import { compareSpecs, isQuality, Specificity } from "./common.ts";
interface MediaTypeSpecificity extends Specificity { type: string; subtype: string; params: { [param: string]: string | undefined };}
const simpleMediaTypeRegExp = /^\s*([^\s\/;]+)\/([^;\s]+)\s*(?:;(.*))?$/;
function quoteCount(str: string): number { let count = 0; let index = 0;
while ((index = str.indexOf(`"`, index)) !== -1) { count++; index++; }
return count;}
function splitMediaTypes(accept: string): string[] { const accepts = accept.split(",");
let j = 0; for (let i = 1; i < accepts.length; i++) { if (quoteCount(accepts[j]) % 2 === 0) { accepts[++j] = accepts[i]; } else { accepts[j] += `,${accepts[i]}`; } }
accepts.length = j + 1;
return accepts;}
function splitParameters(str: string): string[] { const parameters = str.split(";");
let j = 0; for (let i = 1; i < parameters.length; i++) { if (quoteCount(parameters[j]) % 2 === 0) { parameters[++j] = parameters[i]; } else { parameters[j] += `;${parameters[i]}`; } }
parameters.length = j + 1;
return parameters.map((p) => p.trim());}
function splitKeyValuePair(str: string): [string, string | undefined] { const [key, value] = str.split("="); return [key.toLowerCase(), value];}
function parseMediaType( str: string, i: number,): MediaTypeSpecificity | undefined { const match = simpleMediaTypeRegExp.exec(str);
if (!match) { return; }
const params: { [param: string]: string | undefined } = Object.create(null); let q = 1; const [, type, subtype, parameters] = match;
if (parameters) { const kvps = splitParameters(parameters).map(splitKeyValuePair);
for (const [key, val] of kvps) { const value = val && val[0] === `"` && val[val.length - 1] === `"` ? val.substr(1, val.length - 2) : val;
if (key === "q" && value) { q = parseFloat(value); break; }
params[key] = value; } }
return { type, subtype, params, q, i };}
function parseAccept(accept: string): MediaTypeSpecificity[] { const accepts = splitMediaTypes(accept);
const mediaTypes: MediaTypeSpecificity[] = []; for (let i = 0; i < accepts.length; i++) { const mediaType = parseMediaType(accepts[i].trim(), i);
if (mediaType) { mediaTypes.push(mediaType); } }
return mediaTypes;}
function getFullType(spec: MediaTypeSpecificity) { return `${spec.type}/${spec.subtype}`;}
function specify( type: string, spec: MediaTypeSpecificity, index: number,): Specificity | undefined { const p = parseMediaType(type, index);
if (!p) { return; }
let s = 0;
if (spec.type.toLowerCase() === p.type.toLowerCase()) { s |= 4; } else if (spec.type !== "*") { return; }
if (spec.subtype.toLowerCase() === p.subtype.toLowerCase()) { s |= 2; } else if (spec.subtype !== "*") { return; }
const keys = Object.keys(spec.params); if (keys.length) { if ( keys.every((key) => (spec.params[key] || "").toLowerCase() === (p.params[key] || "").toLowerCase() ) ) { s |= 1; } else { return; } }
return { i: index, o: spec.o, q: spec.q, s, };}
function getMediaTypePriority( type: string, accepted: MediaTypeSpecificity[], index: number,) { let priority: Specificity = { o: -1, q: 0, s: 0, i: index };
for (const accepts of accepted) { const spec = specify(type, accepts, index);
if ( spec && ((priority.s || 0) - (spec.s || 0) || (priority.q || 0) - (spec.q || 0) || (priority.o || 0) - (spec.o || 0)) < 0 ) { priority = spec; } }
return priority;}
export function preferredMediaTypes( accept?: string | null, provided?: string[],): string[] { const accepts = parseAccept(accept === undefined ? "*/*" : accept || "");
if (!provided) { return accepts .filter(isQuality) .sort(compareSpecs) .map(getFullType); }
const priorities = provided.map((type, index) => { return getMediaTypePriority(type, accepts, index); });
return priorities .filter(isQuality) .sort(compareSpecs) .map((priority) => provided[priorities.indexOf(priority)]);}