add resolver.MultiResolver (#27)

Co-authored-by: thisisaaronland <thisisaaronland@localhost>

Author: thisisaaronland

resolver/multi.go

@@ -0,0 +1,72 @@
+package resolver
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"net/url"
+)
+
+// type MultiResolver implements the `Resolver` interface for resolving data using one or more `Resolver` instances.
+type MultiResolver struct {
+	Resolver
+	resolvers []Resolver
+}
+
+func init() {
+	ctx := context.Background()
+	RegisterResolver(ctx, "multi", NewMultiResolver)
+}
+
+// NewMultiResolver will return a new `Resolver` instance for resolving	data using one or more `Resolver` instances.
+func NewMultiResolver(ctx context.Context, uri string) (Resolver, error) {
+
+	u, err := url.Parse(uri)
+
+	if err != nil {
+		return nil, fmt.Errorf("Failed to parse URL, %w", err)
+	}
+
+	q := u.Query()
+
+	if !q.Has("resolver") {
+		return nil, fmt.Errorf("URI has no ?resolver= parameters")
+	}
+
+	resolvers := make([]Resolver, len(q["resolver"]))
+
+	for idx, r_uri := range q["resolver"] {
+
+		r, err := NewResolver(ctx, r_uri)
+
+		if err != nil {
+			return nil, fmt.Errorf("Failed to create resolver for '%s', %w", r_uri, err)
+		}
+
+		resolvers[idx] = r
+	}
+
+	multi_r := &MultiResolver{
+		resolvers: resolvers,
+	}
+
+	return multi_r, nil
+}
+
+// GetRepo returns the name of the repository associated with this ID from the first of one or more matching `Resolver` instances.
+func (r *MultiResolver) GetRepo(ctx context.Context, id int64) (string, error) {
+
+	for _, other_r := range r.resolvers {
+
+		repo, err := other_r.GetRepo(ctx, id)
+
+		if err != nil {
+			slog.Debug("Failed to get repo", "id", id, "resolver", fmt.Sprintf("%T", other_r), "error", err)
+			continue
+		}
+
+		return repo, nil
+	}
+
+	return "", fmt.Errorf("Not found")
+}

resolver/multi_test.go

@@ -0,0 +1,44 @@
+package resolver
+
+import (
+	"context"
+	"net/url"
+	"testing"
+)
+
+func TestMultiResolver(t *testing.T) {
+
+	ctx := context.Background()
+
+	resolver_uris := []string{
+		"https://static.sfomuseum.org/findingaid?template=https://raw.githubusercontent.com/sfomuseum-data/{repo}/main/data/",
+		"https://data.whosonfirst.org/findingaid?template=https://raw.githubusercontent.com/whosonfirst-data/{repo}/master/data/",
+	}
+
+	r_query := url.Values{}
+
+	for _, uri := range resolver_uris {
+		r_query.Set("resolver", uri)
+	}
+
+	r_uri := url.URL{}
+	r_uri.Scheme = "multi"
+	r_uri.RawQuery = r_query.Encode()
+
+	r, err := NewResolver(ctx, r_uri.String())
+
+	if err != nil {
+		t.Fatalf("Failed to create new resolver for %s, %v", r_uri.String(), err)
+	}
+
+	id := int64(85865975)
+	repo, err := r.GetRepo(ctx, id)
+
+	if err != nil {
+		t.Fatalf("Failed to get repo for %d, %v", id, err)
+	}
+
+	if repo != "whosonfirst-data-admin-us" {
+		t.Fatalf("Unexpected repo, %s", repo)
+	}
+}