package photos

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	"shared-album/internal/auth"
	"shared-album/internal/httpx"
	"shared-album/internal/models"
	"shared-album/internal/roles"
	"shared-album/internal/sse"
	"shared-album/internal/storage"
)

type AlbumAccess interface {
	Access(ctx context.Context, albumID, userID string) (*models.Album, string, error)
}

type Service struct {
	store   *Store
	albums  AlbumAccess
	storage *storage.Client
	hub     *sse.Hub
}

func NewService(store *Store, albums AlbumAccess, storage *storage.Client, hub *sse.Hub) *Service {
	return &Service{store: store, albums: albums, storage: storage, hub: hub}
}

type UploadInput struct {
	AlbumID  string
	UserID   string
	Filename string
	MimeType string
	Data     []byte
}

func (s *Service) Upload(ctx context.Context, in UploadInput) (*models.Photo, error) {
	_, role, err := s.albums.Access(ctx, in.AlbumID, in.UserID)
	if err != nil {
		return nil, err
	}
	if !roles.CanUpload(role) {
		return nil, httpx.Forbidden("forbidden", "you do not have permission to upload photos")
	}

	mime := in.MimeType
	if mime == "" {
		mime = http.DetectContentType(in.Data)
	}
	if !strings.HasPrefix(mime, "image/") {
		return nil, httpx.BadRequest("invalid_file", "file is not an image")
	}

	width, height, ok := inspect(in.Data)
	if !ok {
		return nil, httpx.BadRequest("invalid_image", "could not decode image")
	}
	meta := extractEXIF(in.Data)

	id := auth.NewID()
	ext := strings.ToLower(filepath.Ext(in.Filename))
	if ext == "" {
		ext = ".bin"
	}
	storageKey := fmt.Sprintf("albums/%s/original/%s%s", in.AlbumID, id, ext)

	if err := s.storage.Put(ctx, storageKey, bytes.NewReader(in.Data), int64(len(in.Data)), mime); err != nil {
		return nil, err
	}

	p := &models.Photo{
		ID:               id,
		AlbumID:          in.AlbumID,
		UploaderID:       in.UserID,
		StorageKey:       storageKey,
		OriginalFilename: in.Filename,
		Size:             int64(len(in.Data)),
		Width:            width,
		Height:           height,
		MimeType:         mime,
		TakenAt:          meta.TakenAt,
		Latitude:         meta.Latitude,
		Longitude:        meta.Longitude,
		EXIF:             meta.Attributes,
	}
	if err := s.store.Create(ctx, p); err != nil {
		return nil, err
	}

	data := in.Data
	go s.processVariants(p.ID, in.AlbumID, data)

	if err := s.attachURLs(ctx, p); err != nil {
		return nil, err
	}
	return p, nil
}

func (s *Service) processVariants(photoID, albumID string, data []byte) {
	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
	defer cancel()

	thumb, preview, err := buildVariants(data)
	if err != nil {
		return
	}
	thumbKey := fmt.Sprintf("albums/%s/thumb/%s.webp", albumID, photoID)
	previewKey := fmt.Sprintf("albums/%s/preview/%s.webp", albumID, photoID)
	if err := s.storage.Put(ctx, thumbKey, bytes.NewReader(thumb), int64(len(thumb)), "image/webp"); err != nil {
		return
	}
	if err := s.storage.Put(ctx, previewKey, bytes.NewReader(preview), int64(len(preview)), "image/webp"); err != nil {
		return
	}
	if err := s.store.SetVariants(ctx, photoID, thumbKey, previewKey); err != nil {
		return
	}
	s.store.SetCoverIfEmpty(ctx, albumID, photoID)
	if p, err := s.store.GetByID(ctx, photoID, ""); err == nil {
		if err := s.attachURLs(ctx, p); err == nil {
			s.hub.Publish(albumID, "photo.created", p)
		}
	}
}

func (s *Service) attachURLs(ctx context.Context, p *models.Photo) error {
	if p.StorageKey != "" {
		url, err := s.storage.PresignGet(ctx, p.StorageKey)
		if err != nil {
			return err
		}
		p.OriginalURL = url
		p.DownloadURL = url
	}
	if p.ThumbKey != "" {
		if url, err := s.storage.PresignGet(ctx, p.ThumbKey); err == nil {
			p.ThumbURL = url
		}
	}
	if p.PreviewKey != "" {
		if url, err := s.storage.PresignGet(ctx, p.PreviewKey); err == nil {
			p.PreviewURL = url
		}
	}
	return nil
}

func (s *Service) List(ctx context.Context, albumID, userID, cursor string, since *time.Time, limit int) ([]models.Photo, string, error) {
	if _, _, err := s.albums.Access(ctx, albumID, userID); err != nil {
		return nil, "", err
	}
	out, err := s.store.List(ctx, ListParams{
		AlbumID: albumID,
		Viewer:  userID,
		Cursor:  cursor,
		Since:   since,
		Limit:   limit,
	})
	if err != nil {
		return nil, "", err
	}
	for i := range out {
		_ = s.attachURLs(ctx, &out[i])
	}
	next := ""
	if since == nil && len(out) == limit && limit > 0 {
		next = out[len(out)-1].ID
	}
	return out, next, nil
}

