package service

import (
	"context"
	"fmt"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
	"github.com/rs/zerolog"
)

const (
	panicRecoveryMsg = "panic recovered"
	defaultLogMsg    = "incoming request"
)

type userCtxKey struct{}

// Get JWT bearer from request's authorization header, parse it with custom user claims, and
// ensure its validity before attaching the claims to the request's context.
func authMiddleware(jwtSecret string, expectedType string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			tokenString, err := getTokenFromRequest(r)
			if err != nil {
				respondError(w, http.StatusUnauthorized, fmt.Sprintf("Unauthorized: %s", err))
			}

			token, err := jwt.ParseWithClaims(tokenString, &userClaims{}, func(token *jwt.Token) (interface{}, error) {
				return []byte(jwtSecret), nil
			})
			if err != nil || !token.Valid {
				respondError(w, http.StatusUnauthorized, "Invalid token")
				return
			}

			claims, ok := token.Claims.(*userClaims)
			if !ok || claims.TokenType != expectedType {
				respondError(w, http.StatusUnauthorized, "Invalid token type")
				return
			}

			ctx := context.WithValue(r.Context(), userCtxKey{}, claims)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// JWT access token parsing, verification, and validation.
func requireAccessToken(jwtSecret string) func(http.Handler) http.Handler {
	return authMiddleware(jwtSecret, "access")
}

// JWT refresh token parsing, verification, and validation.
func requireRefreshToken(jwtSecret string) func(http.Handler) http.Handler {
	return authMiddleware(jwtSecret, "refresh")
}

// Ensure the current user is an administrator.
func adminOnlyMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user, ok := r.Context().Value(userCtxKey{}).(*userClaims)
		if !ok || !user.Admin {
			respondError(w, http.StatusForbidden, "Forbidden")
			return
		}
		next.ServeHTTP(w, r)
	})
}

// Ensure the targeted resource is owned by the current user (i.e. current user's ID matches with
// the one stored into the resource).
func ownerOnlyMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user, ok := r.Context().Value(userCtxKey{}).(*userClaims)
		requestedID := chi.URLParam(r, "id")
		if !ok || user.ID != requestedID {
			respondError(w, http.StatusForbidden, "Forbidden")
			return
		}
		next.ServeHTTP(w, r)
	})
}

// Append user data into request's context based on user ID as a URL parameter.
func userCtx(store UserStore) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			userIDStr := chi.URLParam(r, "id")
			userID, err := uuid.Parse(userIDStr)
			if err != nil {
				respondError(w, http.StatusNotFound, "Invalid user ID")
				return
			}

			user, err := store.GetUserByID(r.Context(), userID)
			if err != nil {
				respondError(w, http.StatusNotFound, "User not found")
				return
			}

			ctx := context.WithValue(r.Context(), userCtxKey{}, user)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// Zerolog compatible logger middleware. Automatically logs and recovers from errors with HTTP 500
// response, by default logs to INFO level.
func loggerMiddleware(log *zerolog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		fn := func(w http.ResponseWriter, r *http.Request) {
			log := log.With().Logger()

			ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)

			t1 := time.Now()
			defer func() {
				t2 := time.Now()

				// Recover automatically and respond with HTTP 500
				if rec := recover(); rec != nil {
					log.Error().
						Str("type", "error").
						Timestamp().
						Interface("recover_info", rec).
						Msg(panicRecoveryMsg)
					http.Error(ww, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
				}

				// Log a regular HTTP request with some metadata
				log.Info().
					Str("type", "access").
					Timestamp().
					Fields(map[string]interface{}{
						"remote_ip":  r.RemoteAddr,
						"url":        r.URL.Path,
						"proto":      r.Proto,
						"method":     r.Method,
						"user_agent": r.Header.Get("User-Agent"),
						"status":     ww.Status(),
						"latency_ms": float64(t2.Sub(t1).Nanoseconds()) / 1000000.0,
						"bytes_in":   r.Header.Get("Content-Length"),
						"bytes_out":  ww.BytesWritten(),
					}).
					Msg(defaultLogMsg)
			}()

			next.ServeHTTP(ww, r)
		}
		return http.HandlerFunc(fn)
	}
}