use std::error::Error;
use std::fmt;
use std::io;
use std::ops::Deref;

use symbols::Symbol;

#[derive(Debug)]
pub enum FileError<E: Error> {
  ExecError(E),
  GenericError
}

impl From<io::Error> for FileError<io::Error> {
  fn from(err: io::Error) -> FileError<io::Error> {
    FileError::ExecError(err)
  }
}

impl<E: Error> Error for FileError<E> {
  fn description(&self) -> &str {
    match self {
      &FileError::ExecError(ref e) => e.description(),
      &FileError::GenericError => "Generic error"
    }
  }
  fn cause(&self) -> Option<&Error> {
    match self {
      &FileError::ExecError(ref e) => Some(e),
      _ => None
    }
  }
}

impl<E: Error> fmt::Display for FileError<E> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "{}", self.description())
  }
}

use std::convert::AsRef;

pub struct File<C, D> where C: Deref<Target=str>, D: AsRef<str> + fmt::Display {
  path: D,
  content: C
}

impl<C, D> File<C, D> where C: Deref<Target=str>, D: AsRef<str> + fmt::Display {
  pub fn new(path: D, content: C) -> Self {
    File {
      path: path,
      content: content
    }
  }
}

use std::fs::File as FsFile;
use std::io::{Read, Write};

impl<C, D> Symbol for File<C, D> where C: Deref<Target=str>, D: AsRef<str> + fmt::Display {
  type Error = FileError<io::Error>;
  fn target_reached(&self) -> Result<bool, Self::Error> {
    let file = FsFile::open(self.path.as_ref());
    // Check if file exists
    if let Err(e) = file {
      return if e.kind() == io::ErrorKind::NotFound {
        Ok(false)
      } else {
        Err(e.into())
      };
    }
    // Check if content is the same
    let file_content = file.unwrap().bytes();
    let content_equal = try!(self.content.bytes().zip(file_content).fold(
      Ok(true),
      |state, (target_byte, file_byte_option)| state.and_then(|s| file_byte_option.map(|file_byte| s && file_byte == target_byte))
    ));
    return Ok(content_equal)
  }

  fn execute(&self) -> Result<(), Self::Error> {
    //try!(self.command_runner.run_with_args("mkdir", &["-p", Path::new(&path).parent().unwrap().to_str().unwrap()]));
    // FIXME: Permissions
    //    try!(create_dir_all(Path::new(&path).parent().unwrap()));
    try!(try!(FsFile::create(self.path.as_ref())).write_all(self.content.as_bytes()));
    Ok(())
  }
}

impl<C, D> fmt::Display for File<C, D> where C: Deref<Target=str>, D: AsRef<str> + fmt::Display {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error>{
    write!(f, "File {}", self.path)
  }
}