<?php
/**
 * Render one selected PDF page locally, then save a separate image.
 *
 * @package AffStackDevImageManager
 */

namespace AffStackDev\ImageManager;

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

/**
 * A PDF page as a picture: one page drawn on this server with Imagick (which reads PDF through Ghostscript), looked at
 * as a private preview, then saved as a new PNG media item; the PDF is never changed.
 */
final class PDF {
	/** 1.9.0 (F-IM-32): Imagick reads PDF only through Ghostscript; the tool is offered where reading a PDF page passed its self-test. */
	public static function available(): bool {
		return ! empty( Compression::capabilities()['imagick-pdf']['available'] );
	}

	/**
	 * The self-test for the encoder list: Imagick reads the one-page test PDF (no customer media) at 72 dpi.
	 *
	 * @return array{available:bool,format:string,selftest:string}
	 */
	public static function selftest(): array {
		$out = array(
			'available' => false,
			'format'    => 'pdf',
			'selftest'  => 'not installed or safe execution unavailable',
		);
		if ( ! class_exists( '\\Imagick' ) || ! extension_loaded( 'imagick' ) || ! \Imagick::queryFormats( 'PDF' ) ) {
			return $out;
		}
		$image = new \Imagick();
		try {
			$image->setResolution( 72, 72 );
			$image->readImageBlob( PDF_Copy::sample() );
			$ok              = 1 === $image->getNumberImages() && 200 === $image->getImageWidth() && 100 === $image->getImageHeight();
			$out['available'] = $ok;
			$out['selftest']  = $ok ? 'pdf page read passed' : 'output rejected';
		} catch ( \Throwable $e ) {
			// Without Ghostscript (or where the host's policy forbids PDF) Imagick cannot read the page at all.
			$out['selftest'] = 'not installed or safe execution unavailable';
		} finally {
			$image->clear();
		}
		return $out;
	}

