<?php
/**
 * The Ask panel.
 *
 * @package SharelyAI
 */

namespace SharelyAI;

defined( 'ABSPATH' ) || exit;

/**
 * An answer written from this site's own pages, with citations.
 *
 * Three ways to place it: the Sharely Ask block, the `[sharelyai_ask]`
 * shortcode wherever an editor wants one, and automatically above the results
 * on the theme's own search page.
 *
 * The markup is rendered empty and filled by the browser. That is what keeps
 * the search page cacheable: nothing visitor-specific is in the HTML, and the
 * one request that varies per visitor is the token route.
 *
 * It brings no look of its own. The box is marked up as core's Search block,
 * so a theme's search styling applies to it; the panel around it takes colour,
 * type, spacing and border from the block supports, which means the editor's
 * sidebar and the theme's `theme.json` both reach it. The stylesheet holds the
 * form in a row and keeps the streamed answer's line breaks, and that is all
 * it does — a panel that insisted on its own palette is a panel that looks
 * wrong on every site but ours.
 */
final class Ask {

	public const SHORTCODE = 'sharelyai_ask';

	public const SCRIPT = 'sharelyai-ask';

	public const STYLE = 'sharelyai-ask';

	/**
	 * Rendered once per page however many times it is asked for.
	 *
	 * @var bool
	 */
	private bool $rendered = false;

	/**
	 * Constructor.
	 *
	 * @param Connection $connection Which workspace.
	 */
	public function __construct( private Connection $connection ) {}

	/**
	 * Hooks the panel up.
	 */
	public function register(): void {
		add_shortcode( self::SHORTCODE, array( $this, 'shortcode' ) );
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue' ) );

		if ( (bool) $this->connection->get( 'ask_on_search', true ) ) {
			// Above the results, where somebody who has just typed a question
			// will see it. Two hooks because there are two kinds of theme, and
			// the first attempt used neither of the right ones:
			//
			// - A **block** theme's search template opens with a `query-title`
			// block ("Search results for …"). Appending after it puts the
			// panel in the one place every block theme has, and it is there
			// even when the search found nothing — which is exactly when
			// somebody wants to ask a question instead.
			// - A **classic** theme has no blocks, so `loop_start` catches its
			// `search.php`. It does not fire when there are no results,
			// which is a limit worth knowing rather than a hook worth
			// forcing.
			//
			// Whichever fires first wins; `panel()` renders once per request.
			add_filter( 'render_block', array( $this, 'after_search_title' ), 10, 2 );
			add_action( 'loop_start', array( $this, 'before_loop' ) );
		}
	}

	/**
	 * Whether Ask can work here at all.
	 */
	private function available(): bool {
		return $this->connection->is_connected() && (bool) $this->connection->get( 'ask_enabled', true );
	}

	/**
	 * `[sharelyai_ask]`.
	 *
	 * @param array<string, string>|string $atts Shortcode attributes.
	 *
	 * @return string
	 */
	public function shortcode( $atts = array() ): string {
		$atts = shortcode_atts(
			array(
				'question'    => '',
				'placeholder' => '',
			),
			is_array( $atts ) ? $atts : array(),
			self::SHORTCODE
		);

		// An author who wrote `question="…"` wants it answered; that is the only
		// reason to put it in the shortcode.
		$question = trim( (string) $atts['question'] );
		$ask_now  = '' !== $question;

		return $this->panel( $question, (string) $atts['placeholder'], '', $ask_now );
	}

	/**
	 * The panel after a block theme's "Search results for …" heading.
	 *
	 * @param string               $content The rendered block.
	 * @param array<string, mixed> $block   The block, parsed.
	 *
	 * @return string
	 */
	public function after_search_title( $content, $block ): string {
		$content = (string) $content;
		if ( ! is_search() || ! is_array( $block ) ) {
			return $content;
		}
		if ( 'core/query-title' !== ( $block['blockName'] ?? '' ) ) {
			return $content;
		}
		// Filled in, not asked. The setting this honours says "Show it above
		// the search results", which is what it now does.
		return $content . $this->panel( get_search_query() );
	}

	/**
	 * The panel above a classic theme's search loop.
	 *
	 * @param \WP_Query $query The query starting its loop.
	 */
	public function before_loop( $query ): void {
		if ( ! $query instanceof \WP_Query || ! $query->is_search() || ! $query->is_main_query() || is_admin() ) {
			return;
		}
		// Only a theme that never fired the archive-description filter gets it
		// here; `panel()` returns nothing the second time it is asked.
		echo wp_kses_post( $this->panel( get_search_query() ) );
	}

	/**
	 * The markup, once.
	 *
	 * @param string $question    What the box starts with. Filled in, not asked
	 *                            — see $ask_now.
	 * @param string $placeholder Placeholder for the box.
	 * @param string $wrapper     Attributes for the outer element, already
	 *                            escaped — what `get_block_wrapper_attributes()`
	 *                            returns when a block is what is rendering this.
	 *                            Empty everywhere else: a shortcode has no block
	 *                            supports to carry.
	 * @param bool   $ask_now     Answer it on load, without the visitor asking.
	 *                            Only ever true because an author said so: the
	 *                            block's "Ask this straight away" field, or the
	 *                            shortcode's `question` attribute. A question
	 *                            that merely arrived from a search is filled in
	 *                            and left alone — see the note below.
	 *
	 * @return string
	 */
	public function panel( string $question = '', string $placeholder = '', string $wrapper = '', bool $ask_now = false ): string {
		if ( $this->rendered || ! $this->available() ) {
			return '';
		}
		$this->rendered = true;

