package luajit

/*
#cgo CFLAGS: -I${SRCDIR}/vendor/luajit/include
#cgo windows LDFLAGS: -L${SRCDIR}/vendor/luajit/windows -lluajit -static
#cgo !windows LDFLAGS: -L${SRCDIR}/vendor/luajit/linux -lluajit -static

#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
#include <stdlib.h>
#include <string.h>

// Helper to simplify some common operations
static int get_abs_index(lua_State *L, int idx) {
    if (idx > 0 || idx <= LUA_REGISTRYINDEX) return idx;
    return lua_gettop(L) + idx + 1;
}

// Combined load and execute with no results
static int do_string(lua_State *L, const char *s) {
    int status = luaL_loadstring(L, s);
    if (status == 0) {
        status = lua_pcall(L, 0, 0, 0);
    }
    return status;
}

// Combined load and execute file
static int do_file(lua_State *L, const char *filename) {
    int status = luaL_loadfile(L, filename);
    if (status == 0) {
        status = lua_pcall(L, 0, 0, 0);
    }
    return status;
}
*/
import "C"
import (
	"fmt"
	"strings"
	"unsafe"
)

// State represents a Lua state
type State struct {
	L *C.lua_State
}

// New creates a new Lua state with all standard libraries loaded
func New() *State {
	L := C.luaL_newstate()
	if L == nil {
		return nil
	}
	C.luaL_openlibs(L)
	return &State{L: L}
}

// Close closes the Lua state and frees resources
func (s *State) Close() {
	if s.L != nil {
		s.Cleanup() // Clean up Go function registry
		C.lua_close(s.L)
		s.L = nil
	}
}

// Stack manipulation methods

// GetTop returns the index of the top element in the stack
func (s *State) GetTop() int {
	return int(C.lua_gettop(s.L))
}

// SetTop sets the stack top to a specific index
func (s *State) SetTop(index int) {
	C.lua_settop(s.L, C.int(index))
}

// PushValue pushes a copy of the value at the given index onto the stack
func (s *State) PushCopy(index int) {
	C.lua_pushvalue(s.L, C.int(index))
}

// Pop pops n elements from the stack
func (s *State) Pop(n int) {
	C.lua_settop(s.L, C.int(-n-1))
}

// Remove removes the element at the given valid index
func (s *State) Remove(index int) {
	C.lua_remove(s.L, C.int(index))
}

// absIndex converts a possibly negative index to its absolute position
func (s *State) absIndex(index int) int {
	if index > 0 || index <= LUA_REGISTRYINDEX {
		return index
	}
	return s.GetTop() + index + 1
}

// Type checking methods

// GetType returns the type of the value at the given index
func (s *State) GetType(index int) LuaType {
	return LuaType(C.lua_type(s.L, C.int(index)))
}

// IsNil checks if the value at the given index is nil
func (s *State) IsNil(index int) bool {
	return s.GetType(index) == TypeNil
}

// IsBoolean checks if the value at the given index is a boolean
func (s *State) IsBoolean(index int) bool {
	return s.GetType(index) == TypeBoolean
}

// IsNumber checks if the value at the given index is a number
func (s *State) IsNumber(index int) bool {
	return C.lua_isnumber(s.L, C.int(index)) != 0
}

// IsString checks if the value at the given index is a string
func (s *State) IsString(index int) bool {
	return C.lua_isstring(s.L, C.int(index)) != 0
}

// IsTable checks if the value at the given index is a table
func (s *State) IsTable(index int) bool {
	return s.GetType(index) == TypeTable
}

// IsFunction checks if the value at the given index is a function
func (s *State) IsFunction(index int) bool {
	return s.GetType(index) == TypeFunction
}

// Value conversion methods

// ToBoolean returns the value at the given index as a boolean
func (s *State) ToBoolean(index int) bool {
	return C.lua_toboolean(s.L, C.int(index)) != 0
}

// ToNumber returns the value at the given index as a number
func (s *State) ToNumber(index int) float64 {
	return float64(C.lua_tonumber(s.L, C.int(index)))
}

