<?php
/**
 * 6rsh Web Chat — website live-chat widget integration.
 *
 * Distinct from SixRsh_Widget, which is the LEGACY click-to-chat WhatsApp
 * button. Both can be installed; this class warns rather than silently
 * disabling the other, because a store owner's configuration is theirs.
 *
 * DESIGN NOTE — why identity needs a round trip:
 * the widget's visitor_token is minted by 6rsh and lives in the browser, so it
 * does not exist when WordPress renders the page. An assertion that is not bound
 * to a specific visitor_token could be lifted from one visitor's page and
 * replayed on an attacker's own session, which is precisely the takeover the
 * signature exists to prevent. So the browser asks WordPress to sign the token it
 * actually holds, and WordPress signs only for the customer its own auth cookie
 * says is logged in.
 *
 * @package SixRsh_WhatsApp
 */

defined( 'ABSPATH' ) || exit;

/**
 * Class SixRsh_Web_Chat
 */
class SixRsh_Web_Chat {

	/** Assertion validity, seconds. Must match the server's ASSERTION_TTL. */
	const ASSERTION_TTL = 300;

	/**
	 * Register frontend hooks.
	 *
	 * @return void
	 */
	public static function init(): void {
		add_action( 'rest_api_init', array( __CLASS__, 'register_routes' ) );

		if ( is_admin() ) {
			return;
		}

		add_action( 'wp_footer', array( __CLASS__, 'render' ), 20 );
	}

	/**
	 * Web Chat settings, with safe defaults.
	 *
	 * @return array
	 */
	private static function settings(): array {
		$settings = get_option( 'sixrsh_settings', array() );
		$web_chat = isset( $settings['web_chat'] ) && is_array( $settings['web_chat'] )
			? $settings['web_chat']
			: array();

		return array(
			'enabled'         => ! empty( $web_chat['enabled'] ),
			'public_key'      => isset( $web_chat['public_key'] ) ? (string) $web_chat['public_key'] : '',
			// Privacy: when a merchant turns identity passing off we send an
			// anonymous session and nothing else. Defaults to ON only because the
			// merchant must explicitly enable Web Chat in the first place.
			'pass_identity'   => ! isset( $web_chat['pass_identity'] ) || ! empty( $web_chat['pass_identity'] ),
			'pass_cart'       => ! isset( $web_chat['pass_cart'] ) || ! empty( $web_chat['pass_cart'] ),
			'position'        => isset( $web_chat['position'] ) && in_array( $web_chat['position'], array( 'left', 'right' ), true )
				? $web_chat['position']
				: 'auto',
			'host'            => isset( $web_chat['host'] ) && $web_chat['host']
				? untrailingslashit( (string) $web_chat['host'] )
				: 'https://www.6rsh.com',
		);
	}

	/**
	 * Inject the loader and the bridge script.
	 *
	 * Never throws, never blocks render, and never emits a notice: a store's
	 * checkout must not care whether 6rsh is reachable.
	 *
	 * @return void
	 */
	public static function render(): void {
		try {
			$settings = self::settings();

			if ( ! $settings['enabled'] || '' === $settings['public_key'] ) {
				return;
			}

			// Never render on the checkout or pay pages: a chat bubble over a
			// payment form costs conversions and is exactly where a script error
			// would be most expensive.
			if ( function_exists( 'is_checkout' ) && is_checkout() ) {
				return;
			}

			// Version-stamped so a widget update actually reaches shoppers.
			// The loader sits behind the host's CDN/Varnish, which rewrites the
			// Cache-Control on this file; without a changing query string a
			// browser (and the edge) would keep serving the copy it cached the
			// first time a visitor loaded the store.
			$loader = add_query_arg( 'v', SIXRSH_VERSION, $settings['host'] . '/webchat/v1/6rsh.js' );

