use std::error::Error;
use std::ffi::OsStr;
use std::fmt;
use std::fs::metadata;
use std::io;
use std::path::Path;

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

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

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

impl<C: CommandRunner, T: AsRef<Path>> GitCheckout<'_, C, T> {
  fn _run_in_target_repo<S: AsRef<OsStr>>(&self, args: &[S]) -> Result<Vec<u8>, Box<dyn Error>> {
    let mut new_args = vec![OsStr::new("-C"), self.target.as_ref().as_ref()];
    new_args.extend(args.iter().map(AsRef::as_ref));
    self.command_runner.get_output("git", &new_args)
  }
}

impl<C: CommandRunner, T: AsRef<Path>> Symbol for GitCheckout<'_, 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))
      };
    }
    self._run_in_target_repo(&["fetch", self.source, self.branch])?;
    // git rev-list resolves tag objects
    let fetch_head = self._run_in_target_repo(&["rev-list", "-1", "FETCH_HEAD"])?;
    let head = self._run_in_target_repo(&["rev-list", "-1", "HEAD"])?;
    Ok(fetch_head == head)
  }

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

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

  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 {}