local lua_opcode_types = {
    "ABC",  "ABx", "ABC",  "ABC",
    "ABC",  "ABx", "ABC",  "ABx",
    "ABC",  "ABC", "ABC",  "ABC",
    "ABC",  "ABC", "ABC",  "ABC",
    "ABC",  "ABC", "ABC",  "ABC",
    "ABC",  "ABC", "AsBx", "ABC",
    "ABC",  "ABC", "ABC",  "ABC",
    "ABC",  "ABC", "ABC",  "AsBx",
    "AsBx", "ABC", "ABC", "ABC",
    "ABx",  "ABC",
}

local lua_opcode_names = {
    "MOVE",     "LOADK",     "LOADBOOL", "LOADNIL",
    "GETUPVAL", "GETGLOBAL", "GETTABLE", "SETGLOBAL",
    "SETUPVAL", "SETTABLE",  "NEWTABLE", "SELF",
    "ADD",      "SUB",       "MUL",      "DIV",
    "MOD",      "POW",       "UNM",      "NOT",
    "LEN",      "CONCAT",    "JMP",      "EQ",
    "LT",       "LE",        "TEST",     "TESTSET",
    "CALL",     "TAILCALL",  "RETURN",   "FORLOOP",
    "FORPREP",  "TFORLOOP",  "SETLIST",  "CLOSE",
    "CLOSURE",  "VARARG"
};

--[[
local lua_opcode_numbers = {};
for number, name in next, lua_opcode_names do
	lua_opcode_numbers[name] = number;
end
--]]

--- Extract bits from an integer
--@author: Stravant
local function get_bits(Bit, Start, End) -- No tail-calls, yay.
    if End then -- Thanks to cntkillme for giving input on this shorter, better approach.
        local Res	= (Bit / 2 ^ (Start - 1)) % 2 ^ ((End - 1) - (Start - 1) + 1);

        return Res - Res % 1;
else
    local Plc = 2 ^ (Start - 1);

    if (Bit % (Plc + Plc) >= Plc) then
        return 1;
    else
        return 0;
    end;
end;
end;

local function decode_bytecode(bytecode)
    local index = 1
    local big_endian = false
    local int_size;
    local size_t;

    -- Actual binary decoding functions. Dependant on the bytecode.
    local get_int, get_size_t;

    -- Binary decoding helper functions
    local get_int8, get_int32, get_int64, get_float64, get_string;
    do
        function get_int8()
            local a = string.byte(bytecode, index, index);
            index = index + 1
            return a
        end
        function get_int32()
			print('idx', index)
            local a, b, c, d = string.byte(bytecode, index, index + 3);
            index = index + 4;
            return d*16777216 + c*65536 + b*256 + a
        end
        function get_int64()
            local a = get_int32();
            local b = get_int32();
            return b*4294967296 + a;
        end
        function get_float64()
            local a = get_int32()
            local b = get_int32()
            return (-2*get_bits(b, 32)+1)*(2^(get_bits(b, 21, 31)-1023))*
                ((get_bits(b, 1, 20)*(2^32) + a)/(2^52)+1)
        end
        function get_string(len)
            local str;
            if len then
                str = string.sub(bytecode, index, index + len - 1);
                index = index + len;
            else
                len = get_size_t();
                if len == 0 then
                    return;
                end
                str = string.sub(bytecode, index, index + len - 1);
                index = index + len;
            end
            return str;
        end
    end

    local function decode_chunk()
        local chunk;
        local instructions = {};
        local constants    = {};
        local prototypes   = {};
        local debug = {
            lines = {};
        };

        chunk = {
            instructions = instructions;
            constants    = constants;
            prototypes   = prototypes;
            debug = debug;
        };

        local num;

        chunk.name       = get_string();-- Function name
        chunk.first_line = get_int();	-- First line
        chunk.last_line  = get_int();	-- Last  line

        if chunk.name then chunk.name = chunk.name:sub(1, -2); end

        chunk.upvalues  = get_int8();
        chunk.arguments = get_int8();
        chunk.varg      = get_int8();
        chunk.stack     = get_int8();

        -- TODO: realign lists to 1
        -- Decode instructions
        do
            num = get_int();
            print('sizecode', num)
            for i = 1, num do
                local instruction = {}

                local data   = get_int32();
                local opcode = get_bits(data, 1, 6);
                local type   = lua_opcode_types[opcode + 1];

                instruction.opcode = opcode;
                instruction.type   = type;
                print('opcode', opcode)

                instruction.A = get_bits(data, 7, 14);
                if type == "ABC" then
                    instruction.B = get_bits(data, 24, 32);
                    instruction.C = get_bits(data, 15, 23);
                elseif type == "ABx" then
                    instruction.Bx = get_bits(data, 15, 32);
                elseif type == "AsBx" then
                    instruction.sBx = get_bits(data, 15, 32) - 131071;
                end

