bookhoard/internal/services/media_scanner_audio.go

package services

// Audiobook ingestion (handoff item 3, Batch A). The m4b path is
// SIDECAR-FIRST: Libation (and Audiobookshelf-compatible tools) write a
// metadata.json next to the file carrying narrators/series/ASIN/chapters;
// ffprobe is the fallback (and the filler) for duration, codec profile,
// bitrate and embedded chapters. ffprobe is an OPTIONAL dependency — when
// absent the book still ingests (filename/folder metadata, no chapters
// until a rescan runs with ffprobe present).
//
// The chapters array written into media_items.audio_metadata IS the
// format abstraction: embedded m4b chapters, folder-as-book files and
// zip-of-audio books all produce {index, title, start, end} entries, so
// the locator {chapter, offset_seconds} and the /chapters endpoint never
// learn which file model produced them.
//
// Multi-file books (layout "folder" | "zip", see
// media_scanner_audio_multifile.go) additionally carry a tracks array:
// one entry per playable file, with its global-seconds start/end and the
// path the /audio/:trackIndex streaming endpoint resolves. Single-file
// books leave layout and tracks empty — the <audio> element streams the
// whole file exactly as before.

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

// AudioChapter is the uniform chapter entry for every audiobook file model.
type AudioChapter struct {
	Index int     `json:"index"`
	Title string  `json:"title"`
	Start float64 `json:"start"`
	End   float64 `json:"end"`
}

// AudioTrack is one playable file of a multi-file audiobook. Path is the
// library-relative file path (layout "folder") or the in-zip entry name
// (layout "zip"); the /audio/:trackIndex endpoint resolves it to bytes.
// Start/End are cumulative global seconds across the book — the same
// coordinate system chapters, bookmarks and audio_offset_seconds use.
type AudioTrack struct {
	Index           int     `json:"index"`
	Path            string  `json:"path"`
	Title           string  `json:"title,omitempty"`
	Start           float64 `json:"start"`
	End             float64 `json:"end"`
	DurationSeconds float64 `json:"duration_seconds,omitempty"`
	SizeBytes       int64   `json:"size_bytes,omitempty"`
}

// AudioMetadataPayload is the JSONB stored in media_items.audio_metadata.
// Only the audio paths read it — ebook paths never do (the kobo_metadata
// precedent).
type AudioMetadataPayload struct {
	Narrators       []string       `json:"narrators,omitempty"`
	DurationSeconds float64        `json:"duration_seconds,omitempty"`
	CodecProfile    string         `json:"codec_profile,omitempty"`
	BitRate         int64          `json:"bit_rate,omitempty"`
	ASIN            string         `json:"asin,omitempty"`
	Abridged        *bool          `json:"abridged,omitempty"`
	Chapters        []AudioChapter `json:"chapters,omitempty"`
	// Layout: "" = single file (the Batch A model), "folder" = a
	// directory of track files, "zip" = a zip archive of tracks.
	Layout string `json:"layout,omitempty"`
	// Tracks: one entry per playable file for multi-file layouts. Empty
	// for single-file books (the whole file IS the track).
	Tracks []AudioTrack `json:"tracks,omitempty"`
}

func isAudioFile(path string) bool {
	switch strings.ToLower(filepath.Ext(path)) {
	case ".m4b", ".m4a", ".mp3", ".flac", ".zip", ".opus", ".ogg", ".oga", ".aac", ".wav":
		return true
	}
	return false
}

// isAudioTrackFile reports whether a path is a PLAYABLE track of a
// multi-file book. Zips are book CONTAINERS (layout "zip"), never tracks
// of a folder book — a nested zip inside a book root must not join the
// track list, and pre-grouping one-track strays were never zips.
func isAudioTrackFile(path string) bool {
	if strings.EqualFold(filepath.Ext(path), ".zip") {
		return false
	}
	return isAudioFile(path)
}

// ffprobeAvailable is resolved once per scan process; a missing binary is
// a degradation, not an error.
var ffprobeAvailable = func() bool {
	_, err := exec.LookPath("ffprobe")
	return err == nil
}()

// ffmpegAvailable mirrors ffprobeAvailable for the embedded-cover
// extractor (ffprobe cannot write image streams; ffmpeg can).
var ffmpegAvailable = func() bool {
	_, err := exec.LookPath("ffmpeg")
	return err == nil
}()

