Fixed prompt cursor adjustment

src/parser/mod.rs

@@ -162,26 +162,44 @@ pub fn parse(
 
 
 pub fn substitute(
-	s: &String, // The string to subsitute
+	s: &String, // The string to substitute
 	c: usize    // Location of the cursor right now
-) -> String{
-	if s == "" { return s.clone() }
+) -> (
+	usize,  // Location of cursor in substituted string
+	String  // String with substitutions
+) {
+	if s == "" { return (c, s.clone()) }
 	let mut new_s = s.clone();
 
+	let l = s.chars().count();
 	let tokens = tokenize(s);
 	let (subs, _) = find_subs(tokens);
+	let mut new_c = l - c;
 
 	for r in subs.iter() {
-		if { // Don't subsitute if our cursor is inside the substitution
+		// find_subs gives substitutions in reverse order.
+
+		if { // Don't substitute if our cursor is inside the substitution
 			c >= r.0.pos &&
 			c < r.0.pos+r.0.len
 		} { continue; }
 
+		if c < r.0.pos {
+			let ct = r.1.chars().count();
+			if ct >= r.0.len {
+				if new_c >= ct - r.0.len {
+					new_c += ct - r.0.len
+				}
+			} else {
+				new_c -= r.0.len - ct
+			}
+		}
+
 		new_s.replace_range(
 			r.0.pos..r.0.pos+r.0.len,
 			&r.1[..]
 		)
 	}
 
-	return new_s;
+	return (new_c, new_s);
 }

src/promptbuffer.rs

@@ -39,11 +39,12 @@ impl PromptBuffer {
 
 
 	pub fn write_prompt(&mut self, stdout: &mut RawTerminal<std::io::Stdout>) -> Result<(), std::io::Error> {
-		let i = self.buffer.chars().count();
-		let i = if i == 0 {0} else {i - self.cursor};
+		let l = self.buffer.chars().count();
+		let i = if l == 0 {0} else {l - self.cursor};
 
 		// Draw prettyprinted expression
-		let s = substitute(&self.get_contents(), i);
+		let (display_cursor, s) = substitute(&self.get_contents(), i);
+
 		write!(
 			stdout, "\r{}{}==>{}{} {}",
 			style::Bold,
@@ -62,11 +63,12 @@ impl PromptBuffer {
 			)?;
 		}
 
+
 		// Move cursor to correct position
-		if self.cursor != 0 {
+		if display_cursor != 0 {
 			write!(
 				stdout, "{}",
-				termion::cursor::Left(self.cursor as u16)
+				termion::cursor::Left(display_cursor as u16)
 			)?;
 			stdout.flush()?;
 		}