/**
 * Shared API client infrastructure: request helper, error class, auth token management.
 */

export const BASE = "/api/v1";
export const AUTH_TOKEN_KEY = "chrysopedia_token";

export class ApiError extends Error {
  constructor(
    public status: number,
    public detail: string,
  ) {
    super(`API ${status}: ${detail}`);
    this.name = "ApiError";
  }
}

function getStoredToken(): string | null {
  try {
    return localStorage.getItem(AUTH_TOKEN_KEY);
  } catch {
    return null;
  }
}

export async function request<T>(url: string, init?: RequestInit): Promise<T> {
  const token = getStoredToken();
  const headers: Record<string, string> = {
    "Content-Type": "application/json",
    ...(init?.headers as Record<string, string>),
  };
  if (token && !headers["Authorization"]) {
    headers["Authorization"] = `Bearer ${token}`;
  }

  const res = await fetch(url, {
    ...init,
    headers,
  });

  if (!res.ok) {
    let detail = res.statusText;
    try {
      const body: unknown = await res.json();
      if (typeof body === "object" && body !== null && "detail" in body) {
        const d = (body as { detail: unknown }).detail;
        detail = typeof d === "string" ? d : Array.isArray(d) ? d.map((e: any) => e.msg || JSON.stringify(e)).join("; ") : JSON.stringify(d);
      }
    } catch {
      // body not JSON — keep statusText
    }
    throw new ApiError(res.status, detail);
  }

  return res.json() as Promise<T>;
}

/**
 * Multipart form-data request — does NOT set Content-Type (browser adds
 * multipart boundary automatically). Still attaches auth token.
 */
export async function requestMultipart<T>(
  url: string,
  formData: FormData,
  init?: RequestInit,
): Promise<T> {
  const token = getStoredToken();
  const headers: Record<string, string> = {
    ...(init?.headers as Record<string, string>),
  };
  if (token && !headers["Authorization"]) {
    headers["Authorization"] = `Bearer ${token}`;
  }

  const res = await fetch(url, {
    method: "POST",
    ...init,
    headers,
    body: formData,
  });

  if (!res.ok) {
    let detail = res.statusText;
    try {
      const body: unknown = await res.json();
      if (typeof body === "object" && body !== null && "detail" in body) {
        const d = (body as { detail: unknown }).detail;
        detail =
          typeof d === "string"
            ? d
            : Array.isArray(d)
              ? d.map((e: any) => e.msg || JSON.stringify(e)).join("; ")
              : JSON.stringify(d);
      }
    } catch {
      // body not JSON — keep statusText
    }
    throw new ApiError(res.status, detail);
  }

  return res.json() as Promise<T>;
}