// extractEmbeddedAudioCover pulls the embedded cover art (mp3 APIC /
// m4b covr / flac picture) out of an audio file with one ffmpeg call —
// the attached picture presents itself as the file's only video stream.
// Writes outputBase+".cover.jpg" following the EPUB sidecar convention
// ("<book>.cover.jpg"). Returns "" when ffmpeg is absent, the file
// carries no picture, or anything fails — purely optional enrichment.
func extractEmbeddedAudioCover(inputPath, outputBase string) string {
	if !ffmpegAvailable {
		return ""
	}
	outPath := outputBase + ".cover.jpg"
	cmd := exec.Command("ffmpeg",
		"-y", "-v", "error",
		"-i", inputPath,
		"-map", "0:v:0",
		"-frames:v", "1",
		outPath,
	)
	if out, err := cmd.CombinedOutput(); err != nil {
		// "matches no streams" is the no-embedded-art case; stay quiet
		// about it, log anything unexpected.
		if len(out) > 0 && !strings.Contains(string(out), "matches no streams") {
			fmt.Printf("ffmpeg cover extraction note for %s: %s\n", inputPath, strings.TrimSpace(string(out)))
		}
		return ""
	}
	if info, err := os.Stat(outPath); err != nil || info.Size() == 0 {
		_ = os.Remove(outPath)
		return ""
	}
	return outPath
}

type ffprobeReport struct {
	Format struct {
		Duration flexFloat `json:"duration"`
		BitRate  flexFloat `json:"bit_rate"`
		// Tags: ffprobe normalizes well-known atoms to lowercase keys but
		// passes freeform keys (Audible's `----:com.apple.iTunes:*`)
		// through verbatim — a map with case-insensitive lookup is the
		// only honest shape. See tag().
		Tags map[string]string `json:"tags"`
	} `json:"format"`
	Streams []struct {
		CodecName  string `json:"codec_name"`
		Profile    string `json:"profile"`
		SampleRate string `json:"sample_rate"`
	} `json:"streams"`
	Chapters []struct {
		ID        int       `json:"id"`
		StartTime flexFloat `json:"start_time"`
		EndTime   flexFloat `json:"end_time"`
		Tags      struct {
			Title string `json:"title"`
		} `json:"tags"`
	} `json:"chapters"`
}

// flexFloat accepts JSON numbers OR number-strings: ffprobe's output
// switched to strings for chapter timings in the ffmpeg 8 build
// (Libation ingest exposed both shapes across formats).
type flexFloat float64

func (f *flexFloat) UnmarshalJSON(data []byte) error {
	s := strings.TrimSpace(string(data))
	s = strings.Trim(s, "\"")
	if s == "" || s == "null" || s == "N/A" {
		*f = 0
		return nil
	}
	v, err := strconv.ParseFloat(s, 64)
	if err != nil {
		return err
	}
	*f = flexFloat(v)
	return nil
}

// runFFProbe shells out to ffprobe for the container facts the sidecar
// doesn't carry (duration/bitrate/codec). Returns nil when ffprobe is
// absent or the probe fails — callers degrade gracefully. Failures log:
// a silent nil made a real exec failure indistinguishable from a missing
// binary (found by the Libation ingest).
func runFFProbe(path string) *ffprobeReport {
	if !ffprobeAvailable {
		fmt.Printf("ffprobe unavailable (not on PATH); audio facts degrade to sidecar-only for %s\n", path)
		return nil
	}
	cmd := exec.Command("ffprobe",
		"-v", "quiet",
		"-print_format", "json",
		"-show_format", "-show_streams", "-show_chapters",
		path,
	)
	out, err := cmd.Output()
	if err != nil {
		fmt.Printf("ffprobe failed for %s: %v\n", path, err)
		return nil
	}
	if len(out) == 0 {
		fmt.Printf("ffprobe produced no output for %s\n", path)
		return nil
	}
	var report ffprobeReport
	if err := json.Unmarshal(out, &report); err != nil {
		fmt.Printf("ffprobe output unparseable for %s: %v\n", path, err)
		return nil
	}
	return &report
}

// tag returns the first non-empty ffprobe tag among the candidate keys,
// matched case-insensitively and trimmed. Empty string when none match.
func (r *ffprobeReport) tag(keys ...string) string {
	if r == nil {
		return ""
	}
	for _, key := range keys {
		for k, v := range r.Format.Tags {
			if strings.EqualFold(k, key) {
				if trimmed := strings.TrimSpace(v); trimmed != "" {
					return trimmed
				}
			}
		}
	}
	return ""
}

