refactor(metrics): use prometheus client and labels

Refactors the metrics package to use the official prometheus golang
client. Tool names are now added as labels instead of custom metrics
to simplify aggregate queries.

PR #48

Author: rhnvrm

app/metrics/daily_metrics_test.go

@@ -1,8 +1,8 @@
 package metrics
 
 import (
-	"bytes"
 	"fmt"
+	"net/http/httptest"
 	"strings"
 	"testing"
 	"time"
@@ -14,150 +14,85 @@ func TestDailyMetrics(t *testing.T) {
 		AutoCleanup: false,
 	})
 
-	today := time.Now().UTC().Format("2006-01-02")
-
 	// Test daily increment methods
 	m.IncrementDaily("tool_calls_quotes")
 	m.IncrementDaily("tool_calls_quotes")
 	m.IncrementDailyBy("tool_calls_login", 3)
 	m.IncrementDaily("tool_errors_quotes_api_error")
 
-	// Test regular increment (non-daily)
-	m.Increment("legacy_counter")
+	// Test that metrics were created by checking HTTP handler output
+	handler := m.HTTPHandler()
+	req := httptest.NewRequest("GET", "/metrics", nil)
+	w := httptest.NewRecorder()
+	handler(w, req)
 
-	// Check internal storage with date suffix
-	expectedQuotesKey := fmt.Sprintf("tool_calls_quotes_%s", today)
-	expectedLoginKey := fmt.Sprintf("tool_calls_login_%s", today)
-	expectedErrorKey := fmt.Sprintf("tool_errors_quotes_api_error_%s", today)
+	output := w.Body.String()
 
-	if got := m.GetCounterValue(expectedQuotesKey); got != 2 {
-		t.Errorf("Expected tool_calls_quotes_%s = 2, got %d", today, got)
-	}
-
-	if got := m.GetCounterValue(expectedLoginKey); got != 3 {
-		t.Errorf("Expected tool_calls_login_%s = 3, got %d", today, got)
-	}
+	today := time.Now().UTC().Format("2006-01-02")
 
-	if got := m.GetCounterValue(expectedErrorKey); got != 1 {
-		t.Errorf("Expected tool_errors_quotes_api_error_%s = 1, got %d", today, got)
+	expectedMetrics := []struct {
+		name  string
+		value string
+	}{
+		{"tool_calls_quotes", "2"},            // incremented twice
+		{"tool_calls_login", "3"},             // incremented by 3
+		{"tool_errors_quotes_api_error", "1"}, // incremented once
 	}
 
-	if got := m.GetCounterValue("legacy_counter"); got != 1 {
-		t.Errorf("Expected legacy_counter = 1, got %d", got)
+	for _, metric := range expectedMetrics {
+		expectedPattern := fmt.Sprintf(`%s{date="%s",service="test-service"} %s`, metric.name, today, metric.value)
+		if !strings.Contains(output, expectedPattern) {
+			t.Errorf("Expected output to contain: %s\nGot: %s", expectedPattern, output)
+		}
 	}
 }
 
-func TestDailyMetricsPrometheusOutput(t *testing.T) {
+func TestDailyMetricsWithLabels(t *testing.T) {
 	m := New(Config{
 		ServiceName: "test-service",
 		AutoCleanup: false,
 	})
 
-	today := time.Now().UTC().Format("2006-01-02")
-
-	// Add some daily metrics
-	m.IncrementDaily("tool_calls_quotes")
-	m.IncrementDaily("tool_calls_quotes")
-	m.IncrementDaily("tool_errors_quotes_api_error")
-
-	// Add a regular metric
-	m.Increment("legacy_counter")
-
-	// Generate Prometheus output
-	var buf bytes.Buffer
-	m.WritePrometheus(&buf)
-	output := buf.String()
-
-	// Check that daily metrics have date labels
-	expectedQuotesLine := fmt.Sprintf(`tool_calls_quotes_total{date="%s",service="test-service"} 2`, today)
-	expectedErrorLine := fmt.Sprintf(`tool_errors_quotes_api_error_total{date="%s",service="test-service"} 1`, today)
-	expectedLegacyLine := `legacy_counter_total{service="test-service"} 1`
-
-	if !strings.Contains(output, expectedQuotesLine) {
-		t.Errorf("Expected output to contain: %s\nGot: %s", expectedQuotesLine, output)
-	}
-
-	if !strings.Contains(output, expectedErrorLine) {
-		t.Errorf("Expected output to contain: %s\nGot: %s", expectedErrorLine, output)
-	}
-
-	if !strings.Contains(output, expectedLegacyLine) {
-		t.Errorf("Expected output to contain: %s\nGot: %s", expectedLegacyLine, output)
-	}
-}
-
-func TestIsDailyMetric(t *testing.T) {
-	m := New(Config{ServiceName: "test"})
-
-	tests := []struct {
-		key      string
-		expected bool
-	}{
-		{"tool_calls_quotes_2025-08-05", true},
-		{"tool_errors_login_session_error_2025-12-31", true},
-		{"legacy_counter", false},
-		{"tool_calls_quotes", false},
-		{"tool_calls_quotes_20250805", false}, // Wrong date format
-		{"tool_calls_quotes_2025-8-5", false}, // Wrong date format
-		{"", false},
-		{"_2025-08-05", false}, // Empty base name
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.key, func(t *testing.T) {
-			if got := m.isDailyMetric(tt.key); got != tt.expected {
-				t.Errorf("isDailyMetric(%q) = %v, want %v", tt.key, got, tt.expected)
-			}
-		})
-	}
-}
+	m.IncrementDailyWithLabels("tool_calls", map[string]string{
+		"tool":         "quotes",
+		"session_type": "mcp",
+	})
+	m.IncrementDailyWithLabels("tool_calls", map[string]string{
+		"tool":         "quotes",
+		"session_type": "mcp",
+	})
 
