Implement redo.

Is this how redo works?

2 files changed, 86 insertions, 49 deletions

diff --git a/src/main.rs b/src/main.rs
index c1131f1..f0a38d8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,13 +5,13 @@ use rope::Rope;
 use std::error::Error;
 use std::ffi::{OsStr, OsString};
 use std::io::{stdin, stdout, Read, Write};
+use std::ops::{Deref, DerefMut};
 use std::path::Path;
 use term::Key;
 
 #[derive(Debug, Clone, Copy)]
 enum Mode {
     Insert,
-    Backspace,
     Normal,
 }
 
@@ -24,7 +24,6 @@ struct State {
     cursor_col: usize,
     line_offset: usize,
     line_cols: usize,
-    prev: Option<Box<State>>,
 }
 
 fn parse_status_report(buf: &[u8]) -> Result<(usize, usize), Box<dyn Error>> {
@@ -46,28 +45,28 @@ fn parse_status_report(buf: &[u8]) -> Result<(usize, usize), Box<dyn Error>> {
     return Ok((row - 1, col - 1));
 }
 
-impl State {
-    fn cursor_pos(&mut self) -> Result<(usize, usize), Box<dyn Error>> {
-        write!(stdout(), "\x1b[6n")
-            .map_err(|err| format!("cursor position: status report: {}", err))?;
-        stdout()
-            .flush()
-            .map_err(|err| format!("cursor position: status report: {}", err))?;
-        let mut buf = vec![0; 20];
-        let n = stdin()
-            .read(&mut buf)
-            .map_err(|err| format!("cursor position: read status report: {}", err))?;
-        buf.truncate(n);
-        let pos = parse_status_report(&buf).map_err(|_| {
-            format!(
-                "cursor position: invalid response: {}",
-                String::from_utf8_lossy(&buf)
-            )
-        })?;
-        return Ok(pos);
-    }
+fn cursor_pos() -> Result<(usize, usize), Box<dyn Error>> {
+    write!(stdout(), "\x1b[6n")
+        .map_err(|err| format!("cursor position: status report: {}", err))?;
+    stdout()
+        .flush()
+        .map_err(|err| format!("cursor position: status report: {}", err))?;
+    let mut buf = vec![0; 20];
+    let n = stdin()
+        .read(&mut buf)
+        .map_err(|err| format!("cursor position: read status report: {}", err))?;
+    buf.truncate(n);
+    let pos = parse_status_report(&buf).map_err(|_| {
+        format!(
+            "cursor position: invalid response: {}",
+            String::from_utf8_lossy(&buf)
+        )
+    })?;
+    return Ok(pos);
+}
 
-    fn repaint_all(&mut self) -> Result<(), Box<dyn Error>> {
+impl State {
+    fn repaint_all(&self) -> Result<(), Box<dyn Error>> {
         let size = term::size()?;
         let mut stdout = stdout().lock();
 
@@ -80,7 +79,7 @@ impl State {
                 break;
             }
             self.buf.line(i).print(&mut stdout)?;
-            let (_, col) = self.cursor_pos()?;
+            let (_, col) = cursor_pos()?;
             if col == usize::from(size.ws_col - 1) {
                 write!(stdout, "\x1b[{}G\x1b[30m\x1b[47m>\x1b[m ", size.ws_col - 1)?;
             }
@@ -96,7 +95,7 @@ impl State {
         let line = self.buf.line(self.row_start + self.cursor_row);
 
         line.print(&mut stdout)?;
-        let (_, col) = self.cursor_pos()?;
+        let (_, col) = cursor_pos()?;
         self.line_cols = col;
         let mut truncated = false;
         if col == usize::from(term_size.ws_col - 1) {
@@ -123,7 +122,7 @@ impl State {
             let x = line.floor_char_boundary(lo + (hi - lo) / 2);
             write!(stdout, "\x1b[G")?;
             line.slice(0, x).print(&mut stdout)?;
-            let (_, col) = self.cursor_pos()?;
+            let (_, col) = cursor_pos()?;
             if col <= self.cursor_col {
                 lo = line.ceil_char_boundary(x + 1);
             } else {
@@ -204,43 +203,66 @@ impl State {
         self.repaint_line_full()?;
         return Ok(());
     }
+}
+
+#[derive(Debug)]
+struct StateHistory {
+    i: usize,
+    history: Vec<State>,
+}
 
