<?php
namespace Agentsia_Agents;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Images of a page and their alternative text, read and fixed by the Agentsia SEO agent.
 *
 *   GET  /wp-json/agentsia/v1/images?url=<page url>   (or ?id=<post id>)
 *   POST /wp-json/agentsia/v1/images/<post id>/alt
 *        { "images": [ { "attachment_id": 12, "alt": "...", "library_alt": "..." }, { "src": "https://...", "alt": "..." } ] }
 *
 * Why the page content is edited too: the block editor and the classic editor copy the alt text INTO the
 * page HTML when the image is inserted. Changing the media library alone leaves every existing page
 * unchanged. So each image is matched in `post_content` (by its `wp-image-<id>` class, or by its exact
 * address when it has no media id) and its `alt` attribute is rewritten; the library alt is updated too
 * (used by featured images and page builders such as Elementor, whose content is not in `post_content`).
 *
 * `library_alt` defaults to `alt`; it only differs when undoing a change (each one is restored).
 * The response is a fresh read of the page: the backend compares it with what it asked for.
 */
final class Images {

	const REST_ROUTE      = '/images';
	private const MAX_ALT = 300;
	private const MAX_ITEMS = 50;

	private static ?self $instance = null;

	public static function instance(): self {
		if ( self::$instance === null ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	public function register(): void {
		add_action( 'rest_api_init', [ $this, 'register_routes' ] );
	}

	public function register_routes(): void {
		register_rest_route(
			Seo_Meta::REST_NAMESPACE,
			self::REST_ROUTE,
			[
				'methods'             => 'GET',
				'callback'            => [ $this, 'handle_read' ],
				'permission_callback' => static function () {
					return current_user_can( 'edit_posts' );
				},
				'args'                => [
					'url' => [ 'type' => 'string' ],
					'id'  => [ 'type' => 'integer' ],
				],
			]
		);
		register_rest_route(
			Seo_Meta::REST_NAMESPACE,
			self::REST_ROUTE . '/(?P<id>\d+)/alt',
			[
				'methods'             => 'POST',
				'callback'            => [ $this, 'handle_write' ],
				'permission_callback' => static function ( \WP_REST_Request $request ) {
					return current_user_can( 'edit_post', (int) $request['id'] );
				},
				'args'                => [
					'id' => [ 'type' => 'integer', 'required' => true ],
				],
			]
		);
	}

	/**
	 * @return \WP_REST_Response|\WP_Error
	 */
	public function handle_read( \WP_REST_Request $request ) {
		$post_id = Seo_Meta::resolve_post_id( $request );
		if ( is_wp_error( $post_id ) ) {
			return $post_id;
		}
		if ( ! current_user_can( 'edit_post', $post_id ) ) {
			return new \WP_Error( 'agentsia_seo_meta_forbidden', __( 'Ce compte ne peut pas modifier cette page.', 'agentsia-agents' ), [ 'status' => 403 ] );
		}
		if ( ! class_exists( '\\WP_HTML_Tag_Processor' ) ) {
			return $this->too_old();
		}
		return new \WP_REST_Response( $this->snapshot( $post_id ), 200 );
	}

	/**
	 * @return \WP_REST_Response|\WP_Error
	 */
	public function handle_write( \WP_REST_Request $request ) {
		$post_id = (int) $request['id'];
		$post    = get_post( $post_id );
		if ( ! $post || ! is_post_type_viewable( $post->post_type ) || $post->post_type === 'attachment' ) {
			return new \WP_Error( 'agentsia_seo_meta_not_found', __( 'Page introuvable.', 'agentsia-agents' ), [ 'status' => 404 ] );
		}
		if ( ! class_exists( '\\WP_HTML_Tag_Processor' ) ) {
			return $this->too_old();
		}

		$params = $request->get_json_params();
		$items  = is_array( $params ) && isset( $params['images'] ) && is_array( $params['images'] ) ? $params['images'] : [];
		if ( empty( $items ) || count( $items ) > self::MAX_ITEMS ) {
			return new \WP_Error( 'agentsia_images_invalid', __( 'Liste d\'images vide ou trop longue (50 maximum).', 'agentsia-agents' ), [ 'status' => 400 ] );
		}

		$changes = [];
		foreach ( $items as $item ) {
			if ( ! is_array( $item ) ) {
				return new \WP_Error( 'agentsia_images_invalid', __( 'Image invalide.', 'agentsia-agents' ), [ 'status' => 400 ] );
			}
			$alt = Seo_Meta::read_text_field( $item, 'alt', self::MAX_ALT );
			if ( is_wp_error( $alt ) ) {
				return $alt;
			}
			if ( $alt === null ) {
				return new \WP_Error( 'agentsia_images_invalid', __( 'Texte alternatif manquant.', 'agentsia-agents' ), [ 'status' => 400 ] );
			}
			$library_alt = array_key_exists( 'library_alt', $item ) ? Seo_Meta::read_text_field( $item, 'library_alt', self::MAX_ALT ) : $alt;
			if ( is_wp_error( $library_alt ) ) {
				return $library_alt;
			}
			$attachment_id = isset( $item['attachment_id'] ) ? (int) $item['attachment_id'] : 0;
			$src           = isset( $item['src'] ) && is_string( $item['src'] ) ? trim( $item['src'] ) : '';
			if ( $attachment_id <= 0 && $src === '' ) {
				return new \WP_Error( 'agentsia_images_invalid', __( 'Chaque image doit porter attachment_id ou src.', 'agentsia-agents' ), [ 'status' => 400 ] );
			}
			if ( $attachment_id > 0 && get_post_type( $attachment_id ) !== 'attachment' ) {
				return new \WP_Error( 'agentsia_images_invalid', __( 'Média introuvable.', 'agentsia-agents' ), [ 'status' => 400, 'attachment_id' => $attachment_id ] );
			}
			$changes[] = [ 'attachment_id' => $attachment_id, 'src' => $src, 'alt' => $alt, 'library_alt' => $library_alt ];
		}

