<?php
namespace AccessNow\SimpleLMS;

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

/**
 * The image at the top of course, lesson and quiz pages, and how it is shown.
 *
 * Courses, units and lessons can each have a header image (their featured image) and a header
 * style. A lesson or quiz without its own uses its unit's, then its course's: the image only when
 * the "header_inherit" setting is on (the default), the style always.
 */
class Lesson_Header {

	/** Post meta holding the style; empty means "same as the level above". */
	const META = '_slms_header_style';

	/** Banner: the whole image. Compact: a short strip. None: no image. */
	const STYLES = array( 'banner', 'compact', 'none' );

	/**
	 * The post and the posts above it, nearest first: quiz, lesson, unit, course.
	 *
	 * @param int $post_id Course, unit, lesson or quiz.
	 * @return int[]
	 */
	public static function chain( $post_id ) {
		$chain = array();
		$id    = (int) $post_id;
		$up    = array(
			'slms_quiz'   => '_slms_parent_lesson',
			'slms_lesson' => '_slms_parent_unit',
			'slms_unit'   => '_slms_parent_course',
		);
		while ( $id && count( $chain ) < 4 ) {
			$chain[] = $id;
			$type    = get_post_type( $id );
			$id      = isset( $up[ $type ] ) ? (int) get_post_meta( $id, $up[ $type ], true ) : 0;
		}
		return $chain;
	}

	/**
	 * The header image's attachment id, or 0.
	 *
	 * @param int $post_id Course, unit, lesson or quiz.
	 * @return int
	 */
	public static function image_id( $post_id ) {
		$chain = self::chain( $post_id );
		if ( ! Settings::get( 'header_inherit', 1 ) ) {
			$chain = array_slice( $chain, 0, 1 );
		}
		foreach ( $chain as $id ) {
			$thumb = (int) get_post_thumbnail_id( $id );
			if ( $thumb ) {
				return $thumb;
			}
		}
		return 0;
	}

	/**
	 * The header style: the nearest one set, or "banner".
	 *
	 * @param int $post_id Course, unit, lesson or quiz.
	 * @return string One of self::STYLES.
	 */
	public static function style( $post_id ) {
		foreach ( self::chain( $post_id ) as $id ) {
			$style = get_post_meta( $id, self::META, true );
			if ( in_array( $style, self::STYLES, true ) ) {
				return $style;
			}
		}
		return 'banner';
	}

	/**
	 * The header for a page: image id and style.
	 *
	 * @param int $post_id Course, lesson or quiz.
	 * @return array{image_id:int,style:string}
	 */
	public static function get( $post_id ) {
		$header = array(
			'image_id' => self::image_id( $post_id ),
			'style'    => self::style( $post_id ),
		);
		/**
		 * The header shown at the top of a course, lesson or quiz page.
		 *
		 * @param array $header  'image_id' (attachment id, 0 for none) and 'style' ('banner', 'compact' or 'none').
		 * @param int   $post_id The course, lesson or quiz.
		 */
		$header = apply_filters( 'accessnow_slms_page_header', $header, $post_id );
		return array(
			'image_id' => isset( $header['image_id'] ) ? absint( $header['image_id'] ) : 0,
			'style'    => isset( $header['style'] ) && in_array( $header['style'], self::STYLES, true ) ? $header['style'] : 'banner',
		);
	}

	/**
	 * Print the header (templates/partials/page-header.php, which themes can override).
	 *
	 * @param int $post_id Course, lesson or quiz.
	 */
	public static function render( $post_id ) {
		$header = self::get( $post_id );
		if ( ! $header['image_id'] || 'none' === $header['style'] ) {
			return;
		}
		Template_Loader::get_partial( 'page-header.php', $header );
	}

	/**
	 * The "Header style" row for the course, unit and lesson settings boxes.
	 *
	 * @param \WP_Post $post The post being edited.
	 */
	public static function render_field( $post ) {
		$value   = get_post_meta( $post->ID, self::META, true );
		$default = array(
			'slms_course' => __( 'Banner (default)', 'accessnow-lms' ),
			'slms_unit'   => __( 'Same as the course', 'accessnow-lms' ),
			'slms_lesson' => __( 'Same as the unit', 'accessnow-lms' ),
		);
		$labels  = array(
			'banner'  => __( 'Banner: the whole image', 'accessnow-lms' ),
			'compact' => __( 'Compact: a short strip', 'accessnow-lms' ),
			'none'    => __( 'None: no image', 'accessnow-lms' ),
		);
		?>
		<tr>
			<th><label for="_slms_header_style"><?php esc_html_e( 'Header style', 'accessnow-lms' ); ?></label></th>
			<td>
				<select name="_slms_header_style" id="_slms_header_style">
					<option value=""><?php echo esc_html( $default[ $post->post_type ] ?? $default['slms_lesson'] ); ?></option>
					<?php foreach ( $labels as $style => $label ) : ?>
						<option value="<?php echo esc_attr( $style ); ?>" <?php selected( $value, $style ); ?>><?php echo esc_html( $label ); ?></option>
					<?php endforeach; ?>
				</select>
				<p class="description"><?php esc_html_e( 'How the header image appears at the top of the page (a course\'s Featured image, a unit\'s or lesson\'s Header image). Lessons and quizzes use their unit\'s or course\'s style and image unless they have their own.', 'accessnow-lms' ); ?></p>
			</td>
		</tr>
		<?php
	}

	/**
	 * Save the "Header style" field. Call only after the settings box's nonce has been checked.
	 *
	 * @param int $post_id Course, unit or lesson.
	 */
	public static function save_field( $post_id ) {
		if ( ! isset( $_POST[ self::META ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Missing -- checked by the caller.
			return;
		}
		$style = self::sanitize_style( sanitize_key( wp_unslash( $_POST[ self::META ] ) ) ); // phpcs:ignore WordPress.Security.NonceVerification.Missing -- checked by the caller.
		if ( '' === $style ) {
			delete_post_meta( $post_id, self::META );
		} else {
			update_post_meta( $post_id, self::META, $style );
		}
	}

	/**
	 * An allowed style, or '' (inherit).
	 *
	 * @param mixed $value Submitted or imported value.
	 * @return string
	 */
	public static function sanitize_style( $value ) {
		return is_string( $value ) && in_array( $value, self::STYLES, true ) ? $value : '';
	}
}