use std::any::{Any, TypeId, type_name};
use std::future::Future;
use std::pin::Pin;

use async_once_cell::OnceCell;
use futures::future::LocalBoxFuture;
use futures::{AsyncWrite, FutureExt};
use orchid_api_traits::{Coding, enc_vec};
use orchid_base::{FmtUnit, Sym, log};

use crate::atom::{
	AtomCtx, AtomFactory, AtomOps, Atomic, AtomicFeaturesImpl, AtomicVariant, MethodSet,
	MethodSetBuilder, err_not_callable, err_not_command,
};
use crate::expr::Expr;
use crate::gen_expr::{GExpr, bot};
use crate::system::{DynSystemCardExt, cted};
use crate::{CmdResult, api};

/// Value of [Atomic::Variant] for a type that implements [ThinAtom]
pub struct ThinVariant;
impl AtomicVariant for ThinVariant {}
impl<A: ThinAtom + Atomic<Variant = ThinVariant>> AtomicFeaturesImpl<ThinVariant> for A {
	fn _factory(self) -> AtomFactory {
		AtomFactory::new(async move || {
			let (id, _) = cted().inst().card().ops::<A>();
			let mut buf = enc_vec(&id);
			self.encode_vec(&mut buf);
			api::LocalAtom { drop: None, data: api::AtomData(buf) }
		})
	}
	fn _info() -> Self::_Info { ThinAtomOps { msbuild: Self::reg_methods(), ms: OnceCell::new() } }
	type _Info = ThinAtomOps<Self>;
}

pub(crate) struct ThinAtomOps<T: ThinAtom> {
	msbuild: MethodSetBuilder<T>,
	ms: OnceCell<MethodSet<T>>,
}
impl<T: ThinAtom> AtomOps for ThinAtomOps<T> {
	fn print<'a>(&self, AtomCtx(buf, _): AtomCtx<'a>) -> LocalBoxFuture<'a, FmtUnit> {
		Box::pin(async move { T::decode_slice(&mut &buf[..]).print().await })
	}
	fn tid(&self) -> TypeId { TypeId::of::<T>() }
	fn name(&self) -> &'static str { type_name::<T>() }
	fn decode<'a>(&'a self, AtomCtx(buf, ..): AtomCtx<'a>) -> LocalBoxFuture<'a, Box<dyn Any>> {
		Box::pin(async { Box::new(T::decode_slice(&mut &buf[..])) as Box<dyn Any> })
	}
	fn call<'a>(&'a self, AtomCtx(buf, ..): AtomCtx<'a>, arg: Expr) -> LocalBoxFuture<'a, GExpr> {
		Box::pin(async move { T::decode_slice(&mut &buf[..]).call(arg).await })
	}
	fn call_ref<'a>(&'a self, AtomCtx(buf, ..): AtomCtx<'a>, arg: Expr) -> LocalBoxFuture<'a, GExpr> {
		Box::pin(async move { T::decode_slice(&mut &buf[..]).call(arg).await })
	}
	fn handle_req<'a>(
		&'a self,
		AtomCtx(buf, ..): AtomCtx<'a>,
		key: Sym,
		req: Box<dyn orchid_base::ReqReader<'a> + 'a>,
	) -> LocalBoxFuture<'a, bool> {
		Box::pin(async move {
			let ms = self.ms.get_or_init(self.msbuild.pack()).await;
			ms.dispatch(&T::decode_slice(&mut &buf[..]), key, req).await
		})
	}
	fn command<'a>(&'a self, AtomCtx(buf, _): AtomCtx<'a>) -> LocalBoxFuture<'a, CmdResult> {
		async move { T::decode_slice(&mut &buf[..]).command().await }.boxed_local()
	}
	fn serialize<'a, 'b: 'a>(
		&'a self,
		ctx: AtomCtx<'a>,
		write: Pin<&'b mut dyn AsyncWrite>,
	) -> LocalBoxFuture<'a, Option<Vec<Expr>>> {
		Box::pin(async {
			T::decode_slice(&mut &ctx.0[..]).encode(write).await.unwrap();
			Some(Vec::new())
		})
	}
	fn deserialize<'a>(
		&'a self,
		data: &'a [u8],
		refs: &'a [Expr],
	) -> LocalBoxFuture<'a, api::LocalAtom> {
		assert!(refs.is_empty(), "Refs found when deserializing thin atom");
		Box::pin(async { T::decode_slice(&mut &data[..])._factory().build().await })
	}
	fn drop<'a>(&'a self, AtomCtx(buf, _): AtomCtx<'a>) -> LocalBoxFuture<'a, ()> {
		Box::pin(async move {
			let string_self = T::decode_slice(&mut &buf[..]).print().await;
			writeln!(log("warn"), "Received drop signal for non-drop atom {string_self:?}").await;
		})
	}
}

/// A simple value that is serializable and does not reference any other values
pub trait ThinAtom: Atomic<Data = Self> + Atomic<Variant = ThinVariant> + Coding + 'static {
	#[allow(unused_variables)]
	fn call(&self, arg: Expr) -> impl Future<Output = GExpr> {
		async move { bot(err_not_callable(&self.print().await).await) }
	}
	#[allow(unused_variables)]
	fn command(&self) -> impl Future<Output = CmdResult> {
		async move { Err(err_not_command(&self.print().await).await.into()) }
	}
	#[allow(unused_variables)]
	fn print(&self) -> impl Future<Output = FmtUnit> {
		async { format!("ThinAtom({})", type_name::<Self>()).into() }
	}
}