feat: add commands with unit tests

app/command/commands/bold-command.spec.ts

@@ -0,0 +1,28 @@
+import { TextDocument } from "../text-document";
+import { BoldCommand } from "./bold-command";
+
+describe('BoldCommand', () => {
+  it('should bold text', () => {
+    const document = new TextDocument();
+    document.setContent('Hello, World!');
+    const boldCommand = new BoldCommand(document, 7, 9);
+    boldCommand.execute();
+    expect(document.getContent()).toBe('Hello, **Wo**rld!');
+  })
+
+  it('should undo bold text', () => {
+    const document = new TextDocument();
+    document.setContent('Hello, World!');
+    const boldCommand = new BoldCommand(document, 7, 9);
+    boldCommand.execute();
+    boldCommand.undo();
+    expect(document.getContent()).toBe('Hello, World!');
+  })
+
+  it('should undo bold text', () => {
+    const document = new TextDocument();
+    document.setContent('Hello, World!');
+    const boldCommand = new BoldCommand(document, 7, 5);
+    expect(() => boldCommand.execute()).toThrow(/Invalid range/);
+  })
+});

app/command/commands/bold-command.ts

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+import { ICommand, IDocument } from "../interface";
+
+export class BoldCommand implements ICommand {
+  private document: IDocument;
+  private from: number;
+  private to: number;
+
+  constructor(document: IDocument, from: number, to: number) {
+    this.document = document;
+    this.from = from;
+    this.to = to;
+  }
+
+  execute(): void {
+    if(this.to <= this.from) throw new Error('Invalid range');
+
+    let doc = this.document.getContent();
+    doc = doc.slice(0, this.from)
+      + "**"
+      + doc.slice(this.from, this.to)
+      + "**"
+      + doc.slice(this.to);
+    this.document.setContent(doc);
+  }
+
+  undo(): void {
+    let doc = this.document.getContent();
+    doc = doc.slice(0, this.from)
+      + doc.slice(this.from+2, this.to+2)
+      + doc.slice(this.to+4);
+    this.document.setContent(doc);
+  }
+}

app/command/commands/erase-command.spec.ts

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+import { TextDocument } from "../text-document";
+import { EraseCommand } from "./erase-command";
+
+describe('EraseCommand', () => {
+  it('should erase', () => {
+    const document = new TextDocument();
+    document.setContent('Hello, World!');
+    const eraseCommand = new EraseCommand(document, 7);
+    eraseCommand.execute();
+    expect(document.getContent()).toBe('Hello,');
+  })
+
+  it('should redo erase', () => {
+    const document = new TextDocument();
+    document.setContent('Hello, World!');
+    const eraseCommand = new EraseCommand(document, 7);
+    eraseCommand.execute();
+    eraseCommand.undo();
+    expect(document.getContent()).toBe('Hello, World!');
+  })
+});

app/command/commands/erase-command.ts

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+import { ICommand, IDocument } from "../interface";
+
+export class EraseCommand implements ICommand {
+  private document: IDocument;
+  private eraseCount: number;
+  private remainingPart: string = '';
+
+  constructor(document: IDocument, eraseCount: number) {
+    this.document = document;
+    this.eraseCount = eraseCount;
+  }
+
+  execute(): void {
+    let doc = this.document.getContent();
+    const newDoc = doc.slice(0, -this.eraseCount);
+    this.remainingPart = doc.slice(doc.length-this.eraseCount);
+    this.document.setContent(newDoc);
+  }
+
+  undo(): void {
+    let doc = this.document.getContent();
+    doc += this.remainingPart;
+    this.document.setContent(doc);
+  }
+}

app/command/commands/index.ts

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+export * from './bold-command';
+export * from './erase-command';
+export * from './write-command';

app/command/commands/write-command.spec.ts

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+import { TextDocument } from "../text-document";
+import { WriteCommand } from "./write-command";
+
+describe('WriteCommand', () => {
+  it('should write text', () => {
+    const document = new TextDocument();
+    const writeCommand = new WriteCommand(document, 'test');
+    writeCommand.execute();
+    expect(document.getContent()).toBe('test');
+  })
+
+  it('should undo write text', () => {
+    const document = new TextDocument();
+    const writeCommand = new WriteCommand(document, 'hello');
+    writeCommand.execute();
+    writeCommand.undo();
+    expect(document.getContent()).toBe('');
+  })
+});

app/command/commands/write-command.ts

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+import { ICommand, IDocument } from "../interface";
+
+export class WriteCommand implements ICommand {
+  private document: IDocument;
+  private text: string;
+
+  constructor(document: IDocument, text: string) {
+    this.document = document;
+    this.text = text;
+  }
+
+  execute(): void {
+    let doc = this.document.getContent();
+    doc += this.text;
+    this.document.setContent(doc);
+  }
+
+  undo(): void {
+    let doc = this.document.getContent();
+    doc = doc.slice(0, -this.text.length);
+    this.document.setContent(doc);
+  }
+}