// backend\meta.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// --------------------------
// generated/meta/<id>/meta.json
// --------------------------

type previewClip struct {
	StartSeconds    float64 `json:"startSeconds"`
	DurationSeconds float64 `json:"durationSeconds"`
}

type previewSpriteMeta struct {
	Path        string  `json:"path"`        // z.B. /api/preview-sprite/<id>
	Count       int     `json:"count"`       // Anzahl Frames im Sprite
	Cols        int     `json:"cols"`        // Spalten im Tile
	Rows        int     `json:"rows"`        // Zeilen im Tile
	StepSeconds float64 `json:"stepSeconds"` // Zeitabstand zwischen Frames
	CellWidth   int     `json:"cellWidth,omitempty"`
	CellHeight  int     `json:"cellHeight,omitempty"`
}

type videoFileMeta struct {
	Size      int64  `json:"size"`
	ModUnix   int64  `json:"modUnix"`
	SourceURL string `json:"sourceUrl,omitempty"`
}

type videoStreamMeta struct {
	Width      int     `json:"width,omitempty"`
	Height     int     `json:"height,omitempty"`
	FPS        float64 `json:"fps,omitempty"`
	Resolution string  `json:"resolution,omitempty"`
}

type videoMediaMeta struct {
	DurationSeconds float64         `json:"durationSeconds"`
	Video           videoStreamMeta `json:"video"`
}

type previewThumbMeta struct {
	Path   string `json:"path,omitempty"`
	Exists bool   `json:"exists,omitempty"`
}

type previewMeta struct {
	Clips  []previewClip      `json:"clips,omitempty"`
	Thumb  *previewThumbMeta  `json:"thumb,omitempty"`
	Sprite *previewSpriteMeta `json:"sprite,omitempty"`
}

type analysisMeta struct {
	Highlights *aiAnalysisMeta `json:"highlights,omitempty"`
}

type postworkHistoryEntry struct {
	Queue       string `json:"queue"`
	Phase       string `json:"phase"`
	State       string `json:"state"`
	Label       string `json:"label,omitempty"`
	Position    int    `json:"position,omitempty"`
	Waiting     int    `json:"waiting,omitempty"`
	Running     int    `json:"running,omitempty"`
	MaxParallel int    `json:"maxParallel,omitempty"`
	TS          int64  `json:"ts"`
}

type postworkCompletedMeta struct {
	Meta    bool `json:"meta,omitempty"`
	Teaser  bool `json:"teaser,omitempty"`
	Thumb   bool `json:"thumb,omitempty"`
	Sprites bool `json:"sprites,omitempty"`
	Analyze bool `json:"analyze,omitempty"`
}

type postworkMeta struct {
	Completed postworkCompletedMeta  `json:"completed,omitempty"`
	History   []postworkHistoryEntry `json:"history,omitempty"`
}

type videoMeta struct {
	Version       int   `json:"version"`
	UpdatedAtUnix int64 `json:"updatedAtUnix"`

	File       videoFileMeta  `json:"file"`
	Media      videoMediaMeta `json:"media"`
	Preview    previewMeta    `json:"preview,omitempty"`
	Analysis   analysisMeta   `json:"analysis,omitempty"`
	Postwork   *postworkMeta  `json:"postwork,omitempty"`
	Validation map[string]any `json:"validation,omitempty"`
}

type aiSegmentMeta struct {
	Label           string   `json:"label"`
	StartSeconds    float64  `json:"startSeconds"`
	EndSeconds      float64  `json:"endSeconds"`
	DurationSeconds float64  `json:"durationSeconds"`
	Score           float64  `json:"score,omitempty"`
	RatingIntensity float64  `json:"ratingIntensity,omitempty"`
	AutoSelected    bool     `json:"autoSelected,omitempty"`
	Position        string   `json:"position,omitempty"`
	Tags            []string `json:"tags,omitempty"`
	MarkerSeconds   float64  `json:"markerSeconds,omitempty"`
	PreviewSeconds  float64  `json:"previewSeconds,omitempty"`
}

