From 4aed8c8b4c276011b45e3a722939ae97fb3e5d11 Mon Sep 17 00:00:00 2001
From: Ruben Verborgh <ruben@verborgh.org>
Date: Tue, 5 Jan 2021 01:17:12 +0100
Subject: [PATCH] refactor: Simplify AcceptPreferenceParser.

---
 src/ldp/http/AcceptPreferenceParser.ts | 59 ++++++++++----------------
 src/util/HeaderUtil.ts                 | 19 ++++++++-
 2 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/src/ldp/http/AcceptPreferenceParser.ts b/src/ldp/http/AcceptPreferenceParser.ts
index f1bd64c10..66330ee01 100644
--- a/src/ldp/http/AcceptPreferenceParser.ts
+++ b/src/ldp/http/AcceptPreferenceParser.ts
@@ -5,52 +5,37 @@ import {
   parseAcceptCharset,
   parseAcceptEncoding,
   parseAcceptLanguage,
+  parseAcceptDateTime,
 } from '../../util/HeaderUtil';
 import type { RepresentationPreferences } from '../representation/RepresentationPreferences';
 import { PreferenceParser } from './PreferenceParser';
 
+const parsers: {
+  name: keyof RepresentationPreferences;
+  header: string;
+  parse: (value: string) => AcceptHeader[];
+}[] = [
+  { name: 'type', header: 'accept', parse: parseAccept },
+  { name: 'charset', header: 'accept-charset', parse: parseAcceptCharset },
+  { name: 'encoding', header: 'accept-encoding', parse: parseAcceptEncoding },
+  { name: 'language', header: 'accept-language', parse: parseAcceptLanguage },
+  { name: 'datetime', header: 'accept-datetime', parse: parseAcceptDateTime },
+];
+
 /**
- * Extracts preferences from the accept-* headers from an incoming {@link HttpRequest}.
+ * Extracts preferences from the Accept-* headers from an incoming {@link HttpRequest}.
  * Supports Accept, Accept-Charset, Accept-Encoding, Accept-Language and Accept-DateTime.
  */
 export class AcceptPreferenceParser extends PreferenceParser {
-  public constructor() {
-    super();
-  }
-
-  public async handle(input: HttpRequest): Promise<RepresentationPreferences> {
-    const result: RepresentationPreferences = {};
-    const headers:
-    { [T in keyof RepresentationPreferences]: { val?: string; func: (inp: string) => AcceptHeader[] }} = {
-      type: { val: input.headers.accept, func: parseAccept },
-      charset: { val: input.headers['accept-charset'] as string, func: parseAcceptCharset },
-      encoding: { val: input.headers['accept-encoding'] as string, func: parseAcceptEncoding },
-      language: { val: input.headers['accept-language'], func: parseAcceptLanguage },
-    };
-    (Object.keys(headers) as (keyof RepresentationPreferences)[]).forEach((key): void => {
-      const preferences = this.parseHeader(headers[key]!.func, headers[key]!.val);
-      if (preferences.length > 0) {
-        result[key] = Object.fromEntries(preferences);
+  public async handle({ headers }: HttpRequest): Promise<RepresentationPreferences> {
+    const preferences: RepresentationPreferences = {};
+    for (const { name, header, parse } of parsers) {
+      const value = headers[header];
+      if (typeof value === 'string') {
+        preferences[name] = Object.fromEntries(parse(value)
+          .map(({ range, weight }): [string, number] => [ range, weight ]));
       }
-    });
-
-    // Accept-DateTime is currently specified to simply have a datetime as value
-    if (input.headers['accept-datetime']) {
-      result.datetime = { [input.headers['accept-datetime'] as string]: 1 };
     }
-
-    return result;
-  }
-
-  /**
-   * Converts a header string using the given parse function to {@link RepresentationPreference}[].
-   * @param input - Input header string.
-   * @param parseFunction - Function that converts header string to {@link AcceptHeader}.
-   *
-   * @returns A list of preferences. Returns an empty list if input was not defined.
-   */
-  private parseHeader(parseFunction: (input: string) => AcceptHeader[], input?: string): [string, number][] {
-    return (input ? parseFunction(input) : [])
-      .map(({ range, weight }): [string, number] => [ range, weight ]);
+    return preferences;
   }
 }
diff --git a/src/util/HeaderUtil.ts b/src/util/HeaderUtil.ts
index 2aac2b947..e411a36f3 100644
--- a/src/util/HeaderUtil.ts
+++ b/src/util/HeaderUtil.ts
@@ -93,6 +93,11 @@ export interface AcceptEncoding extends AcceptHeader { }
  */
 export interface AcceptLanguage extends AcceptHeader { }
 
+/**
+ * Contents of an HTTP Accept-Datetime header.
+ */
+export interface AcceptDatetime extends AcceptHeader { }
+
 // REUSED REGEXES
 const token = /^[a-zA-Z0-9!#$%&'*+-.^_`|~]+$/u;
 
@@ -248,10 +253,10 @@ const parseAcceptPart = (part: string, replacements: Record<string, string>): Ac
  *
  * @returns An array of ranges and weights.
  */
-const parseNoParameters = (input: string): { range: string; weight: number }[] => {
+const parseNoParameters = (input: string): AcceptHeader[] => {
   const parts = splitAndClean(input);
 
-  return parts.map((part): { range: string; weight: number } => {
+  return parts.map((part): AcceptHeader => {
     const [ range, qvalue ] = part.split(';').map((param): string => param.trim());
     const result = { range, weight: 1 };
     if (qvalue) {
@@ -357,6 +362,16 @@ export const parseAcceptLanguage = (input: string): AcceptLanguage[] => {
   return results;
 };
 
+/**
+ * Parses an Accept-DateTime header string.
+ *
+ * @param input - The Accept-DateTime header string.
+ *
+ * @returns An array with a single {@link AcceptDatetime} object.
+ */
+export const parseAcceptDateTime = (input: string): AcceptDatetime[] =>
+  [{ range: input, weight: 1 }];
+
 /**
  * Adds a header value without overriding previous values.
  */