Revamps the album cache service to make it comply with SonarLint. Also adds and renames some models.

src/main/kotlin/net/halfbinary/prettyplayerapi/dispatcher/IODispatcher.kt

@@ -0,0 +1,10 @@
+package net.halfbinary.prettyplayerapi.dispatcher
+
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import org.springframework.context.annotation.Bean
+
+@Bean
+fun getIODispatcher(): CoroutineDispatcher {
+    return Dispatchers.IO
+}

src/main/kotlin/net/halfbinary/prettyplayerapi/model/AlbumInfo.kt

@@ -1,3 +1,7 @@
 package net.halfbinary.prettyplayerapi.model
 
-data class AlbumInfo(val albumTitle: String, val albumFolder: String, val hash: String)
+data class AlbumInfo(
+    val albumTitle: String,
+    val albumArtist: String,
+    val trackList: List<AlbumTrackInfo>
+)

src/main/kotlin/net/halfbinary/prettyplayerapi/model/AlbumTrackInfo.kt

@@ -0,0 +1,7 @@
+package net.halfbinary.prettyplayerapi.model
+
+data class AlbumTrackInfo(
+    val trackNumber: Int,
+    val trackArtist: String,
+    val trackTitle: String
+)

src/main/kotlin/net/halfbinary/prettyplayerapi/service/AlbumCacheService.kt

@@ -2,10 +2,9 @@ package net.halfbinary.prettyplayerapi.service
 
 import com.mpatric.mp3agic.Mp3File
 import io.github.oshai.kotlinlogging.KotlinLogging
-import kotlinx.coroutines.coroutineScope
-import kotlinx.coroutines.launch
+import kotlinx.coroutines.*
 import net.halfbinary.prettyplayerapi.exception.EnvironmentVariableNotFoundException
-import net.halfbinary.prettyplayerapi.model.AlbumInfo
+import net.halfbinary.prettyplayerapi.model.AlbumMetadata
 import net.halfbinary.prettyplayerapi.repository.AlbumRepository
 import org.springframework.stereotype.Service
 import java.awt.Image
@@ -18,7 +17,8 @@ import kotlin.io.path.name
 private val logger = KotlinLogging.logger {}
 
 @Service
-class AlbumCacheService(private val albumRepository: AlbumRepository) {
+class AlbumCacheService(private val albumRepository: AlbumRepository,
+                        private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO) {
 
 
     suspend fun doAlbumCache() {
@@ -32,7 +32,7 @@ class AlbumCacheService(private val albumRepository: AlbumRepository) {
         }
     }
 
-    fun getAlbumCache(): LinkedHashMap<String, AlbumInfo> {
+    fun getAlbumCache(): LinkedHashMap<String, AlbumMetadata> {
         return albumRepository.albumCache
     }
 
@@ -53,7 +53,7 @@ class AlbumCacheService(private val albumRepository: AlbumRepository) {
                 coroutineScope {
                     launch {getAndWriteAlbumImageFile(it.first, folderHash, folder, refresh)}
                 }
-                Pair(folderHash, AlbumInfo(it.second.id3v2Tag.album, it.first.parent, folderHash))
+                Pair(folderHash, AlbumMetadata(it.second.id3v2Tag.album, it.first.parent, folderHash))
             }
 
         albumRepository.albumCache = convertAlbumListToMapForCache(list)
@@ -79,7 +79,7 @@ class AlbumCacheService(private val albumRepository: AlbumRepository) {
         return compareBy({ it.second.id3v2Tag.albumArtist }, {it.second.id3v2Tag.album}, {it.second.id3v2Tag.year})
     }
 
-    fun convertAlbumListToMapForCache(list: List<Pair<String, AlbumInfo>>): java.util.LinkedHashMap<String, AlbumInfo> {
+    fun convertAlbumListToMapForCache(list: List<Pair<String, AlbumMetadata>>): java.util.LinkedHashMap<String, AlbumMetadata> {
         val array = list.toTypedArray()
         return linkedMapOf(*array)
     }
@@ -90,20 +90,26 @@ class AlbumCacheService(private val albumRepository: AlbumRepository) {
         if(refresh || !hashedFile.exists()) {
             logger.debug { "No image for $folder, making one..." }
             val imageByteStream = Mp3File(file).id3v2Tag.albumImage.inputStream()
-            val bufferedImage = ImageIO.read(imageByteStream)
+            val bufferedImage = withContext(ioDispatcher) {
+                ImageIO.read(imageByteStream)
+            }
             val scaledImage = bufferedImage.getScaledInstance(300, 300, Image.SCALE_DEFAULT)
             val outputImage = BufferedImage(300, 300, BufferedImage.TYPE_INT_RGB)
             outputImage.graphics.drawImage(scaledImage, 0, 0, null)
+            withContext(ioDispatcher) {
                 ImageIO.write(outputImage, "jpg", hashedFile)
+            }
             logger.trace { "Wrote new image file for $folder with hash $folderHash" }
         }
     }
 
     companion object {
-        val ALBUM_ROOT_DIR = System.getenv("ALBUM_ROOT_DIR")
-            ?: throw EnvironmentVariableNotFoundException("Environment variable `ALBUM_ROOT_DIR` does not exist, please specify.") //"q:\\CDs"
-        val ALBUM_ART_ROOT_DIR = System.getenv("ALBUM_ART_ROOT_DIR")
-            ?: throw EnvironmentVariableNotFoundException("Environment variable `ALBUM_ART_ROOT_DIR` does not exist, please specify.") //"src/main/resources/images/"
+        private fun getEnv(envName: String): String {
+            return System.getenv(envName)
+                ?: throw EnvironmentVariableNotFoundException(envName)
+        }
+        val ALBUM_ROOT_DIR = getEnv("ALBUM_ROOT_DIR") //"q:\\CDs"
+        val ALBUM_ART_ROOT_DIR = getEnv("ALBUM_ART_ROOT_DIR") //"src/main/resources/images/"
     }
 
 }