// enrichAudioMetadata merges ffprobe facts into the (possibly sidecar-
// seeded) audio payload, creating it when no sidecar existed. Sidecar
// narrators/chapters win (curated); ffprobe fills duration, codec,
// bitrate, and chapters only when the sidecar carried none.
func (s *MediaScanner) enrichAudioMetadata(path string, metadata *MediaMetadata) {
	if metadata == nil {
		return
	}
	payload := metadata.AudioMeta
	if payload == nil {
		payload = &AudioMetadataPayload{}
		metadata.AudioMeta = payload
	}

	report := runFFProbe(path)
	if report == nil {
		fmt.Printf("Audio metadata for %s: sidecar only (ffprobe absent or failed)\n", path)
	} else {
		if payload.DurationSeconds == 0 && report.Format.Duration > 0 {
			payload.DurationSeconds = float64(report.Format.Duration)
		}
		if payload.BitRate == 0 && report.Format.BitRate > 0 {
			payload.BitRate = int64(report.Format.BitRate)
		}
		if payload.CodecProfile == "" && len(report.Streams) > 0 {
			st := report.Streams[0]
			profile := st.CodecName
			if st.Profile != "" && st.Profile != "unknown" {
				profile += " / " + st.Profile
			}
			payload.CodecProfile = profile
		}
		if len(payload.Chapters) == 0 {
			for _, ch := range report.Chapters {
				payload.Chapters = append(payload.Chapters, AudioChapter{
					Index: ch.ID,
					Title: ch.Tags.Title,
					Start: float64(ch.StartTime),
					End:   float64(ch.EndTime),
				})
			}
		}
	}

	// The payload's ASIN mirrors the item column for the resolver; keep
	// them in sync from whichever source set it.
	if payload.ASIN == "" {
		payload.ASIN = metadata.ASIN
	}

	// Promote the editorial facts (A2a columns) when the sidecar's audio
	// payload carries them and the common-field parse left them empty.
	if len(metadata.Narrators) == 0 && len(payload.Narrators) > 0 {
		metadata.Narrators = payload.Narrators
	}
	if payload.Abridged != nil {
		metadata.Abridged = *payload.Abridged
	}

	// Tag fallbacks run LAST in the single-file chain (sidecars → folder
	// structure handled by the caller → tags → filename): they only fill
	// fields the earlier sources left empty.
	applyAudioTagFallbacks(metadata, report)

	// CUE sheets are the last chapter source: sidecar chapters and
	// embedded container chapters (m4b) outrank them.
	if len(payload.Chapters) == 0 {
		if cueChapters := readCueChapters(path); len(cueChapters) > 0 {
			payload.Chapters = cueChapters
			if payload.DurationSeconds == 0 {
				if last := cueChapters[len(cueChapters)-1]; last.End > 0 {
					payload.DurationSeconds = last.End
				}
			}
		}
	}
}

// parseSidecarAudioFields extracts the audio-only fields from a
// Libation/Audiobookshelf metadata.json into the payload (narrators,
// abridged and the curated chapter list).
func parseSidecarAudioFields(path string, data []byte) *AudioMetadataPayload {
	var sidecar struct {
		Narrators []string `json:"narrators"`
		Abridged  *bool    `json:"abridged"`
		ASIN      *string  `json:"asin"`
		Chapters  []struct {
			Start float64 `json:"start"`
			End   float64 `json:"end"`
			Title string  `json:"title"`
			ID    int     `json:"id"`
		} `json:"chapters"`
	}
	if err := json.Unmarshal(data, &sidecar); err != nil {
		return nil
	}
	if len(sidecar.Narrators) == 0 && len(sidecar.Chapters) == 0 && sidecar.ASIN == nil && sidecar.Abridged == nil {
		return nil
	}
	payload := &AudioMetadataPayload{
		Narrators: sidecar.Narrators,
		Abridged:  sidecar.Abridged,
	}
	if sidecar.ASIN != nil {
		payload.ASIN = strings.TrimSpace(*sidecar.ASIN)
	}
	for i, ch := range sidecar.Chapters {
		idx := ch.ID
		if idx == 0 {
			idx = i
		}
		payload.Chapters = append(payload.Chapters, AudioChapter{
			Index: idx,
			Title: strings.TrimSpace(ch.Title),
			Start: ch.Start,
			End:   ch.End,
		})
	}
	return payload
}

// readSidecarAudio is the sidecar hook used by the ABS metadata.json
// path: same file the common-field parser already read, audio fields only.
func readSidecarAudio(path string) *AudioMetadataPayload {
	jsonPath := filepath.Join(filepath.Dir(path), "metadata.json")
	data, err := os.ReadFile(jsonPath)
	if err != nil {
		return nil
	}
	return parseSidecarAudioFields(path, data)
}

// marshalAudioMetadata serializes the payload for the DB column; nil
// payload → nil bytes (NULL column).
func marshalAudioMetadata(payload *AudioMetadataPayload) []byte {
	if payload == nil {
		return nil
	}
	out, err := json.Marshal(payload)
	if err != nil {
		return nil
	}
	return out
}