	/**
	 * Draw one page as a private PNG preview.
	 *
	 * @param int  $id      The PDF attachment.
	 * @param int  $page    The page, 1 to 500.
	 * @param int  $edge    The longest side of the picture, 320 to 2,560 pixels.
	 * @param bool $confirm The owner's confirmation.
	 * @return array The draft.
	 * @throws \RuntimeException With a reason code as its message when the step cannot be done.
	 */
	public static function prepare( int $id, int $page, int $edge, bool $confirm ): array {
		$im_reviewed_owner_lock = Reviewed_Store::enter();
		try {
			if ( ! $confirm ) {
				throw new \RuntimeException( 'media_pdf_confirm' );
			}
			if ( $page < 1 || $page > 500 || $edge < 320 || $edge > 2560 ) {
				throw new \RuntimeException( 'media_pdf_limits' );
			}
			if ( ! self::available() ) {
				throw new \RuntimeException( 'media_pdf_backend' );
			}
			return Media_Actions::locked(
				'attachment:' . $id,
				static function () use ( $id, $page, $edge ) {
					$source = Media_Actions::source( $id, 'application/pdf' );
				// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- Capability-checked PDF conversion uses bounded private local staging for the host image library; only validated generated output is published.
					if ( '%PDF-' !== file_get_contents( $source['path'], false, null, 0, 5 ) ) {
						throw new \RuntimeException( 'media_pdf_invalid' );
					}
					$temp   = Media_Actions::directory() . '/render-' . bin2hex( random_bytes( 16 ) ) . '.png';
					$image  = new \Imagick();
					$limits = array();
					// Respect tighter host limits and restore request-global settings afterwards. No TIME limit (1.9.0,
					// F-IM-36): ImageMagick counts it from the start of the PHP process, so in a web server's PHP worker
					// that has run longer than the limit every render failed; PHP's own time limit still applies.
					foreach ( array(
						'MEMORY'     => 134217728,
						'MAP'        => 134217728,
						'DISK'       => 268435456,
						'AREA'       => 24000000,
						'THREAD'     => 1,
						'WIDTH'      => 16384,
						'HEIGHT'     => 16384,
						'LISTLENGTH' => 4,
					) as  $name => $max ) {
						$constant = '\\Imagick::RESOURCETYPE_' . $name;
						if ( ! defined( $constant ) ) {
							continue;
						}
						$type            = constant( $constant );
						$old             = \Imagick::getResourceLimit( $type );
						$limits[ $type ] = $old;
						\Imagick::setResourceLimit( $type, $old > 0 ? min( $old, $max ) : $max );
					}
					try {
						$image->setResolution( 144, 144 );
						$image->setOption( 'pdf:use-cropbox', 'true' );
						// The source is an existing local attachment; only the bounded page selector is appended.
						$image->readImage( $source['path'] . '[' . ( $page - 1 ) . ']' );
						if ( $image->getNumberImages() !== 1 || $image->getImageWidth() * $image->getImageHeight() > 24000000 ) {
							throw new \RuntimeException( 'media_pdf_limits' );
						}
						$image->setImageBackgroundColor( 'white' );
						$flat = $image->mergeImageLayers( \Imagick::LAYERMETHOD_FLATTEN );
						$image->clear();
						$image = $flat;
						if ( $image->getImageColorspace() !== \Imagick::COLORSPACE_SRGB ) {
							$image->transformImageColorspace( \Imagick::COLORSPACE_SRGB );
						}
						if ( max( $image->getImageWidth(), $image->getImageHeight() ) > $edge ) {
							$image->thumbnailImage( $edge, $edge, true );
						}
						$image->setImagePage( 0, 0, 0, 0 );
						$image->stripImage();
						$image->setImageFormat( 'png' );
						if ( ! $image->writeImage( $temp ) ) {
							throw new \RuntimeException( 'media_pdf_backend' );
						}
						// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- Capability-checked PDF conversion uses bounded private local staging for the host image library; only validated generated output is published.
						@chmod( $temp, 0600 );
						return Media_Draft::store(
							$id,
							'convert',
							$temp,
							$source,
							array(
								'operation'    => 'pdf_page',
								'page'         => $page,
								'maximum_edge' => $edge,
								'background'   => 'white',
								'format'       => 'png',
							)
						);
					} catch ( \ImagickException $e ) {
						throw new \RuntimeException( 'media_pdf_backend' );
					} finally {
						$image->clear();
						foreach ( $limits as  $type => $limit ) {
							\Imagick::setResourceLimit( $type, $limit );
						} if ( is_file( $temp ) ) {
							Reviewed_Store::wp_delete_file( $temp );
						}
					}
				}
			);

