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node_modules/@sveltejs/kit/src/utils/http.js

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+import { BINARY_FORM_CONTENT_TYPE } from '../runtime/form-utils.js';
+
+/**
+ * Given an Accept header and a list of possible content types, pick
+ * the most suitable one to respond with
+ * @param {string} accept
+ * @param {string[]} types
+ */
+export function negotiate(accept, types) {
+	/** @type {Array<{ type: string, subtype: string, q: number, i: number }>} */
+	const parts = [];
+
+	accept.split(',').forEach((str, i) => {
+		const match = /([^/ \t]+)\/([^; \t]+)[ \t]*(?:;[ \t]*q=([0-9.]+))?/.exec(str);
+
+		// no match equals invalid header — ignore
+		if (match) {
+			const [, type, subtype, q = '1'] = match;
+			parts.push({ type, subtype, q: +q, i });
+		}
+	});
+
+	parts.sort((a, b) => {
+		if (a.q !== b.q) {
+			return b.q - a.q;
+		}
+
+		if ((a.subtype === '*') !== (b.subtype === '*')) {
+			return a.subtype === '*' ? 1 : -1;
+		}
+
+		if ((a.type === '*') !== (b.type === '*')) {
+			return a.type === '*' ? 1 : -1;
+		}
+
+		return a.i - b.i;
+	});
+
+	let accepted;
+	let min_priority = Infinity;
+
+	for (const mimetype of types) {
+		const [type, subtype] = mimetype.split('/');
+		const priority = parts.findIndex(
+			(part) =>
+				(part.type === type || part.type === '*') &&
+				(part.subtype === subtype || part.subtype === '*')
+		);
+
+		if (priority !== -1 && priority < min_priority) {
+			accepted = mimetype;
+			min_priority = priority;
+		}
+	}
+
+	return accepted;
+}
+
+/**
+ * Returns `true` if the request contains a `content-type` header with the given type
+ * @param {Request} request
+ * @param  {...string} types
+ */
+function is_content_type(request, ...types) {
+	const type = request.headers.get('content-type')?.split(';', 1)[0].trim() ?? '';
+	return types.includes(type.toLowerCase());
+}
+
+/**
+ * @param {Request} request
+ */
+export function is_form_content_type(request) {
+	// These content types must be protected against CSRF
+	// https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/enctype
+	return is_content_type(
+		request,
+		'application/x-www-form-urlencoded',
+		'multipart/form-data',
+		'text/plain',
+		BINARY_FORM_CONTENT_TYPE
+	);
+}