type aiAnalysisMeta struct {
	Goal           string          `json:"goal,omitempty"`
	Mode           string          `json:"mode,omitempty"`
	Completed      bool            `json:"completed,omitempty"`
	Hits           []analyzeHit    `json:"hits,omitempty"`
	Segments       []aiSegmentMeta `json:"segments,omitempty"`
	Rating         *aiRatingMeta   `json:"rating,omitempty"`
	AnalyzedAtUnix int64           `json:"analyzedAtUnix,omitempty"`
}

func isZeroPostworkCompletedMeta(v postworkCompletedMeta) bool {
	return !v.Meta &&
		!v.Teaser &&
		!v.Thumb &&
		!v.Sprites &&
		!v.Analyze
}

func isZeroPostworkMeta(v *postworkMeta) bool {
	if v == nil {
		return true
	}

	return isZeroPostworkCompletedMeta(v.Completed) && len(v.History) == 0
}

func readVideoMeta(metaPath string, fi os.FileInfo) (dur float64, w int, h int, fps float64, ok bool) {
	m, ok := readVideoMetaIfValid(metaPath, fi)
	if !ok || m == nil {
		return 0, 0, 0, 0, false
	}
	return m.Media.DurationSeconds, m.Media.Video.Width, m.Media.Video.Height, m.Media.Video.FPS, true
}

func readVideoMetaDuration(metaPath string, fi os.FileInfo) (float64, bool) {
	m, ok := readVideoMetaIfValid(metaPath, fi)
	if !ok || m == nil || m.Media.DurationSeconds <= 0 {
		return 0, false
	}
	return m.Media.DurationSeconds, true
}

func metaJSONPathForAssetID(assetID string) (string, error) {
	root, err := generatedMetaRoot()
	if err != nil {
		return "", err
	}
	if strings.TrimSpace(root) == "" {
		return "", appErrorf("generated/meta root leer")
	}
	return filepath.Join(root, assetID, "meta.json"), nil
}

func ensureVideoMetaForFile(ctx context.Context, fullPath string, fi os.FileInfo, sourceURL string) (*videoMeta, bool) {
	stem := strings.TrimSuffix(filepath.Base(fullPath), filepath.Ext(fullPath))
	assetID := stripHotPrefix(strings.TrimSpace(stem))
	if assetID == "" {
		return nil, false
	}

	var err error
	assetID, err = sanitizeID(assetID)
	if err != nil || assetID == "" {
		return nil, false
	}

	metaPath, err := metaJSONPathForAssetID(assetID)
	if err != nil {
		return nil, false
	}

	if m, ok := readVideoMetaIfValid(metaPath, fi); ok {
		return m, true
	}

	if ctx == nil {
		ctx = context.Background()
	}
	cctx, cancel := context.WithTimeout(ctx, 8*time.Second)
	defer cancel()

	if durSem != nil {
		if err := durSem.Acquire(cctx); err != nil {
			return nil, false
		}
		defer durSem.Release()
	}

	dur, derr := durationSecondsCached(cctx, fullPath)
	if derr != nil || dur <= 0 {
		return nil, false
	}

	w, h, fps, perr := probeVideoProps(cctx, fullPath)
	if perr != nil {
		w, h, fps = 0, 0, 0
	}

	_ = os.MkdirAll(filepath.Dir(metaPath), 0o755)

	if err := writeVideoMeta(metaPath, fi, dur, w, h, fps, sourceURL); err != nil {
		return nil, false
	}

	m, ok := readVideoMetaLoose(metaPath)
	if !ok || m == nil {
		return nil, false
	}

	return m, true
}

func attachMetaToJobBestEffort(ctx context.Context, job *RecordJob, fullPath string) {
	if job == nil {
		return
	}
	fullPath = strings.TrimSpace(fullPath)
	if fullPath == "" {
		return
	}

	fi, err := os.Stat(fullPath)
	if err != nil || fi == nil || fi.IsDir() {
		return
	}

