Added simple history

src/main.rs

@@ -1,4 +1,5 @@
 use std::io::{Write, stdout, stdin};
+
 use termion::event::Key;
 use termion::input::TermRead;
 use termion::raw::IntoRawMode;
@@ -6,24 +7,38 @@ use termion::raw::RawTerminal;
 use termion::{color, style};
 
 mod parser;
+mod promptbuffer;
+use crate::promptbuffer::PromptBuffer;
+
 use crate::parser::Token;
 //use crate::parser::ParserError;
 use crate::parser::LineLocation;
 use crate::parser::Eval;
 
 
-fn draw_line(stdout: &mut RawTerminal<std::io::Stdout>, s: &String) -> Result<(), std::io::Error> {
+fn draw_line(
+	stdout: &mut RawTerminal<std::io::Stdout>,
+	s: &String,
+	clear_len: usize
+) -> Result<(), std::io::Error> {
 	write!(
-		stdout, "\r{}{}==>{}{} {s} {}",
+		stdout, "\r{}{}==>{}{} {}",
 		style::Bold,
 		color::Fg(color::Blue),
 		color::Fg(color::Reset),
 		style::Reset,
-
-		// Our string can change by at most one character each iteration.
-		// Clearing is done by inserting an extra space, then moving the cursor left.
-		termion::cursor::Left(1)
+		s
 	)?;
+
+	// If this string is shorter, clear the remaining old one.
+	if clear_len != 0 {
+		write!(
+			stdout, "{}{}",
+			" ".repeat(clear_len as usize),
+			termion::cursor::Left(clear_len as u16)
+		)?;
+	}
+
 	stdout.flush()?;
 
 	return Ok(());
@@ -35,19 +50,26 @@ fn main() -> Result<(), std::io::Error> {
 	//let size = termion::terminal_size().unwrap();  
 	//write!(stdout, "{:?}", size).unwrap();
 
-	let mut s: String = String::with_capacity(64);
+	let mut pb: PromptBuffer = PromptBuffer::new(64);
+	let mut last_len: usize = 0;
 
 	'outer: loop {
 
-		s.clear();
-		draw_line(&mut stdout, &s)?;
+		draw_line(
+			&mut stdout,
+			pb.get_contents(),
+			if pb.get_contents().len() >= last_len
+			{ 0 } else {last_len - pb.get_contents().len()}
+		)?;
+		last_len = pb.get_contents().len();
+		
 
 		let stdin = stdin();
 		for c in stdin.keys() {
 			if let Key::Char(q) = c.as_ref().unwrap() {
 				match q {
 					'\n' => {
-						let s = s.trim().to_string();
+						let s = pb.enter();
 						if s == "" { write!(stdout, "\r\n")?; break; }
 
 						RawTerminal::suspend_raw_mode(&stdout)?;
@@ -56,7 +78,7 @@ fn main() -> Result<(), std::io::Error> {
 						RawTerminal::activate_raw_mode(&stdout)?;
 
 						match g {
-							Ok(g) => {					
+							Ok(g) => {
 								let n = g.eval();
 								if let Token::Number(_, v) = n {
 									write!(
@@ -82,25 +104,32 @@ fn main() -> Result<(), std::io::Error> {
 
 						break;
 					},
-					'/' => { s.push('÷'); },
-					'*' => { s.push('×'); },
-					_ => { s.push(*q); }
+					'/' => { pb.add_char('÷'); },
+					'*' => { pb.add_char('×'); },
+					_ => { pb.add_char(*q); }
 				};
 			} else {
 				match c.unwrap() {
-					Key::Backspace => { s.pop(); },
-					Key::Delete => { s.pop(); },
+					Key::Backspace => { pb.backspace(); },
+					Key::Delete => { pb.delete(); },
 					Key::Left => {},
 					Key::Right => {},
-					Key::Up => {},
-					Key::Down => {},
+					Key::Up => { pb.hist_up(); },
+					Key::Down => { pb.hist_down(); },
 					
 					Key::Ctrl('d') |
 					Key::Ctrl('c') => { break 'outer; },
 					_ => {}
 				};
 			};
-			draw_line(&mut stdout, &s)?;
+			
+			draw_line(
+				&mut stdout,
+				pb.get_contents(),
+				if pb.get_contents().len() >= last_len
+				{ 0 } else {last_len - pb.get_contents().len()}
+			)?;
+			last_len = pb.get_contents().len();
 		}
 	}
 

src/promptbuffer.rs

@@ -0,0 +1,96 @@
+use std::collections::VecDeque;
+
+
+#[derive(Debug)]
+pub struct PromptBuffer {
+	// History
+	hist: VecDeque<String>,
+	hist_maxlen: usize,
+
+	// Counts from back of hist.
+	// 0 means "not on history",
+	// 1 means "on last item of history"
+	hist_cursor: usize,
+
+	buffer: String,
+	buffer_changed: bool,
+	//cursor: usize // Counts from back of buffer
+}
+
+impl PromptBuffer {
+	pub fn new(maxlen: usize) -> PromptBuffer {
+		return PromptBuffer {
+			hist: VecDeque::with_capacity(maxlen/2),
+			hist_maxlen: maxlen,
+			hist_cursor: 0,
+			buffer: String::with_capacity(64),
+			buffer_changed: false
+			//cursor: 0,
+		};
+	}
+
+
+	// Prompt methods
+	pub fn get_contents(&self) -> &String {&self.buffer}
+
+	pub fn enter(&mut self) -> String{
+		let s = String::from(self.buffer.trim());
+		self.buffer.clear();
+		self.hist_cursor = 0;
+		self.buffer_changed = false;
+
+		if s != "" { self.hist.push_back(s.clone()); }
+		return s;
+	}
+
+	// Buffer manipulation
+	pub fn add_char(&mut self, c: char) {
+		self.buffer.push(c);
+		self.buffer_changed = true;
+	}
+	pub fn backspace(&mut self) {
+		if self.buffer.len() != 0 {
+			self.buffer_changed = true;
+			self.buffer.pop();
+		}
+	}
+	pub fn delete(&mut self) {
+		self.backspace();
+	}
+
+
+	// History manipulation
+	pub fn hist_up(&mut self) {
+		if self.buffer_changed && self.buffer.len() != 0 { return; }
+
+		if self.hist_cursor < self.hist.len() {
+			if self.buffer.len() != 0 || !self.buffer_changed {
+				self.hist_cursor += 1;
+			}
+
+			self.buffer_changed = false;
+			if self.hist_cursor == 0 {
+				self.buffer.clear();
+			} else {
+				self.buffer = self.hist[self.hist.len() - self.hist_cursor].clone();
+			}
+		}
+	}
+	pub fn hist_down(&mut self) {
+		if self.buffer_changed && self.buffer.len() != 0 { return; }
+
+		if self.hist_cursor > 0 {
+			self.hist_cursor -= 1;
+
+			self.buffer_changed = false;
+			if self.hist_cursor == 0 {
+				self.buffer.clear();
+			} else {
+				self.buffer = self.hist[self.hist.len() - self.hist_cursor].clone();
+			}
+		} else {
+			self.buffer.clear();
+		}
+	}
+
+}