Add attachment data source.

src/Data/AttachmentDataSource.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace DataKit\Plugin\Data;
+
+use DataKit\DataViews\Data\CsvDataSource;
+use DataKit\DataViews\Data\Exception\DataSourceNotFoundException;
+
+/**
+ * Data source (factory) backed by a WordPress media attachment.
+ *
+ * @since $ver$
+ */
+final class AttachmentDataSource {
+	/**
+	 * Disabled constructor.
+	 *
+	 * Use any of the named constructors.
+	 *
+	 * @since $ver$
+	 */
+	private function __construct() {
+	}
+
+	/**
+	 * Returns a {@see CsvDataSource} for the specified attachment ID.
+	 *
+	 * @since $ver$
+	 *
+	 * @param int $attachment_id The attachment ID.
+	 *
+	 * @return CsvDataSource THe data source.
+	 * @throws DataSourceNotFoundException When the attachment could not be found.
+	 */
+	public static function csv(
+		int $attachment_id,
+		string $separator = ',',
+		string $enclosure = '"',
+		string $escape = '\\'
+	): CsvDataSource {
+		$path = get_attached_file( $attachment_id );
+		if ( ! $path ) {
+			throw new DataSourceNotFoundException( sprintf( 'The attachment ID (%d) is not found.', $attachment_id ) );
+		}
+
+		return new CsvDataSource( $path, $separator, $enclosure, $escape );
+	}
+}