	if job.SizeBytes <= 0 {
		job.SizeBytes = fi.Size()
	}

	m, ok := ensureVideoMetaForFileBestEffort(ctx, fullPath, job.SourceURL)
	if !ok || m == nil {
		return
	}

	job.Meta = m

	if job.DurationSeconds <= 0 && m.Media.DurationSeconds > 0 {
		job.DurationSeconds = m.Media.DurationSeconds
	}
	if job.VideoWidth <= 0 && m.Media.Video.Width > 0 {
		job.VideoWidth = m.Media.Video.Width
	}
	if job.VideoHeight <= 0 && m.Media.Video.Height > 0 {
		job.VideoHeight = m.Media.Video.Height
	}
	if job.FPS <= 0 && m.Media.Video.FPS > 0 {
		job.FPS = m.Media.Video.FPS
	}
}

func ensureVideoMetaForFileBestEffort(ctx context.Context, fullPath string, sourceURL string) (*videoMeta, bool) {
	fullPath = strings.TrimSpace(fullPath)
	if fullPath == "" {
		return nil, false
	}

	fi, err := os.Stat(fullPath)
	if err != nil || fi == nil || fi.IsDir() || fi.Size() <= 0 {
		return nil, false
	}

	if m, ok := ensureVideoMetaForFile(ctx, fullPath, fi, sourceURL); ok && m != nil {
		return m, true
	}

	dur := durationSecondsCacheOnly(fullPath, fi)
	if dur <= 0 {
		return nil, false
	}

	stem := strings.TrimSuffix(filepath.Base(fullPath), filepath.Ext(fullPath))
	assetID := stripHotPrefix(strings.TrimSpace(stem))
	if assetID == "" {
		return nil, false
	}

	assetID, err = sanitizeID(assetID)
	if err != nil || assetID == "" {
		return nil, false
	}

	metaPath, err := metaJSONPathForAssetID(assetID)
	if err != nil || strings.TrimSpace(metaPath) == "" {
		return nil, false
	}

	_ = os.MkdirAll(filepath.Dir(metaPath), 0o755)
	_ = writeVideoMetaDuration(metaPath, fi, dur, sourceURL)

	if m, ok := readVideoMetaIfValid(metaPath, fi); ok && m != nil {
		return m, true
	}

	return nil, false
}

func readVideoMetaIfValid(metaPath string, fi os.FileInfo) (*videoMeta, bool) {
	b, err := os.ReadFile(metaPath)
	if err != nil || len(b) == 0 {
		return nil, false
	}

	var m videoMeta
	if err := json.Unmarshal(b, &m); err != nil {
		return nil, false
	}
	if m.Version != 3 {
		return nil, false
	}
	if m.File.Size != fi.Size() || m.File.ModUnix != fi.ModTime().Unix() {
		return nil, false
	}
	if m.Media.DurationSeconds <= 0 {
		return nil, false
	}

	return &m, true
}

func readVideoMetaLoose(metaPath string) (*videoMeta, bool) {
	b, err := os.ReadFile(metaPath)
	if err != nil || len(b) == 0 {
		return nil, false
	}

	var m videoMeta
	if err := json.Unmarshal(b, &m); err != nil {
		return nil, false
	}

	if m.Version == 0 {
		m.Version = 3
	}

	return &m, true
}

func mergePreviewSpriteMeta(existing, incoming *previewSpriteMeta) *previewSpriteMeta {
	if existing == nil && incoming == nil {
		return nil
	}
	if existing == nil {
		cp := *incoming
		return &cp
	}
	if incoming == nil {
		cp := *existing
		return &cp
	}

	out := *incoming

	if strings.TrimSpace(out.Path) == "" {
		out.Path = existing.Path
	}
	if out.Count <= 0 {
		out.Count = existing.Count
	}
	if out.Cols <= 0 {
		out.Cols = existing.Cols
	}
	if out.Rows <= 0 {
		out.Rows = existing.Rows
	}
	if out.StepSeconds <= 0 {
		out.StepSeconds = existing.StepSeconds
	}
	if out.CellWidth <= 0 {
		out.CellWidth = existing.CellWidth
	}
	if out.CellHeight <= 0 {
		out.CellHeight = existing.CellHeight
	}

