#![feature(associated_type_defaults)]
#![feature(if_let_guard)]

pub(crate) use tengri_core::*;

#[cfg(test)] mod input_test;

/// Event source
pub trait Input: Sized {
    /// Type of input event
    type Event;
    /// Result of handling input
    type Handled; // TODO: make this an Option<Box dyn Command<Self>> containing the undo
    /// Currently handled event
    fn event (&self) -> &Self::Event;
    /// Whether component should exit
    fn is_done (&self) -> bool;
    /// Mark component as done
    fn done (&self);
}

flex_trait_mut!(Handle <E: Input> {
    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
        Ok(None)
    }
});

pub trait Command<S>: Send + Sync + Sized {
    fn execute (&self, state: &mut S) -> Perhaps<Self>;
    fn delegate <T> (&self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
        where Self: Sized
    {
        Ok(self.execute(state)?.map(wrap))
    }
}

impl<S, T: Command<S>> Command<S> for Option<T> {
    fn execute (&self, _: &mut S) -> Perhaps<Self> {
        Ok(None)
    }
    fn delegate <U> (&self, _: &mut S, _: impl Fn(Self)->U) -> Perhaps<U>
        where Self: Sized
    {
        Ok(None)
    }
}

/// Implement [Command] for given `State` and `handler`
#[macro_export] macro_rules! command {
    ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
        impl$(<$($l),+>)? ::tengri::input::Command<$State> for $Command {
            fn execute (&$self, $state: &mut $State) -> Perhaps<Self> {
                Ok($handler)
            }
        }
    };
}

#[macro_export] macro_rules! def_command (($Command:ident: |$state:ident: $State:ty| {
    $($Variant:ident$({$($arg:ident:$Arg:ty),+ $(,)?})?=>$body:expr),* $(,)?
})=>{
    #[derive(Debug)]
    pub enum $Command {
        $($Variant $({ $($arg: $Arg),* })?),*
    }
    impl Command<$State> for $Command {
        fn execute (&self, $state: &mut $State) -> Perhaps<Self> {
            match self {
                $(Self::$Variant $({ $($arg),* })? => $body,)*
                _ => unimplemented!("Command<{}>: {self:?}", stringify!($State)),
            }
        }
    }
});

/// Implement [Handle] for given `State` and `handler`.
#[macro_export] macro_rules! handle {
    (|$self:ident:$State:ty,$input:ident|$handler:expr) => {
        impl<E: Engine> ::tengri::input::Handle<E> for $State {
            fn handle (&mut $self, $input: &E) -> Perhaps<E::Handled> {
                $handler
            }
        }
    };
    ($E:ty: |$self:ident:$State:ty,$input:ident|$handler:expr) => {
        impl ::tengri::input::Handle<$E> for $State {
            fn handle (&mut $self, $input: &$E) ->
                Perhaps<<$E as ::tengri::input::Input>::Handled>
            {
                $handler
            }
        }
    }
}