		$this->enqueue();
		wp_enqueue_script( self::SCRIPT );
		wp_enqueue_style( self::STYLE );
		// Core's Search block styles the box; see Blocks::THEME_STYLE. A block
		// theme ships that stylesheet per-block, so a page with this panel and
		// no Search block on it has to ask for it.
		if ( wp_style_is( Blocks::THEME_STYLE, 'registered' ) ) {
			wp_enqueue_style( Blocks::THEME_STYLE );
		}

		$placeholder = '' !== $placeholder
			? $placeholder
			: __( 'Ask a question about this site…', 'sharelyai' );

		// Unique per panel. One hard-coded id meant that a page with the block
		// and the shortcode on it had two boxes whose labels both pointed at
		// the first one, and a screen reader could not tell them apart.
		$input_id = wp_unique_id( 'sai-ask-input-' );
		$wrapper  = '' !== $wrapper ? $wrapper : 'class="sai-ask"';

		// The box is answered by script, so this form is never really
		// submitted — except when the script has not arrived, or failed, and
		// somebody presses Enter. A form with no action and no fields submits
		// to the current URL with an empty query string, which on a site with
		// plain permalinks is the home page: the visitor asks a question and
		// is thrown off the page. Naming the page it is on, and carrying the
		// fields that identify it, makes that keystroke a reload instead.
		//
		// The input deliberately has no `name`. Giving it one would put the
		// question in the URL, and on the theme's own search page that would
		// replace `s` and stop the page being a search at all.
		list( $action, $carried ) = Blocks::target();

		ob_start();
		?>
		<?php
		// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- get_block_wrapper_attributes() escapes its own output, and the fallback is a literal.
		?>
		<?php
		/*
		 * `data-question` is the instruction to answer on load, so it is only
		 * written when an author asked for that. Searching is not asking: the
		 * Search block and the panel used to share one attribute, so pressing
		 * Search ran a search *and* put the question to the agent — one agent
		 * call per visitor per search, for an answer nobody requested. The
		 * search term is filled into the box instead, one click away.
		 */
		?>
		<section <?php echo $wrapper; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- see above. ?> data-sharelyai-ask
			data-token-url="<?php echo esc_url( rest_url( Rest::NAMESPACE . '/token' ) ); ?>"
			<?php if ( $ask_now && '' !== $question ) : ?>
				data-question="<?php echo esc_attr( $question ); ?>"
			<?php endif; ?>
			>
			<form class="wp-block-search wp-block-search__button-outside wp-block-search__text-button sai-ask__form" role="search" method="get" action="<?php echo esc_url( $action ); ?>" data-sai-form>
				<label class="wp-block-search__label screen-reader-text" for="<?php echo esc_attr( $input_id ); ?>"><?php esc_html_e( 'Ask a question', 'sharelyai' ); ?></label>
				<?php
				// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- built from esc_attr() in Blocks::target().
				echo $carried;
				?>
				<div class="wp-block-search__inside-wrapper">
					<input type="search" id="<?php echo esc_attr( $input_id ); ?>" class="wp-block-search__input sai-ask__input" data-sai-input
						placeholder="<?php echo esc_attr( $placeholder ); ?>"
						value="<?php echo esc_attr( $question ); ?>" autocomplete="off">
					<button type="submit" class="wp-block-search__button wp-element-button sai-ask__send" data-sai-send><?php esc_html_e( 'Ask', 'sharelyai' ); ?></button>
				</div>
			</form>
			<?php // aria-live, because the answer arrives after the page has settled: without it a screen reader never hears that one came. ?>
			<div class="sai-ask__answer" data-sai-answer role="status" aria-live="polite" hidden></div>
			<ol class="sai-ask__sources" data-sai-sources hidden></ol>
			<p class="sai-ask__note" data-sai-note role="status" aria-live="polite" hidden></p>
		</section>
		<?php
		return (string) ob_get_clean();
	}

	/**
	 * Registers the panel's script and styles.
	 *
	 * Registered rather than enqueued: nothing loads on a page with no panel
	 * on it, and `panel()` enqueues them when it renders one.
	 */
	public function enqueue(): void {
		if ( ! wp_script_is( self::SCRIPT, 'registered' ) ) {
			wp_register_script( self::SCRIPT, PLUGIN_URL . 'assets/js/ask.js', array(), Assets::version( 'assets/js/ask.js' ), true );
			wp_set_script_translations( self::SCRIPT, 'sharelyai' );
			wp_localize_script(
				self::SCRIPT,
				'sharelyaiAsk',
				array(
					'thinking'    => __( 'Thinking…', 'sharelyai' ),
					'unavailable' => __( 'Answers are not available right now. The search results below still work.', 'sharelyai' ),
					'sources'     => __( 'Sources', 'sharelyai' ),
					'stop'        => __( 'Stop', 'sharelyai' ),
					'ask'         => __( 'Ask', 'sharelyai' ),
				)
			);
		}
		if ( ! wp_style_is( self::STYLE, 'registered' ) ) {
			wp_register_style( self::STYLE, PLUGIN_URL . 'assets/css/ask.css', array(), Assets::version( 'assets/css/ask.css' ) );
		}
	}
}