Add support for downloading latest Modrinth version

plugin/src/main/kotlin/xyz/jpenilla/runtask/pluginsapi/DownloadPluginsSpec.kt

@@ -142,6 +142,15 @@ public abstract class DownloadPluginsSpec @Inject constructor(
     modrinth.configure { add(id, version) }
   }
 
+  /**
+   * Add a plugin download, downloading the latest available version.
+   *
+   * @param id plugin id on Modrinth
+   */
+  public fun modrinth(id: String) {
+    modrinth.configure { add(id) }
+  }
+
   // github extensions
 
   /**

plugin/src/main/kotlin/xyz/jpenilla/runtask/pluginsapi/PluginApiDownload.kt

@@ -18,6 +18,7 @@ package xyz.jpenilla.runtask.pluginsapi
 
 import org.gradle.api.provider.Property
 import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Optional
 import xyz.jpenilla.runtask.util.HashingAlgorithm
 import xyz.jpenilla.runtask.util.calculateHash
 import xyz.jpenilla.runtask.util.toHexString
@@ -71,10 +72,11 @@ public abstract class ModrinthApiDownload : PluginApiDownload() {
   public abstract val id: Property<String>
 
   @get:Input
+  @get:Optional
   public abstract val version: Property<String>
 
   override fun toString(): String {
-    return "ModrinthApiDownload{url=${url.get()}, id=${id.get()}, version=${version.get()}}"
+    return "ModrinthApiDownload{url=${url.get()}, id=${id.get()}, version=${version.orNull ?: "latest"}}"
   }
 
   override fun equals(other: Any?): Boolean {
@@ -89,13 +91,13 @@ public abstract class ModrinthApiDownload : PluginApiDownload() {
 
     return url.get() == other.url.get() &&
       id.get() == other.id.get() &&
-      version.get() == other.version.get()
+      version.orNull == other.version.orNull
   }
 
   override fun hashCode(): Int {
     var result = url.get().hashCode()
     result = 31 * result + id.get().hashCode()
-    result = 31 * result + version.get().hashCode()
+    result = 31 * result + version.orNull.hashCode()
     return result
   }
 }

plugin/src/main/kotlin/xyz/jpenilla/runtask/pluginsapi/PluginDownloadServiceImpl.kt

@@ -145,17 +145,37 @@ internal abstract class PluginDownloadServiceImpl : PluginDownloadService {
   private fun resolveModrinthPlugin(progressLoggerFactory: ProgressLoggerFactory, download: ModrinthApiDownload): Path {
     val cacheDir = parameters.cacheDirectory.get().asFile.toPath()
 
-    val apiVersion = download.version.get()
     val apiPlugin = download.id.get()
     val apiUrl = download.url.get()
 
     val provider = manifest.modrinthProviders.computeIfAbsent(download.url.get()) { ModrinthProvider() }
     val plugin = provider.computeIfAbsent(download.id.get()) { PluginVersions() }
+
+    val targetDir = cacheDir.resolve(Constants.MODRINTH_PLUGIN_DIR).resolve(apiPlugin)
+
+    // Resolve the version: if not specified, fetch the latest from the versions list endpoint
+    val apiVersion: String
+    if (!download.version.isPresent) {
+      val latestJsonName = "latest-json"
+      val latestJsonVersion = plugin[latestJsonName] ?: PluginVersion(fileName = "$apiPlugin-latest-versions.json", displayName = "modrinth:$apiPlugin:latest:metadata")
+      val latestJsonFile = targetDir.resolve(latestJsonVersion.fileName)
+      val latestRequestUrl = "$apiUrl/v2/project/$apiPlugin/version"
+      val latestJsonPath = download(
+        DownloadCtx(progressLoggerFactory, apiUrl, latestRequestUrl, targetDir, latestJsonFile, latestJsonVersion, setter = { plugin[latestJsonName] = it }, requireValidJar = false)
+      )
+
+      @OptIn(ExperimentalSerializationApi::class)
+      val versionList = latestJsonPath.inputStream().buffered().use {
+        mapper.decodeFromStream<List<ModrinthVersionListEntry>>(it)
+      }
+      apiVersion = versionList.firstOrNull()?.id ?: error("Could not find any versions for modrinth project $apiPlugin")
+    } else {
+      apiVersion = download.version.get()
+    }
+
     val jsonVersionName = "$apiVersion-json"
     val jsonVersion = plugin[jsonVersionName] ?: PluginVersion(fileName = "$apiPlugin-$apiVersion-info.json", displayName = "modrinth:$apiPlugin:$apiVersion:metadata")
 
-    val targetDir =
-      cacheDir.resolve(Constants.MODRINTH_PLUGIN_DIR).resolve(apiPlugin)
     val jsonFile = targetDir.resolve(jsonVersion.fileName)
 
     val versionRequestUrl = "$apiUrl/v2/project/$apiPlugin/version/$apiVersion"
@@ -365,6 +385,11 @@ private data class ModrinthVersionResponse(
   )
 }
 
+@Serializable
+private data class ModrinthVersionListEntry(
+  val id: String
+)
+
 // github types:
 private typealias GitHubProvider = MutableMap<String, GitHubOwner>
 

plugin/src/main/kotlin/xyz/jpenilla/runtask/pluginsapi/modrinth/ModrinthApi.kt

@@ -40,4 +40,11 @@ public interface ModrinthApi : PluginApi<ModrinthApi, ModrinthApiDownload> {
    * @param version plugin version id
    */
   public fun add(id: String, version: String)
+
+  /**
+   * Add a plugin download, downloading the latest available version.
+   *
+   * @param id plugin id on Modrinth
+   */
+  public fun add(id: String)
 }

plugin/src/main/kotlin/xyz/jpenilla/runtask/pluginsapi/modrinth/ModrinthApiImpl.kt

@@ -39,6 +39,13 @@ public abstract class ModrinthApiImpl @Inject constructor(private val name: Stri
     jobs.add(job)
   }
 
+  override fun add(id: String) {
+    val job = objects.newInstance(ModrinthApiDownload::class)
+    job.url.set(url.map { it.trimEnd('/') })
+    job.id.set(id)
+    jobs.add(job)
+  }
+
   override fun copyConfiguration(api: ModrinthApi) {
     url.set(api.url)
     jobs.addAll(api.downloads)