✨ Add thumbnail fetching functionality to SongFinder

This commit introduces the capability of fetching thumbnails for each song in the SongFinder application. This feature is realized through the addition of a new "FindThumbnailService" and supportive configurations, including a dedicated HTTP client "thumbnail-fetcher". This new functionality allows more detailed results to be presented to the users.

songfinder-app/src/main/kotlin/mikufan/cx/songfinder/backend/config/KtorClientConfig.kt

@@ -0,0 +1,30 @@
+package mikufan.cx.songfinder.backend.config
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import io.ktor.client.*
+import io.ktor.client.engine.java.*
+import io.ktor.client.plugins.*
+import io.ktor.client.plugins.contentnegotiation.*
+import io.ktor.http.*
+import io.ktor.serialization.jackson.*
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+
+@Configuration(proxyBeanMethods = false)
+class KtorClientConfig {
+
+  @Bean("thumbnail-fetcher")
+  fun thumbnailFetcher(mapper: ObjectMapper) = HttpClient(Java) {
+    install(ContentNegotiation) {
+      // use spring jackson mapper
+      register(ContentType.Application.Json, JacksonConverter(mapper))
+    }
+    install(UserAgent) {
+      agent = "Song Finder by VocaDB @ https://github.com/CXwudi/song-finder-vocadb"
+    }
+//    BrowserUserAgent()
+
+    followRedirects = true
+
+  }
+}

songfinder-app/src/main/kotlin/mikufan/cx/songfinder/backend/controller/mainpage/ResultCellController.kt

@@ -1,7 +1,10 @@
 package mikufan.cx.songfinder.backend.controller.mainpage
 
 import mikufan.cx.inlinelogging.KInlineLogging
+import mikufan.cx.songfinder.backend.model.PVInfo
 import mikufan.cx.songfinder.backend.model.SongSearchResult
+import mikufan.cx.songfinder.backend.model.ThumbnailInfo
+import mikufan.cx.songfinder.backend.service.FindThumbnailService
 import mikufan.cx.songfinder.backend.service.InputFileLineReader
 import mikufan.cx.songfinder.backend.service.OutputCsvLineWriter
 import mikufan.cx.songfinder.backend.statemodel.*
@@ -16,6 +19,7 @@ class ResultCellController(
   private val searchOptionsStateModel: SearchOptionsStateModel,
   private val searchResultStateModel: SearchResultStateModel,
   private val songSearchIntermediateController: SongSearchIntermediateController,
+  private val findThumbnailService: FindThumbnailService,
 ) {
 
   suspend fun handleRecord(chosenSong: SongSearchResult) {
@@ -34,6 +38,10 @@ class ResultCellController(
       songSearchIntermediateController.triggerSearch(0)
     }
   }
+
+  suspend fun tryGetThumbnail(pv: PVInfo): Result<ThumbnailInfo> {
+    return findThumbnailService.tryGetThumbnail(pv)
+  }
 }
 
 private val log = KInlineLogging.logger()

songfinder-app/src/main/kotlin/mikufan/cx/songfinder/backend/service/FindThumbnailService.kt

@@ -0,0 +1,31 @@
+package mikufan.cx.songfinder.backend.service
+
+import mikufan.cx.songfinder.backend.component.thumbnailfinder.ThumbnailFinder
+import mikufan.cx.songfinder.backend.model.PVInfo
+import mikufan.cx.songfinder.backend.model.ThumbnailInfo
+import org.springframework.stereotype.Service
+
+@Service
+class FindThumbnailService(
+  thumbnailFinders: List<ThumbnailFinder>,
+) {
+
+  private val finderMap = thumbnailFinders.associateBy { it.matchedPvService }
+
+  suspend fun tryGetThumbnail(pv: PVInfo): Result<ThumbnailInfo> {
+    val finder = finderMap[pv.pvService]
+    return if (finder == null) {
+      Result.failure(IllegalArgumentException("No thumbnail finder for pv service ${pv.pvService}"))
+    } else {
+      try {
+        Result.success(finder.findThumbnail(pv))
+      } catch (e: Exception) {
+        Result.failure(e)
+      }
+    }
+  }
+
+  fun evictCache() {
+    TODO("return back here once spring cache is added")
+  }
+}