			$context = array(
				'restUrl'  => esc_url_raw( rest_url( '6rsh/v1/webchat-identity' ) ),
				'nonce'    => wp_create_nonce( 'wp_rest' ),
				'identify' => $settings['pass_identity'] && is_user_logged_in(),
				'cart'     => $settings['pass_cart'] ? self::cart_context() : null,
				'product'  => self::product_context(),
			);
			$position = 'auto' === $settings['position'] ? '' : $settings['position'];
			wp_print_inline_script_tag(
				'(function(w,d,s,k,p){w.SixrshWidget=w.SixrshWidget||{};w.SixrshWidget.key=k;if(p){w.SixrshWidget.position=p;}'
				. 'var f=d.getElementsByTagName(s)[0],j=d.createElement(s);j.async=1;'
				. 'j.src=' . wp_json_encode( $loader ) . ';f.parentNode.insertBefore(j,f);})'
				. '(window,document,"script",' . wp_json_encode( $settings['public_key'] ) . ',' . wp_json_encode( $position ) . ');'
				. 'window.SixrshWooContext=' . wp_json_encode( $context ) . ';'
			);
			wp_enqueue_script(
				'sixrsh-webchat-bridge',
				plugins_url( 'public/webchat-bridge.js', SIXRSH_FILE ),
				array(),
				SIXRSH_VERSION,
				true
			);
		} catch ( \Throwable $e ) {
			// Swallowed ON PURPOSE at the render boundary only: a broken chat
			// widget must never take down a merchant's storefront. It is still
			// recorded so the failure is not invisible.
			if ( class_exists( 'SixRsh_Logger' ) ) {
				SixRsh_Logger::log( 'web_chat_render_failed', $e->getMessage() );
			}
		}
	}

	/**
	 * Register the identity-signing route.
	 *
	 * @return void
	 */
	public static function register_routes(): void {
		register_rest_route(
			'6rsh/v1',
			'/webchat-identity',
			array(
				'methods'             => 'POST',
				'callback'            => array( __CLASS__, 'sign_identity' ),
				// Anyone may call it; the callback itself returns nothing useful
				// unless WordPress says the caller is logged in.
				'permission_callback' => '__return_true',
				'args'                => array(
					'visitor_token' => array(
						'required' => true,
						'type'     => 'string',
					),
				),
			)
		);

		register_rest_route(
			'6rsh/v1',
			'/webchat-cart',
			array(
				'methods'             => 'GET',
				'callback'            => array( __CLASS__, 'rest_cart' ),
				'permission_callback' => '__return_true',
			)
		);
	}

	/**
	 * Current cart, for the bridge's live cart-change pushes.
	 *
	 * Returns the CALLER'S OWN cart — WooCommerce resolves it from their session
	 * cookie, so there is no way to ask for somebody else's basket.
	 *
	 * @return WP_REST_Response
	 */
	public static function rest_cart() {
		$settings = self::settings();

		if ( ! $settings['enabled'] || ! $settings['pass_cart'] ) {
			return new WP_REST_Response( array( 'cart' => null ), 200 );
		}

		if ( function_exists( 'wc_load_cart' ) && ( ! function_exists( 'WC' ) || ! WC()->cart ) ) {
			// REST requests do not initialise the cart; hydrate it from the
			// customer's session the same way class-cart-tracker does.
			wc_load_cart();
		}

		return new WP_REST_Response( array( 'cart' => self::cart_context() ), 200 );
	}

	/**
	 * Sign an identity assertion for the CURRENTLY LOGGED-IN customer.
	 *
	 * The only identity this will ever sign is the one WordPress's own auth
	 * cookie proves. A logged-out caller, or a merchant who disabled identity
	 * passing, gets nothing — not an error the page has to handle, just no
	 * assertion, and the visitor stays anonymous.
	 *
	 * @param WP_REST_Request $request Request.
	 * @return WP_REST_Response
	 */
	public static function sign_identity( $request ) {
		$settings = self::settings();

		if ( ! $settings['enabled'] || ! $settings['pass_identity'] || ! is_user_logged_in() ) {
			return new WP_REST_Response( array( 'assertion' => null ), 200 );
		}

		$token = (string) $request->get_param( 'visitor_token' );

		// The token is a 40-char handle minted by 6rsh; anything else is noise.
		if ( 40 !== strlen( $token ) || ! ctype_alnum( $token ) ) {
			return new WP_REST_Response( array( 'assertion' => null ), 200 );
		}

