// backend\assets_generate.go
package main

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

func formatBytesSI(b int64) string {
	if b < 0 {
		b = 0
	}
	const unit = 1024
	if b < unit {
		return fmt.Sprintf("%d B", b)
	}
	div, exp := int64(unit), 0
	for n := b / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	suffix := []string{"KB", "MB", "GB", "TB", "PB"}
	v := float64(b) / float64(div)
	// 1 Nachkommastelle, außer sehr große ganze Zahlen
	if v >= 10 {
		return fmt.Sprintf("%.0f %s", v, suffix[exp])
	}
	return fmt.Sprintf("%.1f %s", v, suffix[exp])
}

func u64ToI64(x uint64) int64 {
	if x > uint64(maxInt64) {
		return maxInt64
	}
	return int64(x)
}

func isFFmpegInputInvalidError(err error) bool {
	if err == nil {
		return false
	}
	s := strings.ToLower(err.Error())

	// typische ffmpeg/mp4 Fehler bei unvollständigen Dateien
	return strings.Contains(s, "moov atom not found") ||
		strings.Contains(s, "invalid data found when processing input") ||
		strings.Contains(s, "error opening input file") ||
		strings.Contains(s, "error opening input")
}

// -------------------------
// Asset layout helpers
// -------------------------

// Asset "ID" = Dateiname ohne Endung (immer OHNE "HOT " Prefix)
func assetIDFromVideoPath(videoPath string) string {
	base := filepath.Base(strings.TrimSpace(videoPath))
	if base == "" {
		return ""
	}
	id := strings.TrimSuffix(base, filepath.Ext(base))
	id = stripHotPrefix(id)
	return strings.TrimSpace(id)
}

// Liefert die standardisierten Pfade (preview.webp / preview.mp4 / preview-sprite.webp / meta.json)
func assetPathsForID(id string) (assetDir, thumbPath, previewPath, spritePath, metaPath string, err error) {
	id = strings.TrimSpace(id)
	if id == "" {
		return "", "", "", "", "", fmt.Errorf("empty id")
	}

	assetDir, err = ensureGeneratedDir(id)
	if err != nil || strings.TrimSpace(assetDir) == "" {
		return "", "", "", "", "", fmt.Errorf("generated dir: %v", err)
	}

	thumbPath = filepath.Join(assetDir, "preview.webp")
	previewPath = filepath.Join(assetDir, "preview.mp4")
	spritePath = filepath.Join(assetDir, "preview-sprite.webp")

	metaPath, _ = metaJSONPathForAssetID(id) // bevorzugt generated/meta/<id>/meta.json
	if strings.TrimSpace(metaPath) == "" {
		metaPath = filepath.Join(assetDir, "meta.json")
	}

	return assetDir, thumbPath, previewPath, spritePath, metaPath, nil
}

type ensuredMeta struct {
	durSec    float64
	vw, vh    int
	fps       float64
	sourceURL string
	ok        bool // ok = duration + props vorhanden
}

// Stellt sicher:
// - Duration ist berechnet (cache ok)
// - Props (w/h/fps) sind drin (ffprobe wenn nötig)
// - meta.json wird (best-effort) geschrieben, inkl. sourceURL
func ensureVideoMeta(ctx context.Context, videoPath, metaPath, sourceURL string, vfi os.FileInfo) (ensuredMeta, error) {
	out := ensuredMeta{sourceURL: strings.TrimSpace(sourceURL)}

	videoPath = strings.TrimSpace(videoPath)
	metaPath = strings.TrimSpace(metaPath)
	if videoPath == "" || metaPath == "" {
		return out, nil
	}
	if vfi == nil || vfi.IsDir() || vfi.Size() <= 0 {
		return out, nil
	}

