use crate::async_utils::sleep;
use crate::loggers::Logger;
use crate::symbols::Symbol;
use async_trait::async_trait;
use std::error::Error;
use std::fmt;
use std::fmt::Debug;
use std::time::Duration;

#[async_trait(?Send)]
pub trait SymbolRunner {
  async fn run_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
    force: bool,
  ) -> Result<bool, Box<dyn Error>>;
}

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

impl Error for SymbolRunError {
  fn cause(&self) -> Option<&dyn Error> {
    match self {
      Self::Symbol(ref e) => Some(&**e),
      Self::ExecuteDidNotReach(_) => None,
    }
  }
}

impl fmt::Display for SymbolRunError {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    match self {
      Self::Symbol(ref e) => write!(f, "{}", e),
      Self::ExecuteDidNotReach(_) => write!(f, "Target not reached after executing symbol"),
    }
  }
}

#[derive(Clone, Debug, Default)]
pub struct InitializingSymbolRunner;

impl InitializingSymbolRunner {
  pub fn new() -> Self {
    Self
  }

  async fn exec_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
  ) -> Result<(), Box<dyn Error>> {
    logger.info(format!("Executing {:?}", symbol));
    symbol.execute().await?;
    let target_reached = symbol.target_reached().await?;
    logger.trace(format!(
      "Symbol reports target_reached: {:?} (should be true)",
      target_reached
    ));
    if target_reached {
      Ok(())
    } else {
      Err(Box::new(SymbolRunError::ExecuteDidNotReach(())))
    }
  }
}

#[async_trait(?Send)]
impl SymbolRunner for InitializingSymbolRunner {
  async fn run_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
    force: bool,
  ) -> Result<bool, Box<dyn Error>> {
    let executed = if force {
      logger.debug("Forcing symbol execution");
      self.exec_symbol(symbol, logger).await?;
      true
    } else {
      let target_reached = symbol.target_reached().await?;
      if target_reached {
        logger.debug(format!("{:?} already reached", symbol));
      } else {
        logger.trace(format!(
          "Symbol reports target_reached: {:?}",
          target_reached
        ));
        self.exec_symbol(symbol, logger).await?;
      }
      !target_reached
    };
    Ok(executed)
  }
}

#[derive(Clone, Debug)]
pub struct DelayingSymbolRunner<R>(R);

impl<R> DelayingSymbolRunner<R> {
  pub fn new(symbol_runner: R) -> Self {
    Self(symbol_runner)
  }
}

#[async_trait(?Send)]
impl<R> SymbolRunner for DelayingSymbolRunner<R>
where
  R: SymbolRunner,
{
  async fn run_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
    force: bool,
  ) -> Result<bool, Box<dyn Error>> {
    sleep(Duration::from_millis(
      (((std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap()
        .subsec_micros()
        % 20) as f32
        / 2.0)
        .exp()
        / 8.0) as u64,
    ))
    .await;
    self.0.run_symbol(symbol, logger, force).await
  }
}

#[derive(Clone, Debug, Default)]
pub struct DrySymbolRunner;

impl DrySymbolRunner {
  pub fn new() -> Self {
    Self
  }
}

#[async_trait(?Send)]
impl SymbolRunner for DrySymbolRunner {
  async fn run_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
    force: bool,
  ) -> Result<bool, Box<dyn Error>> {
    let would_execute = if force {
      logger.info(format!("Would force-execute {:?}", symbol));
      true
    } else {
      let target_reached = symbol.target_reached().await?;
      logger.debug(format!(
        "Symbol reports target_reached: {:?}",
        target_reached
      ));
      if !target_reached {
        logger.info(format!("Would execute {:?}", symbol));
      }
      !target_reached
    };
    Ok(would_execute)
  }
}

#[derive(Clone, Debug)]
pub struct ReportingSymbolRunner<R>(R);

impl<R> ReportingSymbolRunner<R> {
  pub fn new(symbol_runner: R) -> Self {
    Self(symbol_runner)
  }
}

#[async_trait(?Send)]
impl<R> SymbolRunner for ReportingSymbolRunner<R>
where
  R: SymbolRunner,
{
  async fn run_symbol<S: Symbol + Debug, L: Logger>(
    &self,
    symbol: &S,
    logger: &L,
    force: bool,
  ) -> Result<bool, Box<dyn Error>> {
    logger.debug(format!("Running symbol {:?}", symbol));
    let res = self.0.run_symbol(symbol, logger, force).await;
    if let Err(ref e) = res {
      logger.info(format!("Failed on {:?} with {}, aborting.", symbol, e))
    } else {
      logger.debug(format!("Successfully finished {:?}", symbol))
    }
    res
  }
}

