package imgedit

import (
	"context"
	"encoding/json"
	"io"
	"time"

	"lmika.dev/lmika/weiro/models"
	"lmika.dev/lmika/weiro/services/uploads"
)

type Service struct {
	scratchDir    string
	uploadService *uploads.Service
	sessionStore  *sessionStore
}

func New(
	uploadService *uploads.Service,
	scratchDir string,
) *Service {
	return &Service{
		scratchDir:    scratchDir,
		uploadService: uploadService,
		sessionStore:  &sessionStore{baseDir: scratchDir},
	}
}

func (s *Service) LoadImageVersion(ctx context.Context, sessionID string, versionID string) (mimeType string, rw func() (io.ReadCloser, error), err error) {
	site, user, err := s.fetchSiteAndUser(ctx)
	if err != nil {
		return "", nil, err
	}

	session, err := s.sessionStore.get(sessionID)
	if err != nil {
		return "", nil, err
	} else if session.SiteID != site.ID || session.UserID != user.ID {
		return "", nil, models.PermissionError
	}

	return s.sessionStore.getImage(session, versionID+"."+session.ImageExt)
}

func (s *Service) NewSession(ctx context.Context, baseUploadID int64) (models.ImageEditSession, error) {
	site, user, err := s.fetchSiteAndUser(ctx)
	if err != nil {
		return models.ImageEditSession{}, err
	}

	upload, _, err := s.uploadService.OpenUpload(ctx, baseUploadID)
	if err != nil {
		return models.ImageEditSession{}, err
	}

	var ext string
	switch upload.MIMEType {
	case "image/jpeg":
		ext = "jpg"
	case "image/png":
		ext = "png"
	default:
		return models.ImageEditSession{}, models.UnsupportedImageFormat
	}

	newSession := models.ImageEditSession{
		GUID:         models.NewNanoID(),
		SiteID:       site.ID,
		UserID:       user.ID,
		BaseUploadID: baseUploadID,
		ImageExt:     ext,
		CreatedAt:    time.Now().UTC(),
		UpdatedAt:    time.Now().UTC(),
		Processors: []models.ImageEditProcessor{
			{
				Type:  "copy-upload",
				Props: mustToJSON(models.CopyUploadProps{UploadID: baseUploadID}),
			},
		},
	}

	newSession.RecalcVersionIDs()
	if err := s.sessionStore.create(newSession); err != nil {
		return models.ImageEditSession{}, err
	}

	if _, err := s.reprocess(ctx, newSession); err != nil {
		return models.ImageEditSession{}, err
	}

	return newSession, nil
}

func (s *Service) fetchSiteAndUser(ctx context.Context) (models.Site, models.User, error) {
	user, ok := models.GetUser(ctx)
	if !ok {
		return models.Site{}, models.User{}, models.UserRequiredError
	}

	site, ok := models.GetSite(ctx)
	if !ok {
		return models.Site{}, models.User{}, models.SiteRequiredError
	}

	if site.OwnerID != user.ID {
		return models.Site{}, models.User{}, models.PermissionError
	}

	return site, user, nil
}

func mustToJSON(a any) json.RawMessage {
	b, _ := json.Marshal(a)
	return b
}