PkmnLib_rs/src/ffi/ffi_handle.rs

use crate::static_data::{
    Ability, Form, GrowthRate, Item, LearnableMoves, MoveData, Nature, Parameter, SecondaryEffect, Species,
    StaticStatisticSet, StatisticSet,
};
use anyhow::anyhow;
use hashbrown::HashMap;
use parking_lot::RwLock;
use std::hash::Hash;
use std::sync::atomic::AtomicUsize;
use std::sync::{Arc, LazyLock};

/// This function can be called from the FFI to release a handle when it is no longer needed. This
/// does not drop the object per se, but will reduce the reference count of the object. If the object
/// is then no longer referenced, it will be dropped.
#[no_mangle]
extern "C" fn ffi_release_handle(handle: usize) {
    let mut write_lock = FFI_OBJECTS.write();
    let mut write_lock_inverse = FFI_OBJECTS_INVERSE.write();

    let obj = write_lock.remove(&handle);
    if let Some(obj) = obj {
        write_lock_inverse.remove(&obj);
    }
}

/// A handle of an object that can be passed over FFI. We use this to avoid passing pointers over the
/// FFI boundary. This allows us to be able to move the data around in memory without having to worry
/// about the pointers being invalidated. It also allows us to have a type-safe interface.
#[repr(C)]
pub(super) struct FFIHandle<T> {
    /// An incrementing handle that is unique for each object.
    handle: usize,
    /// The type of the object.
    _marker: std::marker::PhantomData<T>,
}

impl<T> Clone for FFIHandle<T> {
    fn clone(&self) -> Self {
        Self {
            handle: self.handle,
            _marker: std::marker::PhantomData,
        }
    }
}

impl<T> Copy for FFIHandle<T> {}

impl<T> Default for FFIHandle<T> {
    fn default() -> Self {
        Self {
            handle: 0,
            _marker: std::marker::PhantomData,
        }
    }
}

/// An FFIObject we can fetch from the FFIHandle. We store this in a hashmap to be able to fetch
/// the object from the handle, and to be able to drop the object when the FFI is done with the handle
#[derive(Clone)]
#[allow(clippy::missing_docs_in_private_items)] // I'm not documenting these items.
pub(super) enum FFIObject {
    Ability(Arc<dyn Ability>),
    EffectParameter(Arc<Parameter>),
    StatisticSetU8(Arc<StatisticSet<u8>>),
    StatisticSetI8(Arc<StatisticSet<i8>>),
    StatisticSetU32(Arc<StatisticSet<u32>>),
    StaticStatisticSetU16(Arc<StaticStatisticSet<u16>>),
    Form(Arc<dyn Form>),
    LearnableMoves(Arc<dyn LearnableMoves>),
    GrowthRate(Arc<dyn GrowthRate>),
    Item(Arc<dyn Item>),
    SecondaryEffect(Arc<dyn SecondaryEffect>),
    MoveData(Arc<dyn MoveData>),
    Nature(Arc<dyn Nature>),
    Species(Arc<dyn Species>),

    SpeciesLibrary(Arc<dyn crate::static_data::SpeciesLibrary>),
    MoveLibrary(Arc<dyn crate::static_data::MoveLibrary>),
    AbilityLibrary(Arc<dyn crate::static_data::AbilityLibrary>),
    ItemLibrary(Arc<dyn crate::static_data::ItemLibrary>),
    GrowthRateLibrary(Arc<dyn crate::static_data::GrowthRateLibrary>),
    LibrarySettings(Arc<dyn crate::static_data::LibrarySettings>),
    NatureLibrary(Arc<dyn crate::static_data::NatureLibrary>),
    TypeLibrary(Arc<dyn crate::static_data::TypeLibrary>),
    StaticData(Arc<dyn crate::static_data::StaticData>),

    // DynamicData
    TurnChoice(Arc<crate::dynamic_data::TurnChoice>),
    Pokemon(crate::dynamic_data::Pokemon),
    LearnedMove(Arc<crate::dynamic_data::LearnedMove>),
    PokemonParty(Arc<crate::dynamic_data::PokemonParty>),
    BattleParty(Arc<crate::dynamic_data::BattleParty>),
    Battle(crate::dynamic_data::Battle),
    BattleSide(crate::dynamic_data::BattleSide),
    BattleRandom(Arc<crate::dynamic_data::BattleRandom>),