// applyAudioTagFallbacks fills EMPTY media metadata from the file's own
// tags — the last rung of the ingestion precedence chain (curated
// sidecars → folder structure → embedded tags → filename). Field map:
//
//	album / album_artist / artist        → title / author
//	composer                             → narrators (Audible's own
//	  convention: the narrator lives in the composer tag)
//	grouping                             → series
//	----:com.apple.iTunes:SERIES[-PART]  → series + index (Libation
//	  preserves these Audible freeform atoms)
//	----:com.apple.iTunes:SUBTITLE       → joined into the title
//	  ("Title: Subtitle"), mirroring the ABS sidecar path
//	----:com.apple.iTunes:ASIN / ABRIDGED → asin / abridged flag
//	date → publish date; genre → genre
//
// Abridged is the one field where an explicit sidecar false must not be
// overridden by a tag — the payload pointer marks sidecar presence.
func applyAudioTagFallbacks(metadata *MediaMetadata, report *ffprobeReport) {
	if metadata == nil || report == nil {
		return
	}

	if metadata.Title == "" {
		if album := report.tag("album"); album != "" {
			metadata.Title = album
		}
	}
	// Subtitle joins the title Calibre-style, mirroring the ABS sidecar
	// path — there is no separate subtitle column. Skip when the title
	// already contains it (tools sometimes pre-join).
	if subtitle := report.tag("----:com.apple.itunes:subtitle", "subtitle"); subtitle != "" && metadata.Title != "" &&
		!strings.Contains(strings.ToLower(metadata.Title), strings.ToLower(subtitle)) {
		metadata.Title = metadata.Title + ": " + subtitle
	}
	if metadata.Author == "" {
		if artist := report.tag("album_artist"); artist != "" {
			metadata.Author = artist
		} else if artist := report.tag("artist"); artist != "" {
			metadata.Author = artist
		}
	}
	if len(metadata.Narrators) == 0 {
		// Kept as ONE narrator string: composer values have no reliable
		// multi-narrator delimiter, and splitting "Vance, Simon" would
		// manufacture two fake people. Admins can edit the column.
		if composer := report.tag("composer"); composer != "" {
			metadata.Narrators = []string{composer}
			if metadata.AudioMeta != nil && len(metadata.AudioMeta.Narrators) == 0 {
				metadata.AudioMeta.Narrators = []string{composer}
			}
		}
	}
	if metadata.Series == "" {
		if series := report.tag("grouping", "----:com.apple.itunes:series"); series != "" {
			metadata.Series = series
			if part := report.tag("----:com.apple.itunes:series-part"); part != "" {
				if idx, err := strconv.ParseFloat(strings.TrimSpace(part), 64); err == nil {
					metadata.SeriesNumber = idx
				}
			}
		}
	}
	if metadata.ASIN == "" {
		if asin := report.tag("----:com.apple.itunes:asin", "asin"); asin != "" {
			metadata.ASIN = asin
			if metadata.AudioMeta != nil && metadata.AudioMeta.ASIN == "" {
				metadata.AudioMeta.ASIN = asin
			}
		}
	}
	if metadata.AudioMeta == nil || metadata.AudioMeta.Abridged == nil {
		if !metadata.Abridged {
			switch strings.ToLower(report.tag("----:com.apple.itunes:abridged")) {
			case "1", "true", "yes":
				metadata.Abridged = true
				if metadata.AudioMeta != nil {
					abridged := true
					metadata.AudioMeta.Abridged = &abridged
				}
			}
		}
	}
	if metadata.PublishDate.IsZero() {
		if date := report.tag("date"); date != "" {
			for _, layout := range []string{"2006-01-02", "2006-01", "2006"} {
				if t, err := time.Parse(layout, strings.TrimSpace(date)); err == nil {
					metadata.PublishDate = t
					break
				}
			}
		}
	}
	if metadata.Genre == "" {
		metadata.Genre = report.tag("genre")
	}
}

// audioDurationLabel renders the duration for logs/detail surfaces.
func audioDurationLabel(seconds float64) string {
	if seconds <= 0 {
		return "—"
	}
	d := time.Duration(seconds) * time.Second
	h := int(d.Hours())
	m := int(d.Minutes()) % 60
	if h > 0 {
		return fmt.Sprintf("%dh %dm", h, m)
	}
	return fmt.Sprintf("%dm", m)
}

// parseJSONInt reads a RawMessage that may hold a JSON number or a
// number-string; 0 for anything else. Used for sidecar fields whose
// type differs across producing tools (Libation vs Calibre/ABS).
func parseJSONInt(raw json.RawMessage) int {
	if len(raw) == 0 {
		return 0
	}
	trimmed := strings.TrimSpace(string(raw))
	if v, err := strconv.Atoi(strings.Trim(trimmed, "\"")); err == nil {
		return v
	}
	return 0
}