		$api_key = (string) get_option( 'sixrsh_api_key', '' );
		if ( '' === $api_key ) {
			return new WP_REST_Response( array( 'assertion' => null ), 200 );
		}

		$user  = wp_get_current_user();
		$email = strtolower( trim( (string) $user->user_email ) );
		$phone = self::customer_phone( $user->ID );

		$expires = time() + self::ASSERTION_TTL;
		$nonce   = wp_generate_password( 24, false, false );

		$payload = implode(
			'|',
			array( $token, $email, $phone, $expires, $nonce )
		);

		// The shared secret is the SHA-256 of the API key: derivable by both
		// sides, transmitted by neither. The raw key never leaves this server.
		$signature = hash_hmac( 'sha256', $payload, hash( 'sha256', $api_key ) );

		return new WP_REST_Response(
			array(
				'assertion' => array(
					'key_prefix' => substr( $api_key, 0, 12 ) . '...' . substr( $api_key, -4 ),
					'email'      => $email,
					'phone'      => $phone,
					'expires_at' => $expires,
					'nonce'      => $nonce,
					'signature'  => $signature,
				),
				'name'      => $user->display_name,
			),
			200
		);
	}

	/**
	 * Best-effort billing phone for a customer, normalised the way 6rsh stores it.
	 *
	 * @param int $user_id User id.
	 * @return string
	 */
	private static function customer_phone( int $user_id ): string {
		$raw = (string) get_user_meta( $user_id, 'billing_phone', true );
		if ( '' === $raw ) {
			return '';
		}

		$plus   = 0 === strpos( trim( $raw ), '+' );
		$digits = preg_replace( '/\D+/', '', $raw );

		if ( '' === $digits ) {
			return '';
		}

		return $plus ? '+' . $digits : $digits;
	}

	/**
	 * Current cart contents, value and currency.
	 *
	 * @return array|null
	 */
	public static function cart_context(): ?array {
		try {
			if ( ! function_exists( 'WC' ) || ! WC()->cart ) {
				return null;
			}

			$items = array();
			foreach ( WC()->cart->get_cart() as $item ) {
				$product = isset( $item['data'] ) ? $item['data'] : null;
				if ( ! $product ) {
					continue;
				}
				$items[] = array(
					'id'       => (int) $product->get_id(),
					'name'     => (string) $product->get_name(),
					'quantity' => (int) $item['quantity'],
				);
				// A cart summary is context for an agent, not an inventory feed.
				if ( count( $items ) >= 20 ) {
					break;
				}
			}

			return array(
				'items'    => $items,
				'count'    => (int) WC()->cart->get_cart_contents_count(),
				'value'    => (float) WC()->cart->get_cart_contents_total(),
				'currency' => function_exists( 'get_woocommerce_currency' ) ? get_woocommerce_currency() : '',
			);
		} catch ( \Throwable $e ) {
			return null;
		}
	}

	/**
	 * Product / category context for the current page, so the AI can answer
	 * "is this available in M?" without the customer naming the product.
	 *
	 * @return array|null
	 */
	private static function product_context(): ?array {
		try {
			if ( function_exists( 'is_product' ) && is_product() ) {
				$product = function_exists( 'wc_get_product' ) ? wc_get_product( get_the_ID() ) : null;
				if ( ! $product ) {
					return null;
				}

				$terms = get_the_terms( $product->get_id(), 'product_cat' );

				return array(
					'type'     => 'product',
					'id'       => (int) $product->get_id(),
					'name'     => (string) $product->get_name(),
					'price'    => (string) $product->get_price(),
					'in_stock' => (bool) $product->is_in_stock(),
					'category' => ( is_array( $terms ) && $terms ) ? (string) $terms[0]->name : '',
				);
			}

			if ( function_exists( 'is_product_category' ) && is_product_category() ) {
				$term = get_queried_object();

				return array(
					'type' => 'category',
					'id'   => isset( $term->term_id ) ? (int) $term->term_id : 0,
					'name' => isset( $term->name ) ? (string) $term->name : '',
				);
			}

			return null;
		} catch ( \Throwable $e ) {
			return null;
		}
	}
}