Code with Mosh - The Ultimate Design Patterns: Part 1 - Command Pattern - Exercise

Command.java

package com.codewithmosh.command;

public interface Command {
    void execute();
}

ContrastCommand.java

package com.codewithmosh.command;

public class ContrastCommand implements UndoableCommand {
    private float previousContrast;
    private float newContrast;
    private VideoEditor editor;
    private History history;

    public ContrastCommand(float newContrast, VideoEditor editor, History history) {
        this.newContrast = newContrast;
        this.editor = editor;
        this.history = history;
    }

    @Override
    public void execute() {
        previousContrast = editor.getContrast();
        editor.setContrast(newContrast);
        history.push(this);
    }

    @Override
    public void unexecute() {
        editor.setContrast(previousContrast);
    }
}

History.java

package com.codewithmosh.command;

import java.util.ArrayDeque;
import java.util.Deque;

public class History {
    private Deque<UndoableCommand> commands = new ArrayDeque<>();

    public void push(UndoableCommand command) {
//        commands.add(command);
        commands.addFirst(command);
    }

    public UndoableCommand pop() {
        return commands.pop();
    }

    public boolean isEmpty() {
        return commands.isEmpty();
    }
}

Main.java

package com.codewithmosh;

import com.codewithmosh.command.*;

public class Main {

    public static void main(String[] args) {
        var history = new History();
        var editor = new VideoEditor();
        System.out.println(editor.toString());


        var textCommand = new TextCommand("Hello World", editor, history);
        textCommand.execute();
        System.out.println(editor.toString());

        var contrastCommand = new ContrastCommand(0.8f, editor, history);
        contrastCommand.execute();
        System.out.println(editor.toString());

        var contrastCommand2 = new ContrastCommand(1.0f, editor, history);
        contrastCommand2.execute();
        System.out.println(editor.toString());

        var undoCommand = new UndoCommand(history);

        undoCommand.execute();
        System.out.println(editor.toString());

        undoCommand.execute();
        System.out.println(editor.toString());
    }

}

TextCommand.java

package com.codewithmosh.command;

public class TextCommand implements UndoableCommand {
    private String previousContent;
    private String newText;
    private VideoEditor editor;
    private History history;

    public TextCommand(String newText, VideoEditor editor, History history) {
        this.newText = newText;
        this.editor = editor;
        this.history = history;
    }

    @Override
    public void execute() {
        previousContent = editor.getText();
        editor.setText(newText);
        history.push(this);
    }

    @Override
    public void unexecute() {
        editor.setText(previousContent);
    }
}

UndoableCommand.java

package com.codewithmosh.command;

public interface UndoableCommand extends Command {
    void unexecute();
}

UndoCommand.java

package com.codewithmosh.command;

public class UndoCommand implements Command {
    private History history;

    public UndoCommand(History history) {
        this.history = history;
    }

    @Override
    public void execute() {
        if (!history.isEmpty()) {
            history.pop().unexecute();
        }
    }
}

VideoEditor.java

package com.codewithmosh.command;

public class VideoEditor {
    private float contrast = 0.5f;

    public String getText() {
        return text;
    }

    private String text;

    public void setText(String text) {
        this.text = text;
    }

    public void removeText() {
        this.text = "";
    }

    public float getContrast() {
        return contrast;
    }

    public void setContrast(float contrast) {
        this.contrast = contrast;
    }

    @Override
    public String toString() {
        return "VideoEditor{" +
                "contrast=" + contrast +
                ", text='" + text + '\'' +
                '}';
    }
}