	// 1) Try cache/meta first (inkl. w/h/fps)
	if d, mw, mh, mfps, ok := readVideoMeta(metaPath, vfi); ok {
		out.durSec, out.vw, out.vh, out.fps = d, mw, mh, mfps
	} else {
		// 2) Duration berechnen
		dctx, cancel := context.WithTimeout(ctx, 6*time.Second)
		d, derr := durationSecondsCached(dctx, videoPath)
		cancel()
		if derr == nil && d > 0 {
			out.durSec = d
		}
	}

	// 3) Props ggf. nachziehen (ffprobe)
	if out.durSec > 0 && (out.vw <= 0 || out.vh <= 0 || out.fps <= 0) {
		pctx, cancel := context.WithTimeout(ctx, 8*time.Second)
		defer cancel()

		if durSem != nil {
			if err := durSem.Acquire(pctx); err == nil {
				out.vw, out.vh, out.fps, _ = probeVideoProps(pctx, videoPath)
				durSem.Release()
			}
		} else {
			out.vw, out.vh, out.fps, _ = probeVideoProps(pctx, videoPath)
		}
	}

	// 4) meta.json schreiben/aktualisieren (best-effort)
	if out.durSec > 0 {
		_ = writeVideoMeta(metaPath, vfi, out.durSec, out.vw, out.vh, out.fps, out.sourceURL)
	}

	out.ok = out.durSec > 0 && out.vw > 0 && out.vh > 0
	return out, nil
}

type EnsureAssetsResult struct {
	Skipped          bool
	ThumbGenerated   bool
	PreviewGenerated bool
	SpriteGenerated  bool
	MetaOK           bool
}

// Public wrappers (kompatibel zu deinem bisherigen API)

func ensureAssetsForVideo(videoPath string) error {
	// Default: keine SourceURL (für Covers egal)
	return ensureAssetsForVideoWithProgress(videoPath, "", nil)
}

func ensureAssetsForVideoWithSource(videoPath string, sourceURL string) error {
	return ensureAssetsForVideoWithProgress(videoPath, sourceURL, nil)
}

// onRatio: 0..1 (Assets-Gesamtfortschritt)
func ensureAssetsForVideoWithProgress(videoPath string, sourceURL string, onRatio func(r float64)) error {
	ctx := context.Background()
	_, err := ensureAssetsForVideoWithProgressCtx(ctx, videoPath, sourceURL, onRatio)
	return err
}

// Task/Bulk sollte diesen Context-aware Call nutzen.
func ensureAssetsForVideoWithProgressCtx(ctx context.Context, videoPath string, sourceURL string, onRatio func(r float64)) (EnsureAssetsResult, error) {
	res, err := ensureAssetsForVideoDetailed(ctx, videoPath, sourceURL, onRatio)
	return res, err
}

// Core: generiert thumbs/preview/sprite/meta und sagt zurück was passiert ist.
func ensureAssetsForVideoDetailed(ctx context.Context, videoPath string, sourceURL string, onRatio func(r float64)) (EnsureAssetsResult, error) {
	var out EnsureAssetsResult
	var sourceInputInvalid bool

	videoPath = strings.TrimSpace(videoPath)
	if videoPath == "" {
		return out, nil
	}

	fi, statErr := os.Stat(videoPath)
	if statErr != nil || fi.IsDir() || fi.Size() <= 0 {
		return out, nil
	}

	// 🔒 Schutz gegen Race: sehr frische Dateien sind evtl. noch nicht finalisiert/kopiert.
	// Statt direkt zu skippen: kurz warten und dann weitermachen (sonst gibt es keinen Retry).
	if age := time.Since(fi.ModTime()); age < 10*time.Second {
		wait := 10*time.Second - age
		// nicht ewig blocken, respektiere ctx
		if wait > 0 {
			t := time.NewTimer(wait)
			defer t.Stop()
			select {
			case <-t.C:
				// weiter
			case <-ctx.Done():
				return out, ctx.Err()
			}
		}
	}

	id := assetIDFromVideoPath(videoPath)
	if id == "" {
		return out, nil
	}

	_, thumbPath, previewPath, spritePath, metaPath, perr := assetPathsForID(id)
	if perr != nil {
		return out, perr
	}

	progress := func(r float64) {
		if onRatio == nil {
			return
		}
		if r < 0 {
			r = 0
		}
		if r > 1 {
			r = 1
		}
		onRatio(r)
	}

