Initial release

inc/class-plugin.php

+<?php
+/**
+ * Plugin functionality.
+ *
+ * @package ETH_Embed_Anchor_FM
+ */
+
+namespace ETH_Embed_Anchor_FM;
+
+/**
+ * Class Plugin.
+ */
+class Plugin {
+	/**
+	 * Regex pattern to match URL to be oEmbedded.
+	 *
+	 * @var string
+	 */
+	private const OEMBED_FORMAT = '#^https://anchor\.fm/(?!api)([^/]+)/episodes/([^/\s]+)/?#i';
+
+	/**
+	 * Anchor oEmbed endpoint with placeholder.
+	 *
+	 * @var string
+	 */
+	private const OEMBED_ENDPOINT = 'https://anchor.fm/api/v3/episodes/__EPISODE_ID__/oembed';
+
+	/**
+	 * Placeholder in self::OEMBED_ENDPOINT to be replaced with episode ID.
+	 *
+	 * @var string
+	 */
+	private const EPISODE_ID_PLACEHOLDER = '__EPISODE_ID__';
+
+	/**
+	 * Shortcode tag.
+	 *
+	 * @var string
+	 */
+	private const SHORTCODE_TAG = 'eth_anchor_fm';
+
+	/**
+	 * Singleton.
+	 *
+	 * @var Plugin
+	 */
+	private static $_instance = null;
+
+	/**
+	 * Implement singleton.
+	 *
+	 * @return Plugin
+	 */
+	public static function get_instance(): Plugin {
+		if ( ! is_a( self::$_instance, __CLASS__ ) ) {
+			self::$_instance = new self();
+			self::$_instance->_setup();
+		}
+
+		return self::$_instance;
+	}
+
+	/**
+	 * Silence is golden!
+	 */
+	private function __construct() {
+		// Add nothing here.
+	}
+
+	/**
+	 * Register hooks.
+	 *
+	 * @return void
+	 */
+	private function _setup(): void {
+		add_action( 'init', [ $this, 'action_init' ] );
+
+		add_filter(
+			'oembed_fetch_url',
+			[ $this, 'filter_oembed_fetch_url' ],
+			10,
+			3
+		);
+	}
+
+	/**
+	 * Register oEmbed handler.
+	 *
+	 * @return void
+	 */
+	public function action_init(): void {
+		wp_oembed_add_provider(
+			self::OEMBED_FORMAT,
+			self::OEMBED_ENDPOINT,
+			true
+		);
+
+		add_shortcode(
+			self::SHORTCODE_TAG,
+			[ $this, 'do_shortcode' ]
+		);
+	}
+
+	/**
+	 * Filter oEmbed URL.
+	 *
+	 * Anchor.fm's oEmbed endpoint is specific to an episode ID, which must be
+	 * extracted from the episode URL.
+	 *
+	 * @param string $provider URL of the oEmbed provider.
+	 * @param string $url      URL of the content to be embedded.
+	 * @param array  $args     Optional. Additional arguments for retrieving
+	 *                         embed HTML.
+	 * @return string
+	 */
+	public function filter_oembed_fetch_url(
+		string $provider,
+		string $url,
+		array $args = []
+	): string {
+		if ( 0 !== stripos( $provider, self::OEMBED_ENDPOINT ) ) {
+			return $provider;
+		}
+
+		if ( ! preg_match( self::OEMBED_FORMAT, $url, $matches ) ) {
+			return '';
+		}
+
+		$episode_slug_parts = explode( '-', $matches[2] );
+		$id                 = array_pop( $episode_slug_parts );
+
+		$provider = str_replace(
+			self::EPISODE_ID_PLACEHOLDER,
+			$id,
+			self::OEMBED_ENDPOINT
+		);
+
+		// Anchor.fm's oEmbed endpoint offers limited support for arguments.
+		if ( isset( $args['width'], $args['height'] ) ) {
+			$provider = add_query_arg(
+				[
+					'maxwidth'  => (int) $args['width'],
+					'maxheight' => (int) $args['height'],
+				],
+				$provider
+			);
+		}
+
+		return $provider;
+	}
+
+	/**
+	 * Render Anchor.fm iframe embed via a shortcode.
+	 *
+	 * @param array $attrs Shortcode attributes.
+	 * @return string
+	 */
+	public function do_shortcode( array $attrs ): string {
+		$attrs = shortcode_atts(
+			[
+				'src'    => null,
+				'url'    => null,
+				'width'  => '400px',
+				'height' => '102px',
+			],
+			$attrs,
+			self::SHORTCODE_TAG
+		);
+
+		// Fallback in case one passes `url` rather than `src`.
+		if ( empty( $attrs['src'] ) && ! empty( $attrs['url'] ) ) {
+			$attrs['src'] = $attrs['url'];
+		}
+
+		if ( empty( $attrs['src'] ) ) {
+			return '';
+		}
+
+		return sprintf(
+			'<iframe src="%1$s" width="%2$s" height="%3$s" frameborder="0" scrolling="no"></iframe>',
+			esc_url( $attrs['src'] ),
+			esc_attr( $attrs['width'] ),
+			esc_attr( $attrs['height'] )
+		);
+	}
+}