♻️ Refactor ResultGridCell.kt for improving readability and nullability

The ResultGridCell.kt class has been updated for better readability and code handling. We are ensuring nullability and consistency by replacing nullable 'List<PVInfo>?' with non-nullable 'List<PVInfo>'. Small functions are broken down for better readability and understanding. The functions related to Music Information (SongTitle, ArtistField, PublishDateField, SongTypeField, and PvField) have been separated out of MusicInfo. This is to ensure the MusicInfo function is not cluttered and to isolate each field's functionality, making the code more modular and manageable.

songfinder-app/src/main/kotlin/mikufan/cx/songfinder/ui/component/main/ResultGridCell.kt

@@ -35,11 +35,13 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
 import mikufan.cx.songfinder.backend.controller.mainpage.ResultCellController
 import mikufan.cx.songfinder.backend.db.entity.PvService
+import mikufan.cx.songfinder.backend.db.entity.SongType
 import mikufan.cx.songfinder.backend.model.PVInfo
 import mikufan.cx.songfinder.backend.model.SongSearchResult
 import mikufan.cx.songfinder.getSpringBean
 import mikufan.cx.songfinder.ui.common.TooltipAreaWithCard
 import mikufan.cx.songfinder.ui.theme.spacing
+import java.time.LocalDateTime
 import java.time.format.DateTimeFormatter
 
 @Composable
@@ -62,7 +64,7 @@ fun LazyGridItemScope.RealResultGridCell(
   callbacks: ResultCellCallbacks,
   modifier: Modifier = Modifier
 ) {
-  val filteredPvs: List<PVInfo>? by produceState<List<PVInfo>?>(null) {
+  val filteredPvs: List<PVInfo> by produceState(listOf()) {
     value = result.pvs.filter {
       it.pvService in listOf(
         PvService.Youtube,
@@ -84,7 +86,7 @@ fun LazyGridItemScope.RealResultGridCell(
 @Composable
 fun LazyThumbnailImage(
   result: SongSearchResult,
-  pvs: List<PVInfo>?
+  pvs: List<PVInfo>
 ) {
   //TODO: use the first ever available PV's thumbnail, if no PVs, use image not found.
   // If exceptions (typically no available PVs), use image failed to load
@@ -100,10 +102,19 @@ fun LazyThumbnailImage(
   )
 }
 
-@OptIn(ExperimentalFoundationApi::class)
 @Composable
-fun MusicInfo(songInfo: SongSearchResult, filteredPvs: List<PVInfo>?) = Column {
+fun MusicInfo(songInfo: SongSearchResult, filteredPvs: List<PVInfo>) = Column {
   val (id, title, type, vocals, producers, publishDate, _) = songInfo
+  SongTitle(id, title)
+  ArtistField(vocals, producers)
+  PublishDateField(publishDate)
+  SongTypeField(type)
+  PvField(filteredPvs)
+}
+
+@OptIn(ExperimentalFoundationApi::class)
+@Composable
+private fun SongTitle(id: Long, title: String) {
   Row(
     horizontalArrangement = Arrangement.spacedBy(MaterialTheme.spacing.spacing, Alignment.CenterHorizontally),
     modifier = Modifier.fillMaxWidth()
@@ -130,7 +141,11 @@ fun MusicInfo(songInfo: SongSearchResult, filteredPvs: List<PVInfo>?) = Column {
       )
     }
   }
+}
 
+@OptIn(ExperimentalFoundationApi::class)
+@Composable
+private fun ArtistField(vocals: List<String>, producers: List<String>) {
   val artistString by produceState("Loading Artists...") {
     value = getArtistString(vocals, producers)
   }
@@ -141,6 +156,11 @@ fun MusicInfo(songInfo: SongSearchResult, filteredPvs: List<PVInfo>?) = Column {
     overflow = TextOverflow.Ellipsis,
     modifier = Modifier.basicMarquee(),
   )
+}
+
+@OptIn(ExperimentalFoundationApi::class)
+@Composable
+private fun PublishDateField(publishDate: LocalDateTime?) {
   val publishDateText by produceState("Loading...") {
     value = publishDate?.format(DateTimeFormatter.ISO_DATE) ?: "Unknown"
   }
@@ -150,24 +170,21 @@ fun MusicInfo(songInfo: SongSearchResult, filteredPvs: List<PVInfo>?) = Column {
     maxLines = 1,
     modifier = Modifier.basicMarquee(),
   )
+}
+
+@OptIn(ExperimentalFoundationApi::class)
+@Composable
+private fun SongTypeField(type: SongType) {
   Text(
     text = "Song Type: $type",
     style = MaterialTheme.typography.bodyMedium,
     maxLines = 1,
     modifier = Modifier.basicMarquee(),
   )
-  if (filteredPvs == null) {
-    Text(
-      text = "Loading PVs...",
-      style = MaterialTheme.typography.bodyMedium,
-    )
-  } else {
-    PvRows(filteredPvs)
-  }
 }
 
 @Composable
-private fun PvRows(pvs: List<PVInfo>) {
+private fun PvField(pvs: List<PVInfo>) {
   val uriHandler = LocalUriHandler.current
   LazyRow(
     horizontalArrangement = Arrangement.spacedBy(MaterialTheme.spacing.spacingSmall),
@@ -212,8 +229,7 @@ private fun PvRows(pvs: List<PVInfo>) {
   }
 }
 
-
-/* --- Utils ---*/
+/* --------- Utils --------- */
 
 data class ResultCellCallbacks(
   val onCardClicked: (SongSearchResult) -> Unit,