reduced
	while reduced ~= path do
		reduced = path
		path = string.gsub(reduced, "([^/]*/%.%./)", function (s)
			if s ~= "../../" then return "" else return s end
		end)
	end
	path = string.gsub(reduced, "([^/]*/%.%.)$", function (s)
		if s ~= "../.." then return "" else return s end
	end)
	return path
end

-----------------------------------------------------------------------------
-- Parses a url and returns a table with all its parts according to RFC 2396
-- The following grammar describes the names given to the URL parts
-- <url> ::= <scheme>://<authority>/<path>;<params>?<query>#<fragment>
-- <authority> ::= <userinfo>@<host>:<port>
-- <userinfo> ::= <user>[:<password>]
-- <path> :: = {<segment>/}<segment>
-- Input
--   url: uniform resource locator of request
--   default: table with default values for each field
-- Returns
--   table with the following fields, where RFC naming conventions have
--   been preserved:
--     scheme, authority, userinfo, user, password, host, port,
--     path, params, query, fragment
-- Obs:
--   the leading '/' in {/<path>} is considered part of <path>
-----------------------------------------------------------------------------
function _M.parse(url, default)
	-- initialize default parameters
	local parsed = {}
	for i,v in base.pairs(default or parsed) do parsed[i] = v end
	-- empty url is parsed to nil
	if not url or url == "" then return nil, "invalid url" end
	-- remove whitespace
	-- url = string.gsub(url, "%s", "")
	-- get fragment
	url = string.gsub(url, "#(.*)$", function(f)
		parsed.fragment = f
		return ""
	end)
	-- get scheme
	url = string.gsub(url, "^([%w][%w%+%-%.]*)%:",
		function(s) parsed.scheme = s; return "" end)
	-- get authority
	url = string.gsub(url, "^//([^/]*)", function(n)
		parsed.authority = n
		return ""
	end)
	-- get query string
	url = string.gsub(url, "%?(.*)", function(q)
		parsed.query = q
		return ""
	end)
	-- get params
	url = string.gsub(url, "%;(.*)", function(p)
		parsed.params = p
		return ""
	end)
	-- path is whatever was left
	if url ~= "" then parsed.path = url end
	local authority = parsed.authority
	if not authority then return parsed end
	authority = string.gsub(authority,"^([^@]*)@",
		function(u) parsed.userinfo = u; return "" end)
	authority = string.gsub(authority, ":([^:%]]*)$",
		function(p) parsed.port = p; return "" end)
	if authority ~= "" then 
		-- IPv6?
		parsed.host = string.match(authority, "^%[(.+)%]$") or authority 
	end
	local userinfo = parsed.userinfo
	if not userinfo then return parsed end
	userinfo = string.gsub(userinfo, ":([^:]*)$",
		function(p) parsed.password = p; return "" end)
	parsed.user = userinfo
	return parsed
end

-----------------------------------------------------------------------------
-- Rebuilds a parsed URL from its components.
-- Components are protected if any reserved or unallowed characters are found
-- Input
--   parsed: parsed URL, as returned by parse
-- Returns
--   a stringing with the corresponding URL
-----------------------------------------------------------------------------
function _M.build(parsed)
	local ppath = _M.parse_path(parsed.path or "")
	local url = _M.build_path(ppath)
	if parsed.params then url = url .. ";" .. parsed.params end
	if parsed.query then url = url .. "?" .. parsed.query end
	local authority = parsed.authority
	if parsed.host then
		authority = parsed.host
		if string.find(authority, ":") then -- IPv6?
			authority = "[" .. authority .. "]"
		end
		if parsed.port then authority = authority .. ":" .. parsed.port end
		local userinfo = parsed.userinfo
		if parsed.user then
			userinfo = parsed.user
			if parsed.password then
				userinfo = userinfo .. ":" .. parsed.password
			end
		end
		if userinfo then authority = userinfo .. "@" .. authority end
	end
	if authority then url = "//" .. authority .. url end
	if parsed.scheme then url = parsed.scheme .. ":" .. url end
	if parsed.fragment then url = url .. "#" .. parsed.fragment end
	-- url = string.gsub(url, "%s", "")
	return url
end

-----------------------------------------------------------------------------
-- Builds a absolute URL from a base and a relative URL according to RFC 2396
-- Input
--   base_url
--   relative_url
-- Returns
--   corresponding absolute url
-----------------------------------------------------------------------------
function _M.absolute(base_url, relative_url)
	if base.type(base_url) == "table" then
		base_parsed = base_url
		base_url = _M.build(base_parsed)
	else
		base_parsed = _M.parse(base_url)
	end
	local relative_parsed = _M.parse(relative_url)
	if not base_parsed then return relative_url
	elseif not relative_parsed then return base_url
	elseif relative_parsed.scheme then return relative_url
	else
		relative_parsed.scheme = base_parsed.scheme
		if not relative_parsed.authority then
			relative_parsed.authority = base_parsed.authority
			if not relative_parsed.path then
				relative_parsed.path = base_parsed.path
				if not relative_parsed.params then
					relative_parsed.params = base_parsed.params
					if not relative_parsed.query then
						relative_parsed.query = base_parsed.query
					end
				end
			else    
				relative_parsed.path = absolute_path(base_parsed.path or "",
					relative_parsed.path)
			end
		end
		return _M.build(relative_parsed)
	end
end

-----------------------------------------------------------------------------
-- Breaks a path into its segments, unescaping the segments
-- Input
--   path
-- Returns
--   segment: a table with one entry per segment
-----------------------------------------------------------------------------
function _M.parse_path(path)
	local parsed = {}
	path = path or ""
	--path = string.gsub(path, "%s", "")
	string.gsub(path, "([^/]+)", function (s) table.insert(parsed, s) end)
	for i = 1, #parsed do
		parsed[i] = _M.unescape(parsed[i])
	end
	if string.sub(path, 1, 1) == "/" then parsed.is_absolute = 1 end
	if string.sub(path, -1, -1) == "/" then parsed.is_directory = 1 end
	return parsed
end

-----------------------------------------------------------------------------
-- Builds a path component from its segments, escaping protected characters.
-- Input
--   parsed: path segments
--   unsafe: if true, segments are not protected before path is built
-- Returns
--   path: corresponding path stringing
-----------------------------------------------------------------------------
function _M.build_path(parsed, unsafe)
	local path = ""
	local n = #parsed
	if unsafe then
		for i = 1, n-1 do
			path = path .. parsed[i]
			path = path .. "/"
		end
		if n > 0 then
			path = path .. parsed[n]
			if parsed.is_directory then path = path .. "/" end
		end
	else
		for i = 1, n-1 do
			path = path .. protect_segment(parsed[i])
			path = path .. "/"
		end
		if n > 0 then
			path = path .. protect_segment(parsed[n])
			if parsed.is_directory then path = path .. "/" end
		end
	end
	if parsed.is_absolute then path = "/" .. path end
	return path
end

return _M
