// internal/metrics/prometheus.go
package metrics

import (
	"strconv"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

var (
	// HttpRequestsTotal counts the total number of API requests
	HttpRequestsTotal = promauto.NewCounterVec(
		prometheus.CounterOpts{
			Name: "musicapp_http_requests_total",
			Help: "Total number of HTTP requests",
		},
		[]string{"method", "path", "status"},
	)

	// HttpRequestDuration measures how long your API endpoints take to respond
	HttpRequestDuration = promauto.NewHistogramVec(
		prometheus.HistogramOpts{
			Name:    "musicapp_http_request_duration_seconds",
			Help:    "Duration of HTTP requests in seconds",
			Buckets: prometheus.DefBuckets,
		},
		[]string{"method", "path"},
	)
)

func PrometheusMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		start := time.Now()

		c.Next()

		duration := time.Since(start).Seconds()
		status := strconv.Itoa(c.Writer.Status())
		method := c.Request.Method

		// If we used URL.Path, "/tracks/123" and "/tracks/456" would create thousands
		// of different metrics and crash Prometheus. FullPath() gives us "/tracks/:id".
		path := c.FullPath()
		if path == "" {
			path = "unknown"
		}

		// Don't track the /metrics endpoint itself
		if path != "/metrics" {
			HttpRequestsTotal.WithLabelValues(method, path, status).Inc()
			HttpRequestDuration.WithLabelValues(method, path).Observe(duration)
		}
	}
}