MediaCollector.kt

70 lines · 3.0 KB

Changed in: 0.5.0

1	package dev.stave.upnp
2
3	import dev.stave.domain.model.DidlItem
4	import javax.inject.Inject
5	import javax.inject.Singleton
6
7	/**
8	* Recursively walks a UPnP ContentDirectory container and flattens every descendant [DidlItem.Track]
9	* into a single list. Needed because "Queue this artist" or "Play all Jazz" can't map to a single
10	* Browse() call — the tracks live two or three levels down (Artist → Albums → Tracks, Genre →
11	* Artists → Albums → Tracks).
12	*
13	* Intentionally sequential: parallel browsing would saturate a single-threaded MinimServer install
14	* on an older NAS and interleave output in ways that corrupt track order within an album. Order
15	* matters — users expect an album's tracks to arrive in disc/track order, not in whatever order
16	* HTTP responses race back.
17	*/
18	@Singleton
19	class MediaCollector @Inject constructor(
20	private val cd: ContentDirectoryClient,
21	) {
22
23	/**
24	* Gather every playable track under [containerId], walking up to [maxDepth] levels deep.
25	* Depth is bounded because some pathological server configurations (or self-referential
26	* playlists) can loop, and a user triggering "Play genre" should never hang the app.
27	*
28	* Returns an empty list on any Browse failure — partial results would be confusing ("why
29	* did it play 40 of 60 tracks?") so we prefer all-or-nothing per top-level call.
30	*/
31	suspend fun collectTracks(
32	udn: String,
33	containerId: String,
34	maxDepth: Int = 8,
35	): List<DidlItem.Track> {
36	val out = mutableListOf<DidlItem.Track>()
37	val ok = collect(udn, containerId, depth = 0, maxDepth, out)
38	return if (ok) out else emptyList()
39	}
40
41	private suspend fun collect(
42	udn: String,
43	containerId: String,
44	depth: Int,
45	maxDepth: Int,
46	out: MutableList<DidlItem.Track>,
47	): Boolean {
48	if (depth > maxDepth) return true // treat depth cap as a soft stop, not a failure
49	return when (val result = cd.browse(udn, containerId)) {
50	is BrowseResult.Success -> {
51	for (item in result.items) {
52	when (item) {
53	is DidlItem.Track -> out += item
54	is DidlItem.Container -> {
55	// MinimServer's synthetic entries (">> Show All", "[folder view]",
56	// "[untagged]") expose the same tracks that are already reachable
57	// through the tagged hierarchy. Following them would double- or
58	// triple-count tracks in the collected list.
59	if (item.isSynthetic) continue
60	val childOk = collect(udn, item.id, depth + 1, maxDepth, out)
61	if (!childOk) return false
62	}
63	}
64	}
65	true
66	}
67	is BrowseResult.Failure -> false
68	}
69	}
70	}