	// Vorher-Checks (für Result)
	thumbBefore := func() bool {
		if tfi, err := os.Stat(thumbPath); err == nil && !tfi.IsDir() && tfi.Size() > 0 {
			return true
		}
		return false
	}()

	previewBefore := func() bool {
		if pfi, err := os.Stat(previewPath); err == nil && !pfi.IsDir() && pfi.Size() > 0 {
			return true
		}
		return false
	}()

	spriteBefore := func() bool {
		if sfi, err := os.Stat(spritePath); err == nil && !sfi.IsDir() && sfi.Size() > 0 {
			return true
		}
		return false
	}()

	// Meta sicherstellen (dedupliziert)
	meta, _ := ensureVideoMeta(ctx, videoPath, metaPath, sourceURL, fi)
	out.MetaOK = meta.ok

	// Wenn alles da ist: als skipped markieren,
	// aber NICHT sofort returnen, damit meta.json
	// (previewClips / previewSprite) trotzdem sauber geschrieben wird.
	metaHasSprite := false
	if oldMeta, ok := readVideoMetaIfValid(metaPath, fi); ok && oldMeta != nil && oldMeta.PreviewSprite != nil {
		metaHasSprite = true
	}

	metaHasAI := hasAIResultsForOutput(videoPath)

	// Nur dann wirklich komplett "fertig", wenn auch AI vorhanden ist
	if thumbBefore && previewBefore && spriteBefore && meta.ok && metaHasSprite && metaHasAI {
		out.Skipped = true
		progress(1)
		return out, nil
	}

	// Gewichte: thumbs klein, preview groß
	const (
		thumbsW  = 0.25
		previewW = 0.75
	)

	progress(0)

	// ----------------
	// Thumbs (WebP-only)
	// ----------------
	if thumbBefore {
		progress(thumbsW)
	} else {
		progress(0.05)

		func() {
			genCtx, cancel := context.WithTimeout(ctx, 45*time.Second)
			defer cancel()

			// Acquire; wenn Context cancelled → Fehler zurück
			if err := thumbSem.Acquire(genCtx); err != nil {
				// wenn ctx cancelled -> hart zurück, sonst best-effort weiter
				if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
					return
				}
				return
			}
			defer thumbSem.Release()

			progress(0.10)

			// ✅ Immer letztes Frame bevorzugen (Preview soll “Endzustand” zeigen)
			img, e1 := extractLastFrameWebP(videoPath)
			if e1 != nil || len(img) == 0 {
				// Fallback: wenn wir Duration kennen, versuche kurz vor Ende
				if meta.durSec > 0 {
					t := meta.durSec - 0.25
					if t < 0 {
						t = 0
					}
					img, e1 = extractFrameAtTimeWebP(videoPath, t)
				}
				// Letzter Fallback: erstes Frame
				if e1 != nil || len(img) == 0 {
					img, e1 = extractFirstFrameWebPScaled(videoPath, 720, 75)
				}
			}

			progress(0.20)

			if e1 == nil && len(img) > 0 {
				if err := atomicWriteFile(thumbPath, img); err == nil {
					out.ThumbGenerated = true
				} else {
					fmt.Println("⚠️ thumb write:", err)
				}
			}
		}()

		progress(thumbsW)
	}

	// ----------------
	// Preview (MP4 teaser clips)
	// ----------------
	const (
		previewClipLenSec = 0.75
		previewMaxClips   = 12
	)