	return &out
}

func hasAIAnalysisMeta(ai *aiAnalysisMeta) bool {
	if ai == nil {
		return false
	}
	if strings.TrimSpace(ai.Goal) != "" {
		return true
	}
	if strings.TrimSpace(ai.Mode) != "" {
		return true
	}
	if len(ai.Hits) > 0 {
		return true
	}
	if len(ai.Segments) > 0 {
		return true
	}
	if ai.Rating != nil {
		return true
	}
	if ai.AnalyzedAtUnix > 0 {
		return true
	}
	return false
}

func pickAnalysisAIForGoal(a analysisMeta, goal string) *aiAnalysisMeta {
	if hasAIAnalysisMeta(a.Highlights) {
		return a.Highlights
	}

	return nil
}

func readVideoMetaSourceURL(metaPath string, fi os.FileInfo) (string, bool) {
	m, ok := readVideoMetaIfValid(metaPath, fi)
	if !ok || m == nil {
		return "", false
	}
	u := strings.TrimSpace(m.File.SourceURL)
	if u == "" {
		return "", false
	}
	return u, true
}

func writeVideoMeta(
	metaPath string,
	fi os.FileInfo,
	dur float64,
	w int,
	h int,
	fps float64,
	sourceURL string,
) error {
	if strings.TrimSpace(metaPath) == "" || dur <= 0 {
		return nil
	}

	var existing *videoMeta
	if old, ok := readVideoMetaLoose(metaPath); ok && old != nil {
		existing = old
	}

	m := videoMeta{
		Version:       3,
		UpdatedAtUnix: time.Now().Unix(),
		File: videoFileMeta{
			Size:      fi.Size(),
			ModUnix:   fi.ModTime().Unix(),
			SourceURL: strings.TrimSpace(sourceURL),
		},
		Media: videoMediaMeta{
			DurationSeconds: dur,
			Video: videoStreamMeta{
				Width:      w,
				Height:     h,
				FPS:        fps,
				Resolution: formatResolution(w, h),
			},
		},
	}

	if existing != nil {
		m.Preview = existing.Preview
		m.Analysis = existing.Analysis
		m.Validation = existing.Validation
		m.Postwork = existing.Postwork

		if m.File.SourceURL == "" {
			m.File.SourceURL = existing.File.SourceURL
		}
		if m.Media.Video.Width <= 0 {
			m.Media.Video.Width = existing.Media.Video.Width
		}
		if m.Media.Video.Height <= 0 {
			m.Media.Video.Height = existing.Media.Video.Height
		}
		if m.Media.Video.FPS <= 0 {
			m.Media.Video.FPS = existing.Media.Video.FPS
		}
		if m.Media.Video.Resolution == "" {
			m.Media.Video.Resolution = existing.Media.Video.Resolution
		}
	}

	if isZeroPostworkMeta(m.Postwork) {
		m.Postwork = nil
	}

	buf, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return err
	}
	buf = append(buf, '\n')
	return atomicWriteFile(metaPath, buf)
}

func writeVideoMetaAI(
	metaPath string,
	fi os.FileInfo,
	dur float64,
	w int,
	h int,
	fps float64,
	sourceURL string,
	ai *aiAnalysisMeta,
) error {
	if strings.TrimSpace(metaPath) == "" || dur <= 0 {
		return nil
	}

	var existing *videoMeta
	if old, ok := readVideoMetaLoose(metaPath); ok && old != nil {
		existing = old
	}