    // DynamicLibrary
    BattleStatCalculator(Arc<dyn crate::dynamic_data::BattleStatCalculator>),
    DamageLibrary(Arc<dyn crate::dynamic_data::DamageLibrary>),
    MiscLibrary(Arc<dyn crate::dynamic_data::MiscLibrary>),
    ScriptResolver(Arc<dyn crate::dynamic_data::ScriptResolver>),
    DynamicLibrary(Arc<dyn crate::dynamic_data::DynamicLibrary>),

    // Events
    Event(Arc<crate::dynamic_data::EventData>),
}

unsafe impl Send for FFIObject {}

unsafe impl Sync for FFIObject {}

/// The next handle to be used.
static NEXT_HANDLE: AtomicUsize = AtomicUsize::new(1);
/// A lookup to get an actual object from a handle.
static FFI_OBJECTS: LazyLock<RwLock<HashMap<usize, FFIObject>>> = LazyLock::new(|| RwLock::new(HashMap::new()));
/// A lookup to get a handle from an object.
static FFI_OBJECTS_INVERSE: LazyLock<RwLock<HashMap<FFIObject, usize>>> = LazyLock::new(|| RwLock::new(HashMap::new()));

impl<T> FFIHandle<T> {
    /// Get a handle from an object.
    pub fn get_handle(o: FFIObject) -> Self {
        if let Some(handle) = FFI_OBJECTS_INVERSE.read().get(&o) {
            return Self {
                handle: *handle,
                _marker: std::marker::PhantomData,
            };
        }

        let handle = NEXT_HANDLE.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
        FFI_OBJECTS.write().insert(handle, o.clone());
        FFI_OBJECTS_INVERSE.write().insert(o, handle);
        Self {
            handle,
            _marker: std::marker::PhantomData,
        }
    }

    /// An empty handle. This is used when no value is returned. Represented as handle 0
    pub fn none() -> Self {
        Self {
            handle: 0,
            _marker: std::marker::PhantomData,
        }
    }

    /// Get the object from the handle.
    #[allow(clippy::unwrap_used)] // Unwrap used, as it is a potential security bug if this fails
    pub fn resolve(&self) -> FFIObject {
        FFI_OBJECTS
            .read()
            .get(&self.handle)
            .ok_or(anyhow!("Unable to get handle {} from FFI_OBJECTS", self.handle))
            .unwrap()
            .clone()
    }

    /// Check if the handle is empty.
    pub fn is_none(&self) -> bool {
        self.handle == 0
    }
}

#[allow(clippy::from_over_into)]
impl<T> Into<anyhow_ext::Result<FFIObject>> for FFIHandle<T> {
    fn into(self) -> anyhow_ext::Result<FFIObject> {
        Ok(FFI_OBJECTS
            .read()
            .get(&self.handle)
            .ok_or(anyhow!("Unable to get handle"))?
            .clone())
    }
}

impl Eq for FFIObject {}

/// A trait to convert a handle into an object.
#[allow(clippy::wrong_self_convention)]
pub(super) trait FromFFIHandle<T> {
    /// Convert a handle into an object.
    fn from_ffi_handle(&self) -> T;
    /// Convert a handle into an object, returning `None` if the handle is empty.
    fn from_ffi_handle_opt(&self) -> Option<T>;
}

