new: add subtitle translations

data/subtitle/src/commonMain/kotlin/fr/ajaury/gwenedeg/subtitle/data/LrcSubtitleRepository.kt

@@ -12,14 +12,30 @@ internal class LrcSubtitleRepository(
     private val dispatcherProvider: DispatcherProvider,
     private val logger: Logger,
 ) : SubtitleRepository {
-    override suspend fun getSubtitle(content: String): Subtitle =
+    override suspend fun getSubtitle(
+        content: String,
+        translationContent: String?,
+    ): Subtitle =
         withContext(dispatcherProvider.default) {
             try {
-                parser.parse(content = content)
+                val subtitle = parser.parse(content = content)
+                val translation = translationContent?.let { parser.parse(content = it) }
+                subtitle.mergeTranslation(translation)
             } catch (exception: Exception) {
                 val message = "Failed to load subtitle: $content"
                 logger.error(message = message, throwable = exception)
                 throw CantGetSubtitleException(message)
             }
         }
+
+    /** Attaches each [translation] line's text to the matching original line, paired by timestamp. */
+    private fun Subtitle.mergeTranslation(translation: Subtitle?): Subtitle {
+        if (translation == null) return this
+        val translationByStart = translation.lines.associate { it.startMs to it.text }
+        return Subtitle(
+            lines = lines.map { line ->
+                line.copy(translation = translationByStart[line.startMs])
+            },
+        )
+    }
 }

data/subtitle/src/commonMain/kotlin/fr/ajaury/gwenedeg/subtitle/domain/SubtitleLine.kt

@@ -1,7 +1,11 @@
 package fr.ajaury.gwenedeg.subtitle.domain
 
-/** A single timed subtitle cue: [text] becomes active at [startMs]. */
+/**
+ * A single timed subtitle cue: [text] becomes active at [startMs]. [translation] is the optional
+ * translation of [text] in the user's language (e.g. French), shown alongside the original.
+ */
 data class SubtitleLine(
     val startMs: Long,
     val text: String,
+    val translation: String? = null,
 )

data/subtitle/src/commonMain/kotlin/fr/ajaury/gwenedeg/subtitle/domain/SubtitleRepository.kt

@@ -1,5 +1,12 @@
 package fr.ajaury.gwenedeg.subtitle.domain
 
 interface SubtitleRepository {
-    suspend fun getSubtitle(content: String): Subtitle
+    /**
+     * Parses the subtitle [content]. When [translationContent] is provided, each line is matched to
+     * its translation by timestamp.
+     */
+    suspend fun getSubtitle(
+        content: String,
+        translationContent: String? = null,
+    ): Subtitle
 }