	m := videoMeta{
		Version:       3,
		UpdatedAtUnix: time.Now().Unix(),
		File: videoFileMeta{
			Size:      fi.Size(),
			ModUnix:   fi.ModTime().Unix(),
			SourceURL: strings.TrimSpace(sourceURL),
		},
		Media: videoMediaMeta{
			DurationSeconds: dur,
			Video: videoStreamMeta{
				Width:      w,
				Height:     h,
				FPS:        fps,
				Resolution: formatResolution(w, h),
			},
		},
	}

	if existing != nil {
		m.Preview = existing.Preview
		m.Validation = existing.Validation
		m.Postwork = existing.Postwork

		if m.Media.Video.Width <= 0 {
			m.Media.Video.Width = existing.Media.Video.Width
		}
		if m.Media.Video.Height <= 0 {
			m.Media.Video.Height = existing.Media.Video.Height
		}
		if m.Media.Video.FPS <= 0 {
			m.Media.Video.FPS = existing.Media.Video.FPS
		}
		if m.Media.Video.Resolution == "" {
			m.Media.Video.Resolution = existing.Media.Video.Resolution
		}
		if m.File.SourceURL == "" {
			m.File.SourceURL = existing.File.SourceURL
		}
		if m.Media.DurationSeconds <= 0 {
			m.Media.DurationSeconds = existing.Media.DurationSeconds
		}

		// Wichtig:
		// analysis wird NICHT aus existing übernommen.
		// Dadurch verschwinden alte analysis.ai / analysis.nsfw beim nächsten Schreiben.
	}

	if hasAIAnalysisMeta(ai) {
		ai.Goal = "highlights"
		m.Analysis.Highlights = ai
	}

	if isZeroPostworkMeta(m.Postwork) {
		m.Postwork = nil
	}

	buf, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return err
	}
	buf = append(buf, '\n')
	return atomicWriteFile(metaPath, buf)
}

func writeVideoMetaWithPreviewClips(metaPath string, fi os.FileInfo, dur float64, w int, h int, fps float64, sourceURL string, clips []previewClip) error {
	if strings.TrimSpace(metaPath) == "" || dur <= 0 {
		return nil
	}
	assetID := strings.TrimSpace(filepath.Base(filepath.Dir(metaPath)))

	var existing *videoMeta
	if old, ok := readVideoMetaLoose(metaPath); ok && old != nil {
		existing = old
	}

	m := videoMeta{
		Version:       3,
		UpdatedAtUnix: time.Now().Unix(),
		File: videoFileMeta{
			Size:      fi.Size(),
			ModUnix:   fi.ModTime().Unix(),
			SourceURL: strings.TrimSpace(sourceURL),
		},
		Media: videoMediaMeta{
			DurationSeconds: dur,
			Video: videoStreamMeta{
				Width:      w,
				Height:     h,
				FPS:        fps,
				Resolution: formatResolution(w, h),
			},
		},
		Preview: previewMeta{
			Clips: clips,
			Thumb: buildPreviewThumbMeta(assetID),
		},
	}

	if existing != nil {
		m.Analysis = existing.Analysis
		m.Postwork = existing.Postwork

		if existing.Preview.Sprite != nil && m.Preview.Sprite == nil {
			m.Preview.Sprite = existing.Preview.Sprite
		}
		if m.Preview.Thumb == nil && existing.Preview.Thumb != nil {
			m.Preview.Thumb = existing.Preview.Thumb
		}
		if m.File.SourceURL == "" {
			m.File.SourceURL = existing.File.SourceURL
		}
		if m.Media.Video.Width <= 0 {
			m.Media.Video.Width = existing.Media.Video.Width
		}
		if m.Media.Video.Height <= 0 {
			m.Media.Video.Height = existing.Media.Video.Height
		}
		if m.Media.Video.FPS <= 0 {
			m.Media.Video.FPS = existing.Media.Video.FPS
		}
		if m.Media.Video.Resolution == "" {
			m.Media.Video.Resolution = existing.Media.Video.Resolution
		}
	}

	if isZeroPostworkMeta(m.Postwork) {
		m.Postwork = nil
	}

	buf, err := json.Marshal(m)
	if err != nil {
		return err
	}
	buf = append(buf, '\n')
	return atomicWriteFile(metaPath, buf)
}

