Add media type sniffing by extension

packages/common/src/MediaType.ts

@@ -0,0 +1,69 @@
+const mediaTypeExtension = new Map<string, string>();
+const extensionMediaType = new Map<string, string>();
+
+register("application/x-musescore", "mscz");
+register("application/vnd.recordare.musicxml+xml", "musicxml");
+register("application/vnd.recordare.musicxml", "mxl");
+register("application/pdf", "pdf");
+
+register("audio/aac", "aac");
+register("audio/flac", "flac");
+register("audio/midi", "mid", "midi");
+register("audio/mpeg", "mp3");
+register("audio/wav", "wav");
+
+export const ACCEPTED_EXTENSIONS = (() => {
+	const ret = [];
+	for (const extension of extensionMediaType.keys()) {
+		ret.push("." + extension);
+	}
+
+	ret.sort((a, b) => a.localeCompare(b));
+	return ret.join(",");
+})();
+
+function register(mediaType: string, ...extensions: [string, ...string[]]) {
+	const [primaryExtension, ...secondaryExtensions] = extensions;
+
+	mediaTypeExtension.set(mediaType, primaryExtension);
+
+	extensionMediaType.set(primaryExtension, mediaType);
+	for (const extension of secondaryExtensions) {
+		extensionMediaType.set(extension, mediaType);
+	}
+}
+
+export function getMediaTypeForExtension(extension: string): string | undefined {
+	return extensionMediaType.get(extension);
+}
+
+export function getPrimaryExtension(extension: string): string {
+	const mediaType = extensionMediaType.get(extension);
+	if (mediaType === undefined) {
+		return extension;
+	}
+
+	const primaryExtension = mediaTypeExtension.get(mediaType)!;
+	return primaryExtension;
+}
+
+export function getExtensionFromMediaType(mediaType: string): string | undefined {
+	return mediaTypeExtension.get(mediaType);
+}
+
+export function getExtensionFromFilename(filename: string): string | undefined {
+	return filename.match(/(?<=.)[^.]+$/)?.[0];
+}
+
+export function getMediaTypeForFilename(filename: string): string | undefined {
+	const extension = getExtensionFromFilename(filename);
+	if (extension === undefined) {
+		return undefined;
+	}
+
+	return getMediaTypeForExtension(extension);
+}
+
+export function getMediaTypeForFile(file: File): string {
+	return getMediaTypeForFilename(file.name) ?? file.type;
+}