use std::fmt;
use std::io;

use command_runner::CommandRunner;
use symbols::Symbol;

pub struct GitCheckout<'a> {
  target: &'a str,
  source: &'a str,
  branch: &'a str,
  command_runner: &'a CommandRunner
}

impl<'a> GitCheckout<'a> {
  pub fn new(target: &'a str, source: &'a str, branch: &'a str, command_runner: &'a CommandRunner) -> GitCheckout<'a> {
    GitCheckout {
      target: target,
      source: source,
      branch: branch,
      command_runner: command_runner
    }
  }
}

impl<'a> fmt::Display for GitCheckout<'a> {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    write!(f, "Checkout {} (branch {}) into {}", self.source, self.branch, self.target)
  }
}

use std::fs::metadata;

impl<'a> GitCheckout<'a> {
  fn _run_in_target_repo(&self, args: &[&str]) -> Result<Vec<u8>, io::Error> {
    let mut new_args = vec!["-C", self.target];
    new_args.extend_from_slice(args);
    self.command_runner.run_with_args("git", &new_args).map(|res| res.stdout)
  }
}

impl<'a> Symbol for GitCheckout<'a> {
  type Error = io::Error;
  fn target_reached(&self) -> Result<bool, Self::Error> {
    if let Err(e) = metadata(self.target) {
      return if e.kind() == io::ErrorKind::NotFound {
        Ok(false)
      } else {
        Err(e)
      };
    }
    try!(self._run_in_target_repo(&["fetch", self.source, self.branch]));
    let fetch_head = try!(self._run_in_target_repo(&["rev-parse", "FETCH_HEAD"]));
    let head = try!(self._run_in_target_repo(&["rev-parse", "HEAD"]));
    Ok(fetch_head == head)
  }

  fn execute(&self) -> Result<(), Self::Error> {
    if let Err(e) = metadata(self.target) {
      return if e.kind() == io::ErrorKind::NotFound {
        try!(self.command_runner.run_with_args("git", &["clone", "-b", self.branch, self.source, self.target]));
        Ok(())
      } else {
        Err(e)
      };
    }
    try!(self._run_in_target_repo(&["fetch", self.source, self.branch]));
    try!(self._run_in_target_repo(&["merge", "FETCH_HEAD"]));
    Ok(())
  }
}

#[cfg(test)]
mod test {
}