package download

import (
	"archive/zip"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"strings"
)

var versionRe = regexp.MustCompile(`v\d+[\.\d]*`)

type Service struct {
	repo    *Repository
	gameDir string
}

func NewService(repo *Repository, gameDir string) *Service {
	return &Service{repo: repo, gameDir: gameDir}
}

func (s *Service) GetInfo() (*Info, error) {
	return s.repo.GetLatest()
}

func (s *Service) GameFilePath() string {
	return filepath.Join(s.gameDir, "game.zip")
}

// Upload streams the body directly to disk, then extracts metadata from the zip.
func (s *Service) Upload(filename string, body io.Reader, baseURL string) (*Info, error) {
	if err := os.MkdirAll(s.gameDir, 0755); err != nil {
		return nil, fmt.Errorf("디렉토리 생성 실패: %w", err)
	}

	finalPath := s.GameFilePath()
	tmpPath := finalPath + ".tmp"

	f, err := os.Create(tmpPath)
	if err != nil {
		return nil, fmt.Errorf("파일 생성 실패: %w", err)
	}

	n, err := io.Copy(f, body)
	f.Close()
	if err != nil {
		os.Remove(tmpPath)
		return nil, fmt.Errorf("파일 저장 실패: %w", err)
	}

	if err := os.Rename(tmpPath, finalPath); err != nil {
		os.Remove(tmpPath)
		return nil, fmt.Errorf("파일 이동 실패: %w", err)
	}

	version := ""
	if m := versionRe.FindString(filename); m != "" {
		version = m
	}

	fileSize := ""
	if n > 0 {
		mb := float64(n) / 1024 / 1024
		if mb >= 1000 {
			fileSize = fmt.Sprintf("%.1f GB", mb/1024)
		} else {
			fileSize = fmt.Sprintf("%.1f MB", mb)
		}
	}

	fileHash := hashGameExeFromZip(finalPath)

	info, err := s.repo.GetLatest()
	if err != nil {
		info = &Info{}
	}
	info.URL = baseURL + "/api/download/file"
	info.Version = version
	info.FileName = filename
	info.FileSize = fileSize
	info.FileHash = fileHash
	return info, s.repo.Save(info)
}

func hashGameExeFromZip(zipPath string) string {
	r, err := zip.OpenReader(zipPath)
	if err != nil {
		return ""
	}
	defer r.Close()

	for _, f := range r.File {
		if strings.EqualFold(filepath.Base(f.Name), "A301.exe") {
			rc, err := f.Open()
			if err != nil {
				return ""
			}
			h := sha256.New()
			io.Copy(h, rc)
			rc.Close()
			return hex.EncodeToString(h.Sum(nil))
		}
	}
	return ""
}