import type {
  ChatResponse,
  DeleteResponse,
  DocumentsResponse,
  IngestResponse,
} from "./types";

// FastAPI backend base URL for the admin endpoints (called directly from the
// browser; the backend enables CORS for this origin). Exposed to the client,
// so it must be prefixed with NEXT_PUBLIC_.
const API_BASE = (
  process.env.NEXT_PUBLIC_API_URL || "http://127.0.0.1:8080"
).replace(/\/+$/, "");

const configuredIngestTimeoutMs = Number(
  process.env.NEXT_PUBLIC_INGEST_TIMEOUT_MS || 600_000,
);
const INGEST_TIMEOUT_MS =
  Number.isFinite(configuredIngestTimeoutMs) && configuredIngestTimeoutMs > 0
  ? configuredIngestTimeoutMs
  : 600_000;

/** Parse a JSON response, throwing a readable error on failure. */
async function jsonOrThrow<T>(res: Response): Promise<T> {
  if (!res.ok) {
    let message = `Yêu cầu thất bại (mã ${res.status})`;
    try {
      const body = await res.json();
      // Next.js routes use { error }, FastAPI uses { detail }.
      message = body?.error || body?.detail || message;
    } catch {
      // non-JSON error body — keep the status message
    }
    throw new Error(message);
  }
  return res.json() as Promise<T>;
}

/** Chat goes through the Next.js proxy (`/api/chat` → backend `POST /chat`).
 *  Accepts an optional AbortSignal so the store can cancel an in-flight request
 *  when its session is deleted. */
export async function sendChat(
  input: {
    user_id: string;
    session_id: string;
    query: string;
  },
  signal?: AbortSignal,
): Promise<ChatResponse> {
  const res = await fetch("/api/chat", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(input),
    signal,
  });
  return jsonOrThrow<ChatResponse>(res);
}

export async function listDocuments(): Promise<DocumentsResponse> {
  const res = await fetch(`${API_BASE}/documents`, { cache: "no-store" });
  return jsonOrThrow<DocumentsResponse>(res);
}

export async function ingestPdf(file: File): Promise<IngestResponse> {
  const form = new FormData();
  form.append("file", file);
  try {
    const res = await fetch(`${API_BASE}/ingest`, {
      method: "POST",
      body: form,
      signal: AbortSignal.timeout(INGEST_TIMEOUT_MS),
    });
    return jsonOrThrow<IngestResponse>(res);
  } catch (err) {
    if (err instanceof Error && err.name === "TimeoutError") {
      const minutes = Math.round(INGEST_TIMEOUT_MS / 60_000);
      throw new Error(
        `Backend xử lý upload quá lâu (quá ${minutes} phút). Thử tăng NEXT_PUBLIC_INGEST_TIMEOUT_MS nếu tệp lớn hoặc Qdrant Cloud chậm.`,
      );
    }
    throw err;
  }
}

export async function deleteDocument(id: string): Promise<DeleteResponse> {
  const res = await fetch(`${API_BASE}/documents/${encodeURIComponent(id)}`, {
    method: "DELETE",
  });
  return jsonOrThrow<DeleteResponse>(res);
}