// ListPublic lists photos for a share link (access already validated by token).
func (s *Service) ListPublic(ctx context.Context, albumID, cursor string, since *time.Time, limit int) ([]models.Photo, string, error) {
	out, err := s.store.List(ctx, ListParams{
		AlbumID: albumID,
		Viewer:  "",
		Cursor:  cursor,
		Since:   since,
		Limit:   limit,
	})
	if err != nil {
		return nil, "", err
	}
	for i := range out {
		_ = s.attachURLs(ctx, &out[i])
	}
	next := ""
	if since == nil && len(out) == limit && limit > 0 {
		next = out[len(out)-1].ID
	}
	return out, next, nil
}

// GetPublic returns a single photo for a share link.
func (s *Service) GetPublic(ctx context.Context, photoID string) (*models.Photo, error) {
	p, err := s.store.GetByID(ctx, photoID, "")
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, httpx.NotFound("photo_not_found", "photo not found")
		}
		return nil, err
	}
	if err := s.attachURLs(ctx, p); err != nil {
		return nil, err
	}
	return p, nil
}

// DownloadPublic returns a presigned original URL for a share link.
func (s *Service) DownloadPublic(ctx context.Context, photoID string) (string, error) {
	p, err := s.GetPublic(ctx, photoID)
	if err != nil {
		return "", err
	}
	return s.storage.PresignGet(ctx, p.StorageKey)
}

func (s *Service) Get(ctx context.Context, photoID, userID string) (*models.Photo, error) {
	p, err := s.store.GetByID(ctx, photoID, userID)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, httpx.NotFound("photo_not_found", "photo not found")
		}
		return nil, err
	}
	if _, _, err := s.albums.Access(ctx, p.AlbumID, userID); err != nil {
		return nil, err
	}
	if err := s.attachURLs(ctx, p); err != nil {
		return nil, err
	}
	return p, nil
}

func (s *Service) Download(ctx context.Context, photoID, userID string) (string, error) {
	p, err := s.Get(ctx, photoID, userID)
	if err != nil {
		return "", err
	}
	url, err := s.storage.PresignGet(ctx, p.StorageKey)
	if err != nil {
		return "", err
	}
	return url, nil
}

func (s *Service) Rename(ctx context.Context, photoID, userID, filename string) (*models.Photo, error) {
	p, err := s.store.GetByID(ctx, photoID, userID)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, httpx.NotFound("photo_not_found", "photo not found")
		}
		return nil, err
	}
	_, role, err := s.albums.Access(ctx, p.AlbumID, userID)
	if err != nil {
		return nil, err
	}
	own := p.UploaderID == userID
	if !(roles.CanDeleteAnyPhoto(role) || (own && roles.CanDeleteOwnPhoto(role))) {
		return nil, httpx.Forbidden("forbidden", "you cannot rename this photo")
	}
	name := strings.TrimSpace(filename)
	if name == "" {
		return nil, httpx.BadRequest("invalid_filename", "filename is required")
	}
	if len(name) > 255 {
		name = name[:255]
	}
	if err := s.store.UpdateFilename(ctx, photoID, name); err != nil {
		return nil, err
	}
	p.OriginalFilename = name
	if err := s.attachURLs(ctx, p); err != nil {
		return nil, err
	}
	s.hub.Publish(p.AlbumID, "photo.updated", p)
	return p, nil
}

func (s *Service) Delete(ctx context.Context, photoID, userID string) error {
	p, err := s.store.GetByID(ctx, photoID, userID)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			return httpx.NotFound("photo_not_found", "photo not found")
		}
		return err
	}
	_, role, err := s.albums.Access(ctx, p.AlbumID, userID)
	if err != nil {
		return err
	}
	own := p.UploaderID == userID
	if !(roles.CanDeleteAnyPhoto(role) || (own && roles.CanDeleteOwnPhoto(role))) {
		return httpx.Forbidden("forbidden", "you cannot delete this photo")
	}
	if err := s.store.Delete(ctx, photoID); err != nil {
		return err
	}
	keys := []string{p.StorageKey}
	if p.ThumbKey != "" {
		keys = append(keys, p.ThumbKey)
	}
	if p.PreviewKey != "" {
		keys = append(keys, p.PreviewKey)
	}
	_ = s.storage.Delete(ctx, keys...)
	s.hub.Publish(p.AlbumID, "photo.deleted", map[string]string{
		"id": p.ID, "album_id": p.AlbumID, "uploader_id": p.UploaderID,
	})
	return nil
}