package scene

import (
	"context"
	"errors"
	"fmt"

	"github.com/stashapp/stash/pkg/file/video"
	"github.com/stashapp/stash/pkg/logger"
	"github.com/stashapp/stash/pkg/models"
	"github.com/stashapp/stash/pkg/models/paths"
	"github.com/stashapp/stash/pkg/plugin"
	"github.com/stashapp/stash/pkg/plugin/hook"
	"github.com/stashapp/stash/pkg/txn"
)

var (
	ErrNotVideoFile = errors.New("not a video file")
)

type ScanCreatorUpdater interface {
	FindByFileID(ctx context.Context, fileID models.FileID) ([]*models.Scene, error)
	FindByFingerprints(ctx context.Context, fp []models.Fingerprint) ([]*models.Scene, error)
	GetFiles(ctx context.Context, relatedID int) ([]*models.VideoFile, error)

	Create(ctx context.Context, newScene *models.Scene, fileIDs []models.FileID) error
	UpdatePartial(ctx context.Context, id int, updatedScene models.ScenePartial) (*models.Scene, error)
	AddFileID(ctx context.Context, id int, fileID models.FileID) error
}

type ScanGenerator interface {
	Generate(ctx context.Context, s *models.Scene, f *models.VideoFile) error
}

type ScanHandler struct {
	CreatorUpdater ScanCreatorUpdater

	ScanGenerator  ScanGenerator
	CaptionUpdater video.CaptionUpdater
	PluginCache    *plugin.Cache

	FileNamingAlgorithm models.HashAlgorithm
	Paths               *paths.Paths
}

func (h *ScanHandler) validate() error {
	if h.CreatorUpdater == nil {
		return errors.New("CreatorUpdater is required")
	}
	if h.ScanGenerator == nil {
		return errors.New("ScanGenerator is required")
	}
	if h.CaptionUpdater == nil {
		return errors.New("CaptionUpdater is required")
	}
	if !h.FileNamingAlgorithm.IsValid() {
		return errors.New("FileNamingAlgorithm is required")
	}
	if h.Paths == nil {
		return errors.New("Paths is required")
	}

	return nil
}

func (h *ScanHandler) Handle(ctx context.Context, f models.File, oldFile models.File) error {
	if err := h.validate(); err != nil {
		return err
	}

	videoFile, ok := f.(*models.VideoFile)
	if !ok {
		return ErrNotVideoFile
	}

	if oldFile != nil {
		if err := video.CleanCaptions(ctx, videoFile, nil, h.CaptionUpdater); err != nil {
			return fmt.Errorf("cleaning captions: %w", err)
		}
	}

	// try to match the file to a scene
	existing, err := h.CreatorUpdater.FindByFileID(ctx, f.Base().ID)
	if err != nil {
		return fmt.Errorf("finding existing scene: %w", err)
	}

	if len(existing) == 0 {
		// try also to match file by fingerprints
		existing, err = h.CreatorUpdater.FindByFingerprints(ctx, videoFile.Fingerprints)
		if err != nil {
			return fmt.Errorf("finding existing scene by fingerprints: %w", err)
		}
	}

	if len(existing) > 0 {
		updateExisting := oldFile != nil
		if err := h.associateExisting(ctx, existing, videoFile, updateExisting); err != nil {
			return err
		}
	} else {
		// create a new scene
		newScene := models.NewScene()

		logger.Infof("%s doesn't exist. Creating new scene...", f.Base().Path)

		if err := h.CreatorUpdater.Create(ctx, &newScene, []models.FileID{videoFile.ID}); err != nil {
			return fmt.Errorf("creating new scene: %w", err)
		}

		h.PluginCache.RegisterPostHooks(ctx, newScene.ID, hook.SceneCreatePost, nil, nil)

		existing = []*models.Scene{&newScene}
	}

	if oldFile != nil {
		// migrate hashes from the old file to the new
		oldHash := GetHash(oldFile, h.FileNamingAlgorithm)
		newHash := GetHash(f, h.FileNamingAlgorithm)

		if oldHash != "" && newHash != "" && oldHash != newHash {
			MigrateHash(h.Paths, oldHash, newHash)
		}
	}

	// do this after the commit so that cover generation doesn't hold up the transaction
	txn.AddPostCommitHook(ctx, func(ctx context.Context) {
		for _, s := range existing {
			if err := h.ScanGenerator.Generate(ctx, s, videoFile); err != nil {
				// just log if cover generation fails. We can try again on rescan
				logger.Errorf("Error generating content for %s: %v", videoFile.Path, err)
			}
		}
	})

	return nil
}

func (h *ScanHandler) associateExisting(ctx context.Context, existing []*models.Scene, f *models.VideoFile, updateExisting bool) error {
	for _, s := range existing {
		if err := s.LoadFiles(ctx, h.CreatorUpdater); err != nil {
			return err
		}

		found := false
		for _, sf := range s.Files.List() {
			if sf.ID == f.ID {
				found = true
				break
			}
		}

		if !found {
			logger.Infof("Adding %s to scene %s", f.Path, s.DisplayName())

			if err := h.CreatorUpdater.AddFileID(ctx, s.ID, f.ID); err != nil {
				return fmt.Errorf("adding file to scene: %w", err)
			}

			// update updated_at time
			scenePartial := models.NewScenePartial()
			if _, err := h.CreatorUpdater.UpdatePartial(ctx, s.ID, scenePartial); err != nil {
				return fmt.Errorf("updating scene: %w", err)
			}
		}

		if !found || updateExisting {
			h.PluginCache.RegisterPostHooks(ctx, s.ID, hook.SceneUpdatePost, nil, nil)
		}
	}

	return nil
}