--- URI parsing, composition, and relative URL resolution.
-- @author Diego Nehab
-- @author Eddie Bell <ejlbell@gmail.com>

--[[
URI parsing, composition and relative URL resolution
LuaSocket toolkit.
Author: Diego Nehab
RCS ID: $Id: url.lua,v 1.37 2005/11/22 08:33:29 diego Exp $

parse_query and build_query added For nmap (Eddie Bell <ejlbell@gmail.com>) 
--]]

-----------------------------------------------------------------------------
-- Declare module
-----------------------------------------------------------------------------
local string = require("string")
local base = _G
local table = require("table")
module(... or "url",package.seeall)

_VERSION = "URL 1.0"

		--[[ Internal functions --]]

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 {
    "-", "_", ".", "!", "~", "*", "'", "(",
	")", ":", "@", "&", "=", "+", "$", ",",
}

---
-- Protects a path segment, to prevent it from interfering with the
-- URL parsing.
-- @param s Binary string to be encoded.
-- @return Escaped representation of string.
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

---
-- Builds a path from a base path and a relative path
-- @param base_path A base path.
-- @param relative_path A relative path.
-- @return The 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


		--[[ External functions --]]

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


---
-- Decodes an escaped hexadecimal string.
-- @param s Hexadecimal-encoded string.
-- @return Decoded string.
-----------------------------------------------------------------------------
function unescape(s)
    return string.gsub(s, "%%(%x%x)", function(hex)
        return string.char(base.tonumber(hex, 16))
    end)
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.
-- <code>
-- <url> ::= <scheme>://<authority>/<path>;<params>?<query>#<fragment>
-- <authority> ::= <userinfo>@<host>:<port>
-- <userinfo> ::= <user>[:<password>]
-- <path> :: = {<segment>/}<segment>
-- </code>
--
-- The leading <code>/</code> in <code>/<path></code> is considered part of
-- <code><path></code>.
-- @param url URL of request.
-- @param default Table with default values for each field.
-- @return A table with the following fields, where RFC naming conventions have
--   been preserved:
--     <code>scheme</code>, <code>authority</code>, <code>userinfo</code>,
--     <code>user</code>, <code>password</code>, <code>host</code>,
--     <code>port</code>, <code>path</code>, <code>params</code>,
--     <code>query</code>, and <code>fragment</code>.
-----------------------------------------------------------------------------
function 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, "#(.*)$", function(f)
        parsed.fragment = f
        return ""
    end)
    -- get scheme
    url = string.gsub(url, "^([%w][%w%+%-%.]*)%:",
        function(s) parsed.scheme = s; return "" end)
    -- get authority
    url = string.gsub(url, "^//([^/]*)", function(n)
        parsed.authority = n
        return ""
    end)
    -- get query stringing
    url = string.gsub(url, "%?(.*)", function(q)
        parsed.query = q
        return ""
    end)
    -- get params
    url = string.gsub(url, "%;(.*)", function(p)
        parsed.params = p
        return ""
    end)
    -- path is whatever was left
    if url ~= "" then parsed.path = url end
    local authority = parsed.authority
    if not authority then return parsed end
    authority = string.gsub(authority,"^([^@]*)@",
        function(u) parsed.userinfo = u; return "" end)
    authority = string.gsub(authority, ":([^:]*)$",
        function(p) parsed.port = p; return "" end)
    if authority ~= "" then parsed.host = 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.
-- @param parsed Parsed URL, as returned by parse.
-- @return A string with the corresponding URL.
-----------------------------------------------------------------------------
function build(parsed)
    local ppath = parse_path(parsed.path or "")
    local url = 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 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 an absolute URL from a base and a relative URL according to RFC 2396.
-- @param base_url A base URL.
-- @param relative_url A relative URL.
-- @return The corresponding absolute URL.
-----------------------------------------------------------------------------
function absolute(base_url, relative_url)
    if type(base_url) == "table" then
        base_parsed = base_url
        base_url = build(base_parsed)
    else
        base_parsed = parse(base_url)
    end
    local relative_parsed = 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 build(relative_parsed)
    end
end

---
-- Breaks a path into its segments, unescaping the segments.
-- @param path A path to break.
-- @return A table with one entry per segment.
-----------------------------------------------------------------------------
function 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, table.getn(parsed) do
		parsed[i] = 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.
-- @param parsed Path segments.
-- @param unsafe If true, segments are not protected before path is built.
-- @return The corresponding path string
-----------------------------------------------------------------------------
function build_path(parsed, unsafe)
	local path = ""
	local n = table.getn(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

---
-- Breaks a query string into name/value pairs.
--
-- This function takes a <code><query></code> of the form
-- <code>"name1=value1&name2=value2"</code>
-- and returns a table containing the name-value pairs, with the name as the key
-- and the value as its associated value.
-- @param query Query string.
-- @return A table of name-value pairs following the pattern
-- <code>table["name"]</code> = <code>value</code>.
-----------------------------------------------------------------------------
function parse_query(query)
	local parsed = {}
	local pos = 0

	query = string.gsub(query, "&amp;", "&")
	query = string.gsub(query, "&lt;", "<")
	query = string.gsub(query, "&gt;", ">")

	function ginsert(qstr)
		local first, last = string.find(qstr, "=")
		if first then
			parsed[string.sub(qstr, 0, first-1)] = string.sub(qstr, first+1)
		end
	end

	while true do
		local first, last = string.find(query, "&", pos)
		if first then
			ginsert(string.sub(query, pos, first-1));
			pos = last+1
		else
			ginsert(string.sub(query, pos));
			break;
		end
	end
	return parsed
end

---
-- Builds a query string from a table.
--
-- This is the inverse of <code>parse_query</code>.
-- @param query A dictionary table where <code>table['name']</code> =
-- <code>value</code>.
-- @return A query string (like <code>"name=value2&name=value2"</code>).
-----------------------------------------------------------------------------
function build_query(query)
	local qstr = ""

	for i,v in pairs(query) do 
		qstr = qstr .. i .. '=' .. v .. '&'
	end
	return string.sub(qstr, 0, string.len(qstr)-1)
end	
