working on moving left

this is the first actual line-editing and ansi escape handling w00t

src/error.rs

@@ -9,6 +9,9 @@ pub enum Error {
 
     #[error("i/o error: {0}")]
     IOError(#[from] io::Error),
+
+    #[error("input error: {0}")]
+    InputError(String),
 }
 
 impl Error {
@@ -23,4 +26,8 @@ impl Error {
             Err(Error::last_error())
         }
     }
+
+    pub fn input_error<S: Into<String>>(msg: S) -> Self {
+        Error::InputError(msg.into())
+    }
 }

src/input.rs

@@ -145,8 +145,20 @@ impl Reader {
         })
     }
 
-    pub fn next(&mut self) -> Result<Console::INPUT_RECORD> {
-        // All buffered items have been processed, ask the OS for new event records
+    pub fn next(&mut self) -> Result<Event> {
+        let rec = self.next_rec()?;
+        if rec.EventType as u32 == Console::KEY_EVENT {
+            unsafe {
+                let event = rec.Event.KeyEvent;
+                if event.wVirtualKeyCode == 0 && event.uChar.UnicodeChar == 27 {
+                    return Ok(self.next_escape_sequence()?);
+                }
+            }
+        }
+        Ok(rec.into())
+    }
+
+    fn next_rec(&mut self) -> Result<Console::INPUT_RECORD> {
         if self.buf_idx as u32 >= self.buf_len {
             unsafe {
                 Error::check(Console::ReadConsoleInputA(
@@ -162,6 +174,49 @@ impl Reader {
         self.buf_idx += 1;
         return Ok(rec);
     }
+
+    fn next_escape_sequence(&mut self) -> Result<Event> {
+        self.take_bracket()?;
+        match self.next_escape_char()? {
+            'D' => Ok(Event::Left),
+            e => Err(Error::input_error(format!("unexpected escape char: {}", e)).into()),
+        }
+    }
+
+    fn take_bracket(&mut self) -> Result<()> {
+        let rec = self.next_rec()?;
+        if rec.EventType as u32 != Console::KEY_EVENT {
+            Err(Error::input_error("failed to read escape sequence: not a key event").into())
+        } else {
+            unsafe {
+                let event = rec.Event.KeyEvent;
+                if event.wVirtualKeyCode == 0 && event.uChar.UnicodeChar == 91 {
+                    Ok(())
+                } else {
+                    Err(Error::input_error("failed to read escape sequence: not a [").into())
+                }
+            }
+        }
+    }
+
+    fn next_escape_char(&mut self) -> Result<char> {
+        let rec = self.next_rec()?;
+        if rec.EventType as u32 != Console::KEY_EVENT {
+            Err(
+                Error::input_error("failed to read char in escape sequence: not a key event")
+                    .into(),
+            )
+        } else {
+            unsafe {
+                let n = rec.Event.KeyEvent.uChar.UnicodeChar as u32;
+                let c = char::from_u32(n);
+                c.ok_or_else(|| {
+                    let msg = format!("escape key value is not a valid unicode character: {}", n);
+                    Error::input_error(msg).into()
+                })
+            }
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -169,11 +224,9 @@ pub enum Event {
     Focus(bool),
     Menu(u32),
     Key(key::Event),
-    Mouse{
-        x: i16,
-        y: i16,
-    },
+    Mouse { x: i16, y: i16 },
     Size,
+    Left,
 }
 
 const ALT_KEYS: u32 = 0x0002 | 0x0001;

src/line.rs

@@ -5,20 +5,20 @@ use windows::Win32::System::Console;
 
 pub struct Line {
     chars: Vec<char>,
+    cursor: usize,
 }
 
 impl Line {
     pub fn new() -> Self {
-        Self { chars: Vec::new() }
+        Self {
+            chars: Vec::new(),
+            cursor: 0,
         }
-
-    /// adds a character to the end of the line
-    pub fn append(&mut self, c: char) {
-        self.chars.push(c)
     }
 
     pub fn clear(&mut self) {
-        self.chars.clear()
+        self.cursor = 0;
+        self.chars.clear();
     }
 
     pub fn print(&self) -> Result<()> {
@@ -33,4 +33,15 @@ impl Line {
         }
         Ok(())
     }
+
+    pub fn back(&mut self) {
+        if self.cursor > 0 {
+            self.cursor -= 1;
+        }
+    }
+
+    pub fn insert(&mut self, c: char) {
+        self.chars.insert(self.cursor, c);
+        self.cursor += 1;
+    }
 }

src/main.rs

@@ -161,14 +161,12 @@ fn main() -> Result<()> {
 
     prompt.print()?;
     loop {
-        let rec = input.next()?;
-        let event: input::Event = rec.into();
-        match event {
+        match input.next()? {
             input::Event::Key(event) => {
+                debug!("Key Event: {}", event);
                 if event.down {
                     continue;
                 }
-                debug!("Key Event: {}", event);
 
                 if event.code == key::ENTER {
                     newline(stdout)?;
@@ -195,12 +193,18 @@ fn main() -> Result<()> {
                     continue;
                 }
 
+                // TODO: something better here, this is crappy. I should be checking characters
+                // based on their unicode categories, not this garbo
                 if !event.char.is_control() {
+                    line.insert(event.char);
+
                     let mut buf = [0 as u8; 8];
                     let s = event.char.encode_utf8(&mut buf);
-                    s.chars().for_each(|c| line.append(c));
+
+                    // write everything from the current line cursor out to the output buffer. Then
+                    // rewind the cursor in the output buffer to where it was.
                     unsafe {
-                        Error::check(Console::WriteConsoleW(
+                        Error::check(Console::WriteConsoleA(
                             stdout,
                             s.as_bytes(),
                             None,
@@ -209,7 +213,17 @@ fn main() -> Result<()> {
                     }
                     continue;
                 }
+
+                debug!("Unhandled Keyboard Event: {}", event);
+            }
+            input::Event::Left => {
+                debug!("back!");
+                line.back();
+                unsafe {
+                    let text = "\x1b[D";
+                    Error::check(Console::WriteConsoleA(stdout, text.as_bytes(), None, None))?;
                 }
+            },
             input::Event::Focus(true) => {},
             input::Event::Focus(false) => {},
             input::Event::Menu(_command_id) => {},