Command Pattern: Text Editor with undo

Author: fadeevab

Cargo.toml

@@ -17,4 +17,5 @@ members = [
   "structural/flyweight",
   "structural/proxy",
   "behavioral/chain-of-responsibility",
+  "behavioral/command",
 ]

behavioral/command/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+edition = "2021"
+name = "command"
+version = "0.1.0"
+
+[[bin]]
+name = "command"
+path = "main.rs"
+
+[dependencies]
+cursive = {version = "0.19", default-features = false, features = ["termion-backend"]}
+owning_ref = "0.4"

behavioral/command/README.md

@@ -0,0 +1,11 @@
+# Command
+
+Command is behavioral design pattern that converts requests or simple operations into objects.
+
+## Text Editor: Commands and Undo
+
+```bash
+cargo run
+```
+
+![Text Editor screenshot](res/editor.png)

behavioral/command/command.rs

@@ -0,0 +1,12 @@
+mod copy;
+mod cut;
+mod paste;
+
+pub use copy::CopyCommand;
+pub use cut::CutCommand;
+pub use paste::PasteCommand;
+
+pub trait Command {
+    fn execute(&mut self, app: &mut cursive::Cursive) -> bool;
+    fn undo(&mut self, app: &mut cursive::Cursive);
+}

behavioral/command/command/copy.rs

@@ -0,0 +1,21 @@
+use cursive::{views::EditView, Cursive};
+
+use super::Command;
+use crate::AppContext;
+
+#[derive(Default)]
+pub struct CopyCommand;
+
+impl Command for CopyCommand {
+    fn execute(&mut self, app: &mut Cursive) -> bool {
+        let editor = app.find_name::<EditView>("Editor").unwrap();
+        let mut context = app.take_user_data::<AppContext>().unwrap();
+
+        context.clipboard = editor.get_content().to_string();
+
+        app.set_user_data(context);
+        return false;
+    }
+
+    fn undo(&mut self, _: &mut Cursive) {}
+}

behavioral/command/command/cut.rs

@@ -0,0 +1,28 @@
+use cursive::{views::EditView, Cursive};
+
+use super::Command;
+use crate::AppContext;
+
+#[derive(Default)]
+pub struct CutCommand {
+    backup: String,
+}
+
+impl Command for CutCommand {
+    fn execute(&mut self, app: &mut Cursive) -> bool {
+        let mut editor = app.find_name::<EditView>("Editor").unwrap();
+
+        app.with_user_data(|context: &mut AppContext| {
+            self.backup = editor.get_content().to_string();
+            context.clipboard = self.backup.clone();
+            editor.set_content("".to_string());
+        });
+
+        return true;
+    }
+
+    fn undo(&mut self, app: &mut Cursive) {
+        let mut editor = app.find_name::<EditView>("Editor").unwrap();
+        editor.set_content(&self.backup);
+    }
+}

behavioral/command/command/paste.rs

@@ -0,0 +1,27 @@
+use cursive::{views::EditView, Cursive};
+
+use super::Command;
+use crate::AppContext;
+
+#[derive(Default)]
+pub struct PasteCommand {
+    backup: String,
+}
+
+impl Command for PasteCommand {
+    fn execute(&mut self, app: &mut Cursive) -> bool {
+        let mut editor = app.find_name::<EditView>("Editor").unwrap();
+
+        app.with_user_data(|context: &mut AppContext| {
+            self.backup = editor.get_content().to_string();
+            editor.set_content(context.clipboard.clone());
+        });
+
+        return true;
+    }
+
+    fn undo(&mut self, app: &mut Cursive) {
+        let mut editor = app.find_name::<EditView>("Editor").unwrap();
+        editor.set_content(&self.backup);
+    }
+}

behavioral/command/main.rs

@@ -0,0 +1,48 @@
+mod command;
+
+use cursive::{
+    traits::Nameable,
+    views::{Dialog, EditView},
+    Cursive,
+};
+
+use command::{Command, CopyCommand, CutCommand, PasteCommand};
+
+#[derive(Default)]
+struct AppContext {
+    clipboard: String,
+    history: Vec<Box<dyn Command>>,
+}
+
+fn main() {
+    let mut app = cursive::default();
+
+    app.set_user_data(AppContext::default());
+    app.add_layer(
+        Dialog::around(EditView::default().with_name("Editor"))
+            .title("Type and use buttons")
+            .button("Copy", |s| execute(s, CopyCommand::default()))
+            .button("Cut", |s| execute(s, CutCommand::default()))
+            .button("Paste", |s| execute(s, PasteCommand::default()))
+            .button("Undo", |s| undo(s))
+            .button("Quit", |s| s.quit()),
+    );
+
+    app.run();
+}
+
+fn execute(app: &mut Cursive, mut command: impl Command + 'static) {
+    if command.execute(app) {
+        app.with_user_data(|context: &mut AppContext| {
+            context.history.push(Box::new(command));
+        });
+    }
+}
+
+fn undo(app: &mut Cursive) {
+    let mut context = app.take_user_data::<AppContext>().unwrap();
+    if let Some(mut command) = context.history.pop() {
+        command.undo(app)
+    }
+    app.set_user_data(context);
+}