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feat: Fully support Accept* headers
This commit is contained in:
Joachim Van Herwegen
62
src/ldp/http/AcceptPreferenceParser.ts
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62
src/ldp/http/AcceptPreferenceParser.ts
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@@ -0,0 +1,62 @@
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import { HttpRequest } from '../../server/HttpRequest';
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import { PreferenceParser } from './PreferenceParser';
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import { RepresentationPreference } from '../representation/RepresentationPreference';
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import { RepresentationPreferences } from '../representation/RepresentationPreferences';
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import {
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AcceptHeader,
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parseAccept,
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parseAcceptCharset,
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parseAcceptEncoding,
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parseAcceptLanguage,
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} from '../../util/AcceptParser';
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/**
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* Extracts preferences from the accept-* headers from an incoming {@link HttpRequest}.
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* Supports Accept, Accept-Charset, Accept-Encoding, Accept-Language and Accept-DateTime.
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*/
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export class AcceptPreferenceParser extends PreferenceParser {
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public constructor() {
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super();
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}
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public async canHandle(): Promise<void> {
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return undefined;
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}
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public async handle(input: HttpRequest): Promise<RepresentationPreferences> {
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const result: RepresentationPreferences = {};
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const headers: { [T in keyof RepresentationPreferences]: { val: string; func: (input: string) => AcceptHeader[] }} = {
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type: { val: input.headers.accept, func: parseAccept },
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charset: { val: input.headers['accept-charset'] as string, func: parseAcceptCharset },
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encoding: { val: input.headers['accept-encoding'] as string, func: parseAcceptEncoding },
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language: { val: input.headers['accept-language'], func: parseAcceptLanguage },
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};
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Object.keys(headers).forEach((key: keyof RepresentationPreferences): void => {
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const preferences = this.parseHeader(headers[key].val, headers[key].func);
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if (preferences.length > 0) {
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result[key] = preferences;
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}
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});
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// Accept-DateTime is currently specified to simply have a datetime as value
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if (input.headers['accept-datetime']) {
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result.datetime = [{ value: input.headers['accept-datetime'] as string, weight: 1 }];
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}
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return result;
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}
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/**
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* Converts a header string using the given parse function to {@link RepresentationPreference}[].
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* @param input - Input header string.
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* @param parseFunction - Function that converts header string to {@link AcceptHeader}.
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*
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* @returns A list of {@link RepresentationPreference}. Returns an empty list if input was not defined.
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*/
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private parseHeader(input: string, parseFunction: (input: string) => AcceptHeader[]): RepresentationPreference[] {
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if (!input) {
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return [];
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}
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return parseFunction(input).map((accept): RepresentationPreference => ({ value: accept.range, weight: accept.weight }));
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}
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}
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@@ -1,46 +0,0 @@
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import { HttpRequest } from '../../server/HttpRequest';
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import { PreferenceParser } from './PreferenceParser';
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import { RepresentationPreference } from '../representation/RepresentationPreference';
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import { RepresentationPreferences } from '../representation/RepresentationPreferences';
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/**
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* Extracts preferences from the accept-* headers from an incoming {@link HttpRequest}.
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* Parsing of header strings is done naively.