	var computedPreviewClips []previewClip

	if previewBefore {
		// Preview ist schon da -> nicht returnen, weil Sprite evtl. noch fehlt
		progress(thumbsW + previewW)
	} else {
		func() {
			genCtx, cancel := context.WithTimeout(ctx, 3*time.Minute)
			defer cancel()

			progress(thumbsW + 0.02)

			if err := genSem.Acquire(genCtx); err != nil {
				return
			}
			defer genSem.Release()

			progress(thumbsW + 0.05)

			if err := generateTeaserClipsMP4WithProgress(genCtx, videoPath, previewPath, previewClipLenSec, previewMaxClips, func(r float64) {
				if r < 0 {
					r = 0
				}
				if r > 1 {
					r = 1
				}
				progress(thumbsW + r*previewW)
			}); err != nil {
				if isFFmpegInputInvalidError(err) {
					sourceInputInvalid = true
					fmt.Printf("⚠️ preview clips skipped (invalid/incomplete input): %s\n", videoPath)
					return
				}

				fmt.Println("⚠️ preview clips:", err)
				return
			}

			out.PreviewGenerated = true

			// ✅ Preview-Clips berechnen (noch NICHT direkt schreiben)
			if !(meta.durSec > 0) {
				return
			}

			// exakt dieselben Werte wie beim tatsächlichen Preview-Rendern
			opts := TeaserPreviewOptions{
				Segments:        previewMaxClips,
				SegmentDuration: previewClipLenSec,
			}

			starts, segDur, _ := computeTeaserStarts(meta.durSec, opts)

			clips := make([]previewClip, 0, len(starts))
			for _, s := range starts {
				clips = append(clips, previewClip{
					StartSeconds:    math.Round(s*1000) / 1000,
					DurationSeconds: math.Round(segDur*1000) / 1000,
				})
			}

			// ✅ merken für finalen Meta-Write
			computedPreviewClips = clips
		}()
	}

	// ----------------
	// Preview Sprite (festes Layout)
	// ----------------
	var spriteMeta *previewSpriteMeta

	if meta.durSec > 0 {
		cols, rows, count, cellW, cellH := fixedPreviewSpriteLayout()
		stepSec := previewSpriteStepSeconds(meta.durSec)

		spriteMeta = &previewSpriteMeta{
			Path:        fmt.Sprintf("/api/preview-sprite/%s", id),
			Count:       count,
			Cols:        cols,
			Rows:        rows,
			StepSeconds: stepSec,
			CellWidth:   cellW,
			CellHeight:  cellH,
		}
	}

	if !spriteBefore {
		func() {
			if sourceInputInvalid {
				return
			}

			if !(meta.durSec > 0) {
				return
			}

			genCtx, cancel := context.WithTimeout(ctx, 2*time.Minute)
			defer cancel()

			if err := genSem.Acquire(genCtx); err != nil {
				return
			}
			defer genSem.Release()

			cols, rows, _, cellW, cellH := fixedPreviewSpriteLayout()
			stepSec := previewSpriteStepSeconds(meta.durSec)

			if err := generatePreviewSpriteWebP(
				genCtx,
				videoPath,
				spritePath,
				cols,
				rows,
				stepSec,
				cellW,
				cellH,
			); err != nil {
				if sfi, statErr := os.Stat(spritePath); statErr == nil && sfi != nil && !sfi.IsDir() && sfi.Size() > 0 {
					// Sprite existiert am Ende trotzdem -> Warnung unterdrücken
					return
				}

				// Optional: nur kurze Meldung statt voller ffmpeg-Ausgabe
				//fmt.Printf("⚠️ preview sprite failed for %s\n", videoPath)
				return
			}

			out.SpriteGenerated = true
		}()
	}

	// ✅ Final meta write: Clips + Sprite zusammen persistieren
	if meta.durSec > 0 {
		// Falls wir in diesem Lauf keine neuen Clips berechnet haben:
		// alte aus gültigem meta.json übernehmen (best effort)
		if len(computedPreviewClips) == 0 {
			if oldMeta, ok := readVideoMetaIfValid(metaPath, fi); ok && oldMeta != nil && len(oldMeta.PreviewClips) > 0 {
				computedPreviewClips = oldMeta.PreviewClips
			}
		}