impl Hash for FFIObject {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        match self {
            Self::Ability(a) => Arc::as_ptr(a).hash(state),
            Self::EffectParameter(a) => Arc::as_ptr(a).hash(state),
            Self::StatisticSetU8(a) => Arc::as_ptr(a).hash(state),
            Self::StatisticSetI8(a) => Arc::as_ptr(a).hash(state),
            Self::StatisticSetU32(a) => Arc::as_ptr(a).hash(state),
            Self::StaticStatisticSetU16(a) => Arc::as_ptr(a).hash(state),
            Self::Form(a) => Arc::as_ptr(a).hash(state),
            Self::LearnableMoves(a) => Arc::as_ptr(a).hash(state),
            Self::GrowthRate(a) => Arc::as_ptr(a).hash(state),
            Self::Item(a) => Arc::as_ptr(a).hash(state),
            Self::SecondaryEffect(a) => Arc::as_ptr(a).hash(state),
            Self::MoveData(a) => Arc::as_ptr(a).hash(state),
            Self::Nature(a) => Arc::as_ptr(a).hash(state),
            Self::Species(a) => Arc::as_ptr(a).hash(state),
            Self::SpeciesLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::MoveLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::AbilityLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::ItemLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::GrowthRateLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::LibrarySettings(a) => Arc::as_ptr(a).hash(state),
            Self::NatureLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::TypeLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::StaticData(a) => Arc::as_ptr(a).hash(state),
            Self::TurnChoice(a) => Arc::as_ptr(a).hash(state),
            Self::Pokemon(a) => a.as_ptr().hash(state),
            Self::LearnedMove(a) => Arc::as_ptr(a).hash(state),
            Self::PokemonParty(a) => Arc::as_ptr(a).hash(state),
            Self::BattleParty(a) => Arc::as_ptr(a).hash(state),
            Self::Battle(a) => a.as_ptr().hash(state),
            Self::BattleSide(a) => a.as_ptr().hash(state),
            Self::BattleRandom(a) => Arc::as_ptr(a).hash(state),
            Self::BattleStatCalculator(a) => Arc::as_ptr(a).hash(state),
            Self::DamageLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::MiscLibrary(a) => Arc::as_ptr(a).hash(state),
            Self::ScriptResolver(a) => Arc::as_ptr(a).hash(state),
            Self::DynamicLibrary(a) => Arc::as_ptr(a).hash(state),
            FFIObject::Event(a) => Arc::as_ptr(a).hash(state),
        }
    }
}

impl PartialEq for FFIObject {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Self::Ability(a), Self::Ability(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::EffectParameter(a), Self::EffectParameter(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::StatisticSetU8(a), Self::StatisticSetU8(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::StatisticSetI8(a), Self::StatisticSetI8(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::StatisticSetU32(a), Self::StatisticSetU32(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::StaticStatisticSetU16(a), Self::StaticStatisticSetU16(b)) => {
                Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr()
            }
            (Self::Form(a), Self::Form(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::LearnableMoves(a), Self::LearnableMoves(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::GrowthRate(a), Self::GrowthRate(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Item(a), Self::Item(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::SecondaryEffect(a), Self::SecondaryEffect(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::MoveData(a), Self::MoveData(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Nature(a), Self::Nature(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Species(a), Self::Species(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::SpeciesLibrary(a), Self::SpeciesLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::MoveLibrary(a), Self::MoveLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::AbilityLibrary(a), Self::AbilityLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::ItemLibrary(a), Self::ItemLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::GrowthRateLibrary(a), Self::GrowthRateLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::LibrarySettings(a), Self::LibrarySettings(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::NatureLibrary(a), Self::NatureLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::TypeLibrary(a), Self::TypeLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::StaticData(a), Self::StaticData(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::TurnChoice(a), Self::TurnChoice(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Pokemon(a), Self::Pokemon(b)) => a.eq(b),
            (Self::LearnedMove(a), Self::LearnedMove(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::PokemonParty(a), Self::PokemonParty(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::BattleParty(a), Self::BattleParty(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Battle(a), Self::Battle(b)) => a.eq(b),
            (Self::BattleSide(a), Self::BattleSide(b)) => a.eq(b),
            (Self::BattleRandom(a), Self::BattleRandom(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::BattleStatCalculator(a), Self::BattleStatCalculator(b)) => {
                Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr()
            }
            (Self::DamageLibrary(a), Self::DamageLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::MiscLibrary(a), Self::MiscLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::ScriptResolver(a), Self::ScriptResolver(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::DynamicLibrary(a), Self::DynamicLibrary(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            (Self::Event(a), Self::Event(b)) => Arc::as_ptr(a).addr() == Arc::as_ptr(b).addr(),
            _ => false,
        }
    }
}