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*/
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export class SimplePreferenceParser extends PreferenceParser {
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public constructor() {
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super();
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}
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public async canHandle(): Promise<void> {
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return undefined;
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}
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public async handle(input: HttpRequest): Promise<RepresentationPreferences> {
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const type = this.parseHeader(input.headers.accept);
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const charset = this.parseHeader(input.headers['accept-charset'] as string);
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const language = this.parseHeader(input.headers['accept-language']);
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// Datetime can have commas so requires separate rules
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let datetime;
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if (input.headers['accept-datetime']) {
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datetime = [{ value: input.headers['accept-datetime'] as string, weight: 1 }];
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}
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return { type, charset, datetime, language };
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}
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private parseHeader(header: string): RepresentationPreference[] {
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if (!header) {
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return undefined;
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}
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return header.split(',').map((preference): RepresentationPreference => {
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const parts = preference.split(';');
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if (parts.length === 1) {
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return { value: parts[0].trim(), weight: 1 };
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}
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return { value: parts[0].trim(), weight: parseFloat(parts[1].trim().slice('q='.length)) };
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});
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}
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}
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219
src/util/AcceptParser.ts
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219
src/util/AcceptParser.ts
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@@ -0,0 +1,219 @@
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// BNF based on https://tools.ietf.org/html/rfc7231
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//
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// Accept = #( media-range [ accept-params ] )
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// Accept-Charset = 1#( ( charset / "*" ) [ weight ] )
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// Accept-Encoding = #( codings [ weight ] )
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// Accept-Language = 1#( language-range [ weight ] )
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//
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// Content-Type = media-type
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// media-type = type "/" subtype *( OWS ";" OWS parameter )
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//
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// media-range = ( "*/*"
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// / ( type "/" "*" )
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// / ( type "/" subtype )
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// ) *( OWS ";" OWS parameter ) ; media type parameters
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// accept-params = weight *( accept-ext )
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// accept-ext = OWS ";" OWS token [ "=" ( token / quoted-string ) ] ; extension parameters
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//
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// weight = OWS ";" OWS "q=" qvalue
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// qvalue = ( "0" [ "." 0*3DIGIT ] )
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// / ( "1" [ "." 0*3("0") ] )
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//
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// type = token
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// subtype = token
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// parameter = token "=" ( token / quoted-string )
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//
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// quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
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// qdtext = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
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// obs-text = %x80-FF
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// quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
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//
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// charset = token
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//
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// codings = content-coding / "identity" / "*"
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// content-coding = token
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//
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// language-range = (1*8ALPHA *("-" 1*8alphanum)) / "*"
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// alphanum = ALPHA / DIGIT
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//
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// Delimiters are chosen from the set of US-ASCII visual characters not allowed in a token (DQUOTE and "(),/:;<=>?@[\]{}").
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// token = 1*tchar
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// tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
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// / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
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// / DIGIT / ALPHA
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// ; any VCHAR, except delimiters
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//
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// INTERFACES
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/**
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* General interface for all Accept* headers.
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*/
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export interface AcceptHeader {
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/** Requested range. Can be a specific value or `*`, matching all. */
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range: string;
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/** Weight of the preference [0, 1]. */
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weight: number;
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}
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/**
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* Contents of an HTTP Accept header.
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* Range is type/subtype. Both can be `*`.
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*/
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export interface Accept extends AcceptHeader {
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parameters: {
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/** Media type parameters. These are the parameters that came before the q value. */
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mediaType: { [key: string]: string };
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/** Extension parameters. These are the parameters that came after the q value. Value will be an empty string if there was none. */
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extension: { [key: string]: string };
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};
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}
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/**
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* Contents of an HTTP Accept-Charset header.
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*/
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export interface AcceptCharset extends AcceptHeader { }
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/**
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* Contents of an HTTP Accept-Encoding header.
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*/
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export interface AcceptEncoding extends AcceptHeader { }
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/**
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* Contents of an HTTP Accept-Language header.
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*/
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export interface AcceptLanguage extends AcceptHeader { }
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// HELPER FUNCTIONS
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/**
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* Replaces all double quoted strings in the input string with `"0"`, `"1"`, etc.
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* @param input - The Accept header string.
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*
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* @returns The transformed string and a map with keys `"0"`, etc. and values the original string that was there.
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*/
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const transformQuotedStrings = (input: string): { result: string; replacements: { [id: string]: string } } => {
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let idx = 0;
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const replacements: { [id: string]: string } = {};
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const result = input.replace(/"(?:[^"\\]|\\.)*"/gu, (match): string => {
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const replacement = `"${idx}"`;
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replacements[replacement] = match;
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idx += 1;
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return replacement;
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});
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return { result, replacements };
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};
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const splitAndClean = (input: string): string[] =>
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input.split(',')
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.map((part): string => part.trim())
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.filter((part): boolean => part.length > 0);
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/**
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* Parses a single media range with corresponding parameters from an Accept header.
