package middleware

import (
	"net/http"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	chimw "github.com/go-chi/chi/v5/middleware"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

var (
	httpRequestsTotal = promauto.NewCounterVec(
		prometheus.CounterOpts{
			Name: "govai_http_requests_total",
			Help: "HTTP 请求总数，按方法、路由模板、状态码统计。",
		},
		[]string{"method", "route", "status"},
	)
	httpRequestDuration = promauto.NewHistogramVec(
		prometheus.HistogramOpts{
			Name:    "govai_http_request_duration_seconds",
			Help:    "HTTP 请求耗时（秒），按方法与路由模板统计。",
			Buckets: prometheus.DefBuckets,
		},
		[]string{"method", "route"},
	)
)

// Metrics 是记录 Prometheus 指标的全局中间件。
// 使用 chi 的路由模板（而非原始路径）作为标签，避免高基数。
func Metrics(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		ww := chimw.NewWrapResponseWriter(w, r.ProtoMajor)

		next.ServeHTTP(ww, r)

		route := chi.RouteContext(r.Context()).RoutePattern()
		if route == "" {
			route = "unmatched"
		}
		status := ww.Status()
		if status == 0 {
			status = http.StatusOK
		}
		httpRequestsTotal.WithLabelValues(r.Method, route, strconv.Itoa(status)).Inc()
		httpRequestDuration.WithLabelValues(r.Method, route).Observe(time.Since(start).Seconds())
	})
}