feat: add Amazon LWA mock server (testutils + integration mocks)

Mirror the Spotify equivalents: pkg/testutils/amazon/handlers.go provides
HandleToken and HandleProfile for use in unit tests; tests/integration/mocks/amazon.go
wraps them in an AmazonMock with TokenURL() and ProfileURL() accessors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pkg/testutils/amazon/handlers.go

@@ -0,0 +1,93 @@
+// Package amazon provides shared handlers for mocking the Amazon LWA API.
+package amazon
+
+import (
+	"encoding/json"
+	"log"
+	"net/http"
+)
+
+// NewAmazonHandler returns a new http.Handler configured with Amazon LWA mock endpoints.
+func NewAmazonHandler() http.Handler {
+	mux := http.NewServeMux()
+
+	// LWA Token Endpoint (POST body credentials, not Basic Auth)
+	mux.HandleFunc("/auth/o2/token", HandleToken)
+
+	// LWA User Profile Endpoint
+	mux.HandleFunc("/user/profile", HandleProfile)
+
+	return mux
+}
+
+// HandleToken simulates the Amazon LWA token endpoint.
+// Amazon requires client_id and client_secret as POST body fields, not HTTP Basic Auth.
+func HandleToken(w http.ResponseWriter, r *http.Request) {
+	log.Printf("[Amazon Mock] Token request: %s", r.Method)
+
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "Bad request", http.StatusBadRequest)
+		return
+	}
+
+	grantType := r.FormValue("grant_type")
+	log.Printf("[Amazon Mock] Grant type: %s", grantType)
+
+	resp := map[string]interface{}{
+		"access_token":  "Atza|amazon-access-token",
+		"token_type":    "bearer",
+		"expires_in":    3600,
+		"refresh_token": "Atzr|amazon-refresh-token",
+	}
+
+	switch grantType {
+	case "authorization_code":
+		if r.FormValue("code") == "" {
+			http.Error(w, `{"error":"invalid_grant"}`, http.StatusBadRequest)
+			return
+		}
+	case "refresh_token":
+		if r.FormValue("refresh_token") == "" {
+			http.Error(w, `{"error":"invalid_grant"}`, http.StatusBadRequest)
+			return
+		}
+	default:
+		http.Error(w, `{"error":"unsupported_grant_type"}`, http.StatusBadRequest)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+
+	if err := json.NewEncoder(w).Encode(resp); err != nil {
+		log.Printf("Error encoding token response: %v", err)
+	}
+}
+
+// HandleProfile simulates the Amazon LWA user profile endpoint.
+// LWA returns "user_id" and "name" (not "id" / "display_name" like Spotify).
+func HandleProfile(w http.ResponseWriter, r *http.Request) {
+	log.Printf("[Amazon Mock] Profile request: %s", r.Method)
+
+	auth := r.Header.Get("Authorization")
+	if auth != "Bearer Atza|amazon-access-token" {
+		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
+		return
+	}
+
+	resp := map[string]interface{}{
+		"user_id": "amzn1.account.TESTUSER",
+		"name":    "Amazon Test User",
+		"email":   "amazon-test@example.com",
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+
+	if err := json.NewEncoder(w).Encode(resp); err != nil {
+		log.Printf("Error encoding profile response: %v", err)
+	}
+}

tests/integration/mocks/amazon.go

@@ -0,0 +1,39 @@
+package mocks
+
+import (
+	"net/http/httptest"
+
+	"github.com/gesellix/bose-soundtouch/pkg/testutils/amazon"
+)
+
+// AmazonMock simulates Amazon LWA API responses for OAuth and profile interactions.
+type AmazonMock struct {
+	server *httptest.Server
+}
+
+// NewAmazonMock creates and starts a new Amazon LWA mock server.
+func NewAmazonMock() *AmazonMock {
+	return &AmazonMock{
+		server: httptest.NewServer(amazon.NewAmazonHandler()),
+	}
+}
+
+// URL returns the base URL of the mock server.
+func (m *AmazonMock) URL() string {
+	return m.server.URL
+}
+
+// TokenURL returns the LWA token endpoint URL.
+func (m *AmazonMock) TokenURL() string {
+	return m.server.URL + "/auth/o2/token"
+}
+
+// ProfileURL returns the LWA user profile endpoint URL.
+func (m *AmazonMock) ProfileURL() string {
+	return m.server.URL + "/user/profile"
+}
+
+// Close stops the mock server.
+func (m *AmazonMock) Close() {
+	m.server.Close()
+}