-func TestParseDailyMetric(t *testing.T) {
-	m := New(Config{ServiceName: "test"})
+	m.IncrementDailyWithLabels("tool_errors", map[string]string{
+		"tool":         "quotes",
+		"error_type":   "api_error",
+		"session_type": "mcp",
+	})
 
-	tests := []struct {
-		key          string
-		expectedBase string
-		expectedDate string
-	}{
-		{"tool_calls_quotes_2025-08-05", "tool_calls_quotes", "2025-08-05"},
-		{"tool_errors_login_session_error_2025-12-31", "tool_errors_login_session_error", "2025-12-31"},
-		{"legacy_counter", "", ""},             // Not a daily metric
-		{"tool_calls_quotes_20250805", "", ""}, // Wrong date format
-	}
+	handler := m.HTTPHandler()
+	req := httptest.NewRequest("GET", "/metrics", nil)
+	w := httptest.NewRecorder()
+	handler(w, req)
 
-	for _, tt := range tests {
-		t.Run(tt.key, func(t *testing.T) {
-			gotBase, _, gotDate := m.parseDailyMetric(tt.key)
-			if gotBase != tt.expectedBase || gotDate != tt.expectedDate {
-				t.Errorf("parseDailyMetric(%q) = (%q, %q), want (%q, %q)",
-					tt.key, gotBase, gotDate, tt.expectedBase, tt.expectedDate)
-			}
-		})
-	}
+	output := w.Body.String()
+	today := time.Now().UTC().Format("2006-01-02")
 
-	// Test session type parsing
-	sessionTypeTests := []struct {
-		key             string
-		expectedBase    string
-		expectedSession string
-		expectedDate    string
+	expectedPatterns := []struct {
+		description string
+		pattern     string
 	}{
-		{"tool_calls_quotes_sse_2025-08-05", "tool_calls_quotes", "sse", "2025-08-05"},
-		{"tool_calls_quotes_mcp_2025-08-05", "tool_calls_quotes", "mcp", "2025-08-05"},
-		{"tool_calls_quotes_stdio_2025-08-05", "tool_calls_quotes", "stdio", "2025-08-05"},
-		{"tool_calls_quotes_unknown_2025-08-05", "tool_calls_quotes", "unknown", "2025-08-05"},
-		{"tool_calls_quotes_2025-08-05", "tool_calls_quotes", "", "2025-08-05"}, // No session type
-		{"tool_errors_login_session_error_sse_2025-12-31", "tool_errors_login_session_error", "sse", "2025-12-31"},
+		{
+			"tool calls with correct value and labels",
+			fmt.Sprintf(`tool_calls_total{date="%s",service="test-service",session_type="mcp",tool="quotes"} 2`, today),
+		},
+		{
+			"tool errors with correct value and labels",
+			fmt.Sprintf(`tool_errors_total{date="%s",error_type="api_error",service="test-service",session_type="mcp",tool="quotes"} 1`, today),
+		},
 	}
 
-	for _, tt := range sessionTypeTests {
-		t.Run(tt.key+"_session_type", func(t *testing.T) {
-			gotBase, gotSession, gotDate := m.parseDailyMetric(tt.key)
-			if gotBase != tt.expectedBase || gotSession != tt.expectedSession || gotDate != tt.expectedDate {
-				t.Errorf("parseDailyMetric(%q) = (%q, %q, %q), want (%q, %q, %q)",
-					tt.key, gotBase, gotSession, gotDate, tt.expectedBase, tt.expectedSession, tt.expectedDate)
-			}
-		})
+	for _, expected := range expectedPatterns {
+		if !strings.Contains(output, expected.pattern) {
+			t.Errorf("Expected output to contain %s: %s\nFull output: %s", expected.description, expected.pattern, output)
+		}
 	}
 }