alp-node/src/language.ts

framework based on koa 2

import type { Context } from "koa";
import { defineLazyProperty } from "object-properties";
import type { AlpNodeApp } from "./AlpNodeApp";

export interface AlpLanguageContext {
  readonly firstAcceptedLanguage: string;
  readonly language: string;
}
export default function alpLanguage(app: AlpNodeApp): void {
  const config = app.context.config;
  const availableLanguages: string[] = config.get("availableLanguages");
  if (!availableLanguages) {
    throw new Error('Missing config "availableLanguages"');
  }

  defineLazyProperty(
    app.context,
    "language",
    function language(this: Context): string {
      return (
        this.acceptsLanguages(availableLanguages) ||
        availableLanguages[0] ||
        "en"
      );
    },
  );

  defineLazyProperty(
    app.context,
    "firstAcceptedLanguage",
    function firstAcceptedLanguage(this: Context): string {
      return this.acceptsLanguages()[0] || availableLanguages[0] || "en";
    },
  );
}