package attachments

import (
	"context"
	"crypto/md5"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"git.118im.com/im_team/olons_server/internal/config"
	"git.118im.com/im_team/olons_server/internal/store"
)

const maxImageSize = 5 << 20

var ErrImageInvalid = errors.New("image attachment invalid")

type Repository interface {
	CreateAttachment(context.Context, store.AttachmentCreation) (*store.Attachment, error)
}

type Service struct {
	repository Repository
	cfg        config.UploadConfig
}

func New(repository Repository, cfg config.UploadConfig) *Service {
	return &Service{repository: repository, cfg: cfg}
}

func (s *Service) UploadImage(ctx context.Context, memberID int64, name string, reader io.Reader) (*store.Attachment, error) {
	if s.repository == nil || memberID <= 0 {
		return nil, ErrImageInvalid
	}
	data, err := io.ReadAll(io.LimitReader(reader, maxImageSize+1))
	if err != nil || len(data) == 0 || len(data) > maxImageSize {
		return nil, ErrImageInvalid
	}
	mimeType := http.DetectContentType(data)
	extensions := map[string]string{"image/jpeg": ".jpg", "image/png": ".png", "image/webp": ".webp"}
	ext, ok := extensions[mimeType]
	if !ok {
		return nil, ErrImageInvalid
	}
	random := make([]byte, 16)
	if _, err = rand.Read(random); err != nil {
		return nil, err
	}
	fileName := hex.EncodeToString(random) + ext
	if err = os.MkdirAll(s.cfg.Dir, 0o750); err != nil {
		return nil, err
	}
	path := filepath.Join(s.cfg.Dir, fileName)
	if err = os.WriteFile(path, data, 0o640); err != nil {
		return nil, err
	}
	digest := md5.Sum(data)
	publicPath := strings.TrimRight(s.cfg.PublicPath, "/") + "/" + fileName
	attachment, err := s.repository.CreateAttachment(ctx, store.AttachmentCreation{
		MemberID: memberID, Name: filepath.Base(name), MimeType: mimeType, Path: path,
		URL: publicPath, Size: int64(len(data)), Ext: strings.TrimPrefix(ext, "."), MD5: hex.EncodeToString(digest[:]),
	})
	if err != nil {
		_ = os.Remove(path)
		return nil, err
	}
	return attachment, nil
}