67 lines
2.8 KiB
TypeScript
67 lines
2.8 KiB
TypeScript
// The translator: a key + vars → the string to render. Pure and synchronous — views call it
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// as `t("shell.signOut")` and handlers as `ctx.t(...)`.
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//
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// Two rules the rest of the app leans on:
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// · the lookup walks a catalog chain (plugin locale → plugin en-US → core locale → core en-US) and,
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// when nothing has the key, returns the key itself. That is what makes a plain nav label like
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// "Shifts" its own fallback — a manifest needs no catalog to keep working.
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// · the result is raw text. Views escape with <%= %> exactly as they do for any other value, so a
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// translation is never double-escaped, and a message that carries markup is rendered with <%- %>.
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import { isPluralMessage, type Catalog, type PluralMessage } from "./catalog.ts";
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export type TranslateVars = Record<string, number | string>;
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export type Translate = (key: string, vars?: TranslateVars) => string;
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export interface TranslatorOptions {
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catalogs: Catalog[]; // lookup order, most specific first
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locale: string;
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}
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const PLACEHOLDER = /\{\{(\w+)\}\}/g;
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const pluralRules = new Map<string, Intl.PluralRules>();
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export function createTranslator({ catalogs, locale }: TranslatorOptions): Translate {
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return (key, vars) => {
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for (const catalog of catalogs) {
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// Own keys only: `t("toString")` must fall through to the key itself like any other unknown
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// one, not pick up Object.prototype.
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if (!Object.hasOwn(catalog, key)) continue;
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const message = catalog[key];
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if (message === undefined) continue;
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return interpolate(isPluralMessage(message) ? selectPlural(message, locale, vars?.["count"]) : message, vars);
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}
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return key;
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};
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}
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// The form for `count` in this locale, falling back to `other` (and then to any form present, so a
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// half-filled catalog still renders words rather than a blank).
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function selectPlural(message: PluralMessage, locale: string, count: number | string | undefined): string {
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const category = count === undefined ? "other" : rulesFor(locale).select(Number(count));
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return message[category] ?? message.other ?? Object.values(message)[0] ?? "";
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}
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function rulesFor(locale: string): Intl.PluralRules {
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let rules = pluralRules.get(locale);
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if (!rules) {
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try {
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rules = new Intl.PluralRules(locale);
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} catch {
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rules = new Intl.PluralRules("en-US");
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}
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pluralRules.set(locale, rules);
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}
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return rules;
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}
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// An unsupplied {{var}} is left standing: a visible placeholder beats a silent blank.
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function interpolate(text: string, vars: TranslateVars | undefined): string {
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if (vars === undefined) return text;
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return text.replace(PLACEHOLDER, (whole, name: string) => {
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if (!Object.hasOwn(vars, name)) return whole;
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const value = vars[name];
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return value === undefined ? whole : String(value);
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});
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}
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