func writeVideoMetaWithPreviewClipsAndSprite(
	metaPath string,
	fi os.FileInfo,
	dur float64,
	w int,
	h int,
	fps float64,
	sourceURL string,
	clips []previewClip,
	sprite *previewSpriteMeta,
) error {
	if strings.TrimSpace(metaPath) == "" || dur <= 0 {
		return nil
	}
	assetID := strings.TrimSpace(filepath.Base(filepath.Dir(metaPath)))

	var existing *videoMeta
	if old, ok := readVideoMetaLoose(metaPath); ok && old != nil {
		existing = old
	}

	m := videoMeta{
		Version:       3,
		UpdatedAtUnix: time.Now().Unix(),
		File: videoFileMeta{
			Size:      fi.Size(),
			ModUnix:   fi.ModTime().Unix(),
			SourceURL: strings.TrimSpace(sourceURL),
		},
		Media: videoMediaMeta{
			DurationSeconds: dur,
			Video: videoStreamMeta{
				Width:      w,
				Height:     h,
				FPS:        fps,
				Resolution: formatResolution(w, h),
			},
		},
		Preview: previewMeta{
			Clips:  clips,
			Thumb:  buildPreviewThumbMeta(assetID),
			Sprite: sprite,
		},
	}

	if existing != nil {
		m.Analysis = existing.Analysis
		m.Postwork = existing.Postwork

		m.Preview.Sprite = mergePreviewSpriteMeta(existing.Preview.Sprite, m.Preview.Sprite)

		if m.Preview.Thumb == nil && existing.Preview.Thumb != nil {
			m.Preview.Thumb = existing.Preview.Thumb
		}
		if len(m.Preview.Clips) == 0 && len(existing.Preview.Clips) > 0 {
			m.Preview.Clips = existing.Preview.Clips
		}
		if m.File.SourceURL == "" {
			m.File.SourceURL = existing.File.SourceURL
		}
		if m.Media.Video.Width <= 0 {
			m.Media.Video.Width = existing.Media.Video.Width
		}
		if m.Media.Video.Height <= 0 {
			m.Media.Video.Height = existing.Media.Video.Height
		}
		if m.Media.Video.FPS <= 0 {
			m.Media.Video.FPS = existing.Media.Video.FPS
		}
		if m.Media.Video.Resolution == "" {
			m.Media.Video.Resolution = existing.Media.Video.Resolution
		}
		if m.Media.DurationSeconds <= 0 {
			m.Media.DurationSeconds = existing.Media.DurationSeconds
		}
	}

	if isZeroPostworkMeta(m.Postwork) {
		m.Postwork = nil
	}

	buf, err := json.Marshal(m)
	if err != nil {
		return err
	}
	buf = append(buf, '\n')
	return atomicWriteFile(metaPath, buf)
}

func writeVideoMetaDuration(metaPath string, fi os.FileInfo, dur float64, sourceURL string) error {
	return writeVideoMeta(metaPath, fi, dur, 0, 0, 0, sourceURL)
}

func generatedMetaFile(assetID string) (string, error) {
	assetID = stripHotPrefix(strings.TrimSpace(assetID))
	if assetID == "" {
		return "", appErrorf("empty assetID")
	}

	id, err := sanitizeID(assetID)
	if err != nil || id == "" {
		return "", appErrorf("invalid assetID: %w", err)
	}

	return metaJSONPathForAssetID(id)
}

func generatedDirForID(id string) (string, error) {
	id, err := sanitizeID(id)
	if err != nil {
		return "", err
	}
	root, err := generatedMetaRoot()
	if err != nil {
		return "", err
	}
	if strings.TrimSpace(root) == "" {
		return "", appErrorf("generated meta root ist leer")
	}
	return filepath.Join(root, id), nil
}

func ensureGeneratedDir(id string) (string, error) {
	dir, err := generatedDirForID(id)
	if err != nil {
		return "", err
	}
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	return dir, nil
}

