ThumbGenerator: broaden scop to media handler

inc/Service/Media/FallbackMediaHandler.php

@@ -0,0 +1,42 @@
+<?php
+namespace Vichan\Service\Media;
+
+use Vichan\Data\ThumbGenerationResult;
+
+
+class FallbackMediaHandler implements MediaHandler {
+	private string $path;
+	private int $width;
+	private int $height;
+	private string $mime;
+
+
+	public function __construct(ImageMetadataReader $image_metadate_reader, string $default_thumb_path) {
+		$res = $image_metadate_reader->getMetadata($default_thumb_path);
+		$this->path = $default_thumb_path;
+		$this->width = $res->width;
+		$this->height = $res->height;
+		$this->mime = $res->mime;
+	}
+
+	public function supportsMime(string $mime): bool {
+		return true;
+	}
+
+	public function generateThumb(
+		string $source_file_path,
+		string $source_file_mime,
+		string $preferred_out_file_path,
+		string $preferred_out_mime,
+		int $max_width,
+		int $max_height
+	): ThumbGenerationResult {
+		return new ThumbGenerationResult(
+			$this->path,
+			$this->mime,
+			false,
+			\min($this->width, $max_width),
+			\min($this->height, $max_height)
+		);
+	}
+}