dnfjson: use new size-based cache management

- Update timestamps for cache elements whenever a repository is used.
- Call the new `shrink()` function instead of the old `clean()`.
- Remove the old `clean()` function.

internal/dnfjson/cache.go

@@ -48,17 +48,6 @@ func newRPMCache(path string, maxSize uint64) *rpmCache {
 	return r
 }
 
-func (r *rpmCache) clean() error {
-	curSize, err := dirSize(r.root)
-	if err != nil {
-		return err
-	}
-	if curSize > r.maxSize {
-		return os.RemoveAll(r.root)
-	}
-	return nil
-}
-
 // updateInfo updates the repoPaths and repoRecency fields of the rpmCache.
 func (r *rpmCache) updateInfo() {
 	cacheEntries, _ := os.ReadDir(r.root)

internal/dnfjson/dnfjson.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"os/exec"
 	"sort"
+	"time"
 
 	"github.com/osbuild/osbuild-composer/internal/rhsm"
 	"github.com/osbuild/osbuild-composer/internal/rpmmd"
@@ -75,8 +76,11 @@ func (bs *BaseSolver) NewWithConfig(modulePlatformID string, releaseVer string,
 	return s
 }
 
+// CleanCache deletes the least recently used repository metadata caches until
+// the total size of the cache falls below the configured maximum size (see
+// SetMaxCacheSize()).
 func (bs *BaseSolver) CleanCache() error {
-	return bs.cache.clean()
+	return bs.cache.shrink()
 }
 
 // Solver is configured with system information in order to resolve
@@ -115,6 +119,14 @@ func (s *Solver) Depsolve(pkgSets []rpmmd.PackageSet) ([]rpmmd.PackageSpec, erro
 	if err != nil {
 		return nil, err
 	}
+	// touch repos to now
+	now := time.Now().Local()
+	for _, r := range repoMap {
+		// ignore errors
+		_ = s.cache.touchRepo(r.Hash(), now)
+	}
+	s.cache.updateInfo()
+
 	var result packageSpecs
 	if err := json.Unmarshal(output, &result); err != nil {
 		return nil, err
@@ -135,6 +147,14 @@ func (s *Solver) FetchMetadata(repos []rpmmd.RepoConfig) (rpmmd.PackageList, err
 		return nil, err
 	}
 
+	// touch repos to now
+	now := time.Now().Local()
+	for _, r := range repos {
+		// ignore errors
+		_ = s.cache.touchRepo(r.Hash(), now)
+	}
+	s.cache.updateInfo()
+
 	var pkgs rpmmd.PackageList
 	if err := json.Unmarshal(result, &pkgs); err != nil {
 		return nil, err