refactor(downloader): turn DownloadManager into downloader registry

Reshape DownloadManager from a hard-coded VCS match into a registry of
DownloaderInterface instances keyed by source type, mirroring
Composer's DownloadManager — with prefer-source/dist preferences, an
IO handle, and a files cache. ArchiveManager now resolves dist
sources through a shared DownloadManager instead of calling
download_dist directly, and Composer::require / try_load take an IO
so it flows through the factory wiring.

1 files changed, 13 insertions, 6 deletions

diff --git a/crates/mozart-core/src/downloader/git_downloader.rs b/crates/mozart-core/src/downloader/git_downloader.rs
index d4d8c44..6e1351c 100644
--- a/crates/mozart-core/src/downloader/git_downloader.rs
+++ b/crates/mozart-core/src/downloader/git_downloader.rs
@@ -1,12 +1,11 @@
+use crate::downloader::{DownloaderInterface, VcsDownloader};
+use crate::vcs::process::ProcessExecutor;
+use crate::vcs::util::git::GitUtil;
 use anyhow::Result;
 use regex::Regex;
 use std::path::Path;
 use std::sync::LazyLock;
 
-use crate::downloader::VcsDownloader;
-use crate::vcs::process::ProcessExecutor;
-use crate::vcs::util::git::GitUtil;
-
 /// Match `<hex> HEAD` lines in `git show-ref --head -d` output.
 static HEAD_REF_RE: LazyLock<Regex> =
     LazyLock::new(|| Regex::new(r"(?im)^([a-f0-9]+) HEAD$").unwrap());
@@ -19,8 +18,10 @@ pub struct GitDownloader {
 }
 
 impl GitDownloader {
-    pub fn new(git_util: GitUtil) -> Self {
-        Self { git_util }
+    pub fn new(process: ProcessExecutor, cache_dir: std::path::PathBuf) -> Self {
+        Self {
+            git_util: GitUtil::new(process, cache_dir),
+        }
     }
 }
 
@@ -235,6 +236,12 @@ impl VcsDownloader for GitDownloader {
     }
 }
 
+impl DownloaderInterface for GitDownloader {
+    fn as_vcs_downloader(&self) -> Option<&dyn VcsDownloader> {
+        Some(self)
+    }
+}
+
 fn collect_show_ref(process: &ProcessExecutor, target: &Path) -> Result<Option<String>> {
     let output = process.execute(&["git", "show-ref", "--head", "-d"], Some(target))?;
     if output.status != 0 {