// ToString returns the value at the given index as a string
func (s *State) ToString(index int) string {
	var length C.size_t
	cstr := C.lua_tolstring(s.L, C.int(index), &length)
	if cstr == nil {
		return ""
	}
	return C.GoStringN(cstr, C.int(length))
}

// Push methods

// PushNil pushes a nil value onto the stack
func (s *State) PushNil() {
	C.lua_pushnil(s.L)
}

// PushBoolean pushes a boolean value onto the stack
func (s *State) PushBoolean(b bool) {
	var value C.int
	if b {
		value = 1
	}
	C.lua_pushboolean(s.L, value)
}

// PushNumber pushes a number value onto the stack
func (s *State) PushNumber(n float64) {
	C.lua_pushnumber(s.L, C.lua_Number(n))
}

// PushString pushes a string value onto the stack
func (s *State) PushString(str string) {
	cstr := C.CString(str)
	defer C.free(unsafe.Pointer(cstr))
	C.lua_pushlstring(s.L, cstr, C.size_t(len(str)))
}

// Table operations

// CreateTable creates a new table and pushes it onto the stack
func (s *State) CreateTable(narr, nrec int) {
	C.lua_createtable(s.L, C.int(narr), C.int(nrec))
}

// NewTable creates a new empty table and pushes it onto the stack
func (s *State) NewTable() {
	C.lua_createtable(s.L, 0, 0)
}

// GetTable gets a table field (t[k]) where t is at the given index and k is at the top of the stack
func (s *State) GetTable(index int) {
	C.lua_gettable(s.L, C.int(index))
}

// SetTable sets a table field (t[k] = v) where t is at the given index, k is at -2, and v is at -1
func (s *State) SetTable(index int) {
	C.lua_settable(s.L, C.int(index))
}

// GetField gets a table field t[k] and pushes it onto the stack
func (s *State) GetField(index int, key string) {
	ckey := C.CString(key)
	defer C.free(unsafe.Pointer(ckey))
	C.lua_getfield(s.L, C.int(index), ckey)
}

// SetField sets a table field t[k] = v, where v is the value at the top of the stack
func (s *State) SetField(index int, key string) {
	ckey := C.CString(key)
	defer C.free(unsafe.Pointer(ckey))
	C.lua_setfield(s.L, C.int(index), ckey)
}

// Next pops a key from the stack and pushes the next key-value pair from the table at the given index
func (s *State) Next(index int) bool {
	return C.lua_next(s.L, C.int(index)) != 0
}

// PushValue pushes a Go value onto the stack with proper type conversion
func (s *State) PushValue(v interface{}) error {
	switch v := v.(type) {
	case nil:
		s.PushNil()
	case bool:
		s.PushBoolean(v)
	case int:
		s.PushNumber(float64(v))
	case float64:
		s.PushNumber(v)
	case string:
		s.PushString(v)
	case map[string]interface{}:
		// Special case: handle array stored in map
		if arr, ok := v[""].([]float64); ok {
			s.CreateTable(len(arr), 0)
			for i, elem := range arr {
				s.PushNumber(float64(i + 1))
				s.PushNumber(elem)
				s.SetTable(-3)
			}
			return nil
		}
		return s.PushTable(v)
	case []float64:
		s.CreateTable(len(v), 0)
		for i, elem := range v {
			s.PushNumber(float64(i + 1))
			s.PushNumber(elem)
			s.SetTable(-3)
		}
	case []interface{}:
		s.CreateTable(len(v), 0)
		for i, elem := range v {
			s.PushNumber(float64(i + 1))
			if err := s.PushValue(elem); err != nil {
				return err
			}
			s.SetTable(-3)
		}
	default:
		return fmt.Errorf("unsupported type: %T", v)
	}
	return nil
}

// ToValue converts a Lua value at the given index to a Go value
func (s *State) ToValue(index int) (interface{}, error) {
	luaType := s.GetType(index)
	switch luaType {
	case TypeNil:
		return nil, nil
	case TypeBoolean:
		return s.ToBoolean(index), nil
	case TypeNumber:
		return s.ToNumber(index), nil
	case TypeString:
		return s.ToString(index), nil
	case TypeTable:
		return s.ToTable(index)
	default:
		return nil, fmt.Errorf("unsupported type: %s", luaType)
	}
}

