import { logger } from "@utils/logger";
import { ApiClientConfig } from "@utils/types";

export class RateLimiter {
  private maxRequests: number;
  private perMilliseconds: number;
  private requestTimestamps: number[] = [];

  constructor(config: ApiClientConfig) {
    this.maxRequests = config.rateLimit.maxRequests;
    this.perMilliseconds = config.rateLimit.perMilliseconds;
    logger.log(
      `RateLimiter initialized: ${this.maxRequests} requests per ${this.perMilliseconds}ms.`
    );
  }

  private cleanupTimestamps(): void {
    const windowStartTime = Date.now() - this.perMilliseconds;

    this.requestTimestamps = this.requestTimestamps.filter(
      (timestamp) => timestamp >= windowStartTime
    );
  }

  /**
   * Checks if the rate limit has been hit and calculates the required delay.
   * @returns {number} The delay in milliseconds required before the next request can fire.
   * Returns 0 if no delay is needed.
   */
  public checkLimitAndGetDelay(): number {
    this.cleanupTimestamps(); // 👈 Cleanup karna zaroori hai

    const currentRequestCount = this.requestTimestamps.length;

    if (currentRequestCount < this.maxRequests) {
      return 0;
    }

    const oldestTimestamp = this.requestTimestamps[0];

    if (oldestTimestamp === undefined) {
      return 0;
    }

    const windowEndTime = oldestTimestamp + this.perMilliseconds;

    const requiredDelay = windowEndTime - Date.now();

    const delay = Math.max(0, requiredDelay);

    logger.warn(
      `Rate limit hit! Current count: ${currentRequestCount}. Delaying next request for ${delay}ms.`
    );

    return delay;
  }

  public recordRequestStart(): void {
    this.cleanupTimestamps();
    this.requestTimestamps.push(Date.now());
    logger.log(
      `Request recorded. Current window count: ${this.requestTimestamps.length}/${this.maxRequests}`
    );
  }
}