package metrics

import (
	"io"
	"net/http"
	"net/http/httptest"

	"github.com/gofiber/fiber/v2"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	HTTPRequestsTotal = prometheus.NewCounterVec(
		prometheus.CounterOpts{Name: "http_requests_total", Help: "Total HTTP requests"},
		[]string{"method", "path", "status"},
	)
	HTTPRequestDuration = prometheus.NewHistogramVec(
		prometheus.HistogramOpts{Name: "http_request_duration_seconds", Help: "HTTP request duration"},
		[]string{"method", "path"},
	)
	DBConnectionsActive = prometheus.NewGauge(
		prometheus.GaugeOpts{Name: "db_connections_active", Help: "Active DB connections"},
	)
	RedisConnectionsActive = prometheus.NewGauge(
		prometheus.GaugeOpts{Name: "redis_connections_active", Help: "Active Redis connections"},
	)
)

func init() {
	prometheus.MustRegister(HTTPRequestsTotal, HTTPRequestDuration, DBConnectionsActive, RedisConnectionsActive)
}

// Handler returns a Fiber handler that serves the Prometheus metrics endpoint.
// It wraps promhttp.Handler() without requiring the gofiber/adaptor package.
func Handler(c *fiber.Ctx) error {
	handler := promhttp.Handler()
	req, err := http.NewRequest(http.MethodGet, "/metrics", nil)
	if err != nil {
		return c.SendStatus(fiber.StatusInternalServerError)
	}
	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, req)
	result := rec.Result()
	defer result.Body.Close()

	c.Set("Content-Type", result.Header.Get("Content-Type"))
	c.Status(result.StatusCode)
	body, err := io.ReadAll(result.Body)
	if err != nil {
		return c.SendStatus(fiber.StatusInternalServerError)
	}
	return c.Send(body)
}