use std::error::Error;
use std::fmt;

use resources::Resource;
use symbols::Symbol;

pub struct List<'a> {
  symbols: Vec<Box<Symbol + 'a>>
}

impl<'a> List<'a> {
  pub fn new(symbols: Vec<Box<Symbol + 'a>>) -> Self {
    List { symbols: symbols }
  }
}

impl<'a> Symbol for List<'a> {
  fn target_reached(&self) -> Result<bool, Box<Error>> {
    for symbol in &self.symbols {
      match symbol.target_reached() {
        Ok(false) => return Ok(false),
        Err(e) => return Err(e),
        Ok(true) => {}
      }
    }
    Ok(true)
  }

  fn execute(&self) -> Result<(), Box<Error>> {
    for symbol in &self.symbols {
      try!(symbol.execute());
    }
    Ok(())
  }

  fn get_prerequisites(&self) -> Vec<Resource> {
    let mut r = vec![];
    for symbol in &self.symbols {
      for req in symbol.get_prerequisites() {
        if self.provides().map_or(true, |p| !p.contains(&req)) { r.push(req) }
      }
    }
    r
  }

  fn provides(&self) -> Option<Vec<Resource>> {
    let mut r = vec![];
    for symbol in &self.symbols {
      if let Some(provides) = symbol.provides() {
        r.extend(provides.into_iter());
      }
    }
    if r.len() > 0 { Some(r) } else { None }
  }
}

impl<'a> fmt::Display for List<'a> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error>{
    try!(write!(f, "List [ "));
    for symbol in &self.symbols {
      try!(write!(f, "{} ", symbol));
    }
    write!(f, "]")
  }
}

/*
#[cfg(test)]
mod test {
  use std::error::Error;
  use std::fmt;

  use symbols::Symbol;
  use symbols::hook::List;

  struct ErrSymbol(String);
  impl Symbol for ErrSymbol {
    fn target_reached(&self) -> Result<bool, Box<Error>> { Err(self.0.clone().into()) }
    fn execute(&self) -> Result<(), Box<Error>> { Err(self.0.clone().into()) }
  }
  impl fmt::Display for ErrSymbol { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error>{ write!(f, "") } }

  struct OkSymbol(bool);
  impl Symbol for OkSymbol {
    fn target_reached(&self) -> Result<bool, Box<Error>> { Ok(self.0) }
    fn execute(&self) -> Result<(), Box<Error>> { Ok(()) }
  }
  impl fmt::Display for OkSymbol { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error>{ write!(f, "") } }

  #[test]
  fn first_target_reached_fails() {
    let res = List::new(ErrSymbol("first".into()), ErrSymbol("second".into())).target_reached();
    assert_eq!(res.unwrap_err().description(), "first");
  }

  #[test]
  fn first_target_not_reached() {
    let res = List::new(OkSymbol(false), ErrSymbol("second".into())).target_reached();
    assert_eq!(res.unwrap(), false);
  }

  #[test]
  fn second_target_reached_fails() {
    let res = List::new(OkSymbol(true), ErrSymbol("second".into())).target_reached();
    assert_eq!(res.unwrap_err().description(), "second");
  }

  #[test]
  fn second_target_not_reached() {
    let res = List::new(OkSymbol(true), OkSymbol(false)).target_reached();
    assert_eq!(res.unwrap(), false);
  }

  #[test]
  fn everything_reached() {
    let res = List::new(OkSymbol(true), OkSymbol(true)).target_reached();
    assert_eq!(res.unwrap(), true);
  }

  #[test]
  fn first_execute_fails() {
    let res = List::new(ErrSymbol("first".into()), ErrSymbol("second".into())).execute();
    assert_eq!(res.unwrap_err().description(), "first");
  }

  #[test]
  fn second_execute_fails() {
    let res = List::new(OkSymbol(true), ErrSymbol("second".into())).execute();
    assert_eq!(res.unwrap_err().description(), "second");
  }

  #[test]
  fn everything_executes() {
    let res = List::new(OkSymbol(true), OkSymbol(true)).execute();
    assert_eq!(res.unwrap(), ());
  }
}
*/