+impl StateHistory {
     fn set_mode(&mut self, mode: Mode) {
         match (self.mode, mode) {
-            (Mode::Insert, Mode::Insert) => (),
-            (Mode::Insert, _) => {
-                if let Ok((_, col)) = self.cursor_pos() {
+            (Mode::Insert, Mode::Normal) => {
+                if let Ok((_, col)) = cursor_pos() {
                     self.cursor_col = col;
                 }
                 let _ = self.repaint_line_full();
             }
-            (Mode::Normal, Mode::Normal) => (),
-            (Mode::Normal, _) => {
-                let prev = self.prev.take();
-                let mut curr = Box::new(self.clone());
-                curr.prev = prev;
-                self.prev = Some(curr);
+            (Mode::Normal, Mode::Insert) => {
+                let curr = self.clone();
+                self.i += 1;
+                self.history.truncate(self.i);
+                self.history.push(curr);
             }
             _ => (),
         }
         self.mode = mode;
     }
 }
+
+impl Deref for StateHistory {
+    type Target = State;
+
+    fn deref(&self) -> &Self::Target {
+        return &self.history[self.i];
+    }
+}
+
+impl DerefMut for StateHistory {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        return &mut self.history[self.i];
+    }
+}
+
 fn edit(file: &OsStr) -> Result<(), Box<dyn Error>> {
     let _raw_handle =
         term::raw().map_err(|err| format!("cannot put terminal in raw mode: {}", err))?;
 
     let r = Rope::open(Path::new(file))?;
     let size = term::size()?;
-    let mut state = State {
-        buf: r,
-        mode: Mode::Normal,
-        row_start: 0,
-        cursor_row: 0,
-        cursor_col: 0,
-        line_offset: 0,
-        line_cols: 0,
-        prev: None,
+    let mut state = StateHistory {
+        i: 0,
+        history: vec![State {
+            buf: r,
+            mode: Mode::Normal,
+            row_start: 0,
+            cursor_row: 0,
+            cursor_col: 0,
+            line_offset: 0,
+            line_cols: 0,
+        }],
     };
     let _ = state.repaint_all();
     let _ = write!(stdout(), "\x1b[H");
@@ -258,10 +280,20 @@ fn edit(file: &OsStr) -> Result<(), Box<dyn Error>> {
             }
             Key::CtrlZ => {
                 state.set_mode(Mode::Normal);
-                let Some(prev) = state.prev else {
+                if state.i == 0 {
+                    continue;
+                }
+                state.i -= 1;
+                let _ = state.repaint_all();
+                let _ = state.repaint_line_full();
+                let _ = stdout().flush();
+            }
+            Key::CtrlY => {
+                state.set_mode(Mode::Normal);
+                if state.i == state.history.len() - 1 {
                     continue;
-                };
-                state = *prev;
+                }
+                state.i += 1;
                 let _ = state.repaint_all();
                 let _ = state.repaint_line_full();
                 let _ = stdout().flush();
@@ -287,7 +319,7 @@ fn edit(file: &OsStr) -> Result<(), Box<dyn Error>> {
                 let _ = stdout().flush();
             }
             Key::Backspace => {
-                state.set_mode(Mode::Backspace);
+                state.set_mode(Mode::Insert);
                 if state.row_start == 0 && state.cursor_row == 0 && state.line_offset == 0 {
                     continue;
                 }
@@ -299,7 +331,7 @@ fn edit(file: &OsStr) -> Result<(), Box<dyn Error>> {
                 } else {
                     let _ = write!(stdout(), "\x1b[G");
                     let _ = state.buf.slice(line_start, gap_start).print(&mut stdout());
-                    let (_, col) = state.cursor_pos()?;
+                    let (_, col) = cursor_pos()?;
                     state.cursor_col = col;
                 }
                 state.buf = state
diff --git a/src/term.rs b/src/term.rs
index 3a56091..988786d 100644
--- a/src/term.rs
+++ b/src/term.rs
@@ -69,6 +69,7 @@ pub enum Key {
     CtrlQ,
     CtrlS,
     CtrlZ,
+    CtrlY,
     Up,
     Down,
     Left,
@@ -80,6 +81,7 @@ pub enum Key {
 pub fn read_key() -> Result<Key, Box<dyn Error>> {
     const CTRL_Q: u8 = 17;
     const CTRL_S: u8 = 19;
+    const CTRL_Y: u8 = 25;
     const CTRL_Z: u8 = 26;
     const BACKSPACE: u8 = 127;
     const ESC: u8 = 27;
@@ -93,6 +95,9 @@ pub fn read_key() -> Result<Key, Box<dyn Error>> {
         if buf[0] == CTRL_S {
             return Ok(Key::CtrlS);
         }
+        if buf[0] == CTRL_Y {
+            return Ok(Key::CtrlY);
+        }
         if buf[0] == CTRL_Z {
             return Ok(Key::CtrlZ);
         }