package oplcli

import (
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"regexp"
	"strings"
)

func scanGameFileForID(filename string) (string, error) {
	file, err := os.Open(filename)
	if err != nil {
		slog.Error("Failed to open file", "file", filename, "err", err)
		return "", err
	}
	defer file.Close()

	const bufferSize = 1024 * 1024 // 1MB
	buffer := make([]byte, bufferSize)

	n, err := file.Read(buffer)
	if err != nil && n == 0 {
		slog.Error("Failed to read file", "file", file, "err", err)
		return "", err
	}

	id, found := scanBufferForID(buffer[:n])
	if !found {
		slog.Error("No PS2 ID found in the file", "file", file)
		return "", fmt.Errorf("no PS2 game ID found in file")
	}

	return id, nil
}

func scanBufferForID(buffer []byte) (string, bool) {
	pattern := regexp.MustCompile(`(SLUS|SLES|SLPS|SCUS|SCES|SCPS)[_\-\s]?\d{3}[\._\-\s]?\d{2}`)

	match := pattern.Find(buffer)
	if match != nil {
		gameID := string(match)
		return normalizeGameID(gameID), true
	}

	return "", false
}

func normalizeGameID(id string) string {
	re := regexp.MustCompile(`(?i)^([A-Z]{4})[^0-9]*([0-9]{3})[^0-9]*([0-9]{2})$`)
	id = strings.TrimSpace(id)

	matches := re.FindStringSubmatch(id)
	if len(matches) != 4 {
		return ""
	}

	prefix := strings.ToUpper(matches[1])
	number := matches[2] + "." + matches[3]

	return prefix + "_" + number
}

func renameGameFile(filePath, gameName string) (string, error) {
	ext := filepath.Ext(filePath)
	dir := filepath.Dir(filePath)

	newPath := filepath.Join(dir, gameName+ext)

	if filePath == newPath {
		return filePath, nil
	}

	// Do not overwrite existing files
	if _, err := os.Stat(newPath); err == nil {
		return "", fmt.Errorf("file already exists: %s", newPath)
	} else if !os.IsNotExist(err) {
		return "", fmt.Errorf("failed to check destination: %w", err)
	}

	// rename file
	err := os.Rename(filePath, newPath)
	if err != nil {
		return "", fmt.Errorf("failed to rename file: %w", err)
	}

	return newPath, nil
}