function getPublicUiError(status: number): string {
  // Message volontairement generique pour eviter les erreurs techniques en UI.
  if (status === 429) {
    return "Service momentanément indisponible. Merci de réessayer.";
  }
  return "Une erreur temporaire est survenue. Merci de réessayer.";
}

function extractApiMessage(payload: unknown, status: number): string {
  // Priorite aux messages explicites fournis par l'API.
  if (payload && typeof payload === "object") {
    const record = payload as Record<string, unknown>;
    const detail = record.detail;
    if (typeof detail === "string" && detail.trim()) {
      return detail;
    }
    if (detail && typeof detail === "object") {
      const detailRecord = detail as Record<string, unknown>;
      if (typeof detailRecord.message === "string" && detailRecord.message.trim()) {
        return detailRecord.message;
      }
    }
  }
  return getPublicUiError(status);
}

async function readJsonSafely(response: Response): Promise<unknown | null> {
  // Evite les crashes JSON.parse quand le backend repond en texte/plain.
  const raw = await response.text();
  if (!raw) {
    return null;
  }
  try {
    return JSON.parse(raw);
  } catch {
    return null;
  }
}

export async function postJson<T>(url: string, body: unknown): Promise<T> {
  // Client HTTP robuste: jamais d'erreur de parsing brute exposee a l'utilisateur.
  const response = await fetch(url, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body),
  });
  const data = await readJsonSafely(response);
  if (!response.ok) {
    throw new Error(extractApiMessage(data, response.status));
  }
  if (data === null) {
    throw new Error(getPublicUiError(500));
  }
  return data as T;
}

export async function getJson<T>(url: string): Promise<T> {
  // Lecture GET robuste avec meme convention de message UI.
  const response = await fetch(url, { method: "GET" });
  const data = await readJsonSafely(response);
  if (!response.ok) {
    throw new Error(extractApiMessage(data, response.status));
  }
  if (data === null) {
    throw new Error(getPublicUiError(500));
  }
  return data as T;
}