//! # git-recent
//!
//! Prints recently checked out git branches, most recently checked out branch first.
//!
//! Usage: git recent [lines]
//!
//! Options:
//!     lines - number of lines to output [default=10]

use std::io::prelude::*;
use std::io::BufReader;
use std::process::{Command, Stdio};
use std::collections::HashSet;
use std::path::PathBuf;
use std::env;

fn main() {
    let max_lines = env::args().nth(1)
        .and_then(|arg| arg.parse::<usize>().ok())
        .unwrap_or(10);

    let revparse = Command::new("git")
        .arg("rev-parse")
        .arg("--git-dir")
        .stdout(Stdio::piped())
        .output()
        .expect("git-rev-parse command failed")
        .stdout;

    let heads_dir = {
        let mut git_dir = PathBuf::from(String::from_utf8_lossy(&revparse).trim_right().to_owned());
        git_dir.push("refs");
        git_dir.push("heads");
        git_dir
    };

    let reflog = BufReader::new(
        Command::new("git")
        .arg("reflog")
        .stdout(Stdio::piped())
        .spawn()
        .expect("git-reflog command failed")
        .stdout.unwrap());

    let mut seen = HashSet::new();
    let branches = reflog.lines()
        .filter_map(Result::ok)
        .filter(|line| line.contains("checkout: "))
        .filter_map(|line| line.rsplitn(2, ' ').next().map(str::to_owned))
        .filter(|branch| heads_dir.join(branch).exists())
        .filter(|branch| seen.insert(branch.clone()))
        .take(max_lines);

    for branch in branches {
        println!("{}", branch);
    }
}