		} finally {
			Reviewed_Store::leave( $im_reviewed_owner_lock );
		}
	}

	/**
	 * Save the prepared page as a new PNG media item beside the PDF, with its caption, folders and collections.
	 *
	 * @param int    $id      The PDF attachment.
	 * @param string $token   The draft.
	 * @param bool   $confirm The owner's confirmation.
	 * @return int The new attachment.
	 * @throws \RuntimeException With a reason code as its message when the step cannot be done.
	 */
	public static function save( int $id, string $token, bool $confirm ): int {
		$im_reviewed_owner_lock = Reviewed_Store::enter();
		try {
			if ( ! $confirm ) {
				throw new \RuntimeException( 'media_pdf_confirm' );
			}
			return Media_Actions::locked(
				'attachment:' . $id,
				static function () use ( $id, $token ) {
					$draft = Media_Draft::checked( $id, 'convert', $token );
					if ( 'saved' === $draft['state'] ) {
						if ( 'attachment' !== get_post_type( (int) $draft['result'] ) ) {
							throw new \RuntimeException( 'media_draft_missing' );
						}
						return (int) $draft['result'];
					}
					Media_Actions::unchanged( $id, $draft['source'] );
					$path = Media_Draft::path( $draft );
					require_once ABSPATH . 'wp-admin/includes/image.php';
					$receipt = $id . ':' . get_current_user_id() . ':' . $token;
				// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_key,WordPress.DB.SlowDBQuery.slow_db_query_meta_value -- Bounded administrator media listing or per-file upload receipt lookup; taxonomy/metadata selection is required for the requested folder/collection and retry identity.
					$existing = get_posts(
						array(
							'post_type'      => 'attachment',
							'post_status'    => 'inherit',
							'posts_per_page' => 1,
							'fields'         => 'ids',
							// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_key -- Bounded administrator media listing or per-file upload receipt lookup; taxonomy/metadata selection is required for the requested folder/collection and retry identity.
							'meta_key'       => '_afsd_im_pdf_receipt',
							// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_value -- Bounded administrator media listing or per-file upload receipt lookup; taxonomy/metadata selection is required for the requested folder/collection and retry identity.
							'meta_value'     => $receipt,
						)
					);
					$new      = $existing ? (int) $existing[0] : 0;
					if ( $new && ! current_user_can( 'edit_post', $new ) ) {
						throw new \RuntimeException( 'media_action_access' );
					}
					if ( ! $new ) {
						$uploads = wp_upload_dir();
						// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- Capability-checked PDF conversion uses bounded private local staging for the host image library; only validated generated output is published.
						if ( ! empty( $uploads['error'] ) || ! is_writable( $uploads['path'] ) ) {
							throw new \RuntimeException( 'media_action_upload' );
						}
						$name = sanitize_file_name( pathinfo( $draft['source']['path'], PATHINFO_FILENAME ) . '-page-' . (int) $draft['recipe']['page'] . '.png' );
						$dest = trailingslashit( $uploads['path'] ) . wp_unique_filename( $uploads['path'], $name );
						// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink -- Capability-checked PDF conversion uses bounded private local staging for the host image library; only validated generated output is published.
						if ( ! Reviewed_Store::copy( $path, $dest ) || hash_file( 'sha256', $dest ) !== $draft['image']['sha256'] ) {
							@Reviewed_Store::unlink( $dest );
							throw new \RuntimeException( 'media_draft_write' );
						}
						// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- Capability-checked PDF conversion uses bounded private local staging for the host image library; only validated generated output is published.
						@chmod( $dest, 0644 );
						$post = get_post( $id );
						$new  = Reviewed_Store::wp_insert_attachment(
							wp_slash(
								array(
									'post_title'     => $post->post_title . ' — page ' . (int) $draft['recipe']['page'],
									'post_mime_type' => 'image/png',
									'post_status'    => 'inherit',
									'post_excerpt'   => $post->post_excerpt,
									'meta_input'     => array(
										'_afsd_im_pdf_receipt'  => $receipt,
										Editor::SOURCE_META => $id,
										Editor::RECIPE_META => $draft['recipe'],
									),
								)
							),
							$dest,
							0,
							true
						);
						if ( is_wp_error( $new ) || ! $new ) {
							Reviewed_Store::wp_delete_file( $dest );
							throw new \RuntimeException( 'media_draft_write' );
						}
					}
					$meta = Reviewed_Store::wp_generate_attachment_metadata( $new, get_attached_file( $new ) );
					if ( ! is_array( $meta ) || empty( $meta['width'] ) || empty( $meta['height'] ) ) {
						throw new \RuntimeException( 'media_pdf_metadata' );
					}
					Reviewed_Store::wp_update_attachment_metadata( $new, $meta );
					foreach ( array( Library::FOLDER, Library::COLLECTION ) as  $taxonomy ) {
						$terms = Library::term_ids( $id, $taxonomy );
						$set   = Reviewed_Store::wp_set_object_terms( $new, $terms, $taxonomy, false );
						if ( is_wp_error( $set ) ) {
							throw new \RuntimeException( 'media_pdf_metadata' );
						}
					}
					Media_Actions::unchanged( $id, $draft['source'] );
					$draft['state']  = 'saved';
					$draft['result'] = (int) $new;
					Media_Draft::update( $id, 'convert', $draft );
					return (int) $new;
				}
			);

		} finally {
			Reviewed_Store::leave( $im_reviewed_owner_lock );
		}
	}
}