use std::cell::RefCell;
use std::error::Error;
use std::fmt;

use loggers::Logger;
use repository::SymbolRepository;
use symbols::{Symbol, SymbolRunner};

#[derive(Debug)]
pub enum SymbolRunError {
  Symbol(Box<dyn Error>),
  ExecuteDidNotReach(()),
}

impl Error for SymbolRunError {
  fn description(&self) -> &str {
    match self {
      SymbolRunError::Symbol(_) => "Symbol execution error",
      SymbolRunError::ExecuteDidNotReach(_) => "Target not reached after executing symbol",
    }
  }
  fn cause(&self) -> Option<&dyn Error> {
    match self {
      SymbolRunError::Symbol(ref e) => Some(&**e),
      SymbolRunError::ExecuteDidNotReach(_) => None,
    }
  }
}

impl fmt::Display for SymbolRunError {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    match self {
      SymbolRunError::Symbol(ref e) => write!(f, "{}", e),
      SymbolRunError::ExecuteDidNotReach(_) => write!(f, "{}", self.description()),
    }
  }
}

pub struct InitializingSymbolRunner<L: Logger> {
  logger: RefCell<L>,
}

impl<L: Logger> InitializingSymbolRunner<L> {
  pub fn new(logger: L) -> Self {
    Self {
      logger: RefCell::new(logger),
    }
  }
}

impl<L: Logger> SymbolRunner for InitializingSymbolRunner<L> {
  fn run_symbol(&self, symbol: &dyn Symbol) -> Result<(), Box<dyn Error>> {
    let mut logger = self.logger.borrow_mut();
    let target_reached = symbol.target_reached()?;
    if target_reached {
      logger.write(format!("{} already reached", symbol).as_str());
    } else {
      logger.debug(format!("Symbol reports target_reached: {:?}", target_reached).as_str());
      logger.write(format!("Executing {}", symbol).as_str());
      symbol.execute()?;
      let target_reached = symbol.target_reached()?;
      logger.debug(
        format!(
          "Symbol reports target_reached: {:?} (should be true)",
          target_reached
        )
        .as_str(),
      );
      if !target_reached {
        return Err(Box::new(SymbolRunError::ExecuteDidNotReach(())));
      }
    }
    Ok(())
  }
}

pub struct DrySymbolRunner<L: Logger> {
  logger: RefCell<L>,
}

impl<L: Logger> DrySymbolRunner<L> {
  pub fn new(logger: L) -> Self {
    Self {
      logger: RefCell::new(logger),
    }
  }
}

impl<L: Logger> SymbolRunner for DrySymbolRunner<L> {
  fn run_symbol(&self, symbol: &dyn Symbol) -> Result<(), Box<dyn Error>> {
    let mut logger = self.logger.borrow_mut();
    let target_reached = symbol.target_reached()?;
    logger.debug(format!("Symbol reports target_reached: {:?}", target_reached).as_str());
    if !target_reached {
      logger.write(format!("Would execute {}", symbol).as_str());
    }
    Ok(())
  }
}

pub struct ReportingSymbolRunner<'a, R: 'a + SymbolRunner, L: Logger>(&'a R, RefCell<L>);

impl<'a, R, L> ReportingSymbolRunner<'a, R, L>
where
  R: SymbolRunner,
  L: Logger,
{
  pub fn new(symbol_runner: &'a R, logger: L) -> Self {
    ReportingSymbolRunner(symbol_runner, RefCell::new(logger))
  }
}

impl<'a, R, L> SymbolRunner for ReportingSymbolRunner<'a, R, L>
where
  R: SymbolRunner,
  L: Logger,
{
  fn run_symbol(&self, symbol: &dyn Symbol) -> Result<(), Box<dyn Error>> {
    let mut logger = self.1.borrow_mut();
    logger.debug(format!("Running symbol {}", symbol).as_str());
    let res = self.0.run_symbol(symbol);
    match res {
      Err(ref e) => {
        logger.write(format!("Failed on {} with {}, aborting.", symbol, e).as_str());
      }
      Ok(_) => {
        logger.debug(format!("Successfully finished {}", symbol).as_str());
      }
    }
    res
  }
}

use resources::Resource;
use std::collections::HashSet;

pub struct NonRepeatingSymbolRunner<R: SymbolRunner> {
  upstream: R,
  done: RefCell<HashSet<Resource>>,
}

impl<R> NonRepeatingSymbolRunner<R>
where
  R: SymbolRunner,
{
  pub fn new(symbol_runner: R) -> Self {
    NonRepeatingSymbolRunner {
      upstream: symbol_runner,
      done: RefCell::new(HashSet::new()),
    }
  }
}

