package middleware

import (
	"context"
	"encoding/json"
	"net/http"
	"strings"

	"5803025015/w04/internal/models"
)

type contextKey string

const UserIDKey contextKey = "user_id"

func GetUserID(ctx context.Context) string {
	if val, ok := ctx.Value(UserIDKey).(string); ok {
		return val
	}
	return ""
}

type SessionStore interface {
	Get(ctx context.Context, token string) (*models.Session, error)
}

type AuthMiddleware struct {
	sessionStore SessionStore
}

func NewAuthMiddleware(sessionStore SessionStore) *AuthMiddleware {
	return &AuthMiddleware{sessionStore: sessionStore}
}

func writeJSONError(w http.ResponseWriter, status int, msg string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(map[string]string{"error": msg})
}

func (m *AuthMiddleware) RequireAuth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		authHeader := r.Header.Get("Authorization")
		if authHeader == "" {
			writeJSONError(w, http.StatusUnauthorized, "unauthorized")
			return
		}

		const bearerPrefix = "bearer "
		if !strings.HasPrefix(strings.ToLower(authHeader), bearerPrefix) {
			writeJSONError(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		token := strings.TrimSpace(authHeader[len(bearerPrefix):])
		if token == "" {
			writeJSONError(w, http.StatusUnauthorized, "unauthorized")
			return
		}

		session, err := m.sessionStore.Get(r.Context(), token)
		if err != nil || session == nil {
			writeJSONError(w, http.StatusUnauthorized, "unauthorized")
			return
		}

		ctx := context.WithValue(r.Context(), UserIDKey, session.UserID)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (m *AuthMiddleware) RequireAuthFunc(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		m.RequireAuth(next).ServeHTTP(w, r)
	}
}

func RequireAuth(sessionStore SessionStore) func(http.Handler) http.Handler {
	return NewAuthMiddleware(sessionStore).RequireAuth
}