// Global operations

// GetGlobal pushes the global variable with the given name onto the stack
func (s *State) GetGlobal(name string) {
	s.GetField(LUA_GLOBALSINDEX, name)
}

// SetGlobal sets the global variable with the given name to the value at the top of the stack
func (s *State) SetGlobal(name string) {
	s.SetField(LUA_GLOBALSINDEX, name)
}

// Code execution methods

// LoadString loads a Lua chunk from a string without executing it
func (s *State) LoadString(code string) error {
	ccode := C.CString(code)
	defer C.free(unsafe.Pointer(ccode))

	return s.safeCall(func() C.int {
		return C.luaL_loadstring(s.L, ccode)
	})
}

// LoadFile loads a Lua chunk from a file without executing it
func (s *State) LoadFile(filename string) error {
	cfilename := C.CString(filename)
	defer C.free(unsafe.Pointer(cfilename))

	return s.safeCall(func() C.int {
		return C.luaL_loadfile(s.L, cfilename)
	})
}

// Call calls a function with the given number of arguments and results
func (s *State) Call(nargs, nresults int) error {
	return s.safeCall(func() C.int {
		return C.lua_pcall(s.L, C.int(nargs), C.int(nresults), 0)
	})
}

// DoString executes a Lua string and cleans up the stack
func (s *State) DoString(code string) error {
	ccode := C.CString(code)
	defer C.free(unsafe.Pointer(ccode))

	return s.safeCall(func() C.int {
		return C.do_string(s.L, ccode)
	})
}

// DoFile executes a Lua file and cleans up the stack
func (s *State) DoFile(filename string) error {
	cfilename := C.CString(filename)
	defer C.free(unsafe.Pointer(cfilename))

	return s.safeCall(func() C.int {
		return C.do_file(s.L, cfilename)
	})
}

// Execute executes a Lua string and returns the number of results left on the stack
func (s *State) Execute(code string) (int, error) {
	baseTop := s.GetTop()

	ccode := C.CString(code)
	defer C.free(unsafe.Pointer(ccode))

	var nresults int
	err := s.safeCall(func() C.int {
		status := C.luaL_loadstring(s.L, ccode)
		if status != 0 {
			return status
		}

		status = C.lua_pcall(s.L, 0, C.LUA_MULTRET, 0)
		if status == 0 {
			nresults = s.GetTop() - baseTop
		}
		return status
	})

	if err != nil {
		return 0, err
	}

	return nresults, nil
}

// ExecuteWithResult executes a Lua string and returns the first result
func (s *State) ExecuteWithResult(code string) (interface{}, error) {
	top := s.GetTop()
	defer s.SetTop(top) // Restore stack when done

	nresults, err := s.Execute(code)
	if err != nil {
		return nil, err
	}

	if nresults == 0 {
		return nil, nil
	}

	return s.ToValue(-nresults)
}

// Package path operations

// SetPackagePath sets the Lua package.path
func (s *State) SetPackagePath(path string) error {
	path = strings.ReplaceAll(path, "\\", "/") // Convert Windows paths
	return s.DoString(fmt.Sprintf(`package.path = %q`, path))
}

// AddPackagePath adds a path to package.path
func (s *State) AddPackagePath(path string) error {
	path = strings.ReplaceAll(path, "\\", "/") // Convert Windows paths
	return s.DoString(fmt.Sprintf(`package.path = package.path .. ";%s"`, path))
}

// Helper functions

// checkStack ensures there is enough space on the Lua stack
func (s *State) checkStack(n int) error {
	if C.lua_checkstack(s.L, C.int(n)) == 0 {
		return fmt.Errorf("stack overflow (cannot allocate %d slots)", n)
	}
	return nil
}

// safeCall wraps a potentially dangerous C call with stack checking
func (s *State) safeCall(f func() C.int) error {
	// Ensure we have enough stack space
	if err := s.checkStack(LUA_MINSTACK); err != nil {
		return err
	}

	// Make the call
	status := f()

	// Check for errors
	if status != 0 {
		err := &LuaError{
			Code:    int(status),
			Message: s.ToString(-1),
		}
		s.Pop(1) // Remove error message
		return err
	}

	return nil
}