feat(cache): add filesystem-backed cache with TTL expiration and size-limited GC

Implement a cache module with CacheConfig and Cache structs supporting
read/write (string and binary), atomic writes via temp+rename, TTL-based
expiration, and size-limited garbage collection. Wire the repo cache into
packagist.rs and resolver.rs for API response caching, and the files
cache into downloader.rs for dist archive caching. Implement the
clear-cache command with full clear and --gc modes. All existing call
sites pass None for backward compatibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 42 insertions, 2 deletions

diff --git a/crates/mozart/src/commands/clear_cache.rs b/crates/mozart/src/commands/clear_cache.rs
index 638de06..819ca9f 100644
--- a/crates/mozart/src/commands/clear_cache.rs
+++ b/crates/mozart/src/commands/clear_cache.rs
@@ -1,3 +1,4 @@
+use crate::cache::{Cache, build_cache_config};
 use clap::Args;
 
 #[derive(Args)]
@@ -7,6 +8,45 @@ pub struct ClearCacheArgs {
     pub gc: bool,
 }
 
-pub fn execute(_args: &ClearCacheArgs, _cli: &super::Cli) -> anyhow::Result<()> {
-    todo!()
+pub fn execute(args: &ClearCacheArgs, cli: &super::Cli) -> anyhow::Result<()> {
+    let config = build_cache_config(cli);
+
+    if args.gc {
+        // Run GC only (probabilistic under normal circumstances, but forced here)
+        let repo_cache = Cache::repo(&config);
+        let files_cache = Cache::files(&config);
+
+        repo_cache.gc(config.cache_ttl, u64::MAX)?;
+        files_cache.gc(config.cache_files_ttl, config.cache_files_maxsize)?;
+
+        eprintln!("Cache garbage collection complete.");
+        eprintln!("Cache directory: {}", config.cache_dir.display());
+    } else {
+        // Full clear of all cache directories
+        let repo_cache = Cache::repo(&config);
+        let files_cache = Cache::files(&config);
+        repo_cache.clear()?;
+        files_cache.clear()?;
+        // Clear anything else at the root that isn't covered by sub-caches
+        if config.cache_dir.exists() {
+            for entry in std::fs::read_dir(&config.cache_dir)? {
+                let entry = entry?;
+                let path = entry.path();
+                // Skip repo/files subdirs (already cleared above)
+                if path == config.cache_files_dir || path == config.cache_repo_dir {
+                    continue;
+                }
+                if path.is_file() {
+                    std::fs::remove_file(&path)?;
+                } else if path.is_dir() {
+                    std::fs::remove_dir_all(&path)?;
+                }
+            }
+        }
+
+        eprintln!("Cache cleared.");
+        eprintln!("Cache directory: {}", config.cache_dir.display());
+    }
+
+    Ok(())
 }