                instructions[i] = instruction;
            end
        end

        -- Decode constants
        do
            num = get_int();
            print('sizek', num)
            for i = 1, num do
                local constant = {
                    -- type = constant type;
                    -- data = constant data;
                    };
                local type = get_int8();
                constant.type = type;

                if type == 1 then
                    constant.data = (get_int8() ~= 0);
                elseif type == 3 then
                    constant.data = get_float64();
                elseif type == 4 then
                    constant.data = get_string():sub(1, -2);
                end

                constants[i-1] = constant;
            end
        end

        -- Decode Prototypes
        do
            num = get_int();
            print('sizep', num)
            for i = 1, num do
                prototypes[i-1] = decode_chunk();
            end
        end

        -- Decode debug info
        -- Not all of which is used yet.
        do
            -- line numbers
            print('sizelineinfo', num)
            local data = debug.lines
            num = get_int();
            for i = 1, num do
                data[i] = get_int32();
            end

            -- locals
            print('sizelocvars', num)
            num = get_int();
            for i = 1, num do
                get_string():sub(1, -2);	-- local name
                get_int32();	-- local start PC
                get_int32();	-- local end   PC
            end

            -- upvalues
            print('sizeupvalues', num)
            num = get_int();
            for i = 1, num do
                get_string();	-- upvalue name
            end
        end

        return chunk;
    end

    -- Verify bytecode header
    do
        assert(get_string(4) == "\27Lua", "Lua bytecode expected.");
        assert(get_int8() == 0x51, "Only Lua 5.1 is supported.");
        get_int8(); 	-- Oficial bytecode
        big_endian = (get_int8() == 0);
        int_size = get_int8();
        size_t   = get_int8();

        if int_size == 4 then
            get_int = get_int32;
        elseif int_size == 8 then
            get_int = get_int64;
        else
            -- TODO: refactor errors into table
            error("Unsupported bytecode target platform");
        end

        if size_t == 4 then
            get_size_t = get_int32;
        elseif size_t == 8 then
            get_size_t = get_int64;
        else
            error("Unsupported bytecode target platform");
        end

        assert(get_string(3) == "\4\8\0",
            "Unsupported bytecode target platform");
    end

    return decode_chunk();
end

local function handle_return(...)
    local c = select("#", ...)
    local t = {...}
    return c, t
end

local function create_wrapper(cache, upvalues)
    local instructions = cache.instructions;
    local constants    = cache.constants;
    local prototypes   = cache.prototypes;

    local stack, top
    local environment
    local IP = 1;	-- instruction pointer
    local vararg, vararg_size

    local opcode_funcs = {
        [0]  = function(instruction)	-- MOVE
            stack[instruction.A] = stack[instruction.B];
        end,
        [1]  = function(instruction)	-- LOADK
            stack[instruction.A] = constants[instruction.Bx].data;
        end,
        [2]  = function(instruction)	-- LOADBOOL
            stack[instruction.A] = instruction.B ~= 0
            if instruction.C ~= 0 then
                IP = IP + 1
            end
        end,
        [3]  = function(instruction)	-- LOADNIL
            local stack = stack
            for i = instruction.A, instruction.B do
                stack[i] = nil
            end
        end,
        [4] = function(instruction)		-- GETUPVAL
            stack[instruction.A] = upvalues[instruction.B]
        end,
        [5]  = function(instruction)	-- GETGLOBAL
            local key = constants[instruction.Bx].data;
            stack[instruction.A] = environment[key];
        end,
        [6]  = function(instruction)	-- GETTABLE
            local C = instruction.C
            local stack = stack
            C = C > 255 and constants[C-256].data or stack[C]
            stack[instruction.A] = stack[instruction.B][C];
        end,
        [7]  = function(instruction)	-- SETGLOBAL
            local key = constants[instruction.Bx].data;
            environment[key] = stack[instruction.A];
        end,
        [8] = function (instruction)	-- SETUPVAL
            upvalues[instruction.B] = stack[instruction.A]
        end,
        [9] = function (instruction)	-- SETTABLE
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A][B] = C
        end,
        [10] = function (instruction)	-- NEWTABLE
            stack[instruction.A] = {}
        end,
        [11] = function (instruction)	-- SELF
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack = stack

            B = stack[B]
            C = C > 255 and constants[C-256].data or stack[C]

            stack[A+1] = B
            stack[A]   = B[C]
        end,
        [12] = function(instruction)	-- ADD
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B+C;
        end,
        [13] = function(instruction)	-- SUB
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B - C;
        end,
        [14] = function(instruction)	-- MUL
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B * C;
        end,
        [15] = function(instruction)	--DIV
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B / C;
        end,
        [16] = function(instruction) 	-- MOD
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B % C;
        end,
        [17] = function(instruction)	-- POW
            local B = instruction.B;
            local C = instruction.C;
            local stack, constants = stack, constants;

