geam-core 0.2.0

use crate::host::{
    HostExternalPayloadBuilder, HostProfile, HostStoredType, HostStoredValue, HostType, HostTypeAt,
    HostTypeSequence,
};
use crate::provider::ProviderExternalItem;
use crate::provider::advanced::{Retained, StoredDynamic};
use std::marker::PhantomData;

/// Generated identity for one external declaration that may own retained values.
#[doc(hidden)]
pub trait ProviderStoredOwner: 'static {}

/// Retains one low-level generic argument for a macro-authored payload.
///
/// This bridge exists for built-in providers that still consume the typed-host
/// SDK while a sibling component has moved to the authoring macros.
#[doc(hidden)]
pub fn retain_argument<Profile, Arguments, Owner, Index>(
    builder: &mut HostExternalPayloadBuilder<'_, Profile, Arguments>,
    value: <<Arguments as HostTypeAt<Index>>::Type as HostType>::Value<'_>,
) -> Retained<Owner, Index>
where
    Profile: HostProfile,
    Arguments: HostTypeSequence + HostTypeAt<Index>,
    Owner: ProviderStoredOwner,
{
    Retained::new(builder.store_argument::<Index>(value))
}

/// Retains one low-level value with its exact specialized type.
#[doc(hidden)]
pub fn retain_dynamic<Profile, Arguments, Owner, Type>(
    builder: &mut HostExternalPayloadBuilder<'_, Profile, Arguments>,
    value: Type::Value<'_>,
) -> StoredDynamic<Owner>
where
    Profile: HostProfile,
    Arguments: HostTypeSequence,
    Owner: ProviderStoredOwner,
    Type: HostType,
{
    StoredDynamic::new(builder.store_dynamic::<Type>(value))
}

/// One generic Gleam value retained by a macro-authored external payload.
///
/// Providers create stored values through [`super::Call::store`] and restore
/// fields exposed by a generated external input through [`super::Call::restore`].
/// A stored value is neither cloneable nor copyable and cannot be constructed
/// independently of its generated external owner.
pub struct Stored<Type, Context = MissingStoredContext> {
    context: Context,
    type_: PhantomData<fn() -> Type>,
}

#[doc(hidden)]
pub struct MissingStoredContext;

/// A retained value being assembled into one generated external payload.
#[doc(hidden)]
pub struct ProviderStoredOutput<'call, Owner, Index, Host> {
    value: HostStoredValue<HostStoredType<Index>>,
    call: PhantomData<&'call ()>,
    owner: PhantomData<fn() -> (Owner, Host)>,
}

/// A borrowed retained field selected from one generated external input.
#[doc(hidden)]
pub struct ProviderStoredInput<'value, Owner, Index, Host> {
    value: &'value HostStoredValue<HostStoredType<Index>>,
    context: PhantomData<fn() -> (Owner, Host)>,
}

/// The exact retained payload view inserted into one generated external input.
#[doc(hidden)]
pub struct ProviderExternalInputContext<'call, Payload, Arguments>
where
    Arguments: HostTypeSequence,
{
    value: ProviderExternalItem<Payload>,
    context: PhantomData<&'call Arguments>,
}

#[doc(hidden)]
pub struct MissingExternalInputContext;

#[doc(hidden)]
pub struct ProviderExternalOutput<Payload> {
    value: Result<Payload, ProviderExternalItem<Payload>>,
}

#[doc(hidden)]
pub struct MissingExternalOutputContext;

impl<Type, Owner, Index, Host> Stored<Type, ProviderStoredOutput<'_, Owner, Index, Host>>
where
    Owner: ProviderStoredOwner,
{
    #[doc(hidden)]
    pub fn from_output(value: HostStoredValue<HostStoredType<Index>>) -> Self {
        Self {
            context: ProviderStoredOutput {
                value,
                call: PhantomData,
                owner: PhantomData,
            },
            type_: PhantomData,
        }
    }

    #[doc(hidden)]
    pub fn into_host(self) -> HostStoredValue<HostStoredType<Index>> {
        self.context.value
    }

    /// Moves this newly stored value into an advanced persistent payload.
    pub fn into_retained(self) -> Retained<Owner, Index> {
        Retained::new(self.context.value)
    }
}

impl<'value, Type, Owner, Index, Host> Stored<Type, ProviderStoredInput<'value, Owner, Index, Host>>
where
    Owner: ProviderStoredOwner,
{
    #[doc(hidden)]
    pub fn from_input(value: &'value HostStoredValue<HostStoredType<Index>>) -> Self {
        Self {
            context: ProviderStoredInput {
                value,
                context: PhantomData,
            },
            type_: PhantomData,
        }
    }

    #[doc(hidden)]
    pub fn from_retained(value: &'value Retained<Owner, Index>) -> Self {
        Self::from_input(value.host())
    }

    pub(crate) fn host(&self) -> &'value HostStoredValue<HostStoredType<Index>> {
        self.context.value
    }
}

impl<Payload> ProviderExternalOutput<Payload> {
    #[doc(hidden)]
    pub fn new(payload: Payload) -> Self {
        Self { value: Ok(payload) }
    }

    #[doc(hidden)]
    pub fn from_input(value: ProviderExternalItem<Payload>) -> Self {
        Self { value: Err(value) }
    }

    #[doc(hidden)]
    pub fn into_value(self) -> Result<Payload, ProviderExternalItem<Payload>> {
        self.value
    }
}

impl<'call, Payload, Arguments> ProviderExternalInputContext<'call, Payload, Arguments>
where
    Arguments: HostTypeSequence,
{
    #[doc(hidden)]
    pub fn from_host(value: ProviderExternalItem<Payload>) -> Self {
        Self {
            value,
            context: PhantomData,
        }
    }

    #[doc(hidden)]
    pub fn payload(&self) -> &Payload {
        &self.value
    }

    #[doc(hidden)]
    pub fn into_output(self) -> ProviderExternalOutput<Payload> {
        ProviderExternalOutput::from_input(self.value)
    }
}

#[cfg(test)]
mod tests {
    use super::{ProviderStoredOwner, retain_argument, retain_dynamic};
    use crate::host::test::{TestHostCallRuntime, TestHostProfile, TestRunState};
    use crate::host::{
        CallArguments, HostExternalPayloadBuilder, HostTypeIndex0, HostTypeList, HostTypeListEnd,
    };
    use crate::plan::ValueType;
    use crate::provider::advanced::{DynamicKind, Retained, StoredDynamic};
    use num_bigint::BigInt;

    struct Payload;

    impl ProviderStoredOwner for Payload {}

    #[test]
    fn retention_bridges_preserve_the_declared_owner_and_runtime_type() {
        type Arguments = HostTypeList<BigInt, HostTypeListEnd>;

        let mut state = TestRunState::default();
        let arguments = CallArguments::new(Vec::new(), Vec::new());
        let mut runtime = TestHostCallRuntime::new(&mut state, arguments);
        let mut builder =
            HostExternalPayloadBuilder::<TestHostProfile, Arguments>::new(&mut runtime);

        let retained: Retained<Payload, HostTypeIndex0> =
            retain_argument(&mut builder, BigInt::from(7));
        let dynamic: StoredDynamic<Payload> =
            retain_dynamic::<_, Arguments, _, BigInt>(&mut builder, BigInt::from(8));

        assert_eq!(retained.host().value.type_(), &ValueType::Int);
        assert_eq!(dynamic.kind(), DynamicKind::Int);
    }
}