use crate::resources::{BorrowResource, DefaultResources, Resource};
use crate::schema::SymbolRunner;
use crate::symbols::Symbol;
use crate::to_artifact::ToArtifact;
use crate::{DefaultBuilder, DefaultLocator, ResourceLocator, SymbolBuilder};
use std::collections::HashSet;
use std::error::Error;
use std::fmt::Debug;
use std::hash::Hash;
use std::marker::PhantomData;

pub trait CanHandle<X: ToArtifact> {
  fn handle(&mut self, x: X) -> Result<(X::Artifact, bool), Box<dyn Error>>;
}

macro_rules! can_handle {
  ( $($name:ident)* ) => (
    #[allow(non_snake_case)]
    impl<_SR: SymbolRunner, _L, _R: Hash + Eq, _B, $($name: Resource,)*>
      CanHandle<($($name,)*)>
      for Setup<_SR, _L, _R, _B>
      where
      $(
        _B: SymbolBuilder<$name>,
        <_B as SymbolBuilder<$name>>::Symbol: Runnable + Debug,
        _L: ResourceLocator<$name>,
        _R: From<$name> + BorrowResource<$name>,
        Self: CanHandle<<_B as SymbolBuilder<$name>>::Prerequisites> +
          CanHandle<<_L as ResourceLocator<$name>>::Prerequisites>
      ),*
    {
      fn handle(&mut self, ($($name,)*): ($($name,)*)) -> Result<(($($name::Artifact,)*), bool), Box<dyn Error>>
      {
        $(let $name = self.add($name)?;)*
        Ok((($($name.0,)*), false $(|| $name.1)*))
      }
    }
  );
}

for_each_tuple!(can_handle);

// This is for self-referential T
// FIXME: Wait for specialization
impl<_SR: SymbolRunner, _L, _R: Hash + Eq, _B, T: Resource> CanHandle<Option<T>>
  for Setup<_SR, _L, _R, _B>
where
  _B: SymbolBuilder<T>,
  <_B as SymbolBuilder<T>>::Symbol: Runnable + Debug,
  _L: ResourceLocator<T, Prerequisites = Option<T>>,
  _R: From<T> + BorrowResource<T>,
  Self: CanHandle<<_B as SymbolBuilder<T>>::Prerequisites>,
{
  fn handle(
    &mut self,
    r: Option<T>,
  ) -> Result<(<Option<T> as ToArtifact>::Artifact, bool), Box<dyn Error>> {
    Ok(match r {
      Some(r) => {
        let (result, did_run) = self.add(r)?;
        (Some(result), did_run)
      }
      None => (None, false),
    })
  }
}

impl<_SR: SymbolRunner, _L, _R: Hash + Eq, _B, T: Resource> CanHandle<T> for Setup<_SR, _L, _R, _B>
where
  _B: SymbolBuilder<T>,
  <_B as SymbolBuilder<T>>::Symbol: Runnable + Debug,
  _L: ResourceLocator<T>,
  _R: From<T> + Debug + BorrowResource<T>,
  Self: CanHandle<<_B as SymbolBuilder<T>>::Prerequisites>
    + CanHandle<<_L as ResourceLocator<T>>::Prerequisites>,
{
  fn handle(&mut self, r: T) -> Result<(<T as ToArtifact>::Artifact, bool), Box<dyn Error>> {
    self.add(r)
  }
}

pub struct Setup<
  SR,
  L = DefaultLocator,
  R = DefaultResources<'static, &'static str>,
  B = DefaultBuilder,
> {
  symbol_runner: SR,
  resources: HashSet<R>,
  phantom: PhantomData<(L, B)>,
}

// https://github.com/rust-lang/rust/issues/27336
impl<SR> Setup<SR> {
  pub fn new(symbol_runner: SR) -> Self {
    Self {
      symbol_runner,
      resources: Default::default(),
      phantom: Default::default(),
    }
  }
}

impl<SR, L, R: Hash + Eq, B> Setup<SR, L, R, B> {
  pub fn new_with(symbol_runner: SR) -> Self {
    Self {
      symbol_runner,
      resources: Default::default(),
      phantom: Default::default(),
    }
  }
}

pub trait Runnable {
  fn run<R: SymbolRunner>(&self, runner: &R, force: bool) -> Result<bool, Box<dyn Error>>;
}

impl<S: Symbol + Debug> Runnable for S {
  fn run<R: SymbolRunner>(&self, runner: &R, force: bool) -> Result<bool, Box<dyn Error>> {
    runner.run_symbol(self, force)
  }
}