            B = B > 255 and constants[B-256].data or stack[B];
            C = C > 255 and constants[C-256].data or stack[C];

            stack[instruction.A] = B ^ C;
        end,
        [18] = function(instruction)	-- UNM
            stack[instruction.A] = -stack[instruction.B]
        end,
        [19] = function(instruction)	-- NOT
            stack[instruction.A] = not stack[instruction.B]
        end,
        [20] = function(instruction)	-- LEN
            stack[instruction.A] = #stack[instruction.B]
        end,
        [21] = function(instruction)	-- CONCAT
            local B = instruction.B
            local result = stack[B]
            for i = B+1, instruction.C do
                result = result .. stack[i]
            end
            stack[instruction.A] = result
        end,
        [22] = function(instruction)	-- JUMP
            IP = IP + instruction.sBx
        end,
        [23] = function(instruction)	-- EQ
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack, constants = stack, constants

            A = A ~= 0
            if (B > 255) then B = constants[B-256].data else B = stack[B] end
            if (C > 255) then C = constants[C-256].data else C = stack[C] end
            if (B == C) ~= A then
                IP = IP + 1
            end
        end,
        [24] = function(instruction)	-- LT
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack, constants = stack, constants

            A = A ~= 0
            B = B > 255 and constants[B-256].data or stack[B]
            C = C > 255 and constants[C-256].data or stack[C]
            if (B < C) ~= A then
                IP = IP + 1
            end
        end,
        [25] = function(instruction)	-- LT
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack, constants = stack, constants

            A = A ~= 0
            B = B > 255 and constants[B-256].data or stack[B]
            C = C > 255 and constants[C-256].data or stack[C]
            if (B <= C) ~= A then
                IP = IP + 1
            end
        end,
        [26] = function(instruction)	-- TEST
            local A = stack[instruction.A];
            if (not not A) == (instruction.C == 0) then
                IP = IP + 1
            end
        end,
        [27] = function(instruction)	-- TESTSET
            local stack = stack
            local B = stack[instruction.B]

            if (not not B) == (instruction.C == 0) then
                IP = IP + 1
            else
                stack[instruction.A] = B
            end
        end,
        [28] = function(instruction)	-- CALL
            local A = instruction.A;
            local B = instruction.B;
            local C = instruction.C;
            local stack = stack;
            local args, results;
            local limit, loop

            args = {};
            if B ~= 1 then
                if B ~= 0 then
                    limit = A+B-1;
                else
                    limit = top
                end

                loop = 0
                for i = A+1, limit do
                    loop = loop + 1
                    args[loop] = stack[i];
                end

                limit, results = handle_return(stack[A](unpack(args, 1, limit-A)))
            else
                limit, results = handle_return(stack[A]())
            end

            top = A - 1

            if C ~= 1 then
                if C ~= 0 then
                    limit = A+C-2;
                else
                    limit = limit+A
                end

                loop = 0;
                for i = A, limit do
                    loop = loop + 1;
                    stack[i] = results[loop];
                end
            end
        end,
        [29] = function (instruction)	-- TAILCALL
            local A = instruction.A;
            local B = instruction.B;
            local C = instruction.C;
            local stack = stack;
            local args, results;
            local top, limit, loop = top

            args = {};
            if B ~= 1 then
                if B ~= 0 then
                    limit = A+B-1;
                else
                    limit = top
                end

                loop = 0
                for i = A+1, limit do
                    loop = loop + 1
                    args[#args+1] = stack[i];
                end

                results = {stack[A](unpack(args, 1, limit-A))};
            else
                results = {stack[A]()};
            end

            return true, results
        end,
        [30] = function(instruction) -- RETURN
            --TODO: CLOSE
            local A = instruction.A;
            local B = instruction.B;
            local stack = stack;
            local limit;
            local loop, output;

            if B == 1 then
                return true;
            end
            if B == 0 then
                limit = top
            else
                limit = A + B - 2;
            end

            output = {};
            local loop = 0
            for i = A, limit do
                loop = loop + 1
                output[loop] = stack[i];
            end
            return true, output;
        end,
        [31] = function(instruction)	-- FORLOOP
            local A = instruction.A
            local stack = stack

            local step = stack[A+2]
            local index = stack[A] + step
            stack[A] = index

            if step > 0 then
                if index <= stack[A+1] then
                    IP = IP + instruction.sBx
                    stack[A+3] = index
                end
            else
                if index >= stack[A+1] then
                    IP = IP + instruction.sBx
                    stack[A+3] = index
                end
            end
        end,
        [32] = function(instruction)	-- FORPREP
            local A = instruction.A
            local stack = stack

            stack[A] = stack[A] - stack[A+2]
            IP = IP + instruction.sBx
        end,
        [33] = function(instruction)	-- TFORLOOP
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack = stack

