// backend/meta.go
package main

import (
	"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 videoMeta struct {
	Version         int     `json:"version"`
	DurationSeconds float64 `json:"durationSeconds"`
	FileSize        int64   `json:"fileSize"`
	FileModUnix     int64   `json:"fileModUnix"`

	VideoWidth  int     `json:"videoWidth,omitempty"`
	VideoHeight int     `json:"videoHeight,omitempty"`
	FPS         float64 `json:"fps,omitempty"`
	Resolution  string  `json:"resolution,omitempty"` // z.B. "1920x1080"

	SourceURL    string        `json:"sourceUrl,omitempty"`
	PreviewClips []previewClip `json:"previewClips,omitempty"`

	UpdatedAtUnix int64 `json:"updatedAtUnix"`
}

// liest Meta (v2 ODER altes v1) und validiert gegen fi (Size/ModTime)
func readVideoMeta(metaPath string, fi os.FileInfo) (dur float64, w int, h int, fps float64, ok bool) {
	b, err := os.ReadFile(metaPath)
	if err != nil || len(b) == 0 {
		return 0, 0, 0, 0, false
	}

	// 1) Neues Format (oder v1 mit gleichen Feldern)
	var m videoMeta
	if err := json.Unmarshal(b, &m); err == nil && (m.Version == 2 || m.Version == 1) {
		if m.FileSize != fi.Size() || m.FileModUnix != fi.ModTime().Unix() {
			return 0, 0, 0, 0, false
		}
		if m.DurationSeconds <= 0 {
			return 0, 0, 0, 0, false
		}
		return m.DurationSeconds, m.VideoWidth, m.VideoHeight, m.FPS, true
	}

	// 2) Fallback: ganz altes v1-Format (nur Duration etc.)
	var m1 struct {
		Version         int     `json:"version"`
		DurationSeconds float64 `json:"durationSeconds"`
		FileSize        int64   `json:"fileSize"`
		FileModUnix     int64   `json:"fileModUnix"`
		UpdatedAtUnix   int64   `json:"updatedAtUnix"`
	}
	if err := json.Unmarshal(b, &m1); err != nil {
		return 0, 0, 0, 0, false
	}
	if m1.Version != 1 {
		return 0, 0, 0, 0, false
	}
	if m1.FileSize != fi.Size() || m1.FileModUnix != fi.ModTime().Unix() {
		return 0, 0, 0, 0, false
	}
	if m1.DurationSeconds <= 0 {
		return 0, 0, 0, 0, false
	}
	return m1.DurationSeconds, 0, 0, 0, true
}

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

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

// Voll-Write (wenn du dur + props schon hast)
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
	}
	m := videoMeta{
		Version:         2,
		DurationSeconds: dur,
		FileSize:        fi.Size(),
		FileModUnix:     fi.ModTime().Unix(),
		VideoWidth:      w,
		VideoHeight:     h,
		FPS:             fps,
		Resolution:      formatResolution(w, h),
		SourceURL:       strings.TrimSpace(sourceURL),
		UpdatedAtUnix:   time.Now().Unix(),
	}
	buf, err := json.Marshal(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
	}
	m := videoMeta{
		Version:         2,
		DurationSeconds: dur,
		FileSize:        fi.Size(),
		FileModUnix:     fi.ModTime().Unix(),
		VideoWidth:      w,
		VideoHeight:     h,
		FPS:             fps,
		Resolution:      formatResolution(w, h),
		SourceURL:       strings.TrimSpace(sourceURL),
		PreviewClips:    clips,
		UpdatedAtUnix:   time.Now().Unix(),
	}
	buf, err := json.Marshal(m)
	if err != nil {
		return err
	}
	buf = append(buf, '\n')
	return atomicWriteFile(metaPath, buf)
}

// Duration-only Write (ohne props)
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 "", fmt.Errorf("empty assetID")
	}

	// exakt wie beim Schreiben normalisieren
	id, err := sanitizeID(assetID)
	if err != nil || id == "" {
		return "", fmt.Errorf("invalid assetID: %w", err)
	}

	return metaJSONPathForAssetID(id)
}

// ✅ Neu: /generated/meta/<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 "", fmt.Errorf("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, "thumbs.webp"), nil
}

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

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

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