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

use std::ops::Deref;

use crate::rstd::*;

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);
    fn into_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 [`InliningFactory`] be implemented.
pub trait StaticPair<'a, Ctx: Context<'a>>:
    '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: MentionableBase<'a, Ctx, Fctr = Self::FA>;
    /// Second element's type. Must equal [`StaticPairSerializable::SB`].
    type B: MentionableBase<'a, Ctx, Fctr = Self::FB>;
    /// First element's factory.
    type FA: FactoryBase<'a, Ctx, Mtbl = Self::A> + InliningFactory<'a, Ctx>;
    /// Second element's factory.
    type FB: FactoryBase<'a, Ctx, Mtbl = Self::B> + ParseMode;
    /// See [`FactoryBase::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: ParseError<'a, Ctx, Self::FA>,
    ) -> Self::ParseError;
    /// Regularise the error returned while parsing the second element.
    fn from_error_b(
        factory_data: &Self::FactoryData,
        error: ParseError<'a, Ctx, Self::FB>,
    ) -> 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: Context<'a>, 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: Context<'a>, SP: StaticPair<'a, Ctx>> MentionableBase<'a, Ctx>
    for StaticPairObject<SP>
{
    type Fctr = StaticPairFactory<'a, Ctx, SP>;

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

impl<'a, Ctx: Context<'a>, SP: StaticPair<'a, Ctx>> MentionableTop<'a, Ctx> for StaticPairObject<SP>
where
    SP::A: Mentionable<'a, Ctx>,
    SP::B: Mentionable<'a, Ctx>,
{
    fn points_typed(&self, points: &mut impl PointsVisitor<'a, Ctx>) {
        let (a, b) = self.pair.elements();
        a.points_typed(points);
        b.points_typed(points);
    }
}

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

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

    type ParseError = SP::ParseError;
}

impl<'a, Ctx: Context<'a>, SP: StaticPair<'a, Ctx>> ImplMode for StaticPairFactory<'a, Ctx, SP> {
    type Mode = <SP::FB as ParseMode>::Mode;
}

impl<'a, Ctx: Context<'a>, SP: StaticPair<'a, Ctx>> QRegularFactory<'a, Ctx>
    for StaticPairFactory<'a, Ctx, SP>
where
    SP::FB: RegularFactory<'a, Ctx>,
{
    fn qrdeserialize(&self, inctx: impl InCtx<'a, Ctx>) -> ParseResult<'a, Ctx, Self> {
        let (fa, fb) = SP::factories(&self.factory_data);
        let (a, inctx) = fa
            .ideserialize(inctx)
            .map_err(|e| SP::from_error_a(&self.factory_data, e))?;
        let b = fb
            .rdeserialize(inctx)
            .map_err(|e| SP::from_error_b(&self.factory_data, e))?;
        Ok(StaticPairObject {
            pair: SP::from_parsed(&self.factory_data, a, b),
        })
    }

    fn qrextend(&self, mentionable: Self::Mtbl, tail: &[u8]) -> ParseResult<'a, Ctx, Self> {
        let (_, fb) = SP::factories(&self.factory_data);
        let (a, b) = mentionable.pair.into_elements();
        match fb.rextend(b, tail) {
            Ok(b) => Ok(SP::from_parsed(&self.factory_data, a, b).into()),
            Err(e) => Err(SP::from_error_b(&self.factory_data, e)),
        }
    }
}

impl<'a, Ctx: Context<'a>, SP: StaticPair<'a, Ctx>> InliningFactory<'a, Ctx>
    for StaticPairFactory<'a, Ctx, SP>
where
    SP::FB: InliningFactory<'a, Ctx>,
{
    fn extension_error(&self, tail: &[u8]) -> Self::ParseError {
        let (_, fb) = SP::factories(&self.factory_data);
        SP::from_error_b(&self.factory_data, fb.extension_error(tail))
    }

    fn ideserialize<I: InCtx<'a, Ctx>>(&self, inctx: I) -> IParseResult<'a, Ctx, Self, I> {
        let (fa, fb) = SP::factories(&self.factory_data);
        let (a, inctx) = fa
            .ideserialize(inctx)
            .map_err(|e| SP::from_error_a(&self.factory_data, e))?;
        let (b, inctx) = fb
            .ideserialize(inctx)
            .map_err(|e| SP::from_error_b(&self.factory_data, e))?;
        Ok((
            StaticPairObject {
                pair: SP::from_parsed(&self.factory_data, a, b),
            },
            inctx,
        ))
    }
}

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

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