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use std::fs::OpenOptions;
use std::io::{self, BufRead, BufReader, BufWriter, Write};
use std::path::Path;
#[derive(Default)]
pub struct History {
idx: usize,
lines: Vec<String>,
}
impl History {
pub fn new() -> History {
History {
idx: 0,
lines: Vec::new(),
}
}
pub fn add_line(&mut self, line: String) {
// When a line is added, we need to do so and reset the index so that the next
// previous_line()/next_line() operations start from the beginning again.
if !line.is_empty() {
self.lines.insert(0, line)
}
self.idx = 0;
}
pub fn next_line(&mut self) -> String {
match self.idx {
0 => String::new(),
_ => {
self.idx -= 1;
self.lines[self.idx].clone()
}
}
}
pub fn previous_line(&mut self) -> String {
match self.lines.len() {
0 => String::new(),
len if self.idx < len => {
let line = self.lines[self.idx].clone();
self.idx += 1;
line
}
_ => self.lines[self.idx - 1].clone(),
}
}
pub fn load_from_file<P: AsRef<Path>>(&mut self, path: P) -> io::Result<()> {
let file = OpenOptions::new().read(true).open(path)?;
let lines: Vec<String> = BufReader::new(file)
.lines()
.collect::<Result<Vec<_>, _>>()?;
lines.into_iter().for_each(|ln| self.add_line(ln));
Ok(())
}
pub fn save_to_file<P: AsRef<Path>>(&self, path: P, limit: usize) -> io::Result<()> {
if limit == 0 || self.lines.is_empty() {
return Ok(());
}
let file = OpenOptions::new()
.write(true)
.create(true)
.truncate(true)
.open(path)?;
let mut f = BufWriter::new(file);
self.lines
.iter()
.take(limit)
.rev()
.try_for_each(|ln| writeln!(f, "{ln}"))
}
}
#[cfg(test)]
mod tests {
use super::*;
use tempfile::TempDir;
#[test]
fn t_empty_history_returns_nothing() {
let mut h = History::new();
assert_eq!(h.previous_line(), "");
assert_eq!(h.previous_line(), "");
assert_eq!(h.next_line(), "");
assert_eq!(h.next_line(), "");
}
#[test]
fn t_one_line_in_history() {
let mut h = History::new();
h.add_line("testline".to_string());
assert_eq!(h.previous_line(), "testline");
assert_eq!(h.previous_line(), "testline");
assert_eq!(h.next_line(), "testline");
assert_eq!(h.next_line(), "");
}
#[test]
fn t_multiple_lines_in_history() {
let mut h = History::new();
h.add_line("testline".to_string());
h.add_line("foobar".to_string());
assert_eq!(h.previous_line(), "foobar");
assert_eq!(h.previous_line(), "testline");
assert_eq!(h.next_line(), "testline");
assert_eq!(h.previous_line(), "testline");
assert_eq!(h.next_line(), "testline");
assert_eq!(h.next_line(), "foobar");
assert_eq!(h.next_line(), "");
assert_eq!(h.next_line(), "");
}
#[test]
fn t_save_and_load_history() {
let tmp_dir = TempDir::new().unwrap();
let file_path = tmp_dir.path().join("history.cmdline");
let mut h = History::new();
h.add_line("testline".to_string());
h.add_line("foobar".to_string());
// no file is created/opened if limit is zero
h.save_to_file(file_path.clone(), 0).unwrap();
assert!(!file_path.exists());
// lines are written to file
h.save_to_file(file_path.clone(), 10).unwrap();
assert!(file_path.exists());
// lines are loaded to new History
let mut loaded_h = History::new();
loaded_h.load_from_file(file_path).unwrap();
assert_eq!(loaded_h.previous_line(), "foobar");
assert_eq!(loaded_h.previous_line(), "testline");
assert_eq!(loaded_h.next_line(), "testline");
assert_eq!(loaded_h.next_line(), "foobar");
assert_eq!(loaded_h.next_line(), "");
}
#[test]
fn t_save_and_load_limited_history() {
let tmp_dir = TempDir::new().unwrap();
let file_path = tmp_dir.path().join("history.cmdline");
let max_lines = 3;
let mut h = History::new();
h.add_line("1".to_string());
h.add_line("2".to_string());
h.add_line("3".to_string());
h.add_line("4".to_string());
// lines are written to file
h.save_to_file(file_path.clone(), max_lines).unwrap();
assert!(file_path.exists());
// lines are loaded to new History
let mut loaded_h = History::new();
loaded_h.load_from_file(file_path).unwrap();
assert_eq!(loaded_h.previous_line(), "4");
assert_eq!(loaded_h.previous_line(), "3");
assert_eq!(loaded_h.previous_line(), "2");
assert_eq!(loaded_h.previous_line(), "2");
}
}
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