/// Helper macro to implement the `From` trait for a `FFIObject` enum variant, and the `FromFFIHandle`
/// trait for a `FFIHandle` enum variant.
macro_rules! ffi_obj_conversions {
    ($res_type:ty, $ffi_obj_name:ident) => {
        impl From<$res_type> for FFIObject {
            fn from(a: $res_type) -> Self {
                Self::$ffi_obj_name(a)
            }
        }

        impl FromFFIHandle<$res_type> for FFIHandle<$res_type> {
            fn from_ffi_handle(&self) -> $res_type {
                match self.resolve() {
                    FFIObject::$ffi_obj_name(a) => a.clone(),
                    _ => panic!("Invalid handle"),
                }
            }

            fn from_ffi_handle_opt(&self) -> Option<$res_type> {
                if (self.is_none()) {
                    return None;
                }
                match self.resolve() {
                    FFIObject::$ffi_obj_name(a) => Some(a.clone()),
                    _ => panic!("Invalid handle"),
                }
            }
        }
    };
}

ffi_obj_conversions!(Arc<dyn Ability>, Ability);
ffi_obj_conversions!(Arc<Parameter>, EffectParameter);
ffi_obj_conversions!(Arc<StatisticSet<i8>>, StatisticSetI8);
ffi_obj_conversions!(Arc<StatisticSet<u8>>, StatisticSetU8);
ffi_obj_conversions!(Arc<StatisticSet<u32>>, StatisticSetU32);
ffi_obj_conversions!(Arc<StaticStatisticSet<u16>>, StaticStatisticSetU16);
ffi_obj_conversions!(Arc<dyn Form>, Form);
ffi_obj_conversions!(Arc<dyn LearnableMoves>, LearnableMoves);
ffi_obj_conversions!(Arc<dyn GrowthRate>, GrowthRate);
ffi_obj_conversions!(Arc<dyn Item>, Item);
ffi_obj_conversions!(Arc<dyn SecondaryEffect>, SecondaryEffect);
ffi_obj_conversions!(Arc<dyn MoveData>, MoveData);
ffi_obj_conversions!(Arc<dyn Nature>, Nature);
ffi_obj_conversions!(Arc<dyn Species>, Species);
ffi_obj_conversions!(Arc<dyn crate::static_data::SpeciesLibrary>, SpeciesLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::MoveLibrary>, MoveLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::AbilityLibrary>, AbilityLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::ItemLibrary>, ItemLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::GrowthRateLibrary>, GrowthRateLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::LibrarySettings>, LibrarySettings);
ffi_obj_conversions!(Arc<dyn crate::static_data::NatureLibrary>, NatureLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::TypeLibrary>, TypeLibrary);
ffi_obj_conversions!(Arc<dyn crate::static_data::StaticData>, StaticData);
ffi_obj_conversions!(Arc<crate::dynamic_data::TurnChoice>, TurnChoice);
ffi_obj_conversions!(crate::dynamic_data::Pokemon, Pokemon);
ffi_obj_conversions!(Arc<crate::dynamic_data::LearnedMove>, LearnedMove);
ffi_obj_conversions!(Arc<crate::dynamic_data::PokemonParty>, PokemonParty);
ffi_obj_conversions!(Arc<crate::dynamic_data::BattleParty>, BattleParty);
ffi_obj_conversions!(crate::dynamic_data::Battle, Battle);
ffi_obj_conversions!(crate::dynamic_data::BattleSide, BattleSide);
ffi_obj_conversions!(Arc<crate::dynamic_data::BattleRandom>, BattleRandom);
ffi_obj_conversions!(Arc<dyn crate::dynamic_data::BattleStatCalculator>, BattleStatCalculator);
ffi_obj_conversions!(Arc<dyn crate::dynamic_data::DamageLibrary>, DamageLibrary);
ffi_obj_conversions!(Arc<dyn crate::dynamic_data::MiscLibrary>, MiscLibrary);
ffi_obj_conversions!(Arc<dyn crate::dynamic_data::ScriptResolver>, ScriptResolver);
ffi_obj_conversions!(Arc<dyn crate::dynamic_data::DynamicLibrary>, DynamicLibrary);
ffi_obj_conversions!(Arc<crate::dynamic_data::EventData>, Event);