		// 1. Media library (shared by every page using the image; also what Elementor & co. display).
		foreach ( $changes as $change ) {
			if ( $change['attachment_id'] > 0 && $change['library_alt'] !== null && current_user_can( 'edit_post', $change['attachment_id'] ) ) {
				if ( $change['library_alt'] === '' ) {
					delete_post_meta( $change['attachment_id'], '_wp_attachment_image_alt' );
				} else {
					update_post_meta( $change['attachment_id'], '_wp_attachment_image_alt', wp_slash( $change['library_alt'] ) );
				}
			}
		}

		// 2. The alt attribute copied into the page HTML.
		$content = (string) $post->post_content;
		$updated = $this->rewrite_alts( $content, $changes );
		if ( $updated !== $content ) {
			// Only `alt` attribute values change, escaped by the tag processor. Without this, an editor
			// lacking `unfiltered_html` would see kses strip every iframe, form or script the page had.
			$had_kses = has_filter( 'content_save_pre', 'wp_filter_post_kses' );
			kses_remove_filters();
			$saved = wp_update_post( [ 'ID' => $post_id, 'post_content' => wp_slash( $updated ) ], true );
			if ( $had_kses ) {
				kses_init_filters();
			}
			if ( is_wp_error( $saved ) ) {
				return new \WP_Error( 'agentsia_images_save_failed', $saved->get_error_message(), [ 'status' => 500 ] );
			}
		}
		clean_post_cache( $post_id );

		return new \WP_REST_Response( $this->snapshot( $post_id ), 200 );
	}

	/** Rewrites the alt of every <img> matching a change (media id class first, exact address otherwise). */
	private function rewrite_alts( string $content, array $changes ): string {
		$tags = new \WP_HTML_Tag_Processor( $content );
		while ( $tags->next_tag( 'img' ) ) {
			$id  = $this->attachment_id_of( $tags );
			$src = (string) $tags->get_attribute( 'src' );
			foreach ( $changes as $change ) {
				$matches = $change['attachment_id'] > 0 ? $id === $change['attachment_id'] : ( $id === 0 && $src === $change['src'] );
				if ( $matches ) {
					$tags->set_attribute( 'alt', $change['alt'] );
					break;
				}
			}
		}
		return $tags->get_updated_html();
	}

	private function attachment_id_of( \WP_HTML_Tag_Processor $tags ): int {
		$class = (string) $tags->get_attribute( 'class' );
		return preg_match( '/\bwp-image-(\d+)\b/', $class, $m ) ? (int) $m[1] : 0;
	}

	private function snapshot( int $post_id ): array {
		$images = [];
		$tags   = new \WP_HTML_Tag_Processor( (string) get_post_field( 'post_content', $post_id ) );
		while ( $tags->next_tag( 'img' ) ) {
			$id       = $this->attachment_id_of( $tags );
			$alt      = $tags->get_attribute( 'alt' );
			$images[] = [
				'attachment_id' => $id > 0 ? $id : null,
				'src'           => (string) $tags->get_attribute( 'src' ),
				'alt'           => is_string( $alt ) ? $alt : null,
				'library_alt'   => $id > 0 ? Seo_Meta::nullable_string( get_post_meta( $id, '_wp_attachment_image_alt', true ) ) : null,
				'in_content'    => true,
				'featured'      => false,
			];
		}
		$thumbnail = (int) get_post_thumbnail_id( $post_id );
		if ( $thumbnail > 0 ) {
			$library  = Seo_Meta::nullable_string( get_post_meta( $thumbnail, '_wp_attachment_image_alt', true ) );
			$images[] = [
				'attachment_id' => $thumbnail,
				'src'           => (string) wp_get_attachment_url( $thumbnail ),
				'alt'           => $library,
				'library_alt'   => $library,
				'in_content'    => false,
				'featured'      => true,
			];
		}

		return [
			'id'             => $post_id,
			'type'           => get_post_type( $post_id ),
			'link'           => get_permalink( $post_id ),
			'post_title'     => get_the_title( $post_id ),
			// Page builders keep their layout outside `post_content`: only the library alt reaches them.
			'builder'        => get_post_meta( $post_id, '_elementor_edit_mode', true ) === 'builder' ? 'elementor' : null,
			'images'         => $images,
			'plugin_version' => AGENTSIA_AGENTS_VERSION,
		];
	}

	private function too_old(): \WP_Error {
		return new \WP_Error( 'agentsia_seo_meta_provider_unsupported', __( 'WordPress 6.2 ou plus est requis pour modifier les images.', 'agentsia-agents' ), [ 'status' => 501 ] );
	}
}