feat: expose daily metric query api

go/vehicle-gateway/cmd/realtime-api/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"database/sql"
 	"encoding/json"
 	"net/http"
 	"os"
@@ -11,12 +12,14 @@ import (
 	"syscall"
 	"time"
 
+	_ "github.com/go-sql-driver/mysql"
 	"github.com/redis/go-redis/v9"
 	"github.com/segmentio/kafka-go"
 
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/observability"
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/realtime"
+	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/stats"
 )
 
 func main() {
@@ -45,9 +48,36 @@ func main() {
 		logger.Warn("KAFKA_BROKERS is empty; realtime api will serve existing redis data only")
 	}
 
+	mux := http.NewServeMux()
+	mux.Handle("/api/realtime/vehicles/", realtime.NewHandler(repository))
+	closeStats := func() {}
+	if dsn := strings.TrimSpace(os.Getenv("MYSQL_DSN")); dsn != "" {
+		db, err := sql.Open("mysql", dsn)
+		if err != nil {
+			logger.Error("stats mysql open failed", "error", err)
+			os.Exit(1)
+		}
+		if err := db.PingContext(ctx); err != nil {
+			_ = db.Close()
+			logger.Error("stats mysql ping failed", "error", err)
+			os.Exit(1)
+		}
+		closeStats = func() { _ = db.Close() }
+		mux.Handle("/api/stats/daily-metrics", stats.NewMetricHandler(stats.NewMetricRepository(db)))
+		logger.Info("stats mysql query enabled")
+	} else {
+		mux.HandleFunc("/api/stats/daily-metrics", func(w http.ResponseWriter, _ *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusServiceUnavailable)
+			_ = json.NewEncoder(w).Encode(map[string]any{"error": "MYSQL_DSN is not configured"})
+		})
+		logger.Warn("MYSQL_DSN is empty; stats query api disabled")
+	}
+	defer closeStats()
+
 	server := &http.Server{
 		Addr:              env("HTTP_ADDR", ":20210"),
-		Handler:           realtime.NewHandler(repository),
+		Handler:           mux,
 		ReadHeaderTimeout: 5 * time.Second,
 	}
 	go func() {