music: add m3u exporting backend

Add the backend for exporting playlists to m3u files.

app/src/main/java/org/oxycblt/auxio/music/MusicViewModel.kt

@@ -28,7 +28,7 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
 import org.oxycblt.auxio.list.ListSettings
-import org.oxycblt.auxio.music.external.PlaylistImporter
+import org.oxycblt.auxio.music.external.ExternalPlaylistManager
 import org.oxycblt.auxio.util.Event
 import org.oxycblt.auxio.util.MutableEvent
 import org.oxycblt.auxio.util.logD
@@ -44,7 +44,7 @@ class MusicViewModel
 constructor(
     private val listSettings: ListSettings,
     private val musicRepository: MusicRepository,
-    private val playlistImporter: PlaylistImporter
+    private val externalPlaylistManager: ExternalPlaylistManager
 ) : ViewModel(), MusicRepository.UpdateListener, MusicRepository.IndexingListener {
 
     private val _indexingState = MutableStateFlow<IndexingState?>(null)
@@ -128,11 +128,11 @@ constructor(
      * Import a playlist from a file [Uri]. Errors pushed to [importError].
      *
      * @param uri The [Uri] of the file to import.
-     * @see PlaylistImporter
+     * @see ExternalPlaylistManager
      */
     fun importPlaylist(uri: Uri) =
         viewModelScope.launch(Dispatchers.IO) {
-            val importedPlaylist = playlistImporter.import(uri)
+            val importedPlaylist = externalPlaylistManager.import(uri)
             if (importedPlaylist == null) {
                 _importError.put(Unit)
                 return@launch

app/src/main/java/org/oxycblt/auxio/music/external/ExternalModule.kt

@@ -26,7 +26,7 @@ import dagger.hilt.components.SingletonComponent
 @Module
 @InstallIn(SingletonComponent::class)
 interface ExternalModule {
-    @Binds fun playlistImporter(playlistImporter: PlaylistImporterImpl): PlaylistImporter
+    @Binds fun playlistImporter(playlistImporter: ExternalPlaylistManagerImpl): ExternalPlaylistManager
 
     @Binds fun m3u(m3u: M3UImpl): M3U
 }

app/src/main/java/org/oxycblt/auxio/music/external/M3U.kt

@@ -18,15 +18,21 @@
  
 package org.oxycblt.auxio.music.external
 
+import android.content.Context
+import dagger.hilt.android.qualifiers.ApplicationContext
+import org.oxycblt.auxio.music.Playlist
 import java.io.BufferedReader
+import java.io.File
 import java.io.InputStream
 import java.io.InputStreamReader
 import javax.inject.Inject
 import org.oxycblt.auxio.music.fs.Components
 import org.oxycblt.auxio.music.fs.Path
 import org.oxycblt.auxio.music.metadata.correctWhitespace
-import org.oxycblt.auxio.util.logW
+import org.oxycblt.auxio.music.resolveNames
-import java.io.File
+import org.oxycblt.auxio.util.logE
+import java.io.BufferedWriter
+import java.io.OutputStream
 
 /**
  * Minimal M3U file format implementation.
@@ -44,9 +50,18 @@ interface M3U {
      * @return An [ImportedPlaylist] containing the paths to the files listed in the M3U file,
      */
     fun read(stream: InputStream, workingDirectory: Path): ImportedPlaylist?
+
+    /**
+     * Writes the given [playlist] to the given [outputStream] in the M3U format,.
+     * @param playlist The playlist to write.
+     * @param outputStream The stream to write the M3U file to.
+     * @param workingDirectory The directory that the M3U file is contained in. This is used to
+     * create relative paths to where the M3U file is assumed to be stored.
+     */
+    fun write(playlist: Playlist, outputStream: OutputStream, workingDirectory: Path)
 }
 
-class M3UImpl @Inject constructor() : M3U {
+class M3UImpl @Inject constructor(@ApplicationContext private val context: Context) : M3U {
     override fun read(stream: InputStream, workingDirectory: Path): ImportedPlaylist? {
         val reader = BufferedReader(InputStreamReader(stream))
         val paths = mutableListOf<Path>()
@@ -81,7 +96,7 @@ class M3UImpl @Inject constructor() : M3U {
             }
 
             if (path == null) {
-                logW("Expected a path, instead got an EOF")
+                logE("Expected a path, instead got an EOF")
                 break@consumeFile
             }
 
@@ -89,15 +104,17 @@ class M3UImpl @Inject constructor() : M3U {
             // signified by either the typical ./ or the absence of any separator at all.
             // so we may need to resolve it into an absolute path before moving ahead.
             val components = Components.parse(path)
-            val absoluteComponents = if (path.startsWith(File.separatorChar)) {
+            val absoluteComponents =
+                if (path.startsWith(File.separatorChar)) {
                     // Already an absolute path, do nothing. Theres still some relative-ness here,
-                // as we assume that the path is still in the same volume as the working directory.
+                    // as we assume that the path is still in the same volume as the working
+                    // directory.
                     // Unsure if any program goes as far as writing out the full unobfuscated
                     // absolute path.
                     components
                 } else {
                     // Relative path, resolve it
-                resolveRelativePath(components, workingDirectory.components)
+                    components.absoluteTo(workingDirectory.components)
                 }
 
             paths.add(Path(workingDirectory.volume, absoluteComponents))
@@ -111,22 +128,62 @@ class M3UImpl @Inject constructor() : M3U {
         }
     }
 
