implement default discovery handler

handlers/discovery/discovery.go

@@ -0,0 +1,93 @@
+package discovery
+
+import (
+	"context"
+	"regexp"
+	"strings"
+
+	"github.com/google/uuid"
+	"github.com/iden3/iden3comm/v2/packers"
+	"github.com/iden3/iden3comm/v2/protocol"
+)
+
+// Featurer interface for feature handlers
+// # Experimental
+type Featurer interface {
+	Handle(ctx context.Context) []protocol.DiscoverFeatureDisclosure
+}
+
+// Discovery handler
+// # Experimental
+type Discovery struct {
+	features map[protocol.DiscoveryProtocolFeatureType]Featurer
+}
+
+// New creates a new Discovery handler
+// # Experimental
+func New(features map[protocol.DiscoveryProtocolFeatureType]Featurer) *Discovery {
+	return &Discovery{
+		features: features,
+	}
+}
+
+// Handle processes a DiscoverFeatureQueriesMessage and returns a DiscoverFeatureDiscloseMessage
+// # Experimental
+func (d *Discovery) Handle(ctx context.Context,
+	discoverInputMessage protocol.DiscoverFeatureQueriesMessage) (protocol.DiscoverFeatureDiscloseMessage, error) {
+	queries := discoverInputMessage.Body.Queries
+
+	var (
+		disclosures []protocol.DiscoverFeatureDisclosure
+		err         error
+	)
+
+	for _, query := range queries {
+		var disclosuresToAppend []protocol.DiscoverFeatureDisclosure
+		if featurer, ok := d.features[query.FeatureType]; ok {
+			disclosuresToAppend = featurer.Handle(ctx)
+		}
+
+		disclosuresToAppend, err = d.handleMatch(disclosuresToAppend, query.Match)
+		if err != nil {
+			return protocol.DiscoverFeatureDiscloseMessage{}, err
+		}
+		disclosures = append(disclosures, disclosuresToAppend...)
+	}
+
+	return protocol.DiscoverFeatureDiscloseMessage{
+		ID:       uuid.NewString(),
+		Typ:      packers.MediaTypePlainMessage,
+		Type:     protocol.DiscoverFeatureDiscloseMessageType,
+		ThreadID: discoverInputMessage.ThreadID,
+		Body: protocol.DiscoverFeatureDiscloseMessageBody{
+			Disclosures: disclosures,
+		},
+		From: discoverInputMessage.To,
+		To:   discoverInputMessage.From,
+	}, nil
+}
+
+func (d *Discovery) handleMatch(disclosures []protocol.DiscoverFeatureDisclosure, match string) ([]protocol.DiscoverFeatureDisclosure, error) {
+	if match == "" || match == "*" {
+		return disclosures, nil
+	}
+
+	regExp, err := wildcardToRegExp(match)
+	if err != nil {
+		return nil, err
+	}
+	var filtered []protocol.DiscoverFeatureDisclosure
+	for _, disclosure := range disclosures {
+		if regExp.MatchString(disclosure.ID) {
+			filtered = append(filtered, disclosure)
+		}
+	}
+	return filtered, nil
+}
+
+func wildcardToRegExp(match string) (*regexp.Regexp, error) {
+	// Escape special regex characters and replace `*` with `.*`
+	regexPattern := regexp.QuoteMeta(match)
+	regexPattern = strings.ReplaceAll(regexPattern, "\\*", ".*")
+	return regexp.Compile("^" + regexPattern + "$")
+}