refactor(client): move card resolver to card package and improve the error message

CHANGELOG.md

@@ -1,8 +1,14 @@
 # changelog
 
+## v0.2.4
+
+- move card resolver to client/card package (#33)
+- Rename `WithOptions` to `WithHeaders` in card_resolver (#33)
+- Improved the error message for `GetCard()` in card_resolver (#33)
+
 ## v0.2.3
 
-fix: add nil check for message in MessageSend and MessageSendStream to prevent panic(#20)
+- fix: add nil check for message in MessageSend and MessageSendStream to prevent panic(#20)
 
 ## v0.2.2
 1. Ensured final events are always enqueued and processed (#17)

sdk/client/card/card_resolver.go

@@ -0,0 +1,121 @@
+// Copyright 2025 yeeaiclub
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package card
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	log "github.com/yeeaiclub/a2a-go/internal/logger"
+	"github.com/yeeaiclub/a2a-go/sdk/types"
+)
+
+// A2ACardResolver is responsible for retrieving agent card information from a specified endpoint.
+// It provides a way to fetch [types.AgentCard] data using HTTP requests with configurable options.
+type A2ACardResolver struct {
+	client        *http.Client      // HTTP client used for making requests
+	baseUrl       string            // Base URL of the agent service
+	agentCardPath string            // Path to the agent card endpoint
+	options       map[string]string // HTTP headers to include in requests
+}
+
+// NewA2ACardResolver creates a new instance of A2ACardResolver with the provided configuration.
+func NewA2ACardResolver(client *http.Client, baseURL string, options ...A2ACardResolverOption) *A2ACardResolver {
+	r := A2ACardResolver{
+		client:        client,
+		baseUrl:       baseURL,
+		agentCardPath: types.AgentCardPath, // Default path from types package
+	}
+
+	// Apply all provided configuration options
+	for _, opt := range options {
+		r = opt.Option(r)
+	}
+	return &r
+}
+
+// GetAgentCard retrieves an agent card from the configured base URL.
+// It sends an HTTP GET request to the agent card endpoint and returns the parsed card data.
+func (a *A2ACardResolver) GetAgentCard(ctx context.Context) (*types.AgentCard, error) {
+	targetURL, err := url.JoinPath(a.baseUrl, a.agentCardPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to construct url %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, targetURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to construct request %w", err)
+	}
+
+	if a.options != nil {
+		for key, value := range a.options {
+			req.Header.Set(key, value)
+		}
+	}
+
+	resp, err := a.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			log.Error(ctx, "failed to close response body", err)
+		}
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("failed to get agent card: status code %d", resp.StatusCode)
+	}
+
+	var card types.AgentCard
+	err = json.NewDecoder(resp.Body).Decode(&card)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse body: %w", err)
+	}
+	return &card, nil
+}
+
+// A2ACardResolverOption defines an interface for configuring A2ACardResolver instances.
+type A2ACardResolverOption interface {
+	Option(resolver A2ACardResolver) A2ACardResolver
+}
+
+type A2ACardResolverOptionFunc func(resolver A2ACardResolver) A2ACardResolver
+
+// Option applies the function to the resolver and returns the updated resolver.
+func (fn A2ACardResolverOptionFunc) Option(resolver A2ACardResolver) A2ACardResolver {
+	return fn(resolver)
+}
+
+// WithAgentCardPath configures the specific path used to retrieve the agent card.
+// By default, the resolver uses the standard path defined in types.AgentCardPath.
+func WithAgentCardPath(path string) A2ACardResolverOption {
+	return A2ACardResolverOptionFunc(func(resolver A2ACardResolver) A2ACardResolver {
+		resolver.agentCardPath = path
+		return resolver
+	})
+}
+
+// WithHeader configures custom HTTP headers to be included in the agent card request.
+func WithHeader(header map[string]string) A2ACardResolverOption {
+	return A2ACardResolverOptionFunc(func(resolver A2ACardResolver) A2ACardResolver {
+		resolver.options = header
+		return resolver
+	})
+}

sdk/client/card_resolver_test.go → sdk/client/card/card_resolver_test.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package client
+package card
 
 import (
 	"encoding/json"
@@ -28,11 +28,11 @@ import (
 func TestGetAgentCard(t *testing.T) {
 	testcases := []struct {
 		name string
-		want types.AgentCard
+		want *types.AgentCard
 	}{
 		{
 			name: "success response",
-			want: types.AgentCard{
+			want: &types.AgentCard{
 				Name:               "hello, word",
 				Description:        "a hello word agent",
 				DefaultInputModes:  []string{"text"},
@@ -57,7 +57,7 @@ func TestGetAgentCard(t *testing.T) {
 				http.DefaultClient,
 				server.URL,
 			)
-			card, err := resolver.GetAgentCard()
+			card, err := resolver.GetAgentCard(t.Context())
 			require.NoError(t, err)
 			assert.Equal(t, tc.want, card)
 		})