package main

import (
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/gin-gonic/gin"
)

// ✅ GOOD: Define metrics
var (
	requestCount = prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "http_requests_total",
			Help: "Total HTTP requests",
		},
		[]string{"method", "path", "status"},
	)

	requestDuration = prometheus.NewHistogramVec(
		prometheus.HistogramOpts{
			Name: "http_request_duration_seconds",
			Help: "HTTP request duration",
		},
		[]string{"method", "path"},
	)

	activeConnections = prometheus.NewGauge(
		prometheus.GaugeOpts{
			Name: "active_connections",
			Help: "Active connections",
		},
	)
)

func init() {
	prometheus.MustRegister(requestCount)
	prometheus.MustRegister(requestDuration)
	prometheus.MustRegister(activeConnections)
}

// ✅ GOOD: Metrics middleware
func metricsMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		start := time.Now()
		activeConnections.Inc()
		defer activeConnections.Dec()

		c.Next()

		duration := time.Since(start).Seconds()
		requestCount.WithLabelValues(
			c.Request.Method,
			c.Request.URL.Path,
			strconv.Itoa(c.Writer.Status()),
		).Inc()

		requestDuration.WithLabelValues(
			c.Request.Method,
			c.Request.URL.Path,
		).Observe(duration)
	}
}

// ✅ GOOD: Expose metrics
func setupMetrics(router *gin.Engine) {
	router.GET("/metrics", gin.WrapH(promhttp.Handler()))
}

# ✅ GOOD: Prometheus configuration
global:
  scrape_interval: 15s
  evaluation_interval: 15s

scrape_configs:
  - job_name: 'go-app'
    static_configs:
      - targets: ['localhost:8080']
    metrics_path: '/metrics'

# ✅ GOOD: Prometheus and Grafana setup
version: '3.8'

services:
  prometheus:
    image: prom/prometheus:latest
    ports:
      - "9090:9090"
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
    command:
      - '--config.file=/etc/prometheus/prometheus.yml'

  grafana:
    image: grafana/grafana:latest
    ports:
      - "3000:3000"
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=admin
    volumes:
      - grafana_data:/var/lib/grafana

volumes:
  grafana_data:

// ✅ GOOD: Counter for totals
requestCount.Inc()

// ✅ GOOD: Gauge for current values
activeConnections.Set(float64(count))

// ✅ GOOD: Histogram for distributions
requestDuration.Observe(duration)

// ✅ GOOD: Meaningful labels
requestCount.WithLabelValues(method, path, status).Inc()

// ❌ BAD: No labels
requestCount.Inc()

// ✅ GOOD: Monitor important metrics
- Request count
- Request duration
- Error rate
- Active connections
- Database connections