package observability

import (
	"context"
	"log/slog"
	"net"
	"net/http"
	"runtime/debug"
	"time"

	"github.com/google/uuid"
)

type contextKey string

const requestIDContextKey contextKey = "request_id"

func Chain(h http.Handler, middlewares ...func(http.Handler) http.Handler) http.Handler {
	for i := len(middlewares) - 1; i >= 0; i-- {
		h = middlewares[i](h)
	}
	return h
}

func RequestID() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			requestID := r.Header.Get("X-Request-Id")
			if requestID == "" {
				requestID = uuid.NewString()
			}
			w.Header().Set("X-Request-Id", requestID)
			ctx := context.WithValue(r.Context(), requestIDContextKey, requestID)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

func Recover(log *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			defer func() {
				if recovered := recover(); recovered != nil {
					log.Error("panic recovered",
						slog.Any("panic", recovered),
						slog.String("request_id", RequestIDFromContext(r.Context())),
						slog.String("stack", string(debug.Stack())),
					)
					http.Error(w, "internal server error", http.StatusInternalServerError)
				}
			}()
			next.ServeHTTP(w, r)
		})
	}
}

func AccessLog(log *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			recorder := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
			started := time.Now()
			next.ServeHTTP(recorder, r)

			log.Info("http request",
				slog.String("request_id", RequestIDFromContext(r.Context())),
				slog.String("method", r.Method),
				slog.String("path", r.URL.Path),
				slog.Int("status", recorder.status),
				slog.Duration("duration", time.Since(started)),
				slog.String("remote_addr", stripPort(r.RemoteAddr)),
			)
		})
	}
}

func Timeout(timeout time.Duration) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		if timeout <= 0 {
			return next
		}
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ctx, cancel := context.WithTimeout(r.Context(), timeout)
			defer cancel()
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

func RequestIDFromContext(ctx context.Context) string {
	value, _ := ctx.Value(requestIDContextKey).(string)
	return value
}

type statusRecorder struct {
	http.ResponseWriter
	status int
}

func (s *statusRecorder) WriteHeader(statusCode int) {
	s.status = statusCode
	s.ResponseWriter.WriteHeader(statusCode)
}

func stripPort(remote string) string {
	host, _, err := net.SplitHostPort(remote)
	if err != nil {
		return remote
	}
	return host
}