fix(logger): add logging for request retries

backend/internal/zarinhub/client_test.go

@@ -1,12 +1,15 @@
 package zarinhub
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 	"time"
 )
@@ -667,3 +670,97 @@ func TestClientStopsRetryOnContextCancellation(t *testing.T) {
 		t.Errorf("request count = %d, want 1", requestCount)
 	}
 }
+
+func TestClientRetryLogging(t *testing.T) {
+	const expectedIBAN = "IR820540102680020817909002"
+	requestCount := 0
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requestCount++
+		if requestCount == 1 {
+			w.WriteHeader(http.StatusServiceUnavailable)
+			fmt.Fprint(w, `{"error":"temporary outage"}`)
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprintf(w, `{
+			"data":{"iban":%q},
+			"meta":{"isSuccess":true,"errors":[]}
+		}`, expectedIBAN)
+	}))
+	defer server.Close()
+
+	var logBuf bytes.Buffer
+	logger := slog.New(slog.NewJSONHandler(&logBuf, nil))
+
+	client := NewClient(
+		&http.Client{Timeout: time.Second},
+		server.URL,
+		&fakeTokenProvider{tokens: []string{"test-token"}},
+		2,
+		logger,
+	)
+	client.retryWait = func(ctx context.Context, delay time.Duration) bool {
+		return true
+	}
+
+	result, err := client.Convert(context.Background(), "6037997512345678")
+	if err != nil {
+		t.Fatalf("Convert() unexpected error = %v", err)
+	}
+	if result.IBAN != expectedIBAN {
+		t.Errorf("IBAN = %q, want %q", result.IBAN, expectedIBAN)
+	}
+
+	logs := logBuf.String()
+
+	if !strings.Contains(logs, "[INITIAL] zarinhub request") {
+		t.Errorf("expected logs to contain '[INITIAL] zarinhub request', got:\n%s", logs)
+	}
+	if !strings.Contains(logs, `"is_retry":false`) {
+		t.Errorf("expected logs to contain '\"is_retry\":false', got:\n%s", logs)
+	}
+
+	if !strings.Contains(logs, "[RETRY] zarinhub request attempt 1") {
+		t.Errorf("expected logs to contain '[RETRY] zarinhub request attempt 1', got:\n%s", logs)
+	}
+	if !strings.Contains(logs, "[RETRY] zarinhub request failed, retrying in") {
+		t.Errorf("expected logs to contain '[RETRY] zarinhub request failed, retrying in', got:\n%s", logs)
+	}
+	if !strings.Contains(logs, `"is_retry":true`) {
+		t.Errorf("expected logs to contain '\"is_retry\":true', got:\n%s", logs)
+	}
+}
+
+func TestClientRetryLoggingExhausted(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusServiceUnavailable)
+		fmt.Fprint(w, `{"error":"down"}`)
+	}))
+	defer server.Close()
+
+	var logBuf bytes.Buffer
+	logger := slog.New(slog.NewJSONHandler(&logBuf, nil))
+
+	client := NewClient(
+		&http.Client{Timeout: time.Second},
+		server.URL,
+		&fakeTokenProvider{tokens: []string{"test-token"}},
+		1,
+		logger,
+	)
+	client.retryWait = func(ctx context.Context, delay time.Duration) bool {
+		return true
+	}
+
+	_, err := client.Convert(context.Background(), "6037997512345678")
+	if !errors.Is(err, ErrUnavailable) {
+		t.Fatalf("error = %v, want ErrUnavailable", err)
+	}
+
+	logs := logBuf.String()
+	if !strings.Contains(logs, "[RETRY] zarinhub request failed: all retries exhausted") {
+		t.Errorf("expected logs to contain exhausted retries message, got:\n%s", logs)
+	}
+}