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extern crate ansi_escapes;
use std::io::Error;
use std::io::Write;
pub struct LogUpdate<W: Write> {
stream: W,
previous_line_count: u16,
cursor_is_hidden: bool,
}
impl<W: Write> LogUpdate<W> {
pub fn new(mut stream: W) -> Result<Self, Error> {
try!(write!(stream, "{}", ansi_escapes::CursorHide));
try!(stream.flush());
Ok(LogUpdate { stream: stream, previous_line_count: 0, cursor_is_hidden: true })
}
pub fn render(&mut self, text: &str) -> Result<(), Error> {
try!(write!(self.stream, "{}{}\n", ansi_escapes::EraseLines(self.previous_line_count), text));
try!(self.stream.flush());
self.previous_line_count = text.chars().filter(|x| *x == '\n').count() as u16 + 2;
Ok(())
}
pub fn clear(&mut self) -> Result<(), Error> {
try!(write!(self.stream, "{}", ansi_escapes::EraseLines(self.previous_line_count)));
try!(self.stream.flush());
self.previous_line_count = 0;
Ok(())
}
pub fn done(&mut self) -> Result<(), Error> {
if self.cursor_is_hidden {
try!(write!(self.stream, "{}", ansi_escapes::CursorShow));
try!(self.stream.flush());
}
self.previous_line_count = 0;
self.cursor_is_hidden = false;
Ok(())
}
}
impl<W: Write> Drop for LogUpdate<W> {
fn drop(&mut self) {
if self.cursor_is_hidden {
write!(self.stream, "{}", ansi_escapes::CursorShow).unwrap();
self.stream.flush().unwrap();
}
}
}
#[cfg(test)]
extern crate tempfile;
#[cfg(test)]
mod tests {
use tempfile::tempfile;
use std::fs::File;
use std::io::{Read, Seek, SeekFrom};
use super::LogUpdate;
#[test]
fn it_handles_most_common_use_case() {
let mut file: File = tempfile().unwrap();
let mut log_update = LogUpdate::new(file.try_clone().unwrap()).unwrap();
log_update.render("test1").unwrap();
log_update.render("test2").unwrap();
log_update.done().unwrap();
file.seek(SeekFrom::Start(0)).unwrap();
let mut buf = String::new();
file.read_to_string(&mut buf).unwrap();
assert_eq!(concat!("\x1B[?25l", "test1\n", "\x1B[1000D\x1B[K\x1B[1A\x1B[1000D\x1B[K", "test2\n", "\x1B[?25h"), buf);
}
#[test]
fn it_restores_cursor_when_dropped() {
let mut file: File = tempfile().unwrap();
let mut log_update = LogUpdate::new(file.try_clone().unwrap()).unwrap();
log_update.render("test").unwrap();
drop(log_update);
file.seek(SeekFrom::Start(0)).unwrap();
let mut buf = String::new();
file.read_to_string(&mut buf).unwrap();
assert_eq!(concat!("\x1B[?25l", "test\n", "\x1B[?25h"), buf);
}
}