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 and (later) folder-as-book
// files both produce {index, title, start, end} entries, so the locator
// {chapter, offset_seconds} and the /chapters endpoint never learn which
// file model produced them.

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"`
}

// 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"`
	Chapters        []AudioChapter `json:"chapters,omitempty"`
}

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

// 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
}()

type ffprobeReport struct {
	Format struct {
		Duration flexFloat `json:"duration"`
		BitRate  flexFloat `json:"bit_rate"`
	} `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
}

// 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
	}
}

// parseSidecarAudioFields extracts the audio-only fields from a
// Libation/Audiobookshelf metadata.json into the payload (narrators and
// the curated chapter list).
func parseSidecarAudioFields(path string, data []byte) *AudioMetadataPayload {
	var sidecar struct {
		Narrators []string `json:"narrators"`
		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 {
		return nil
	}
	payload := &AudioMetadataPayload{
		Narrators: sidecar.Narrators,
	}
	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
}

// 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
}