#!/usr/local/bin/lua

--[[
Copyright (c) 2011, 2012 James Turner <james@calminferno.net>

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
]]

local tincan     = require("tincan")
local print_buff = {}

local function term_print(...)
    local args, n = {...}, select("#", ...)

    for i = 1, n do
        args[i] = tostring(args[i])
    end

    table.insert(print_buff, table.concat(args, "\t"))
end

local env = {
    _VERSION     = _VERSION,
    assert       = assert,
    error        = error,
    getmetatable = getmetatable,
    ipairs       = ipairs,
    next         = next,
    pairs        = pairs,
    pcall        = pcall,
    print        = term_print,
    rawequal     = rawequal,
    rawget       = rawget,
    rawlen       = rawlen,
    rawset       = rawset,
    select       = select,
    setmetatable = setmetatable,
    tonumber     = tonumber,
    tostring     = tostring,
    type         = type,
    xpcall       = xpcall,
    bit32 = {
        arshift = bit32.arshift,
        band    = bit32.band,
        bnot    = bit32.bnot,
        bor     = bit32.bor,
        btest   = bit32.btest,
        bxor    = bit32.bxor,
        extract = bit32.extract,
        lrotate = bit32.lrotate,
        lshift  = bit32.lshift,
        replace = bit32.replace,
        rrotate = bit32.rrotate,
        rshift  = bit32.rshift
    },
    coroutine = {
        create  = coroutine.create,
        resume  = coroutine.resume,
        running = coroutine.running,
        status  = coroutine.status,
        wrap    = coroutine.wrap,
        yield   = coroutine.yield
    },
    math = {
        abs        = math.abs,
        acos       = math.acos,
        asin       = math.asin,
        atan       = math.atan,
        atan2      = math.atan2,
        ceil       = math.ceil,
        cos        = math.cos,
        cosh       = math.cosh,
        deg        = math.deg,
        exp        = math.exp,
        floor      = math.floor,
        fmod       = math.fmod,
        frexp      = math.frexp,
        huge       = math.huge,
        ldexp      = math.ldexp,
        log        = math.log,
        max        = math.max,
        min        = math.min,
        modf       = math.modf,
        pi         = math.pi,
        pow        = math.pow,
        rad        = math.rad,
        random     = math.random,
        randomseed = math.randomseed,
        sin        = math.sin,
        sinh       = math.sinh,
        sqrt       = math.sqrt,
        tan        = math.tan,
        tanh       = math.tanh
    },
    string = {
        byte    = string.byte,
        char    = string.char,
        dump    = string.dump,
        find    = string.find,
        format  = string.format,
        gmatch  = string.gmatch,
        gsub    = string.gsub,
        len     = string.len,
        lower   = string.lower,
        match   = string.match,
        rep     = string.rep,
        reverse = string.reverse,
        sub     = string.sub,
        upper   = string.upper
    },
    table = {
        concat = table.concat,
        insert = table.insert,
        pack   = table.pack,
        remove = table.remove,
        sort   = table.sort,
        unpack = table.unpack
    }
}

env._G = env

local function eval(expr, hash)
    local func, err, stat, val

    tincan.load("trylua.db")
    local history = tincan.get(hash)

    if history then
        for _, stmt in ipairs(history) do
            func = load(stmt, "", "t", env)

            if func then
                _, val = pcall(func)
            end
        end
    else
        history = {}
    end

    print_buff = {}

    expr = string.gsub(expr, "^%s*=%s*", "return ")

    if not expr then
        return "expression is nil"
    end

    func, err = load(expr, "", "t", env)

    if func then
        stat, val = pcall(func)

        if not stat then
            err = val
        else
            if #print_buff > 0 then
                val = table.concat(print_buff, "\n")
            else
                local beginner = "return"

                if val == nil and string.sub(expr, 0, #beginner) ~= beginner then
                    val = ""
                end
            end

            table.insert(history, expr)
            tincan.set(hash, history)
            tincan.save("trylua.db")

            return tostring(val)
        end
    end

    if err then
        local ender = "<eof>"
        err         = tostring(err)
        err         = string.gsub(err, '^%[string ".*"%]:[0-9]+: ', "")

        if string.sub(err, -#ender) == ender then
            return "continued"
        end

        return err
    end
end

local function url_decode(str)
    str = string.gsub(str, "+", " ")
    str = string.gsub(str, "%%(%x%x)", function(h)
        return string.char(tonumber(h, 16))
    end)
    str = string.gsub(str, "\r\n", "\n")

    return str
end

local info   = os.getenv("QUERY_STRING") or ""
local params = {}

for key, value in string.gmatch(info .. "&", "(.-)%=(.-)%&") do
    params[key] = url_decode(value)
end

if params.expr and params.hash then
    local res = eval(params.expr, params.hash)

    print("Content-type: text/plain\n")
    print(res)
else
    print("Content-type: text/plain\n")
end