Render the contents and set up a functioning cursor

editor-challenge/src/main.rs

@@ -3,7 +3,10 @@ use crossterm::{
     terminal::{disable_raw_mode, enable_raw_mode},
 };
 use std::{
-    io::{self, Read},
+    env,
+    fs::File,
+    io::{self, BufRead, BufReader, Read},
+    path::PathBuf,
     sync::mpsc,
     thread,
     time::{Duration, Instant},
@@ -20,7 +23,113 @@ const TITLE: &str = "Text Editor Challenge";
 const COPYRIGHT: &str = "(c) Savanni D'Gerinel - all rights reserved";
 const TICK_RATE_MS: u64 = 200;
 
-fn render<T>(terminal: &mut Terminal<T>) -> Result<(), anyhow::Error>
+#[derive(Default)]
+struct Document {
+    rows: Vec<String>
+}
+
+impl Document {
+    fn contents(&self) -> String {
+        self.rows.join("\n")
+    }
+
+    fn row_length(&self, idx: usize) -> usize {
+        self.rows[idx].len()
+    }
+
+    fn row_count(&self) -> usize {
+        self.rows.len()
+    }
+}
+
+#[derive(Default)]
+struct AppState {
+    path: Option<PathBuf>,
+    cursor: Cursor,
+    contents: Document, // Obviously this is bad, but it's also only temporary.
+}
+
+impl AppState {
+    fn open(path: PathBuf) -> Self {
+        let mut file = File::open(path.clone()).unwrap();
+        let mut reader = BufReader::new(file);
+        let contents = reader
+            .lines()
+            .collect::<Result<Vec<String>, std::io::Error>>()
+            .unwrap();
+
+        Self {
+            path: Some(path),
+            cursor: Default::default(),
+            contents: Document{ rows: contents },
+        }
+    }
+
+    fn cursor_up(&mut self) {
+        self.cursor.cursor_up(&self.contents);
+    }
+
+    fn cursor_down(&mut self) {
+        self.cursor.cursor_down(&self.contents);
+    }
+
+    fn cursor_right(&mut self) {
+        self.cursor.cursor_right(&self.contents);
+    }
+
+    fn cursor_left(&mut self) {
+        self.cursor.cursor_left();
+    }
+}
+
+#[derive(Default)]
+struct Cursor {
+    row: usize,
+    column: usize,
+    desired_column: usize,
+}
+
+impl Cursor {
+    fn cursor_up(&mut self, doc: &Document) {
+        if self.row > 0 {
+            self.row -= 1;
+        }
+        self.correct_columns(doc);
+    }
+
+    fn cursor_down(&mut self, doc: &Document) {
+        if self.row < doc.row_count() - 1 {
+            self.row += 1;
+        }
+        self.correct_columns(doc);
+    }
+
+    fn correct_columns(&mut self, doc: &Document) {
+        let row_len = doc.row_length(self.row);
+        if self.desired_column < row_len {
+            self.column = self.desired_column;
+        } else {
+            self.column = row_len;
+        }
+    }
+
+    fn cursor_right(&mut self, doc: &Document) {
+        if self.column < doc.row_length(self.row) {
+            self.column += 1;
+        }
+        self.desired_column = self.column;
+    }
+
+    fn cursor_left(&mut self) {
+        if self.column > 0 {
+            self.column -= 1;
+        }
+        self.desired_column = self.column;
+    }
+
+}
+
+fn render<T>(app_state: &AppState, terminal: &mut Terminal<T>) -> Result<(), anyhow::Error>
 where
     T: tui::backend::Backend,
 {
@@ -39,7 +148,13 @@ where
             )
             .split(size);
 
-        let title = Paragraph::new(TITLE)
+        let title = Paragraph::new(
+            app_state
+                .path
+                .clone()
+                .map(|path| path.to_string_lossy().to_owned().into())
+                .unwrap_or("No file opened".to_owned()),
+        )
         .style(Style::default().fg(Color::LightCyan))
         .alignment(Alignment::Center)
         .block(
@@ -62,6 +177,15 @@ where
                     .border_type(BorderType::Plain),
             );
         rect.render_widget(cp, chunks[2]);
+
+        // TODO: rework scrolling as soon as I have a working cursor
+        let contents = Paragraph::new(app_state.contents.contents()).scroll((0, 0));
+        rect.render_widget(contents, chunks[1]);
+
+        // TODO: keeping track of the index of the top row and subtract that from the cursor row.
+        let row = app_state.cursor.row as u16;
+        let column = app_state.cursor.column as u16;
+        rect.set_cursor(chunks[1].x + column, chunks[1].y + row);
     })?;
     Ok(())
 }
@@ -94,6 +218,7 @@ fn handle_input(tx: mpsc::Sender<Event<KeyEvent>>, tick_rate: Duration) {
 }
 
 fn app_loop<T>(
+    mut app_state: AppState,
     terminal: &mut Terminal<T>,
     rx: mpsc::Receiver<Event<KeyEvent>>,
 ) -> Result<(), anyhow::Error>
@@ -101,7 +226,7 @@ where
     T: tui::backend::Backend,
 {
     loop {
-        render(terminal)?;
+        render(&app_state, terminal)?;
 
         let event = rx.recv()?;
 
@@ -111,6 +236,18 @@ where
             {
                 break;
             }
+            Event::Input(KeyEvent { code, .. }) if code == KeyCode::Down => {
+                app_state.cursor_down();
+            }
+            Event::Input(KeyEvent { code, .. }) if code == KeyCode::Up => {
+                app_state.cursor_up();
+            }
+            Event::Input(KeyEvent { code, .. }) if code == KeyCode::Right => {
+                app_state.cursor_right();
+            }
+            Event::Input(KeyEvent { code, .. }) if code == KeyCode::Left => {
+                app_state.cursor_left();
+            }
             _ => {}
         }
     }
@@ -118,6 +255,15 @@ where
 }
 
 fn main() -> Result<(), anyhow::Error> {
+    let args = env::args().collect::<Vec<String>>();
+
+    let file_name = if args.len() > 1 { Some(&args[1]) } else { None };
+
+    let app_state = match file_name {
+        Some(name) => AppState::open(name.into()),
+        None => Default::default(),
+    };
+
     let (tx, rx) = mpsc::channel();
 
     let tick_rate = Duration::from_millis(TICK_RATE_MS);
@@ -132,7 +278,7 @@ fn main() -> Result<(), anyhow::Error> {
     let mut terminal = Terminal::new(backend)?;
     let _ = terminal.clear()?;
 
-    let result = app_loop(&mut terminal, rx);
+    let result = app_loop(app_state, &mut terminal, rx);
 
     disable_raw_mode()?;
     terminal.show_cursor()?;