macro_rules! runnable_for_tuple {
  ( $($name:ident)* ) => (
    #[allow(non_snake_case)]
    impl<$($name: Symbol + Debug,)*> Runnable for ($($name,)*) {
      #[allow(unused)]
      fn run<_R: SymbolRunner>(&self, runner: &_R, force: bool) -> Result<bool, Box<dyn Error>> {
        let ($($name,)*) = self;
        let mut result = false;
        $(result = runner.run_symbol($name, force || result)? || result;)*
        Ok(result)
      }
    }
  );
}

for_each_tuple!(runnable_for_tuple);

impl<SR: SymbolRunner, L, Rs: Hash + Eq, B> Setup<SR, L, Rs, B> {
  pub fn add<R: Resource>(&mut self, resource: R) -> Result<(R::Artifact, bool), Box<dyn Error>>
  where
    B: SymbolBuilder<R>,
    <B as SymbolBuilder<R>>::Symbol: Runnable + Debug,
    L: ResourceLocator<R>,
    Rs: From<R> + BorrowResource<R>,
    Self: CanHandle<B::Prerequisites> + CanHandle<<L as ResourceLocator<R>>::Prerequisites>,
  {
    self.add_force(resource, false)
  }

  pub fn add_force<R: Resource>(
    &mut self,
    resource: R,
    force_run: bool,
  ) -> Result<(R::Artifact, bool), Box<dyn Error>>
  where
    B: SymbolBuilder<R>,
    <B as SymbolBuilder<R>>::Symbol: Runnable + Debug,
    L: ResourceLocator<R>,
    Rs: From<R> + BorrowResource<R>,
    Self: CanHandle<B::Prerequisites> + CanHandle<<L as ResourceLocator<R>>::Prerequisites>,
  {
    let (target, target_prereqs) = L::locate(&resource);
    let storable_resource = Rs::from(resource);
    let did_run = if self.resources.get(&storable_resource).is_some() {
      assert!(
        !force_run,
        "Forcing to run an already-added resource is a logical error"
      );
      false
    } else {
      let (_, target_prereqs_did_run) = self.handle(target_prereqs)?;
      let (symbol, prereqs_did_run) =
        self.get_symbol(storable_resource.borrow_resource().unwrap(), &target)?;
      self.resources.insert(storable_resource);
      self.run_symbol(
        symbol,
        force_run || target_prereqs_did_run || prereqs_did_run,
      )?
    };
    Ok((target, did_run))
  }

  fn get_symbol<R: Resource>(
    &mut self,
    resource: &R,
    target: &R::Artifact,
  ) -> Result<(<B as SymbolBuilder<R>>::Symbol, bool), Box<dyn Error>>
  where
    B: SymbolBuilder<R>,
    Self: CanHandle<B::Prerequisites>,
  {
    let (prereqs, prereqs_did_run) = self.handle(B::prerequisites(resource))?;
    Ok((B::create(resource, target, prereqs), prereqs_did_run))
  }

  pub fn run_symbol<S: Runnable>(&self, symbol: S, force: bool) -> Result<bool, Box<dyn Error>> {
    symbol.run(&self.symbol_runner, force)
  }
}

#[cfg(test)]
mod test {
  use crate::resources::{BorrowResource, Resource};
  use crate::schema::SymbolRunner;
  use crate::symbols::Symbol;
  use crate::to_artifact::ToArtifact;
  use crate::{ResourceLocator, Setup, SymbolBuilder};
  use std::cell::RefCell;
  use std::error::Error;
  use std::fmt::Debug;
  use std::rc::Rc;

  struct TestSymbolRunner {
    count: Rc<RefCell<usize>>,
  }

  impl SymbolRunner for TestSymbolRunner {
    fn run_symbol<S: Symbol + Debug>(
      &self,
      symbol: &S,
      force: bool,
    ) -> Result<bool, Box<dyn Error>> {
      let run = force || !symbol.target_reached()?;
      if run {
        *self.count.borrow_mut() += 1;
      }
      Ok(run)
    }
  }

  #[derive(Debug, PartialEq, Eq, Hash)]
  struct TestResource<T>(&'static str, T);
  impl<T> Resource for TestResource<T> {
    type Artifact = ();
  }

