non-persistent history

src/edit.rs

@@ -193,6 +193,11 @@ pub struct Editor {
 
     /// this thing draws our prompt
     prompt: Prompt,
+
+    /// Our current position when scrolling through the history. A hist_pos of 0 means that we're
+    /// not looking at the history. hist_pos of 1 means that we're looking at the first most-recent
+    /// command entered.
+    hist_pos: usize,
 }
 
 impl Editor {
@@ -202,6 +207,7 @@ impl Editor {
             buffer: Buffer::new(),
             display: output::Writer::stdout()?,
             prompt: Prompt::new(),
+            hist_pos: 0,
         })
     }
 
@@ -223,7 +229,7 @@ impl Editor {
                     Status::Ongoing
                 }
                 Control(cc) => self.handle_control(cc)?,
-                Escape(escape) => self.handle_escape(escape)?,
+                Escape(escape) => self.handle_escape(escape, history)?,
                 Size => {
                     debug!("ignoring size event");
                     Status::Ongoing
@@ -240,7 +246,10 @@ impl Editor {
             match status {
                 Status::Ongoing => {}
                 Status::Done => return Ok(None),
-                Status::Submit(e) => return Ok(Some(e)),
+                Status::Submit(e) => {
+                    self.hist_pos = 0;
+                    return Ok(Some(e));
+                }
             }
         }
     }
@@ -261,12 +270,13 @@ impl Editor {
         Ok(Status::Ongoing)
     }
 
-    fn handle_escape(&mut self, esc: Escape) -> Result<Status> {
+    fn handle_escape(&mut self, esc: Escape, history: &History) -> Result<Status> {
         use Escape::*;
         match esc {
             Left => self.back(1)?,
             Right => self.forward(1)?,
-            Up => self.prev_history()?,
+            Up => self.prev_history(history)?,
+            Down => self.next_history(history)?,
             Home => self.seek_left()?,
             End => self.seek_right()?,
             esc => debug!("  Ignored escape: {esc:?}"),
@@ -424,7 +434,41 @@ impl Editor {
         Ok(())
     }
 
-    fn prev_history(&mut self) -> Result<()> {
+    fn prev_history(&mut self, history: &History) -> Result<()> {
+        let text = match history.look_back(self.hist_pos + 1) {
+            Some(s) => {
+                self.hist_pos += 1;
+                s
+            }
+            None => return Ok(()),
+        };
+        self.seek_right()?;
+        self.clear_left()?;
+        for c in text.chars() {
+            self.insert(c)?;
+        }
+        Ok(())
+    }
+
+    fn next_history(&mut self, history: &History) -> Result<()> {
+        if self.hist_pos <= 1 {
+            self.seek_right()?;
+            self.clear_left()?;
+            self.hist_pos = 0;
+            return Ok(());
+        }
+        let text = match history.look_back(self.hist_pos - 1) {
+            Some(s) => {
+                self.hist_pos -= 1;
+                s
+            }
+            None => return Ok(()),
+        };
+        self.seek_right()?;
+        self.clear_left()?;
+        for c in text.chars() {
+            self.insert(c)?;
+        }
         Ok(())
     }
 }

src/history.rs

@@ -10,4 +10,11 @@ impl History {
     pub fn add<S: Into<String>>(&mut self, event: S) {
         self.events.push(event.into());
     }
+
+    pub fn look_back(&self, idx: usize) -> Option<&str> {
+        if idx > self.events.len() {
+            return None;
+        }
+        Some(&self.events[self.events.len() - idx])
+    }
 }

src/interactive.rs

@@ -49,6 +49,7 @@ impl Session {
                 Some(text) => text,
                 None => break,
             };
+            history.add(text.clone());
             let command = match parse(&text) {
                 Ok(ast) => ast,
                 Err(e) => {

src/prompt.rs

@@ -15,6 +15,11 @@ impl Prompt {
             //               |        |          +-------- clear styles
             //               |        |          |      +- show cursor
             //               v        v          v      v
+            #[cfg(debug_assertions)]
+            s: String::from("\x1b[?25l\x1b[31m ▷ \x1b[0m\x1b[?25h"),
+
+            #[allow(dead_code)]
+            #[cfg(not(debug_assertions))]
             s: String::from("\x1b[?25l\x1b[32m ▷ \x1b[0m\x1b[?25h"),
         }
     }