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/**
* 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'
);
}
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