impl<R: SymbolRunner> SymbolRunner for NonRepeatingSymbolRunner<R> {
  fn run_symbol(&self, symbol: &dyn Symbol) -> Result<(), Box<dyn Error>> {
    if let Some(resources) = symbol.provides() {
      let mut done = self.done.borrow_mut();
      let mut has_to_run = false;
      for resource in resources {
        if !done.contains(&resource) {
          has_to_run = true;
          assert!(done.insert(resource.clone()));
        }
      }
      if !has_to_run {
        return Ok(());
      }
    }
    self.upstream.run_symbol(&*symbol)
  }
}
use std::marker::PhantomData;

pub struct RequirementsResolvingSymbolRunner<
  'a,
  's,
  R: 'a + SymbolRunner,
  G: 'a + SymbolRepository<'s>,
>(R, &'a G, PhantomData<Box<dyn Symbol + 's>>);

impl<'s, 'a: 's, R, G> RequirementsResolvingSymbolRunner<'a, 's, R, G>
where
  R: SymbolRunner,
  G: SymbolRepository<'s>,
{
  pub fn new(symbol_runner: R, symbol_repo: &'a G) -> Self {
    RequirementsResolvingSymbolRunner(symbol_runner, symbol_repo, PhantomData)
  }
}

impl<'s, 'a: 's, R, G> SymbolRunner for RequirementsResolvingSymbolRunner<'a, 's, R, G>
where
  R: SymbolRunner,
  G: SymbolRepository<'s>,
{
  fn run_symbol(&self, symbol: &dyn Symbol) -> Result<(), Box<dyn Error>> {
    for resource in symbol.get_prerequisites() {
      if let Some(dep) = self.1.get_symbol(&resource) {
        dep.as_action(self).run()?;
      }
    }
    self.0.run_symbol(&*symbol)
  }
}

// FIXME: Add ExpectingSymbolRunner

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

  use loggers::Logger;
  use schema::InitializingSymbolRunner;
  use schema::SymbolRunner;
  use symbols::{Action, OwnedSymbolAction, Symbol, SymbolAction};

  #[derive(Debug, PartialEq, Clone)]
  enum DummySymbolError {
    Error(()),
  }

  impl Error for DummySymbolError {
    fn description(&self) -> &str {
      return "Description";
    }
  }

  impl fmt::Display for DummySymbolError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
      write!(f, "Dummy symbol error")
    }
  }

  struct DummySymbol<'a> {
    _execute: &'a dyn Fn() -> Result<(), Box<dyn Error>>,
    _target_reached: &'a dyn Fn() -> Result<bool, Box<dyn Error>>,
  }

  impl<'b> Symbol for DummySymbol<'b> {
    fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
      (self._target_reached)()
    }
    fn execute(&self) -> Result<(), Box<dyn Error>> {
      (self._execute)()
    }

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

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

  impl<'a> fmt::Display for DummySymbol<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
      write!(f, "Dummy symbol")
    }
  }

  impl<'a> DummySymbol<'a> {
    fn new(
      target_reached: &'a dyn Fn() -> Result<bool, Box<dyn Error>>,
      execute: &'a dyn Fn() -> Result<(), Box<dyn Error>>,
    ) -> DummySymbol<'a> {
      DummySymbol {
        _target_reached: target_reached,
        _execute: execute,
      }
    }
  }

  struct DummyLogger {
    log: Vec<String>,
  }

  impl DummyLogger {
    fn new() -> DummyLogger {
      DummyLogger { log: Vec::new() }
    }
  }

  impl Logger for DummyLogger {
    fn write(&mut self, line: &str) {
      self.log.push(From::from(line));
    }
    fn debug(&mut self, line: &str) {
      self.log.push(From::from(line));
    }
  }

  #[test]
  fn nothing_needed_to_be_done() {
    let result = InitializingSymbolRunner::new(DummyLogger::new())
      .run_symbol(&DummySymbol::new(&|| Ok(true), &|| Ok(())));
    assert!(result.is_ok());
  }

  #[test]
  fn everything_is_ok() {
    let first = RefCell::new(true);
    let result = InitializingSymbolRunner::new(DummyLogger::new()).run_symbol(&DummySymbol::new(
      &|| {
        let mut _first = first.borrow_mut();
        Ok(if *_first {
          *_first = false;
          true
        } else {
          false
        })
      },
      &|| Ok(()),
    ));
    assert!(result.is_ok());
  }

  #[test]
  fn executing_did_not_change_state() {
    let result = InitializingSymbolRunner::new(DummyLogger::new())
      .run_symbol(&DummySymbol::new(&|| Ok(false), &|| Ok(())));
    assert_eq!(
      result.unwrap_err().description(),
      "Target not reached after executing symbol"
    );
  }

  #[test]
  fn executing_did_not_work() {
    let err = InitializingSymbolRunner::new(DummyLogger::new())
      .run_symbol(&DummySymbol::new(&|| Ok(false), &|| {
        Err(Box::new(DummySymbolError::Error(())))
      }))
      .unwrap_err();
    assert_eq!(err.description(), "Description");
  }
}