#[cfg(test)]
mod test {
  use super::{DrySymbolRunner, InitializingSymbolRunner, ReportingSymbolRunner, SymbolRunner};
  use crate::async_utils::sleep;
  use crate::async_utils::{run, try_join};
  use crate::loggers::StoringLogger;
  use crate::symbols::Symbol;
  use async_trait::async_trait;
  use std::cell::RefCell;
  use std::error::Error;
  use std::fmt;
  use std::fmt::Debug;
  use std::time::Duration;

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

  impl Error for DummySymbolError {}

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

  #[derive(Debug)]
  struct DummySymbol<T, E> {
    _target_reached: RefCell<T>,
    _execute: RefCell<E>,
  }

  #[async_trait(?Send)]
  impl<
      E: Iterator<Item = Result<(), Box<dyn Error>>>,
      T: Iterator<Item = Result<bool, Box<dyn Error>>>,
    > Symbol for DummySymbol<T, E>
  {
    async fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
      self._target_reached.borrow_mut().next().unwrap()
    }
    async fn execute(&self) -> Result<(), Box<dyn Error>> {
      self._execute.borrow_mut().next().unwrap()
    }
  }

  impl<
      E: Iterator<Item = Result<(), Box<dyn Error>>>,
      T: Iterator<Item = Result<bool, Box<dyn Error>>>,
    > DummySymbol<T, E>
  {
    fn new<
      IE: IntoIterator<IntoIter = E, Item = Result<(), Box<dyn Error>>>,
      IT: IntoIterator<IntoIter = T, Item = Result<bool, Box<dyn Error>>>,
    >(
      target_reached: IT,
      execute: IE,
    ) -> Self {
      Self {
        _target_reached: RefCell::new(target_reached.into_iter()),
        _execute: RefCell::new(execute.into_iter()),
      }
    }
  }

  fn run_symbol<S: Symbol + Debug>(s: S) -> Result<bool, Box<dyn Error>> {
    run(InitializingSymbolRunner::new().run_symbol(&s, &StoringLogger::new(), false))
  }

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

  #[test]
  fn everything_is_ok() {
    let result = run_symbol(DummySymbol::new(vec![Ok(false), Ok(true)], vec![Ok(())]));
    assert!(result.is_ok());
  }

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

  #[test]
  fn executing_did_not_work() {
    let result = run_symbol(DummySymbol::new(
      vec![Ok(false)],
      vec![Err(Box::new(DummySymbolError::Error(())) as Box<dyn Error>)],
    ));
    assert_eq!(result.unwrap_err().to_string(), "Dummy symbol error");
  }

  #[derive(Debug)]
  struct SleeperSymbol;

  #[async_trait(?Send)]
  impl Symbol for SleeperSymbol {
    async fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
      sleep(Duration::from_millis(0)).await;
      Ok(true)
    }
    async fn execute(&self) -> Result<(), Box<dyn Error>> {
      unimplemented!();
    }
  }

  #[test]
  fn actually_support_parallel_execution() {
    run(async {
      let s1 = SleeperSymbol;
      let s2 = DummySymbol::new(vec![Ok(false), Ok(true)], vec![Ok(())]);

      let l1 = StoringLogger::new();
      let l2 = StoringLogger::new();
      let runner1 = InitializingSymbolRunner::new();
      let result = try_join!(
        runner1.run_symbol(&s1, &l1, false),
        runner1.run_symbol(&s2, &l2, false),
      )
      .unwrap();
      assert_eq!(result, (false, true));

      let s2 = DummySymbol::new(vec![Ok(false), Ok(true)], vec![Ok(())]);
      let l1 = StoringLogger::new();
      let l2 = StoringLogger::new();
      let runner2 = DrySymbolRunner::new();
      let result = try_join!(
        runner2.run_symbol(&s1, &l1, false),
        runner2.run_symbol(&s2, &l2, false),
      )
      .unwrap();
      assert_eq!(result, (false, true));

      let s2 = DummySymbol::new(vec![Ok(false), Ok(true)], vec![Ok(())]);
      let l1 = StoringLogger::new();
      let l2 = StoringLogger::new();
      let runner3 = ReportingSymbolRunner::new(runner1);
      let result = try_join!(
        runner3.run_symbol(&s1, &l1, false),
        runner3.run_symbol(&s2, &l2, false),
      )
      .unwrap();
      assert_eq!(result, (false, true));
    });
  }
}