use std::any::{Any, TypeId};
use std::fmt::Debug;

use seq_macro::seq;

use crate::lock::{Lock, WriteGuard};
use crate::system::{ComponentRefMut, Input as SystemInput};
use crate::type_name::TypeName;

pub mod local;

pub trait Component: SystemInput + Any + TypeName
{
    fn drop_last(&self) -> bool;

    #[doc(hidden)]
    fn as_any_mut(&mut self) -> &mut dyn Any;

    #[doc(hidden)]
    fn as_any(&self) -> &dyn Any;
}

impl dyn Component
{
    pub fn downcast_mut<Real: 'static>(&mut self) -> Option<&mut Real>
    {
        self.as_any_mut().downcast_mut()
    }

    pub fn downcast_ref<Real: 'static>(&self) -> Option<&Real>
    {
        self.as_any().downcast_ref()
    }

    pub fn is<Other: 'static>(&self) -> bool
    {
        self.as_any().is::<Other>()
    }
}

impl Debug for dyn Component
{
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
    {
        formatter.debug_struct("Component").finish_non_exhaustive()
    }
}

impl TypeName for Box<dyn Component>
{
    fn type_name(&self) -> &'static str
    {
        self.as_ref().type_name()
    }
}

/// A sequence of components.
pub trait Sequence
{
    type Refs<'component>
    where
        Self: 'component;

    fn into_vec(self) -> Vec<Box<dyn Component>>;

    fn type_ids() -> Vec<TypeId>;

    fn from_components<'component>(
        components: impl Iterator<Item = &'component Lock<Box<dyn Component>>>,
    ) -> Self::Refs<'component>;
}

macro_rules! inner {
    ($c: tt) => {
        seq!(I in 0..=$c {
            impl<#(Comp~I: Component,)*> Sequence for (#(Comp~I,)*) {
                type Refs<'component> = (#(ComponentRefMut<'component, Comp~I>,)*)
                    where Self: 'component;

                fn into_vec(self) -> Vec<Box<dyn Component>>
                {
                    Vec::from_iter([#(Box::new(self.I) as Box<dyn Component>,)*])
                }

                fn type_ids() -> Vec<TypeId>
                {
                    vec![
                        #(
                            TypeId::of::<Comp~I>(),
                        )*
                    ]
                }

                fn from_components<'component>(
                    components: impl Iterator<Item = &'component Lock<Box<dyn Component>>>,
                ) -> Self::Refs<'component>
                {
                    #(
                        let mut comp_~I: Option<WriteGuard<Box<dyn Component>>> = None;
                    )*

                    for comp in components {
                        let comp_ref = comp
                            .write_nonblock()
                            .expect("Failed to acquire read-write component lock");

                        #(
                            if comp_ref.is::<Comp~I>() {
                                comp_~I = Some(comp_ref);
                                continue;
                            }
                        )*
                    }

                    (#(
                        ComponentRefMut::new(
                            comp_~I.unwrap(),
                        ),
                    )*)
                }
            }
        });
    };
}

seq!(C in 0..=64 {
    inner!(C);
});