Try to be smart about TTML sides

Author: nift4

app/src/main/java/org/akanework/gramophone/logic/utils/Flags.kt

@@ -2,6 +2,7 @@ package org.akanework.gramophone.logic.utils
 
 object Flags {
     const val TEST_RG_OFFLOAD = false // test only
+    const val TTML_AGENT_SMART_SIDES = true
 
     // Before turning it on in prod we need i18n.
     const val FORMAT_INFO_DIALOG = true // TODO(ASAP)

app/src/main/java/org/akanework/gramophone/logic/utils/SemanticLyrics.kt

@@ -19,6 +19,7 @@ import org.akanework.gramophone.logic.utils.SemanticLyrics.UnsyncedLyrics
 import org.akanework.gramophone.logic.utils.SemanticLyrics.Word
 import org.xmlpull.v1.XmlPullParser
 import org.xmlpull.v1.XmlPullParserException
+import uk.akane.libphonograph.putIfAbsentSupport
 import java.io.StringReader
 import java.nio.charset.Charset
 import java.util.concurrent.atomic.AtomicReference
@@ -1521,6 +1522,19 @@ fun parseTtml(audioMimeType: String?, lyricText: String): SemanticLyrics? {
         } while (cur != -1)
         out
     }
+    // start left if person is first, and right if sample is first.
+    val agentToSide = hashMapOf<String?, Boolean /* true = right */>()
+    if (Flags.TTML_AGENT_SMART_SIDES) {
+        var agent: String? = null
+        var side = state.paragraphs.firstOrNull()?.let { peopleToType[it.agent] == "other" } == true
+        state.paragraphs.forEach {
+            if (agent != it.agent) {
+                agent = it.agent
+                agentToSide.putIfAbsentSupport(it.agent, side)
+                side = agentToSide[it.agent]!!
+            }
+        }
+    }
     val hasAtLeastTwoPeople = people["person"]?.let { it.size > 1 } == true
     if (paragraphs.find { it.time != null } == null) {
         return UnsyncedLyrics(paragraphs.map {
@@ -1530,10 +1544,10 @@ fun parseTtml(audioMimeType: String?, lyricText: String): SemanticLyrics? {
             val isOther = peopleToType[it.agent] == "other"
             // first person goes left, second right, third left, fourth right, and so on.
             // and the same goes for "other" except that we start on the right here.
-            val isVoice2 =
-                it.agent != null && (people[peopleToType[it.agent]] ?: throw NullPointerException(
+            val isVoice2 = agentToSide[it.agent] ?:
+                (it.agent != null && (people[peopleToType[it.agent]] ?: throw NullPointerException(
                     "expected to find ${it.agent} (${peopleToType[it.agent]}) in $people"
-                )).indexOf(it.agent) % 2 == (if (isOther) 0 else 1)
+                )).indexOf(it.agent) % 2 == (if (isOther) 0 else 1))
             val speaker = when {
                 isGroup && isBg -> SpeakerEntity.GroupBackground
                 isGroup -> SpeakerEntity.Group