//! Generic implementation for objects that are structured
//! like a pair of two other objects.

use std::ops::Deref;

use crate::std::*;

use super::*;

/// Trait to represent serialisation of object's data.
/// Due to serialisation being [Context]-free in RADN,
/// this functionality is in a separate trait.
pub trait StaticPairSerializable {
    /// First element's type. Must equal [`StaticPair::A`].
    type SA: Serializable;
    /// Second element's type. Must equal [`StaticPair::B`].
    type SB: Serializable;

    /// Borrow both elements.
    fn elements(&self) -> (&Self::SA, &Self::SB);
}

/// Trait to be implemented on object data.
///
/// [`StaticPair::FA`]/[`StaticPair::FB`] are required members
/// for clarity and [`StaticPair`]'s simpler implementation
/// at the cost of having to specify two extra fields.
///
/// Note: [`StaticPair::FA`] requires [`InlineableFactory`] be implemented.
pub trait StaticPair<'a, Ctx: 'a + Context>:
    'a + StaticPairSerializable<SA = Self::A, SB = Self::B>
{
    /// [Factory] data. May, depending on the usecase, include factory (factories) on the element(s).
    type FactoryData: 'a + Send + Sync + Clone;
    /// First element's type. Must equal [`StaticPairSerializable::SA`].
    type A: Mentionable<'a, Ctx, Fctr = Self::FA>;
    /// Second element's type. Must equal [`StaticPairSerializable::SB`].
    type B: Mentionable<'a, Ctx, Fctr = Self::FB>;
    /// First element's factory.
    type FA: Factory<'a, Ctx, Mtbl = Self::A> + InlineableFactory;
    /// Second element's factory.
    type FB: Factory<'a, Ctx, Mtbl = Self::B>;
    /// See [Factory::ParseError].
    type ParseError: 'a + Error;

    /// Borrow both elements' factories.
    fn factories(factory_data: &Self::FactoryData) -> (&Self::FA, &Self::FB);
    /// Construct the object from the elements.
    fn from_parsed(factory_data: &Self::FactoryData, a: Self::A, b: Self::B) -> Self;
    /// Regularise the error returned while parsing the first element.
    fn from_error_a(
        factory_data: &Self::FactoryData,
        error: <Self::FA as Factory<'a, Ctx>>::ParseError,
    ) -> Self::ParseError;
    /// Regularise the error returned while parsing the second element.
    fn from_error_b(
        factory_data: &Self::FactoryData,
        error: <Self::FB as Factory<'a, Ctx>>::ParseError,
    ) -> Self::ParseError;
    /// Derive factory data from the object data.
    fn factory_data(&self) -> Self::FactoryData;
}

/// Generic implementation of a [Mentionable] for [StaticPair]s.
pub struct StaticPairObject<SP> {
    pair: SP,
}

impl<SP> From<SP> for StaticPairObject<SP> {
    fn from(value: SP) -> Self {
        StaticPairObject { pair: value }
    }
}

impl<SP> AsRef<SP> for StaticPairObject<SP> {
    fn as_ref(&self) -> &SP {
        &self.pair
    }
}

impl<SP> Deref for StaticPairObject<SP> {
    type Target = SP;

    fn deref(&self) -> &Self::Target {
        &self.pair
    }
}

/// Generic implementation of a [Factory] for [StaticPair]s.
pub struct StaticPairFactory<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> {
    factory_data: SP::FactoryData,
}

impl<SP: StaticPairSerializable> Serializable for StaticPairObject<SP> {
    fn serialize(&self, serializer: &mut dyn Serializer) {
        let (a, b) = self.pair.elements();
        a.serialize(serializer);
        b.serialize(serializer);
    }
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> Mentionable<'a, Ctx> for StaticPairObject<SP> {
    type Fctr = StaticPairFactory<'a, Ctx, SP>;

    fn factory(&self) -> Self::Fctr {
        StaticPairFactory {
            factory_data: self.pair.factory_data(),
        }
    }

    fn points_typed(&self, points: &mut impl TakesPoints<'a, Ctx>) {
        let (a, b) = self.pair.elements();
        a.points_typed(points);
        b.points_typed(points);
    }
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> Clone for StaticPairFactory<'a, Ctx, SP> {
    fn clone(&self) -> Self {
        Self {
            factory_data: self.factory_data.clone(),
        }
    }
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> Factory<'a, Ctx>
    for StaticPairFactory<'a, Ctx, SP>
{
    type Mtbl = StaticPairObject<SP>;

    type ParseError = SP::ParseError;

    fn deserialize(
        &self,
        deserializer: &mut dyn Deserializer,
        resolver: Rc<dyn Resolver<'a, Ctx>>,
        addresses: &mut Addresses,
    ) -> ParseResult<'a, Ctx, Self> {
        let (fa, fb) = SP::factories(&self.factory_data);
        let a: SP::A = match fa.deserialize(deserializer, resolver.clone(), addresses) {
            Ok(a) => a,
            Err(error) => return Err(SP::from_error_a(&self.factory_data, error)),
        };
        let b: SP::B = match fb.deserialize(deserializer, resolver, addresses) {
            Ok(b) => b,
            Err(error) => return Err(SP::from_error_b(&self.factory_data, error)),
        };
        Ok(StaticPairObject {
            pair: SP::from_parsed(&self.factory_data, a, b),
        })
    }

    fn unexpected_tail(&self, tail: &[u8]) -> Self::ParseError {
        let (_, fb) = SP::factories(&self.factory_data);
        SP::from_error_b(&self.factory_data, fb.unexpected_tail(tail))
    }
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> InlineableFactory
    for StaticPairFactory<'a, Ctx, SP>
where
    SP::FB: InlineableFactory,
{
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> FixedSizeFactory
    for StaticPairFactory<'a, Ctx, SP>
where
    SP::FA: FixedSizeFactory,
    SP::FB: FixedSizeFactory,
{
    fn size(&self) -> usize {
        let (fa, fb) = SP::factories(&self.factory_data);
        fa.size() + fb.size()
    }
}

impl<'a, Ctx: 'a + Context, SP: StaticPair<'a, Ctx>> ConstSizeFactory
    for StaticPairFactory<'a, Ctx, SP>
where
    SP::FA: ConstSizeFactory,
    SP::FB: ConstSizeFactory,
{
    const SIZE: usize = SP::FA::SIZE + SP::FB::SIZE;
}