fix: separate golang license caches from mod dir (#2852)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

internal/cache/resolver.go

@@ -0,0 +1,83 @@
+package cache
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"path"
+
+	"github.com/anchore/syft/internal"
+	"github.com/anchore/syft/internal/log"
+)
+
+// Resolver interface provides a single Resolve method, which will return from cache
+// or call the provided resolve function to get the value if not available in cache
+type Resolver[T any] interface {
+	// Resolve attempts to resolve the given key from cache and convert it to the type of the cache,
+	// or calls the resolver function if unable to resolve a cached value
+	Resolve(key string, resolver resolverFunc[T]) (T, error)
+}
+
+// GetResolver returns a cache resolver for persistent cached data across Syft runs, stored in a unique
+// location based on the provided name and versioned by the type
+func GetResolver[T any](name, version string) Resolver[T] {
+	typeHash := hashType[T]()
+	versionKey := path.Join(version, typeHash)
+	return &cacheResolver[T]{
+		name:  fmt.Sprintf("%s/%s", name, versionKey),
+		cache: manager.GetCache(name, versionKey),
+	}
+}
+
+const resolverKeySuffix = ".json"
+
+type resolverFunc[T any] func() (T, error)
+
+type cacheResolver[T any] struct {
+	name  string
+	cache Cache
+}
+
+var _ interface {
+	Resolver[int]
+} = (*cacheResolver[int])(nil)
+
+func (r *cacheResolver[T]) Resolve(key string, resolver resolverFunc[T]) (T, error) {
+	key += resolverKeySuffix
+
+	rdr, err := r.cache.Read(key)
+	if rdr == nil || err != nil {
+		return r.resolveAndCache(key, resolver)
+	}
+	defer internal.CloseAndLogError(rdr, key)
+
+	dec := json.NewDecoder(rdr)
+	if dec == nil {
+		log.Tracef("error getting cache json decoder for %s %v: %v", r.name, key, err)
+		return r.resolveAndCache(key, resolver)
+	}
+	var t T
+	err = dec.Decode(&t)
+	if err != nil {
+		log.Tracef("error decoding cached entry for %s %v: %v", r.name, key, err)
+		return r.resolveAndCache(key, resolver)
+	}
+	// no error, able to resolve from cache
+	return t, nil
+}
+
+func (r *cacheResolver[T]) resolveAndCache(key string, resolver func() (T, error)) (T, error) {
+	t, err := resolver()
+	if err != nil {
+		return t, err
+	}
+	var data bytes.Buffer
+	enc := json.NewEncoder(&data)
+	enc.SetEscapeHTML(false)
+	err = enc.Encode(t)
+	if err != nil {
+		return t, err
+	}
+	err = r.cache.Write(key, &data)
+	return t, err
+}