⚡ Eliminate runBlocking on main thread in command resolvers and fix HttpClient resource leaks

[Nlkomaru]

Summary

Performance issues that can cause server lag during tab completion and resource exhaustion during long runs.

Issue 1: runBlocking on main thread in tab completion

Location:

• paper/.../utils/command/resolver/RepositoryPluginParameterType.kt (lines 54-56, 76-78)
• paper/.../utils/command/resolver/InstalledPluginParameterType.kt (lines 54-58, 77-81)
• paper/.../utils/command/resolver/VersionSpecifierParameterType.kt (lines 67-74)

Both parse() and defaultSuggestions() use runBlocking which blocks the main server thread during tab completion. Network or disk I/O in these paths can cause visible server lag or TPS drops.

Fix: Pre-build an async cache of suggestions (refreshed periodically or on plugin state changes). Tab completion should read from memory-only cache, never from disk/network.

Issue 2: HttpClient created per-request and never closed

Location: paper/.../infrastructure/downloader/DownloaderRepositoryImpl.kt (lines 108-145, 232-245)

Each call to getLatestVersion(), getVersionByName(), getAllVersions(), and downloadByVersion() creates new instances of GithubDownloader, SpigotDownloader, ModrinthDownloader — each of which creates a new HttpClient. These clients are never closed, leaking threads and sockets.

Fix: Register a singleton HttpClient in Koin. Inject it into downloader instances. Close it in onDisable().

Issue 3: Entire JAR loaded into memory before writing to disk

Location: paper/.../infrastructure/downloader/AbstractPluginDownloader.kt (line 68)

tempFile.writeBytes(fileResponse.body())

The body() call loads the entire HTTP response into memory as a ByteArray. Large plugins (10+ MB) will cause unnecessary memory pressure.

Fix: Use bodyAsChannel() or streaming API to write directly to the temp file.

Impact

• Server lag during tab completion (noticeable to players)
• Thread/socket exhaustion over time (potential OOM or connection pool exhaustion)
• Memory spikes during plugin downloads