func formatResolution(w, h int) string {
	if w <= 0 || h <= 0 {
		return ""
	}
	return fmt.Sprintf("%dx%d", w, h)
}

func generatedThumbFile(id string) (string, error) {
	dir, err := generatedDirForID(id)
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, "preview.jpg"), nil
}

func generatedPreviewFile(id string) (string, error) {
	dir, err := generatedDirForID(id)
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, "preview.mp4"), nil
}

func generatedPreviewSpriteFile(id string) (string, error) {
	dir, err := generatedDirForID(id)
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, "preview-sprite.jpg"), nil
}

func buildPreviewThumbMeta(assetID string) *previewThumbMeta {
	assetID = stripHotPrefix(strings.TrimSpace(assetID))
	if assetID == "" {
		return nil
	}

	thumbPath, err := generatedThumbFile(assetID)
	if err != nil || strings.TrimSpace(thumbPath) == "" {
		return nil
	}

	if _, err := os.Stat(thumbPath); err != nil {
		return nil
	}

	return &previewThumbMeta{
		Path:   "/api/generated/cover?id=" + assetID,
		Exists: true,
	}
}

func ensureGeneratedDirs() error {
	root, err := generatedMetaRoot()
	if err != nil {
		return err
	}
	if strings.TrimSpace(root) == "" {
		return appErrorf("generated meta root ist leer")
	}
	return os.MkdirAll(root, 0o755)
}

func sanitizeID(id string) (string, error) {
	id = strings.TrimSpace(id)
	if id == "" {
		return "", appErrorf("id fehlt")
	}
	if strings.ContainsAny(id, `/\`) {
		return "", appErrorf("ungültige id")
	}
	return id, nil
}

func writeVideoAIForFile(
	ctx context.Context,
	fullPath string,
	sourceURL string,
	ai *aiAnalysisMeta,
) error {
	fullPath = strings.TrimSpace(fullPath)
	if fullPath == "" || ai == nil {
		return nil
	}

	fi, err := os.Stat(fullPath)
	if err != nil || fi == nil || fi.IsDir() || fi.Size() <= 0 {
		return appErrorf("datei nicht gefunden")
	}

	m, ok := ensureVideoMetaForFileBestEffort(ctx, fullPath, sourceURL)
	if !ok || m == nil {
		return appErrorf("meta konnte nicht erzeugt werden")
	}

	stem := strings.TrimSuffix(filepath.Base(fullPath), filepath.Ext(fullPath))
	assetID := stripHotPrefix(strings.TrimSpace(stem))
	if assetID == "" {
		return appErrorf("asset id fehlt")
	}

	assetID, err = sanitizeID(assetID)
	if err != nil || assetID == "" {
		return appErrorf("asset id ungültig: %w", err)
	}

	metaPath, err := metaJSONPathForAssetID(assetID)
	if err != nil {
		return err
	}

	if strings.TrimSpace(sourceURL) == "" {
		sourceURL = m.File.SourceURL
	}

	return writeVideoMetaAI(
		metaPath,
		fi,
		m.Media.DurationSeconds,
		m.Media.Video.Width,
		m.Media.Video.Height,
		m.Media.Video.FPS,
		sourceURL,
		ai,
	)
}

func readVideoMetaAIForGoal(metaPath string, goal string) (map[string]any, bool) {
	b, err := os.ReadFile(metaPath)
	if err != nil || len(b) == 0 {
		return nil, false
	}

	var m map[string]any
	dec := json.NewDecoder(strings.NewReader(string(b)))
	dec.UseNumber()
	if err := dec.Decode(&m); err != nil {
		return nil, false
	}

	rawAnalysis, ok := m["analysis"].(map[string]any)
	if !ok || rawAnalysis == nil {
		return nil, false
	}

	// Neuer einziger Zweig.
	if highlights, ok := rawAnalysis["highlights"].(map[string]any); ok && highlights != nil {
		return highlights, true
	}

	return nil, false
}