mempool/frontend/src/app/components/fees-box/fees-box.component.ts

import { Component, OnInit, ChangeDetectionStrategy } from '@angular/core';
import { StateService } from 'src/app/services/state.service';
import { map, filter } from 'rxjs/operators';
import { merge, Observable } from 'rxjs';
import { MempoolBlock } from 'src/app/interfaces/websocket.interface';

interface FeeEstimations {
  fastestFee: number;
  halfHourFee: number;
  hourFee: number;
}

@Component({
  selector: 'app-fees-box',
  templateUrl: './fees-box.component.html',
  styleUrls: ['./fees-box.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class FeesBoxComponent implements OnInit {
  feeEstimations$: Observable<FeeEstimations>;
  isLoadingWebSocket$: Observable<boolean>;
  defaultFee: number;

  constructor(
    private stateService: StateService,
  ) { }

  ngOnInit(): void {
    this.defaultFee = this.stateService.network === 'liquid' ? 0.1 : 1;

    this.isLoadingWebSocket$ = this.stateService.isLoadingWebSocket$;
    this.feeEstimations$ = this.stateService.mempoolBlocks$
      .pipe(
        map((pBlocks) => {
          if (!pBlocks.length) {
            return {
              'fastestFee': this.defaultFee,
              'halfHourFee': this.defaultFee,
              'hourFee': this.defaultFee,
            };
          }

          const firstMedianFee = this.optimizeMedianFee(pBlocks[0]);
          const secondMedianFee = pBlocks[1] ? this.optimizeMedianFee(pBlocks[1], firstMedianFee) : this.defaultFee;
          const thirdMedianFee = pBlocks[2] ? this.optimizeMedianFee(pBlocks[2], secondMedianFee) : this.defaultFee;

          return {
            'fastestFee': firstMedianFee,
            'halfHourFee': secondMedianFee,
            'hourFee': thirdMedianFee,
          };
        })
      );
  }

  optimizeMedianFee(pBlock: MempoolBlock, previousFee?: number): number {
    const useFee = previousFee ? (pBlock.medianFee + previousFee / 2) : pBlock.medianFee;
    if (pBlock.blockVSize <= 500000) {
      return this.defaultFee;
    }
    if (pBlock.blockVSize <= 950000) {
      const multiplier = (pBlock.blockVSize - 500000) / 500000;
      return Math.max(Math.round(useFee * multiplier), this.defaultFee);
    }
    return Math.round(useFee);
  }

}