import { createHash } from "node:crypto";
import type { KisCredentialInput } from "@/lib/kis/config";
import { getKisConfig, getKisWebSocketUrl } from "@/lib/kis/config";

/**
 * @file lib/kis/approval.ts
 * @description KIS 웹소켓 approval key 발급/캐시 관리
 */

interface KisApprovalResponse {
  approval_key?: string;
  msg1?: string;
  msg_cd?: string;
  error?: string;
  error_description?: string;
}

interface KisApprovalCache {
  approvalKey: string;
  expiresAt: number;
}

const approvalCacheMap = new Map<string, KisApprovalCache>();
const approvalIssueInFlightMap = new Map<string, Promise<KisApprovalCache>>();
const APPROVAL_REFRESH_BUFFER_MS = 60 * 1000;

function hashKey(value: string) {
  return createHash("sha256").update(value).digest("hex");
}

function getApprovalCacheKey(credentials?: KisCredentialInput) {
  const config = getKisConfig(credentials);
  return `${config.tradingEnv}:${hashKey(config.appKey)}`;
}

/**
 * KIS 웹소켓 approval key 발급
 * @param credentials 사용자 입력 키(선택)
 * @returns approval key + expiresAt
 * @see app/api/kis/ws/approval/route.ts POST - 실시간 차트 연결 시 호출
 */
async function issueKisApprovalKey(credentials?: KisCredentialInput): Promise<KisApprovalCache> {
  const config = getKisConfig(credentials);

  const response = await fetch(`${config.baseUrl}/oauth2/Approval`, {
    method: "POST",
    headers: {
      "content-type": "application/json; charset=utf-8",
    },
    body: JSON.stringify({
      grant_type: "client_credentials",
      appkey: config.appKey,
      secretkey: config.appSecret,
    }),
    cache: "no-store",
  });

  const rawText = await response.text();
  const payload = tryParseApprovalResponse(rawText);

  if (!response.ok || !payload.approval_key) {
    const detail = [payload.msg1, payload.error_description, payload.error, payload.msg_cd]
      .filter(Boolean)
      .join(" / ");

    throw new Error(
      detail
        ? `KIS 웹소켓 승인키 발급 실패 (${config.tradingEnv}, ${response.status}): ${detail}`
        : `KIS 웹소켓 승인키 발급 실패 (${config.tradingEnv}, ${response.status})`,
    );
  }

  // 공식 샘플은 1일 단위 재발급을 권장하므로 토큰과 동일하게 보수적으로 23시간 캐시합니다.
  return {
    approvalKey: payload.approval_key,
    expiresAt: Date.now() + 23 * 60 * 60 * 1000,
  };
}

/**
 * approval 응답을 안전하게 JSON으로 파싱합니다.
 * @param rawText fetch 응답 원문
 * @returns KisApprovalResponse
 */
function tryParseApprovalResponse(rawText: string): KisApprovalResponse {
  try {
    return JSON.parse(rawText) as KisApprovalResponse;
  } catch {
    return {
      msg1: rawText.slice(0, 200),
    };
  }
}

/**
 * 웹소켓 승인키를 반환합니다.
 * @param credentials 사용자 입력 키(선택)
 * @returns approval key
 */
export async function getKisApprovalKey(credentials?: KisCredentialInput) {
  const cacheKey = getApprovalCacheKey(credentials);
  const cached = approvalCacheMap.get(cacheKey);

  if (cached && cached.expiresAt - APPROVAL_REFRESH_BUFFER_MS > Date.now()) {
    return cached.approvalKey;
  }

  const inFlight = approvalIssueInFlightMap.get(cacheKey);
  if (inFlight) {
    const shared = await inFlight;
    return shared.approvalKey;
  }

  const nextPromise = issueKisApprovalKey(credentials);
  approvalIssueInFlightMap.set(cacheKey, nextPromise);
  const next = await nextPromise.finally(() => {
    approvalIssueInFlightMap.delete(cacheKey);
  });

  approvalCacheMap.set(cacheKey, next);
  return next.approvalKey;
}

/**
 * 거래 모드에 맞는 KIS 웹소켓 URL을 반환합니다.
 * @param credentials 사용자 입력 키(선택)
 * @returns websocket url
 */
export function resolveKisWebSocketUrl(credentials?: KisCredentialInput) {
  const config = getKisConfig(credentials);
  return getKisWebSocketUrl(config.tradingEnv);
}

/**
 * 승인키 캐시를 제거합니다.
 * @param credentials 사용자 입력 키(선택)
 */
export function clearKisApprovalKeyCache(credentials?: KisCredentialInput) {
  const cacheKey = getApprovalCacheKey(credentials);
  approvalCacheMap.delete(cacheKey);
  approvalIssueInFlightMap.delete(cacheKey);
}