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* For every parameter value that is a double quoted string,
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* we check if it is a key in the replacements map.
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* If yes the value from the map gets inserted instead.
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* @param part - A string corresponding to a media range and its corresponding parameters.
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* @param replacements - The double quoted strings that need to be replaced.
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*
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* @returns {@link Accept} object corresponding to the header string.
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*/
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const parseAcceptPart = (part: string, replacements: { [id: string]: string }): Accept => {
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const [ range, ...parameters ] = part.split(';').map((param): string => param.trim());
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let weight = 1;
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const mediaTypeParams: { [key: string]: string } = {};
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const extensionParams: { [key: string]: string } = {};
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let map = mediaTypeParams;
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parameters.forEach((param): void => {
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const [ name, value ] = param.split('=');
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let actualValue = value;
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if (value && value.length > 0 && value.startsWith('"') && replacements[value]) {
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actualValue = replacements[value];
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}
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if (name === 'q') {
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// Extension parameters appear after the q value
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map = extensionParams;
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weight = parseFloat(actualValue);
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} else {
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// Value is optional for extension parameters
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map[name] = actualValue || '';
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}
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});
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return {
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range,
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weight,
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parameters: {
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mediaType: mediaTypeParams,
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extension: extensionParams,
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},
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};
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};
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/**
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* Parses an Accept-* header where each part is only a value and a weight, so roughly /.*(q=.*)?/ separated by commas.
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* @param input - Input header string.
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*
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* @returns An array of ranges and weights.
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*/
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const parseNoParameters = (input: string): { range: string; weight: number }[] => {
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const parts = splitAndClean(input);
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return parts.map((part): { range: string; weight: number } => {
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const [ range, qvalue ] = part.split(';').map((param): string => param.trim());
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const result = { range, weight: 1 };
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if (qvalue) {
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result.weight = parseFloat(qvalue.split('=')[1]);
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}
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return result;
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}).sort((left, right): number => right.weight - left.weight);
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};
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// EXPORTED FUNCTIONS
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/**
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* Parses an Accept header string.
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* No validation is done so this assumes a valid input string.
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*
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* @param input - The Accept header string.
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*
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* @returns An array of {@link Accept} objects, sorted by weight.
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*/
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export const parseAccept = (input: string): Accept[] => {
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// Quoted strings could prevent split from having correct results
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const { result, replacements } = transformQuotedStrings(input);
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return splitAndClean(result)
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.map((part): Accept => parseAcceptPart(part, replacements))
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.sort((left, right): number => right.weight - left.weight);
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};
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/**
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* Parses an Accept-Charset header string.
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* No validation is done so this assumes a valid input string.
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*
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* @param input - The Accept-Charset header string.
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*
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* @returns An array of {@link AcceptCharset} objects, sorted by weight.
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*/
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export const parseAcceptCharset = (input: string): AcceptCharset[] => parseNoParameters(input);
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/**
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* Parses an Accept-Encoding header string.
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* No validation is done so this assumes a valid input string.
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*
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* @param input - The Accept-Encoding header string.
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*
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* @returns An array of {@link AcceptEncoding} objects, sorted by weight.
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*/
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export const parseAcceptEncoding = (input: string): AcceptEncoding[] => parseNoParameters(input);
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/**
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* Parses an Accept-Language header string.
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* No validation is done so this assumes a valid input string.
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*
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* @param input - The Accept-Language header string.
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*
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* @returns An array of {@link AcceptLanguage} objects, sorted by weight.
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*/
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export const parseAcceptLanguage = (input: string): AcceptLanguage[] => parseNoParameters(input);
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