/*
 * Copyright (c) Double Symmetry GmbH
 * Commercial use requires a license. See https://rntp.dev/pricing
 */

package com.doublesymmetry.trackplayer.models

import androidx.media3.common.MediaMetadata
import androidx.media3.common.Metadata
import androidx.media3.common.util.UnstableApi
import androidx.media3.extractor.metadata.icy.IcyInfo

/**
 * Pure helper that turns a media3 [Metadata] bundle (delivered via
 * [androidx.media3.common.Player.Listener.onMetadata]) into a
 * [MetadataReceivedEvent] suitable for emitting to JS.
 *
 * Lives outside [com.doublesymmetry.trackplayer.TrackPlayerModule] so it can be
 * unit-tested without spinning up a player.
 */
@UnstableApi
internal object StreamMetadataExtractor {

  /**
   * Returns a [MetadataReceivedEvent] aggregated from all entries in [metadata],
   * or `null` if none of the entries contributed any user-visible fields.
   *
   * Behavior:
   * - Each entry's [Metadata.Entry.populateMediaMetadata] is invoked. media3's
   *   built-in handlers cover ID3 ([androidx.media3.extractor.metadata.id3.TextInformationFrame]
   *   `TIT2`/`TPE1`/`TALB`/`TCON`/…), ICY ([IcyInfo] → title), Vorbis
   *   comments, MP4 MDTA, and more.
   * - ICY's `StreamTitle` is conventionally formatted as `"Artist - Title"`
   *   (Shoutcast/Icecast practice, not a spec). When [populateMediaMetadata]
   *   leaves `artist` unset, we attempt to split on the first ` - ` to recover
   *   artist + title separately. Same heuristic V4 and the iOS engine use.
   * - [IcyInfo.url] is mapped into `artworkUri` to mirror the iOS behavior of
   *   surfacing ICY `StreamUrl` (which some stations use to ship the current
   *   track's artwork).
   */
  fun extract(metadata: Metadata): MetadataReceivedEvent? {
    val builder = MediaMetadata.Builder()
    var icyUrl: String? = null
    for (i in 0 until metadata.length()) {
      val entry = metadata.get(i)
      entry.populateMediaMetadata(builder)
      if (entry is IcyInfo) {
        entry.url?.takeIf { it.isNotEmpty() }?.let { icyUrl = it }
      }
    }
    val built = builder.build()
    var title = built.title?.toString()
    var artist = built.artist?.toString()

    if (artist == null && title != null) {
      val (parsedTitle, parsedArtist) = parseStreamTitle(title!!)
      title = parsedTitle
      artist = parsedArtist
    }

    val albumTitle = built.albumTitle?.toString()
    val artworkUri = built.artworkUri?.toString() ?: icyUrl
    val genre = built.genre?.toString()

    if (title == null && artist == null && albumTitle == null && artworkUri == null && genre == null) {
      return null
    }
    return MetadataReceivedEvent(
      title = title,
      artist = artist,
      albumTitle = albumTitle,
      artworkUri = artworkUri,
      genre = genre,
    )
  }

  /**
   * Splits an ICY `StreamTitle` payload into `(title, artist)` using the
   * de-facto Shoutcast convention `"Artist - Title"`.
   *
   * Returns `(trimmed, null)` when no ` - ` separator is present (e.g. talk
   * radio with a single show title), and `(null, null)` for blank input.
   * Only the first occurrence of ` - ` is treated as the separator, so a
   * title containing additional `" - "` substrings (e.g. `"Artist - Song - Remix"`)
   * yields `artist="Artist"`, `title="Song - Remix"`.
   */
  fun parseStreamTitle(raw: String): Pair<String?, String?> {
    val trimmed = raw.trim()
    if (trimmed.isEmpty()) return null to null
    val sep = trimmed.indexOf(" - ")
    if (sep >= 0) {
      val artist = trimmed.substring(0, sep).trim()
      val title = trimmed.substring(sep + 3).trim()
      return title.ifEmpty { null } to artist.ifEmpty { null }
    }
    return trimmed to null
  }
}