import { writable, derived } from 'svelte/store';
import type { AuthState } from '$lib/types/client';
import { STORAGE_KEY_AUTH_TOKEN, STORAGE_KEY_USER_PROFILE } from '$lib/utils/constants';
import { getItem, setItem, removeItem } from '$lib/services/storage';

/**
 * Auth store managing user authentication state
 * Persists token and user info to localStorage
 */

// Create initial state from localStorage if available
function createInitialState(): AuthState {
	const token = getItem<string>(STORAGE_KEY_AUTH_TOKEN);
	const user = getItem<AuthState['user']>(STORAGE_KEY_USER_PROFILE);

	if (token && user) {
		// Check if token is expired
		const tokenExpiry = user.tokenExpiry;
		if (tokenExpiry && Date.now() < tokenExpiry) {
			return {
				user,
				token,
				tokenExpiry,
				isAuthenticated: true
			};
		}
	}

	return {
		user: null,
		token: null,
		tokenExpiry: null,
		isAuthenticated: false
	};
}

// Create the auth store
function createAuthStore() {
	const { subscribe, set, update } = writable<AuthState>(createInitialState());

	return {
		subscribe,
		
		/**
		 * Set authenticated user and token
		 */
		login: (user: NonNullable<AuthState['user']>, token: string, tokenExpiry?: number) => {
			const expiry = tokenExpiry || Date.now() + 24 * 60 * 60 * 1000; // Default 24h
			
			const newState: AuthState = {
				user: { ...user, tokenExpiry: expiry },
				token,
				tokenExpiry: expiry,
				isAuthenticated: true
			};
			
			// Persist to storage
			setItem(STORAGE_KEY_AUTH_TOKEN, token);
			setItem(STORAGE_KEY_USER_PROFILE, newState.user);
			
			set(newState);
		},
		
		/**
		 * Clear authentication state
		 */
		logout: () => {
			// Clear storage
			removeItem(STORAGE_KEY_AUTH_TOKEN);
			removeItem(STORAGE_KEY_USER_PROFILE);
			
			set({
				user: null,
				token: null,
				tokenExpiry: null,
				isAuthenticated: false
			});
		},
		
		/**
		 * Update user profile
		 */
		updateUser: (user: NonNullable<AuthState['user']>) => {
			update((state) => {
				if (!state.isAuthenticated) return state;
				
				const newUser = { ...state.user, ...user };
				setItem(STORAGE_KEY_USER_PROFILE, newUser);
				
				return {
					...state,
					user: newUser
				};
			});
		},
		
		/**
		 * Check if token is expired and logout if needed
		 */
		checkExpiration: () => {
			update((state) => {
				if (!state.isAuthenticated || !state.tokenExpiry) return state;
				
				if (Date.now() >= state.tokenExpiry) {
					// Token expired - clear state
					removeItem(STORAGE_KEY_AUTH_TOKEN);
					removeItem(STORAGE_KEY_USER_PROFILE);
					
					return {
						user: null,
						token: null,
						tokenExpiry: null,
						isAuthenticated: false
					};
				}
				
				return state;
			});
		}
	};
}

export const authStore = createAuthStore();

// Derived store for checking if authenticated
export const isAuthenticated = derived(
	authStore,
	($auth) => $auth.isAuthenticated
);

// Derived store for getting current user
export const currentUser = derived(
	authStore,
	($auth) => $auth.user
);

// Check token expiration every minute
if (typeof window !== 'undefined') {
	setInterval(() => {
		authStore.checkExpiration();
	}, 60 * 1000);
}