package string

import (
	"regexp"
	"unicode/utf8"

	luajit "git.sharkk.net/Sky/LuaJIT-to-Go"
)

func GetFunctionList() map[string]luajit.GoFunction {
	return map[string]luajit.GoFunction{
		"string_slice":         string_slice,
		"string_reverse":       string_reverse,
		"string_length":        string_length,
		"string_byte_length":   string_byte_length,
		"regex_replace":        regex_replace,
		"string_is_valid_utf8": string_is_valid_utf8,
	}
}

func string_slice(s *luajit.State) int {
	str := s.ToString(1)
	start := int(s.ToNumber(2))

	if !utf8.ValidString(str) {
		s.PushNil()
		s.PushString("invalid UTF-8")
		return 2
	}

	runes := []rune(str)
	length := len(runes)
	startIdx := max(start-1, 0) // Convert from 1-indexed
	if startIdx >= length {
		s.PushString("")
		return 1
	}

	endIdx := length
	if s.GetTop() >= 3 && !s.IsNil(3) {
		end := int(s.ToNumber(3))
		if end < 0 {
			endIdx = length + end + 1
		} else {
			endIdx = end
		}
		if endIdx < 0 {
			endIdx = 0
		}
		if endIdx > length {
			endIdx = length
		}
	}

	if startIdx >= endIdx {
		s.PushString("")
		return 1
	}

	s.PushString(string(runes[startIdx:endIdx]))
	return 1
}

func string_reverse(s *luajit.State) int {
	str := s.ToString(1)

	if !utf8.ValidString(str) {
		s.PushNil()
		s.PushString("invalid UTF-8")
		return 2
	}

	runes := []rune(str)
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}
	s.PushString(string(runes))
	return 1
}

func string_length(s *luajit.State) int {
	str := s.ToString(1)
	s.PushNumber(float64(utf8.RuneCountInString(str)))
	return 1
}

func string_byte_length(s *luajit.State) int {
	str := s.ToString(1)
	s.PushNumber(float64(len(str)))
	return 1
}

func regex_replace(s *luajit.State) int {
	pattern := s.ToString(1)
	str := s.ToString(2)
	replacement := s.ToString(3)

	re, err := regexp.Compile(pattern)
	if err != nil {
		s.PushString(str)
		return 1
	}

	result := re.ReplaceAllString(str, replacement)
	s.PushString(result)
	return 1
}

func string_is_valid_utf8(s *luajit.State) int {
	str := s.ToString(1)
	s.PushBoolean(utf8.ValidString(str))
	return 1
}