use crate::*;

/** Implement `Command` for given `State` and collection 
 *  of `Variant` to `handler` mappings. */
#[macro_export] macro_rules! defcom {
    ([$self:ident, $state:ident:$State:ty] $(($Command:ident $((
        $Variant:ident [$($($param:ident: $Param:ty),+)?] $expr:expr
    ))*))*) => {
        $(#[derive(Clone, Debug)] pub enum $Command {
            $($Variant $(($($Param),+))?),*
        })*
        $(command!(|$self: $Command, $state: $State|match $self {
            $($Command::$Variant $(($($param),+))? => $expr),*
        });)*
    };
    (|$self:ident, $state:ident:$State:ty| $($Command:ident { $(
        $Variant:ident $(($($param:ident: $Param:ty),+))? => $expr:expr
    )* $(,)? })*) => {
        $(#[derive(Clone, Debug)] pub enum $Command {
            $($Variant $(($($Param),+))?),*
        })*
        $(command!(|$self: $Command, $state: $State|match $self {
            $($Command::$Variant $(($($param),+))? => $expr),*
        });)*
    };
}

/** 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$(<$($l),+>)? Command<$State> for $Command {
            fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
                Ok($handler)
            }
        }
    };
}

/** Implement `DslCommand` for given `State` and `Command` */
#[cfg(feature = "dsl")]
#[macro_export] macro_rules! atom_command {
    ($Command:ty : |$state:ident:<$State:ident: $Trait:path>| { $((
        // identifier
        $key:literal [
            // named parameters
            $(
                // argument name
                $arg:ident
                // if type is not provided defaults to Dsl
                $(
                    // type:name separator
                    :
                    // argument type
                    $type:ty
                )?
            ),*
            // rest of parameters
            $(, ..$rest:ident)?
        ]
        // bound command:
        $command:expr
    ))* }) => {
        impl<'a, $State: $Trait> TryFromDsl<'a, $State> for $Command {
            fn try_from_expr ($state: &$State, iter: TokenIter) -> Option<Self> {
                let iter = iter.clone();
                match iter.next() {
                    $(Some(Token { value: Value::Key($key), .. }) => {
                        let iter = iter.clone();
                        $(
                            let next = iter.next();
                            if next.is_none() { panic!("no argument: {}", stringify!($arg)); }
                            let $arg = next.unwrap();
                            $(let $arg: Option<$type> = Context::<$type>::get($state, &$arg.value);)?
                        )*
                        $(let $rest = iter.clone();)?
                        return $command
                    },)*
                    _ => None
                }
                None
            }
        }
    };
    ($Command:ty : |$state:ident:$State:ty| { $((
        // identifier
        $key:literal [
            // named parameters
            $(
                // argument name
                $arg:ident
                // if type is not provided defaults to Dsl
                $(
                    // type:name separator
                    :
                    // argument type
                    $type:ty
                )?
            ),*
            // rest of parameters
            $(, ..$rest:ident)?
        ]
        // bound command:
        $command:expr
    ))* }) => {
        impl<'a> TryFromDsl<'a, $State> for $Command {
            fn try_from_expr ($state: &$State, iter: TokenIter) -> Option<Self> {
                let mut iter = iter.clone();
                match iter.next() {
                    $(Some(Token { value: Value::Key($key), .. }) => {
                        let mut iter = iter.clone();
                        $(
                            let next = iter.next();
                            if next.is_none() { panic!("no argument: {}", stringify!($arg)); }
                            let $arg = next.unwrap();
                            $(let $arg: Option<$type> = Context::<$type>::get($state, &$arg.value);)?
                        )*
                        $(let $rest = iter.clone();)?
                        return $command
                    }),*
                    _ => None
                }
            }
        }
    };
    (@bind $state:ident =>$arg:ident ? : $type:ty) => {
        let $arg: Option<$type> = Context::<$type>::get($state, $arg);
    };
    (@bind $state:ident => $arg:ident : $type:ty) => {
        let $arg: $type = Context::<$type>::get_or_fail($state, $arg);
    };
}