test-assignment-payments/src/transaction/transaction.controller.ts

import { Controller, Post, UsePipes, Body } from '@nestjs/common';
import _ from 'lodash';
import {
  ExchangeRateInput,
  ExchangeRateResponse,
} from 'src/exchange-rate/exchange-rate.dto';
import { ExchangeRateService } from 'src/exchange-rate/exchange-rate.service';
import { TransactionService } from './transaction.service';
import { transactionBodySchema } from './transaction.validation';
import { BodyValidationPipe } from '../pipes/body.validation.pipe';
import {
  Currency,
  TransactionInput,
  DiscountRuleForClientById,
  DefaultCommissionPercentage,
  DefaultCommissionAmount,
  HighTurnoverDiscount,
} from './transaction.dto';
import { Transaction } from './transaction.entity';

type TransactionRuleData = Pick<Transaction, 'base_amount' | 'client_id'>;

@Controller('transaction')
export class TransactionController {
  constructor(
    private readonly transactionService: TransactionService,
    private readonly exchangeRateService: ExchangeRateService,
  ) {}

  @Post()
  @UsePipes(new BodyValidationPipe(transactionBodySchema))
  async commission(
    @Body() transactionInput: TransactionInput,
  ): Promise<string> {
    return JSON.stringify({
      amount:
        transactionInput.currency !== Currency.EUR
          ? (await this.getAmountWithExchange(transactionInput)).toFixed(2)
          : (await this.getAmountWithoutExchange(transactionInput)).toFixed(2),
      currency: Currency.EUR,
    });
  }

  getClientDeposit = async (transactionInput: TransactionRuleData) => {
    try {
      const deposit =
        await this.transactionService.findByClientIdWithinActualMonth(
          transactionInput.client_id,
        );

      if (deposit) {
        const initialDeposit = 0;
        const totalDeposit = (await deposit).reduce(
          (prevAmmount, transactionAmmount) =>
            prevAmmount + transactionAmmount.base_amount,
          initialDeposit,
        );

        return totalDeposit;
      }
    } catch (error) {
      console.log(error);
    }
    return 0;
  };

  turnoverRule = async (transactionInput: TransactionRuleData) => {
    try {
      const clientDeposit = await this.getClientDeposit(transactionInput);
      if (clientDeposit) {
        return clientDeposit > 1000 ? HighTurnoverDiscount.amount : false;
      }
    } catch (error) {
      console.log(error);
    }
  };

  discountRule(transactionInput: TransactionRuleData) {
    return transactionInput.client_id === 42
      ? DiscountRuleForClientById.client_42
      : false;
  }

  defaultRule(transactionInput: TransactionRuleData) {
    const commissionAmount =
      (transactionInput.base_amount * DefaultCommissionPercentage.percentage) /
      100;
    return commissionAmount < DefaultCommissionAmount.amount
      ? DefaultCommissionAmount.amount
      : commissionAmount;
  }

  async applyRules(
    rules: ((
      transactionInput: TransactionRuleData,
    ) => number | false | undefined | Promise<number | false | undefined>)[],
    transactionInput: TransactionRuleData,
  ) {
    const commissions = await Promise.all(
      [...rules, this.defaultRule].map((rule) => rule(transactionInput)),
    );
    return Math.min(..._.compact(commissions));
  }

  getExchangeRate(exchangeRateInput: ExchangeRateInput) {
    return new Promise<ExchangeRateResponse>((resolve, reject) => {
      try {
        this.exchangeRateService.convertCurrency(exchangeRateInput).subscribe({
          next: resolve,
          error: reject,
        });
      } catch (error) {
        reject(error);
      }
    });
  }

  async getAmountWithExchange(transactionInput: TransactionInput) {
    const exchangeRateResponse = await this.getExchangeRate({
      date: transactionInput.date,
    });

    const transactionAmount = parseInt(transactionInput.amount);
    const transactionData = {
      date: transactionInput.date,
      amount: transactionAmount,
      currency: transactionInput.currency,
      client_id: transactionInput.client_id,
      base_currency: Currency.EUR,
      base_amount:
        transactionAmount / exchangeRateResponse[transactionInput.currency],
    };

    const commissionAmount = this.applyRules(
      [this.turnoverRule, this.discountRule],
      transactionData,
    );

    commissionAmount
      .then((commission) =>
        this.transactionService.insertOne({
          ...transactionData,
          commission,
        }),
      )
      .catch((error) => console.log(error));

    return commissionAmount;
  }

  async getAmountWithoutExchange(transactionInput: TransactionInput) {
    const transactionData = {
      date: transactionInput.date,
      amount: parseInt(transactionInput.amount),
      currency: transactionInput.currency,
      client_id: transactionInput.client_id,
      base_currency: Currency.EUR,
      base_amount: parseInt(transactionInput.amount),
    };

    const commissionAmount = await this.applyRules(
      [this.turnoverRule, this.discountRule],
      transactionData,
    );
    try {
      this.transactionService
        .insertOne({
          ...transactionData,
          commission: commissionAmount,
        })
        .catch((error) => console.log(error));
    } catch (error) {
      console.log(error);
      throw error;
    }

    return commissionAmount;
  }
}