import axios from 'axios';
import { providers } from 'ethers';

// class to fetch gas station parameter
// This class returns the gas in gwei
export class GasStation {
  private maticGasStationUrl: string;
  private mumbaiGasStationUrl: string;

  private chainId: number;
  private provider: providers.Provider;

  constructor(provider: providers.Provider) {
    this.maticGasStationUrl = 'https://gasstation-mainnet.matic.network/v2';
    this.mumbaiGasStationUrl = 'https://gasstation-mumbai.matic.today/v2';
    this.provider = provider;
  }

  // fetch gas station parameters
  public async fetchGasStationParameters(
    chainId: number,
  ): Promise<GasStationParameters> {
    let url: string | null = null;

    // select the gas station url based on the chain id
    if (chainId === 137) {
      url = this.maticGasStationUrl;
    } else if (this.chainId === 80001) {
      url = this.mumbaiGasStationUrl;
    }

    // if url is available in case of polygon based chains
    if (url) {
      const response = await axios({
        method: 'get',
        url: url,
      }).then((response) => {
        return response.data;
      });

      // gas parameters in gwei
      const gasStationParameters = new GasStationParameters(
        response.safeLow,
        response.standard,
        response.fast,
      );
      return gasStationParameters;
    } else {
      // fetch the gas params from the current block
      return await this.fetchGasParamsFromBlock();
    }
  }

  // get latest parameter in gwei
  private async fetchGasParamsFromBlock(): Promise<GasStationParameters> {
    const block: providers.FeeData = await this.provider.getFeeData();

    // convert block gas params from wei to gwei
    const gasParams: GasParam = {
      maxPriorityFee:
        block.maxPriorityFeePerGas?.div('1000000000').toNumber() || 0,
      maxFee: block.maxFeePerGas?.div('1000000000').toNumber() || 0,
    };

    const gasStationParameters = new GasStationParameters(
      gasParams,
      gasParams,
      gasParams,
    );

    return gasStationParameters;
  }
}

export interface GasParam {
  maxPriorityFee: number;
  maxFee: number;
}

// gas station parameters
export class GasStationParameters {
  public safelow: GasParam;
  public standard: GasParam;
  public fast: GasParam;

  constructor(safelow: GasParam, standard: GasParam, fast: GasParam) {
    this.safelow = safelow;
    this.standard = standard;
    this.fast = fast;
  }
}