add domain entities and ports

package.json

@@ -24,6 +24,7 @@
     "@nestjs/common": "^7.6.15",
     "@nestjs/core": "^7.6.15",
     "@nestjs/platform-express": "^7.6.15",
+    "bignumber.js": "^9.0.1",
     "reflect-metadata": "^0.1.13",
     "rimraf": "^3.0.2",
     "rxjs": "^6.6.6"

src/domains/entities/account.entity.ts

@@ -0,0 +1,64 @@
+import { MoneyEntity } from './money.entity';
+import { ActivityWindowEntity } from './activity-window.entity';
+import { ActivityEntity } from './activity.entity';
+
+export type AccountId = string;
+
+export class AccountEntity {
+  constructor(
+    private readonly _id: AccountId,
+    private readonly _baseLineBalance: MoneyEntity,
+    private readonly _activityWindow: ActivityWindowEntity,
+  ) {}
+
+  get id(): string {
+    return this._id;
+  }
+
+  get baseLineBalance(): MoneyEntity {
+    return this._baseLineBalance;
+  }
+
+  get activityWindow(): ActivityWindowEntity {
+    return this._activityWindow;
+  }
+
+  public calculateBalance(): MoneyEntity {
+    return MoneyEntity.add(
+      this._baseLineBalance,
+      this._activityWindow.calculateBalance(this.id),
+    );
+  }
+
+  public withdraw(money: MoneyEntity, targetAccountId: AccountId): boolean {
+    if (!this._mayWithdrawMoney(money)) {
+      return false;
+    }
+
+    const withdrawal: ActivityEntity = new ActivityEntity(
+      this.id,
+      targetAccountId,
+      new Date(),
+      money,
+    );
+
+    this._activityWindow.addActivity(withdrawal);
+    return true;
+  }
+
+  public deposite(money: MoneyEntity, sourceAccountId: AccountId): boolean {
+    const deposite: ActivityEntity = new ActivityEntity(
+      sourceAccountId,
+      this.id,
+      new Date(),
+      money,
+    );
+
+    this._activityWindow.addActivity(deposite);
+    return true;
+  }
+
+  private _mayWithdrawMoney(money: MoneyEntity) {
+    return MoneyEntity.add(this.calculateBalance(), money.negate());
+  }
+}

src/domains/entities/activity-window.entity.ts

@@ -0,0 +1,30 @@
+import { ActivityEntity } from './activity.entity';
+import { AccountId } from './account.entity';
+import { MoneyEntity } from './money.entity';
+
+export class ActivityWindowEntity {
+  private readonly _activities: ActivityEntity[] = [];
+
+  get activities(): ActivityEntity[] {
+    return this._activities;
+  }
+
+  addActivity(activity: ActivityEntity) {
+    this.activities.push(activity);
+    return this;
+  }
+
+  public calculateBalance(accountId: AccountId): MoneyEntity {
+    const depositeBalance = this.activities
+      .filter((activity) => activity.targetAccountId === accountId)
+      .map((activity) => activity.money)
+      .reduce(MoneyEntity.add, MoneyEntity.ZERO());
+
+    const withdrawalBalance = this.activities
+      .filter((activity) => activity.sourceAccountId === accountId)
+      .map((activity) => activity.money)
+      .reduce(MoneyEntity.add, MoneyEntity.ZERO());
+
+    return MoneyEntity.add(depositeBalance, withdrawalBalance.negate());
+  }
+}

src/domains/entities/activity.entity.ts

@@ -0,0 +1,27 @@
+import { AccountId } from './account.entity';
+import { MoneyEntity } from './money.entity';
+
+export class ActivityEntity {
+  constructor(
+    private readonly _sourceAccountId: AccountId,
+    private readonly _targetAccountId: AccountId,
+    private readonly _timestamp: Date,
+    private readonly _money: MoneyEntity,
+  ) {}
+
+  get sourceAccountId(): string {
+    return this._sourceAccountId;
+  }
+
+  get targetAccountId(): string {
+    return this._targetAccountId;
+  }
+
+  get timestamp(): Date {
+    return this._timestamp;
+  }
+
+  get money(): MoneyEntity {
+    return this._money;
+  }
+}

src/domains/entities/money.entity.ts

@@ -0,0 +1,29 @@
+import { BigNumber } from 'bignumber.js';
+
+export class MoneyEntity {
+  constructor(private readonly _amount: BigNumber) {}
+
+  static ZERO() {
+    return new MoneyEntity(new BigNumber(0));
+  }
+
+  static of(value: number) {
+    return new MoneyEntity(new BigNumber(value));
+  }
+
+  get amount(): BigNumber {
+    return this._amount;
+  }
+
+  static add(a: MoneyEntity, b: MoneyEntity): MoneyEntity {
+    return new MoneyEntity(a.amount.plus(b.amount));
+  }
+
+  negate() {
+    return new MoneyEntity(this.amount.negated());
+  }
+
+  isPositiveOrZero(): boolean {
+    return this.amount.comparedTo(0) >= 0;
+  }
+}

src/domains/ports/in/get-account-balance.query.ts

@@ -0,0 +1,5 @@
+import {AccountId} from "../../entities/account.entity";
+
+export interface GetAccountBalanceQuery {
+  getAccountBalance(accountId: AccountId);
+}

src/domains/ports/in/send-money.command.ts

@@ -0,0 +1,22 @@
+import { AccountId } from '../../entities/account.entity';
+import { MoneyEntity } from '../../entities/money.entity';
+
+export class SendMoneyCommand {
+  constructor(
+    private readonly _sourceAccountId: AccountId,
+    private readonly _targetAccountId: AccountId,
+    private readonly _money: MoneyEntity,
+  ) {}
+
+  get sourceAccountId(): string {
+    return this._sourceAccountId;
+  }
+
+  get targetAccountId(): string {
+    return this._targetAccountId;
+  }
+
+  get money(): MoneyEntity {
+    return this._money;
+  }
+}

src/domains/ports/in/send-money.use-case.ts

@@ -0,0 +1,5 @@
+import { SendMoneyCommand } from './send-money.command';
+
+export interface SendMoneyUseCase {
+  sendMoney(command: SendMoneyCommand);
+}

src/domains/ports/out/load-account.port.ts

@@ -0,0 +1,5 @@
+import { AccountId } from '../../entities/account.entity';
+
+export interface LoadAccountPort {
+  loadAccount(accountId: AccountId);
+}

src/domains/ports/out/update-account-state.port.ts

@@ -0,0 +1,5 @@
+import { AccountEntity } from '../../entities/account.entity';
+
+export interface UpdateAccountStatePort {
+  updateActivities(account: AccountEntity);
+}