/**
 * The translation boundary.
 *
 * Everything above this interface deals in "French in, English out". The
 * adapter below it deals with whatever shape the service of the day happens to
 * have — which matters here, because api.loxi.ch is neither Anthropic- nor
 * OpenAI-compatible and a future move to either should not reach the callers.
 */

export type TranslationRequest = {
  text: string;
  /** Times and numbers must survive unchanged, so the prompt says so. */
  signal?: AbortSignal;
};

export type TranslationOutcome =
  | { ok: true; text: string; model: string }
  | { ok: false; error: string };

export interface TranslationProvider {
  /** A stable name, stored alongside the cached result. */
  readonly model: string;
  translate(request: TranslationRequest): Promise<TranslationOutcome>;
}

/**
 * The instruction sent with every message.
 *
 * Written as one block because the loxi endpoint takes a single prompt string
 * rather than a system/user pair. The constraints are the ones that matter on
 * an e-ink panel 800 pixels wide: no added quotes, no commentary, no growth.
 */
export function buildPrompt(text: string): string {
  return [
    "Traduis en anglais le message d'affichage suivant, destiné à la vitrine d'une boutique de tricot.",
    '',
    'Contraintes impératives :',
    "- Réponds UNIQUEMENT avec la traduction, sans guillemets ajoutés, sans préambule, sans commentaire.",
    '- Ton sobre et commercial, pas de familiarité ajoutée.',
    '- Conserve à l’identique les horaires, les dates et les nombres.',
    `- La traduction ne doit pas dépasser ${Math.ceil(text.length * 1.2)} caractères.`,
    '',
    'Message à traduire :',
    text,
  ].join('\n');
}

/**
 * Cleans what a model returns.
 *
 * Models wrap answers in quotes and prefix them with "Translation:" often
 * enough that stripping it here is cheaper than re-prompting, and a stray
 * quotation mark on the shop window looks like a mistake.
 */
export function cleanTranslation(raw: string): string {
  let text = raw.trim();

  text = text.replace(/^(?:translation|traduction)\s*:\s*/i, '').trim();

  const pairs: [string, string][] = [
    ['"', '"'],
    ['«', '»'],
    ['“', '”'],
    ["'", "'"],
  ];
  for (const [open, close] of pairs) {
    if (text.startsWith(open) && text.endsWith(close) && text.length > open.length + close.length) {
      text = text.slice(open.length, text.length - close.length).trim();
      break;
    }
  }

  // A multi-line answer means the model explained itself; keep the first line.
  const [firstLine] = text.split('\n');
  return (firstLine ?? '').trim();
}