Integrate validated catalog loading (T-201)

core/catalog/client.go

@@ -0,0 +1,48 @@
+package catalog
+
+import "context"
+
+// Client composes signed loading, protocol validation and target filtering.
+type Client struct {
+	loader *Loader
+	parser Parser
+	target Target
+}
+
+// NewClient creates the formal Catalog loading path. Protocol validation is
+// installed on Loader so invalid remote data cannot replace the usable cache.
+func NewClient(
+	verifier Verifier,
+	fetcher Fetcher,
+	cache Cache,
+	target Target,
+) *Client {
+	parser := Parser{ExpectedChannel: target.Channel}
+	return &Client{
+		loader: NewLoader(verifier, fetcher, cache, parser),
+		parser: parser,
+		target: target,
+	}
+}
+
+// Load returns a verified, validated and target-filtered Catalog.
+func (client *Client) Load(ctx context.Context) (Catalog, error) {
+	result, err := client.loader.Load(ctx)
+	if err != nil {
+		return Catalog{}, err
+	}
+	manifest, err := client.parser.Parse(result.Document)
+	if err != nil {
+		return Catalog{}, err
+	}
+	entries, err := Filter(manifest, client.target)
+	if err != nil {
+		return Catalog{}, err
+	}
+	return Catalog{
+		Manifest: manifest,
+		Entries:  entries,
+		Source:   result.Source,
+		Warning:  result.Warning,
+	}, nil
+}