-- Prosody IM v0.1

-- Copyright (C) 2008 Matthew Wild

-- Copyright (C) 2008 Waqas Hussain

-- 

-- This program is free software; you can redistribute it and/or

-- modify it under the terms of the GNU General Public License

-- as published by the Free Software Foundation; either version 2

-- of the License, or (at your option) any later version.

-- 

-- This program is distributed in the hope that it will be useful,

-- but WITHOUT ANY WARRANTY; without even the implied warranty of

-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

-- GNU General Public License for more details.

-- 

-- You should have received a copy of the GNU General Public License

-- along with this program; if not, write to the Free Software

-- Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

--

local file = nil;

local last = nil;

local function read(expected)

	local ch;

	if last then

		ch = last; last = nil;

	else ch = file:read(1); end

	if expected and ch ~= expected then error("expected: "..expected.."; got: "..(ch or "nil")); end

	return ch;

end

local function pushback(ch)

	if last then error(); end

	last = ch;

end

local function peek()

	if not last then last = read(); end

	return last;

end

local _A, _a, _Z, _z, _0, _9, __, _space = string.byte("AaZz09_ ", 1, 8);

local function isAlpha(ch)

	ch = string.byte(ch) or 0;

	return (ch >= _A and ch <= _Z) or (ch >= _a and ch <= _z);

end

local function isNumeric(ch)

	ch = string.byte(ch) or 0;

	return (ch >= _0 and ch <= _9);

end

local function isVar(ch)

	ch = string.byte(ch) or 0;

	return (ch >= _A and ch <= _Z) or (ch >= _a and ch <= _z) or (ch >= _0 and ch <= _9) or ch == __;

end

local function isSpace(ch)

	ch = string.byte(ch) or "x";

	return ch <= _space;

end

local function readString()

	read("\""); -- skip quote

	local slash = nil;

	local str = "";

	while true do

		local ch = read();

		if ch == "\"" and not slash then break; end

		str = str..ch;

	end

	str = str:gsub("\\.", {["\\b"]="\b", ["\\d"]="\d", ["\\e"]="\e", ["\\f"]="\f", ["\\n"]="\n", ["\\r"]="\r", ["\\s"]="\s", ["\\t"]="\t", ["\\v"]="\v", ["\\\""]="\"", ["\\'"]="'", ["\\\\"]="\\"});

	return str;

end

local function readSpecialString()

	read("<"); read("<"); -- read <<

	local str = "";

	if peek() == "\"" then

	elseif peek() ~= ">" then

		error();

	end

	read(">"); read(">"); -- read >>

	return str;

end

local function readVar()

	local var = read();

	while isVar(peek()) do

		var = var..read();

	end

	return var;

end

local function readNumber()

	local num = read();

	while isNumeric(peek()) do

		num = num..read();

	end

	return tonumber(num);

end

local readItem = nil;

local function readTuple()

	local t = {};

	read(); -- read { or [

	while true do

		local item = readItem();

		if not item then break; end

		table.insert(t, item);

	end

	read(); -- read } or ]

	return t;

end

readItem = function()

	local ch = peek();

	if ch == nil then return nil end

	if ch == "{" or ch == "[" then

		return readTuple();

	elseif isAlpha(ch) then

		return readVar();

	elseif isNumeric(ch) then

		return readNumber();

	elseif ch == "\"" then

		return readString();

	elseif ch == "<" then

		return readSpecialString();

	elseif isSpace(ch) or ch == "," or ch == "|" then

		read();

		return readItem();

	else

		--print("Unknown char: "..ch);

		return nil;

	end

end

local function readChunk()

	local x = readItem();

	if x then read("."); end

	return x;

end

local function readFile(filename)

	file = io.open(filename);

	if not file then error("File not found: "..filename); os.exit(0); end

	return function()

		local x = readChunk();

		if not x and peek() then error("Invalid char: "..peek()); end

		return x;

	end;

end

module "erlparse"

function parseFile(file)

	return readFile(file);

end

return _M;