detectFromCookie

Kind: Function

Source: src/middleware/language/language.ts

Part of: Middleware

Detects language from cookie

detectFromCookie reads the language preference stored in a cookie and returns the detected language value. It is used by the language middleware to select a request language before applying language-dependent behavior.

Signature

ts
function detectFromCookie(c: Context, options: DetectorOptions): string | undefined

Parameters

Returns: string | undefined

Diagram

mermaid
graph LR
  Request[Incoming request] --> Cookie[Cookie header]
  Cookie --> Detect[detectFromCookie]
  Detect --> Language[Detected language]
  Language --> Middleware[Language middleware]

Usage

ts
import { detectFromCookie } from './middleware/language/language';

const cookieHeader = request.headers.get('cookie') ?? undefined;
const language = detectFromCookie(cookieHeader);

if (language) {
  request.language = language;
}

AI Coding Instructions

• Keep cookie parsing and language detection within detectFromCookie; callers should pass the request cookie value rather than parse it themselves.
• Handle missing, malformed, or unsupported cookie values without throwing during request processing.
• Keep detected language values aligned with the languages supported by the language middleware.
• Apply the detected value before fallback language selection so explicit user preferences take precedence.