-    private fun resolveRelativePath(
+    override fun write(
-        relative: Components,
+        playlist: Playlist,
+        outputStream: OutputStream,
+        workingDirectory: Path
+    ) {
+        val writer = outputStream.bufferedWriter()
+        // Try to be as compliant to the spec as possible while also cramming it full of extensions
+        // I imagine other players will use.
+        writer.writeLine("#EXTM3U")
+        writer.writeLine("#EXTENC:UTF-8")
+        writer.writeLine("#PLAYLIST:${playlist.name}")
+        for (song in playlist.songs) {
+            val relativePath = song.path.components.relativeTo(workingDirectory.components)
+            writer.writeLine("#EXTINF:${song.durationMs},${song.name.resolve(context)}")
+            writer.writeLine("#EXTALB:${song.album.name.resolve(context)}")
+            writer.writeLine("#EXTART:${song.artists.resolveNames(context)}")
+            writer.writeLine("#EXTGEN:${song.genres.resolveNames(context)}")
+            writer.writeLine(relativePath.toString())
+        }
+    }
+
+    private fun BufferedWriter.writeLine(line: String) {
+        write(line)
+        newLine()
+    }
+
+    private fun Components.absoluteTo(
         workingDirectory: Components
     ): Components {
-        var components = workingDirectory
+        var absoluteComponents = workingDirectory
-        for (component in relative.components) {
+        for (component in components) {
             when (component) {
                 // Parent specifier, go "back" one directory (in practice cleave off the last
                 // component)
-                ".." -> components = components.parent()
+                ".." -> absoluteComponents = absoluteComponents.parent()
                 // Current directory, the components are already there.
                 "." -> {}
                 // New directory, add it
-                else -> components = components.child(component)
+                else -> absoluteComponents = absoluteComponents.child(component)
             }
         }
-        return components
+        return absoluteComponents
     }
+
+    private fun Components.relativeTo(
+        workingDirectory: Components
+    ): Components {
+        var relativeComponents = Components.parse(".")
+        var commonIndex = 0
+        while (commonIndex < components.size &&
+            commonIndex < workingDirectory.components.size &&
+            components[commonIndex] == workingDirectory.components[commonIndex]) {
+            ++commonIndex
+            relativeComponents = relativeComponents.child("..")
+        }
+        return relativeComponents.concat(depth(commonIndex))
+    }
+
 }

app/src/main/java/org/oxycblt/auxio/music/external/PlaylistImporter.kt

@@ -1,63 +0,0 @@
-/*
- * Copyright (c) 2023 Auxio Project
- * PlaylistImporter.kt is part of Auxio.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.music.external
-
-import android.content.Context
-import android.net.Uri
-import dagger.hilt.android.qualifiers.ApplicationContext
-import javax.inject.Inject
-import org.oxycblt.auxio.music.fs.DocumentPathFactory
-import org.oxycblt.auxio.music.fs.Path
-import org.oxycblt.auxio.music.fs.contentResolverSafe
-
-/**
- * Generic playlist file importing abstraction.
- *
- * @see ImportedPlaylist
- * @see M3U
- * @author Alexander Capehart (OxygenCobalt)
- */
-interface PlaylistImporter {
-    suspend fun import(uri: Uri): ImportedPlaylist?
-}
-
-/**
- * A playlist that has been imported.
- *
- * @property name The name of the playlist. May be null if not provided.
- * @property paths The paths of the files in the playlist.
- * @see PlaylistImporter
- * @see M3U
- */
-data class ImportedPlaylist(val name: String?, val paths: List<Path>)
-
-class PlaylistImporterImpl
-@Inject
-constructor(
-    @ApplicationContext private val context: Context,
-    private val documentPathFactory: DocumentPathFactory,
-    private val m3u: M3U
-) : PlaylistImporter {
-    override suspend fun import(uri: Uri): ImportedPlaylist? {
-        val filePath = documentPathFactory.unpackDocumentUri(uri) ?: return null
-        return context.contentResolverSafe.openInputStream(uri)?.use {
-            return m3u.read(it, filePath.directory)
-        }
-    }
-}

app/src/main/java/org/oxycblt/auxio/music/fs/Fs.kt

@@ -26,7 +26,6 @@ import android.webkit.MimeTypeMap
 import java.io.File
 import javax.inject.Inject
 import org.oxycblt.auxio.R
-import org.oxycblt.auxio.util.logD
 
 /**
  * An abstraction of an android file system path, including the volume and relative path.
@@ -117,11 +116,26 @@ value class Components private constructor(val components: List<String>) {
      */
     fun child(name: String) =
         if (name.isNotEmpty()) {
-            Components(components + name.trimSlashes()).also { logD(it.components) }
+            Components(components + name.trimSlashes())
         } else {
             this
         }
 
+    /**
+     * Removes the first [n] elements of the path, effectively resulting in a path that is n
+     * levels deep.
+     * @param n The number of elements to remove.
+     * @return The new [Components] instance.
+     */
+    fun depth(n: Int) = Components(components.drop(n))
+
+    /**
+     * Concatenates this [Components] instance with another.
+     * @param other The [Components] instance to concatenate with.
+     * @return The new [Components] instance.
+     */
+    fun concat(other: Components) = Components(components + other.components)
+
     companion object {
         /**
          * Parses a path string into a [Components] instance by the system path separator.