use std::error::Error;
use std::fmt;
use std::io;
use std::path::Path;

use command_runner::CommandRunner;
use resources::Resource;
use symbols::{Action, OwnedSymbolAction, Symbol, SymbolAction, SymbolRunner};

pub struct GitCheckout<'a, C: 'a + CommandRunner, T: AsRef<str>> {
  target: T,
  source: &'a str,
  branch: &'a str,
  command_runner: &'a C
}

impl<'a, C: CommandRunner, T: AsRef<str>> GitCheckout<'a, C, T> {
  pub fn new(target: T, source: &'a str, branch: &'a str, command_runner: &'a C) -> Self {
    GitCheckout { target, source, branch, command_runner }
  }
}

impl<'a, C: CommandRunner, T: AsRef<str>> fmt::Display for GitCheckout<'a, C, T> {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    write!(f, "Checkout {} (branch {}) into {}", self.source, self.branch, self.target.as_ref())
  }
}

use std::fs::metadata;

impl<'a, C: CommandRunner, T: AsRef<str>> GitCheckout<'a, C, T> {
  fn _run_in_target_repo(&self, args: &[&str]) -> Result<Vec<u8>, Box<dyn Error>> {
    let mut new_args = vec!["-C", self.target.as_ref()];
    new_args.extend_from_slice(args);
    self.command_runner.get_output("git", &new_args)
  }
}

impl<'a, C: CommandRunner, T: AsRef<str>> Symbol for GitCheckout<'a, C, T> {
  fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
    if let Err(e) = metadata(self.target.as_ref()) {
      return if e.kind() == io::ErrorKind::NotFound {
        Ok(false)
      } else {
        Err(Box::new(e))
      };
    }
    try!(self._run_in_target_repo(&["fetch", self.source, self.branch]));
    // git rev-list resolves tag objects
    let fetch_head = try!(self._run_in_target_repo(&["rev-list", "-1", "FETCH_HEAD"]));
    let head = try!(self._run_in_target_repo(&["rev-list", "-1", "HEAD"]));
    Ok(fetch_head == head)
  }

  fn execute(&self) -> Result<(), Box<dyn Error>> {
    if !Path::new(self.target.as_ref()).exists() {
      return self.command_runner.run_successfully("git", &["clone", "--depth", "1", "-b", self.branch, self.source, self.target.as_ref()]);
    }
    try!(self._run_in_target_repo(&["fetch", self.source, self.branch]));
    try!(self._run_in_target_repo(&["merge", "FETCH_HEAD"]));
    Ok(())
  }

  fn get_prerequisites(&self) -> Vec<Resource> {
    vec![ Resource::new("dir", Path::new(self.target.as_ref()).parent().unwrap().to_string_lossy()) ]
  }

  fn provides(&self) -> Option<Vec<Resource>> {
    Some(vec![ Resource::new("dir", self.target.as_ref().to_string()) ])
  }

  fn as_action<'b>(&'b self, runner: &'b dyn SymbolRunner) -> Box<dyn Action + 'b> {
    Box::new(SymbolAction::new(runner, self))
  }

  fn into_action<'b>(self: Box<Self>, runner: &'b dyn SymbolRunner) -> Box<dyn Action + 'b> where Self: 'b {
    Box::new(OwnedSymbolAction::new(runner, *self))
  }
}

#[cfg(test)]
mod test {
}