import type { CreateFlowState } from "../../app/create/types";

const jsonHeaders = { "Content-Type": "application/json" };

async function parseJson<T>(response: Response): Promise<T> {
  const data = (await response.json()) as T;
  return data;
}

/** Supports legacy `{ error: string }` and `{ error: { message: string } }` from API routes. */
function readApiErrorMessage(data: unknown): string {
  if (!data || typeof data !== "object" || !("error" in data)) {
    return "Request failed";
  }
  const err = (data as { error: unknown }).error;
  if (typeof err === "string") {
    return err;
  }
  if (err && typeof err === "object" && "message" in err) {
    const m = (err as { message: unknown }).message;
    if (typeof m === "string") {
      return m;
    }
  }
  return "Request failed";
}

export async function fetchAuthSession(): Promise<{
  user: { id: string; email: string } | null;
}> {
  const res = await fetch("/api/auth/session", {
    credentials: "include",
  });
  if (!res.ok) {
    return { user: null };
  }
  return parseJson(res);
}

export async function requestMagicLink(
  email: string,
  nextPath?: string,
): Promise<{ ok: true } | { ok: false; error: string; retryAfterMs?: number }> {
  const res = await fetch("/api/auth/magic-link/request", {
    method: "POST",
    credentials: "include",
    headers: jsonHeaders,
    body: JSON.stringify({
      email,
      ...(nextPath ? { next: nextPath } : {}),
    }),
  });
  const data = await parseJson<{ error?: string; retryAfterMs?: number }>(res);
  if (!res.ok) {
    return {
      ok: false,
      error: readApiErrorMessage(data),
      retryAfterMs:
        typeof data.retryAfterMs === "number" ? data.retryAfterMs : undefined,
    };
  }
  return { ok: true };
}

export async function logout(): Promise<void> {
  await fetch("/api/auth/logout", {
    method: "POST",
    credentials: "include",
  });
}

export async function fetchDraftFromServer(): Promise<CreateFlowState | null> {
  const res = await fetch("/api/drafts/me", { credentials: "include" });
  if (res.status === 401) return null;
  if (!res.ok) return null;
  const data = await parseJson<{ draft: { payload: unknown } | null }>(res);
  if (!data.draft?.payload || typeof data.draft.payload !== "object") {
    return null;
  }
  return data.draft.payload as CreateFlowState;
}

export async function saveDraftToServer(
  state: CreateFlowState,
): Promise<boolean> {
  const res = await fetch("/api/drafts/me", {
    method: "PUT",
    credentials: "include",
    headers: jsonHeaders,
    body: JSON.stringify({ payload: state }),
  });
  return res.ok;
}

export async function publishRule(input: {
  title: string;
  summary?: string;
  document: Record<string, unknown>;
}): Promise<{ ok: true; id: string; title: string } | { error: string }> {
  const res = await fetch("/api/rules", {
    method: "POST",
    credentials: "include",
    headers: jsonHeaders,
    body: JSON.stringify({
      title: input.title,
      summary: input.summary,
      document: input.document,
    }),
  });
  const data = await parseJson<{
    error?: string;
    rule?: { id: string; title: string };
  }>(res);
  if (!res.ok || !data.rule) {
    return { error: readApiErrorMessage(data) };
  }
  return { ok: true, id: data.rule.id, title: data.rule.title };
}