import { AUTH_USER_ID, CLAIM_NAME } from "@/src/shared/config";
import { getCookie, removeCookie, setCookie } from "@/src/shared/lib/cookie";

type JwtPayload = {
  sub?: string; // 토큰 subject
  exp?: number; // 만료 시각(초 단위)
  iat?: number; // 발급 시각(초 단위)
  [key: string]: unknown;
};

export class TokenManager {
  private static instance: TokenManager;
  private refreshTimer: NodeJS.Timeout | null = null;

  private constructor() {}

  public static getInstance(): TokenManager {
    if (!TokenManager.instance) {
      TokenManager.instance = new TokenManager();
    }
    return TokenManager.instance;
  }

  public getToken(key: string): string | undefined {
    return getCookie(key);
  }

  private parseJwt(token: string): JwtPayload {
    const parts = token.split(".");
    if (parts.length !== 3) {
      throw new Error("유효한 JWT 형식이 아닙니다.");
    }

    const base64Url = parts[1] ?? ""; // Payload를 가져온다.
    const base64 = base64Url.replace(/-/g, "+").replace(/_/g, "/");
    const padded = base64.padEnd(Math.ceil(base64.length / 4) * 4, "=");
    const jsonPayload = decodeURIComponent(
      atob(padded)
        .split("")
        .map((char) => `%${char.charCodeAt(0).toString(16).padStart(2, "0")}`)
        .join("")
    );

    return JSON.parse(jsonPayload) as JwtPayload;
  }

  public getRemainingMsFromToken(key: string = CLAIM_NAME): number | null {
    const token = this.getToken(key);
    if (!token) {
      return null;
    }

    try {
      const payload = this.parseJwt(token);
      if (typeof payload.exp !== "number") {
        return null;
      }

      return payload.exp * 1000 - Date.now();
    } catch (error) {
      console.error("JWT 파싱 오류:", error);
      return null;
    }
  }

  public isExpiredToken(key: string = CLAIM_NAME): boolean {
    const remainingMs = this.getRemainingMsFromToken(key);
    return remainingMs === null || remainingMs <= 0;
  }

  public setToken(key: string, value: string): void {
    setCookie(key, value, {
      secure: window.location.protocol === "https:",
      sameSite: "lax",
    });
  }

  public removeToken(key: string): void {
    removeCookie(key);
  }

  public setupRefreshTimer(
    callback: () => Promise<void>,
    expirationTime: number,
  ): void {
    if (this.refreshTimer) {
      clearTimeout(this.refreshTimer);
    }

    this.refreshTimer = setTimeout(() => {
      callback().catch((error) => {
        console.error("Silent refresh failed:", error);
        this.clearAuthToken();
      });
    }, expirationTime - 60000);
  }

  public clearAuthToken(): void {
    if (this.refreshTimer) {
      clearTimeout(this.refreshTimer);
      this.refreshTimer = null;
    }

    this.removeToken(CLAIM_NAME);
    this.removeToken(AUTH_USER_ID);
  }
}

export const tokenManager = TokenManager.getInstance();