  #[derive(Debug, Hash, PartialEq, Eq)]
  enum Resources {
    A(TestResource<&'static str>),
    B(TestResource<()>),
  }
  impl From<TestResource<&'static str>> for Resources {
    fn from(from: TestResource<&'static str>) -> Self {
      Self::A(from)
    }
  }
  impl From<TestResource<()>> for Resources {
    fn from(from: TestResource<()>) -> Self {
      Self::B(from)
    }
  }

  impl BorrowResource<TestResource<&'static str>> for Resources {
    fn borrow_resource(&self) -> Option<&TestResource<&'static str>> {
      match self {
        Self::A(a) => Some(a),
        _ => None,
      }
    }
  }
  impl BorrowResource<TestResource<()>> for Resources {
    fn borrow_resource(&self) -> Option<&TestResource<()>> {
      match self {
        Self::B(b) => Some(b),
        _ => None,
      }
    }
  }

  struct TestResourceLocator;
  impl<T> ResourceLocator<TestResource<T>> for TestResourceLocator {
    type Prerequisites = ();
    fn locate(_resource: &TestResource<T>) -> (<TestResource<T> as ToArtifact>::Artifact, ()) {
      ((), ())
    }
  }

  struct TestSymbolBuilder;
  impl SymbolBuilder<TestResource<&'static str>> for TestSymbolBuilder {
    type Symbol = TestSymbol;
    type Prerequisites = TestResource<()>;

    fn prerequisites(resource: &TestResource<&'static str>) -> Self::Prerequisites {
      TestResource(resource.1, ())
    }
    fn create(
      resource: &TestResource<&'static str>,
      (): &(),
      _inputs: <Self::Prerequisites as ToArtifact>::Artifact,
    ) -> Self::Symbol {
      TestSymbol {
        reached: resource.0.chars().next().unwrap().is_uppercase(),
      }
    }
  }
  impl SymbolBuilder<TestResource<()>> for TestSymbolBuilder {
    type Symbol = TestSymbol;
    type Prerequisites = ();

    fn prerequisites(_resource: &TestResource<()>) -> Self::Prerequisites {}
    fn create(resource: &TestResource<()>, (): &(), (): ()) -> Self::Symbol {
      TestSymbol {
        reached: resource.0.chars().next().unwrap().is_uppercase(),
      }
    }
  }

  #[derive(Debug)]
  struct TestSymbol {
    reached: bool,
  }
  impl Symbol for TestSymbol {
    fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
      Ok(self.reached)
    }
    fn execute(&self) -> Result<(), Box<dyn Error>> {
      Ok(())
    }
  }

  fn get_setup() -> (
    Rc<RefCell<usize>>,
    Setup<TestSymbolRunner, TestResourceLocator, Resources, TestSymbolBuilder>,
  ) {
    let count = Rc::new(RefCell::new(0));
    let runner = TestSymbolRunner {
      count: Rc::clone(&count),
    };
    (count, Setup::new_with(runner))
  }

  #[test]
  fn correctly_uses_force() {
    let (count, mut setup) = get_setup();
    setup.add(TestResource("A", "b")).unwrap();
    assert_eq!(*count.borrow(), 2);
    setup.add(TestResource("A", "b")).unwrap();
    assert_eq!(*count.borrow(), 2);

    let (count, mut setup) = get_setup();
    setup.add(TestResource("A", "B")).unwrap();
    assert_eq!(*count.borrow(), 0);
  }

  #[test]
  fn correctly_handles_symbol_tuples() {
    let (count, setup) = get_setup();
    setup
      .run_symbol(
        (TestSymbol { reached: false }, TestSymbol { reached: false }),
        false,
      )
      .unwrap();
    assert_eq!(*count.borrow(), 2);

    let (count, setup) = get_setup();
    setup
      .run_symbol(
        (TestSymbol { reached: true }, TestSymbol { reached: false }),
        false,
      )
      .unwrap();
    assert_eq!(*count.borrow(), 1);

    // An unreached symbol forces all further symbols
    let (count, setup) = get_setup();
    setup
      .run_symbol(
        (TestSymbol { reached: false }, TestSymbol { reached: true }),
        false,
      )
      .unwrap();
    assert_eq!(*count.borrow(), 2);

    let (count, setup) = get_setup();
    setup
      .run_symbol(
        (TestSymbol { reached: true }, TestSymbol { reached: true }),
        false,
      )
      .unwrap();
    assert_eq!(*count.borrow(), 0);

    let (count, setup) = get_setup();
    setup
      .run_symbol(
        (TestSymbol { reached: true }, TestSymbol { reached: true }),
        true,
      )
      .unwrap();
    assert_eq!(*count.borrow(), 2);
  }
}