            local offset = A+2
            local result = {stack[A](stack[A+1], stack[A+2])}
            for i = 1, C do
                stack[offset+i] = result[i]
            end

            if stack[A+3] ~= nil then
                stack[A+2] = stack[A+3]
            else
                IP = IP + 1
            end
        end,
        [34] = function(instruction)	-- SETLIST
            local A = instruction.A
            local B = instruction.B
            local C = instruction.C
            local stack = stack

            if C == 0 then
                error("NYI: extended SETLIST")
            else
                local offset = (C - 1) * 50
                local t = stack[A]

                if B == 0 then
                    B = top
                end
                for i = 1, B do
                    t[offset+i] = stack[A+i]
                end
            end
        end,
        [35] = function(instruction)	-- CLOSE
            io.stderr:write("NYI: CLOSE")
            io.stderr:flush()
        end,
        [36] = function(instruction)	-- CLOSURE
            local proto = prototypes[instruction.Bx]
            local instructions = instructions
            local stack = stack

            local indices = {}
            local new_upvals = setmetatable({},
                {
                    __index = function(t, k)
                        local upval = indices[k]
                        return upval.segment[upval.offset]
                    end,
                    __newindex = function(t, k, v)
                        local upval = indices[k]
                        upval.segment[upval.offset] = v
                    end
                }
            )
            for i = 1, proto.upvalues do
                local movement = instructions[IP]
                if movement.opcode == 0 then -- MOVE
                    indices[i-1] = {segment = stack, offset = movement.B}
                elseif instructions[IP].opcode == 4 then -- GETUPVAL
                    indices[i-1] = {segment = upvalues, offset = movement.B}
                end
                IP = IP + 1
            end

            local _, func = create_wrapper(proto, new_upvals)
            stack[instruction.A] = func
        end,
        [37] = function(instruction)	-- VARARG
            local A = instruction.A
            local B = instruction.B
            local stack, vararg = stack, vararg

            for i = A, A + (B > 0 and B - 1 or vararg_size) do
                stack[i] = vararg[i - A]
            end
        end,
    }

    local function loop()
        local instructions = instructions
        local instruction, a, b

        while true do
            instruction = instructions[IP];
            IP = IP + 1
            print(instruction, instruction.opcode)
            a, b = opcode_funcs[instruction.opcode](instruction);
            if a then
                return b;
            end
        end
    end

    local debugging = {
        get_stack = function()
            return stack;
        end;
        get_IP = function()
            return IP;
        end
    };

    local function func(...)
        local local_stack = {};
        local ghost_stack = {};

        top = -1
        stack = setmetatable(local_stack, {
            __index = ghost_stack;
            __newindex = function(t, k, v)
                if k > top and v then
                    top = k
                end
                ghost_stack[k] = v
            end;
        })
        local args = {...};
        vararg = {}
        vararg_size = select("#", ...) - 1
        for i = 0, vararg_size do
            local_stack[i] = args[i+1];
            vararg[i] = args[i+1]
        end

        environment = getfenv(0);
        IP = 1;
        local thread = coroutine.create(loop)
        local a, b = coroutine.resume(thread)

        if a then
            if b then
                return unpack(b);
            end
            return;
        else
            if advanced_debug then
            --TODO advanced debugging
            else
                --TODO error converting
                local name = cache.name;
                local line = cache.debug.lines[IP];
                local err  = b:gsub("(.-:)", "");
                local output = "";

                output = output .. (name and name .. ":" or "");
                output = output .. (line and line .. ":" or "");
                output = output .. b
                --[[
				output = ("%s (Instruction=%s)"):format(output,
					lua_opcode_names[select(2,debug.getlocal(loop,1, 1)).opcode+1])
				--]]
                error(output, 0);
            end
        end
    end

    return debugging, func;
end

load_bytecode = function(bytecode)
    local cache = decode_bytecode(bytecode);
    local _, func = create_wrapper(cache);
    return func;
end;

load_bytecode("\27\76\117\97\81\0\1\4\4\4\8\0\25\0\0\0\112\114\105\110\116\105\100\101\110\116\105\116\121\40\41\32\119\97\114\110\34\104\105\34\0\0\0\0\0\0\0\0\0\0\0\2\2\6\0\0\0\5\0\0\0\28\64\128\0\5\64\0\0\65\128\0\0\28\64\0\1\30\0\128\0\3\0\0\0\4\14\0\0\0\112\114\105\110\116\105\100\101\110\116\105\116\121\0\4\5\0\0\0\119\97\114\110\0\4\3\0\0\0\104\105\0\0\0\0\0\6\0\0\0\1\0\0\0\1\0\0\0\1\0\0\0\1\0\0\0\1\0\0\0\1\0\0\0\0\0\0\0\0\0\0\0")()