		// Falls wir in diesem Lauf kein neues spriteMeta gesetzt haben:
		// altes aus gültigem meta.json übernehmen
		if spriteMeta == nil {
			if oldMeta, ok := readVideoMetaIfValid(metaPath, fi); ok && oldMeta != nil && oldMeta.PreviewSprite != nil {
				spriteMeta = oldMeta.PreviewSprite
			}
		}

		_ = writeVideoMetaWithPreviewClipsAndSprite(
			metaPath,
			fi,
			meta.durSec,
			meta.vw,
			meta.vh,
			meta.fps,
			meta.sourceURL,
			computedPreviewClips,
			spriteMeta,
		)
	}

	progress(1)
	return out, nil
}

func hasAIResultsForOutput(outPath string) bool {
	outPath = strings.TrimSpace(outPath)
	if outPath == "" {
		return false
	}

	id := assetIDFromVideoPath(outPath)
	if id == "" {
		return false
	}

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

	b, err := os.ReadFile(metaPath)
	if err != nil || len(b) == 0 {
		return false
	}

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

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

	rawHits, hasHits := aiMap["hits"].([]any)
	rawSegs, hasSegs := aiMap["segments"].([]any)

	return (hasHits && len(rawHits) > 0) || (hasSegs && len(rawSegs) > 0)
}

type PrepareSplitResult struct {
	AssetsReady  bool
	AnalyzeReady bool
	SpriteReady  bool
	MetaOK       bool
}

func prepareVideoForSplit(ctx context.Context, videoPath, sourceURL, goal string) (PrepareSplitResult, error) {
	var out PrepareSplitResult

	videoPath = strings.TrimSpace(videoPath)
	if videoPath == "" {
		return out, fmt.Errorf("empty videoPath")
	}

	fi, err := os.Stat(videoPath)
	if err != nil || fi == nil || fi.IsDir() || fi.Size() <= 0 {
		return out, fmt.Errorf("video datei nicht gefunden")
	}

	// 1) Assets sicherstellen (preview.webp / preview.mp4 / preview-sprite.webp / meta.json)
	assetsRes, err := ensureAssetsForVideoDetailed(ctx, videoPath, sourceURL, nil)
	if err != nil {
		return out, err
	}

	_ = assetsRes

	id := assetIDFromVideoPath(videoPath)
	if id == "" {
		return out, fmt.Errorf("konnte asset id nicht ableiten")
	}

	ps := previewSpriteTruthForID(id)
	out.SpriteReady = ps.Exists
	out.AssetsReady = ps.Exists
	out.MetaOK = true

	// 2) AI-Segmente prüfen
	if hasAIResultsForOutput(videoPath) {
		out.AnalyzeReady = true
		return out, nil
	}

	goal = strings.ToLower(strings.TrimSpace(goal))
	if goal == "" {
		goal = "nsfw"
	}

	// 3) AI nur ausführen, wenn Sprite vorhanden ist
	if !ps.Exists {
		return out, nil
	}

	durationSec, _ := durationSecondsForAnalyze(ctx, videoPath)
	hits, aerr := analyzeVideoFromSprite(ctx, videoPath, goal)
	if aerr != nil {
		return out, nil
	}

	segments := buildSegmentsFromAnalyzeHits(hits, durationSec)

	ai := &aiAnalysisMeta{
		Goal:           goal,
		Mode:           "sprite",
		Hits:           hits,
		Segments:       segments,
		AnalyzedAtUnix: time.Now().Unix(),
	}

	if werr := writeVideoAIForFile(ctx, videoPath, sourceURL, ai); werr != nil {
		return out, nil
	}

	out.AnalyzeReady = len(segments) > 0
	return out, nil
}