//! Adapter for serde's DeserializeSeed trait.

use core::{marker::PhantomData, ops::ControlFlow};

use serde::{
    de::{DeserializeSeed, SeqAccess},
    forward_to_deserialize_any, Deserialize, Deserializer,
};

use crate::{
    any::static_wrapper::OwnedStatic,
    any_trait,
    protocol::{
        visitor::{Sequence, SequenceScope, Status, Value},
        AsObj, AsyncEffect, Yield, Effect, SyncEffect,
    },
    AsVisitor, Builder as _,
};

pub enum Error<T> {
    Pending(T),
    Incomplete,
    Custom,
}

#[cfg(feature = "std")]
impl<T> std::error::Error for Error<T> {}

impl<T> core::fmt::Debug for Error<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::Pending(_) => write!(f, "Pending"),
            Self::Incomplete => write!(f, "Incomplete"),
            Self::Custom => write!(f, "Custom"),
        }
    }
}

pub struct Builder<'ctx, T: DeserializeSeed<'ctx>, E>(
    Result<T::Value, Error<T>>,
    PhantomData<fn() -> E>,
);

impl<'ctx, T: DeserializeSeed<'ctx>, E: Effect<'ctx, ControlFlow<(), ()>>> crate::Builder<'ctx, E>
    for Builder<'ctx, T, E>
where
    Self: AsVisitor<'ctx, E>,
{

    type Error = Error<T>;

    type Value = T::Value;

    fn build<'a>(self) -> Result<Self::Value, Self::Error> where Self: 'a {
        self.0
    }

    type Seed = T;

    fn from_seed(seed: Self::Seed) -> Self {
        Self(Err(Error::Pending(seed)), PhantomData)
    }

    type Effect = SyncEffect;
}

impl<'ctx, T: DeserializeSeed<'ctx>> AsVisitor<'ctx, SyncEffect> for Builder<'ctx, T, SyncEffect> {
    fn as_visitor(&mut self) -> crate::protocol::Visitor<'_, 'ctx, SyncEffect> {
        self
    }
}

impl<'ctx, T: DeserializeSeed<'ctx> + Send> AsVisitor<'ctx, AsyncEffect>
    for Builder<'ctx, T, AsyncEffect>
where
    T::Value: Send,
{
    fn as_visitor(&mut self) -> crate::protocol::Visitor<'_, 'ctx, AsyncEffect> {
        self
    }
}

any_trait! {
    impl['a, 'ctx, T: DeserializeSeed<'ctx>, E] Builder<'ctx, T, E> = [
        dyn Value<'ctx, OwnedStatic<bool>, SyncEffect> + 'a,
        dyn Sequence<'ctx, SyncEffect> + 'a,
    ]
}

enum InjectedValue<'a, 'ctx, T> {
    Bool(bool),
    Sequence(&'a mut dyn SequenceScope<'ctx, SyncEffect>),
    Extra(PhantomData<T>),
}

impl<'ctx, T: DeserializeSeed<'ctx>, E> Value<'ctx, OwnedStatic<bool>, SyncEffect> for Builder<'ctx, T, E> {
    #[inline]
    fn visit<'a>(
        &'a mut self,
        OwnedStatic(bool_value): OwnedStatic<bool>,
    ) -> Yield<'a, 'ctx, ControlFlow<(), ()>, SyncEffect>
    where
        'ctx: 'a,
    {
        let pending = core::mem::replace(&mut self.0, Err(Error::Incomplete));
        let Err(Error::Pending(value)) = pending else {
            todo!()
        };

        self.0 = value.deserialize(InjectedValue::Bool(bool_value));

        if self.0.is_err() {
            ControlFlow::Break(())
        } else {
            ControlFlow::Continue(())
        }
    }
}

impl<'ctx, T: DeserializeSeed<'ctx>, E> Sequence<'ctx, SyncEffect> for Builder<'ctx, T, E> {
    #[inline]
    fn visit<'a>(&'a mut self, scope: &'a mut dyn SequenceScope<'ctx, SyncEffect>) -> Yield<'a, 'ctx, ControlFlow<(), ()>, SyncEffect>
    where
        'ctx: 'a,
    {
        let pending = core::mem::replace(&mut self.0, Err(Error::Incomplete));
        let Err(Error::Pending(value)) = pending else {
            todo!()
        };

        self.0 = value.deserialize(InjectedValue::Sequence(scope));

        if self.0.is_err() {
            ControlFlow::Break(())
        } else {
            ControlFlow::Continue(())
        }
    }
}

impl<T> core::fmt::Display for Error<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "{:?}", self)
    }
}

impl<T> serde::de::Error for Error<T> {
    fn custom<U>(_msg: U) -> Self
    where
        U: core::fmt::Display,
    {
        Error::Custom
    }
}

impl<'a, 'ctx, T> Deserializer<'ctx> for InjectedValue<'a, 'ctx, T> {
    type Error = Error<T>;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'ctx>,
    {
        match self {
            InjectedValue::Bool(value) => visitor.visit_bool(value),
            InjectedValue::Sequence(scope) => visitor.visit_seq(SequenceAccess(scope, PhantomData)),
            InjectedValue::Extra(_) => unreachable!(),
        }
    }

    forward_to_deserialize_any! {
        <W: Visitor<'ctx>>
        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
        bytes byte_buf option unit unit_struct newtype_struct seq tuple
        tuple_struct map struct enum identifier ignored_any
    }
}

struct SequenceAccess<'a, 'ctx, T>(&'a mut dyn SequenceScope<'ctx, SyncEffect>, PhantomData<T>);

impl<'a, 'ctx, T> SeqAccess<'ctx> for SequenceAccess<'a, 'ctx, T> {
    type Error = Error<T>;

    fn next_element_seed<U>(&mut self, seed: U) -> Result<Option<U::Value>, Self::Error>
    where
        U: serde::de::DeserializeSeed<'ctx>,
    {
        let mut builder = Builder::<_, SyncEffect>::from_seed(seed);
        match self.0.next(builder.as_visitor()) {
            ControlFlow::Continue(Status::Continue) => match builder.build() {
                Ok(value) => Ok(Some(value)),
                Err(error) => Err(Error::Incomplete),
            },
            ControlFlow::Continue(Status::Done) => Ok(None),
            ControlFlow::Break(()) => Err(Error::Incomplete), // use the one from builder
                                                              // if any.
        }
    }
}