package glua

/*
 * Self-contained Go-Lua binding, which handles inter-FFI errors seamlessly unlike others.
 * */

// #cgo pkg-config: lua
// #cgo LDFLAGS: -L./ -lcglua
// #include<lua.h>
// #include<lualib.h>
// #include<lauxlib.h>
// #include<stdlib.h>
// extern int glua_metatable_call(lua_State*);
// extern int glua_metatable_gc(lua_State*);
// extern int glua_metatable_tostring(lua_State*);
import "C"

import "fmt"

import "unsafe"

type Function func(l *Lua) int

type FuncStatePair struct {
	fn Function
	l *Lua
}
var FuncIDs map[uint64]FuncStatePair = make(map[uint64]FuncStatePair)
var NextFuncID uint64 = 0

//export glua_go_call_func
func glua_go_call_func(id C.uint64_t) (ret C.int) {
	pair := FuncIDs[uint64(id)]
	
	defer func() {
		if r := recover(); r != nil {
			pair.l.PushString(fmt.Sprint(r))
			ret = -1
		}
	}()
	
	return C.int(pair.fn(pair.l))
}

//export glua_go_remove_func
func glua_go_remove_func(id C.uint64_t) {
	delete(FuncIDs, uint64(id))
}

type Lua struct {
	state *C.lua_State
}

func NewState() Lua {
	l := Lua{C.luaL_newstate()}
	
	C.luaL_newmetatable(l.state, C.CString("GLUA_FUNCTION"))
		C.lua_pushcclosure(l.state, C.lua_CFunction(C.glua_metatable_call), 0)
		l.SetField(-2, "__call")
		
		C.lua_pushcclosure(l.state, C.lua_CFunction(C.glua_metatable_gc), 0)
		l.SetField(-2, "__gc")
		
		C.lua_pushcclosure(l.state, C.lua_CFunction(C.glua_metatable_tostring), 0)
		l.SetField(-2, "__tostring")
	l.Pop(1)
	
	return l
}

func (l Lua) Close() {
	C.lua_close(l.state)
}

func (l Lua) OpenLibs() {
	C.luaL_openlibs(l.state)
}

func (l Lua) NewTable() {
	C.lua_createtable(l.state, 0, 0)
}

func (l Lua) SetField(offset int, name string) {
	cstr := C.CString(name)
	C.lua_setfield(l.state, C.int(offset), cstr)
	C.free(unsafe.Pointer(cstr))
}

func (l Lua) SetGlobal(name string) {
	cstr := C.CString(name)
	C.lua_setglobal(l.state, cstr)
	C.free(unsafe.Pointer(cstr))
}

func (l Lua) GetGlobal(name string) {
	cstr := C.CString(name)
	C.lua_getglobal(l.state, cstr)
	C.free(unsafe.Pointer(cstr))
}

func (l Lua) DoFile(filepath string) int {
	cstr := C.CString(filepath)
	defer C.free(unsafe.Pointer(cstr))
	
	err := int(C.luaL_loadfilex(l.state, cstr, nil))
	if err != 0 {
		return err
	}
	
	err = int(C.lua_pcallk(l.state, 0, -1, 0, 0, nil))
	if err != 0 {
		return err
	}
	
	return 0
}

func (l Lua) ToInteger(offset int) int64 {
	return int64(C.lua_tointegerx(l.state, C.int(offset), nil))
}

func (l Lua) ToNumber(offset int) float64 {
	return float64(C.lua_tonumberx(l.state, C.int(offset), nil))
}

func (l Lua) ToBoolean(offset int) bool {
	return C.lua_toboolean(l.state, C.int(offset)) != 0
}

func (l Lua) ToString(offset int) string {
	var len C.size_t
	cstr := C.lua_tolstring(l.state, C.int(offset), &len)
	return C.GoStringN(cstr, C.int(len))
}

func (l Lua) PushInteger(i int64) {
	C.lua_pushinteger(l.state, C.lua_Integer(i))
}

func (l Lua) PushNumber(f float64) {
	C.lua_pushnumber(l.state, C.lua_Number(f))
}

func (l Lua) PushString(s string) {
	cstr := C.CString(s)
	C.lua_pushstring(l.state, cstr)
	C.free(unsafe.Pointer(cstr))
}

func (l Lua) PushFunction(fn Function) {
	i := NextFuncID
	for true {
		if _, exists := FuncIDs[i]; !exists {
			break
		}
		i += 1
	}
	
	ud := C.lua_newuserdatauv(l.state, 8, 1)
	
	*(*C.uint64_t)(ud) = C.uint64_t(i)
	
	cstr := C.CString("GLUA_FUNCTION")
	C.luaL_setmetatable(l.state, cstr)
	C.free(unsafe.Pointer(cstr))
	
	FuncIDs[i] = FuncStatePair{fn, &l};
}

func (l Lua) PushValue(offset int) {
	C.lua_pushvalue(l.state, C.int(offset));
}

func (l Lua) Pop(count int) {
	C.lua_settop(l.state, C.int(-count - 1));
}

func (l Lua) Call(nargs int, nresults int, msgh int) int {
	err := int(C.lua_pcallk(l.state, C.int(nargs), C.int(nresults), C.int(msgh), 0, nil))
	if err == 2 {
		l.PushValue(-1)
		why := l.ToString(-1)
		l.Pop(1)
		
		panic(why)
	}
	return err
}

func (l Lua) ProtectedCall(nargs int, nresults int, msgh int) int {
	return int(C.lua_pcallk(l.state, C.int(nargs), C.int(nresults), C.int(msgh), 0, nil))
}

func (l Lua) UnsafeCall(nargs int, nresults int) {
	C.lua_callk(l.state, C.int(nargs), C.int(nresults), 0, nil)
}