bevy_mod_scripting_rune 0.8.0

use std::{marker::PhantomData, sync::Arc};

use bevy::prelude::*;
use bevy_mod_scripting_core::{
    prelude::*,
    systems::{self, CachedScriptState},
    world::{WorldPointer, WorldPointerGuard},
};
use prelude::{RuneDocFragment, RuneFile, RuneLoader};
use rune::{
    runtime::{Args, RuntimeContext, VmError, VmResult},
    Context, Diagnostics, Source, Sources, Unit, Vm,
};

mod assets;
mod docs;

pub mod prelude {
    pub use crate::{
        assets::{RuneFile, RuneLoader},
        docs::RuneDocFragment,
        RuneArgs, RuneEvent, RuneScriptContext, RuneScriptHost,
    };
    pub use rune::{self, runtime::Args, Context};
}

/// Super trait adding additional bounds to Rune's `Args` trait.
/// It's gets automatically implemented for any type that implments `Args`,
/// so you should never have to manually implement it.
pub trait RuneArgs: Args + Clone + Send + Sync + 'static {}

impl<T: Args + Clone + Send + Sync + 'static> RuneArgs for T {}

/// A Rune script hook.
#[derive(Debug, Clone, Event)]
pub struct RuneEvent<A: RuneArgs> {
    /// The name of the Rune function to call.
    pub hook_name: String,
    /// The arguments to supply the function being invoked. If you
    /// don't need any arguments, `()` is a good default value.
    pub args: A,
    /// The target set of scripts that should handle this event.
    pub recipients: Recipients,
}

impl<A: RuneArgs> ScriptEvent for RuneEvent<A> {
    fn recipients(&self) -> &Recipients {
        &self.recipients
    }
}

/// A cached Rune Vm used to execute units.
struct RuneVm(Vm);

impl Default for RuneVm {
    fn default() -> Self {
        Self(Vm::new(
            Arc::new(RuntimeContext::default()),
            Arc::new(Unit::default()),
        ))
    }
}

/// Script context for a rune script.
pub struct RuneScriptContext {
    pub unit: Arc<Unit>,
    pub runtime_context: Arc<RuntimeContext>,
}

#[derive(Resource)]
/// Rune script host. Enables Rune scripting.
pub struct RuneScriptHost<A: RuneArgs> {
    _ph: PhantomData<A>,
}

impl<A: RuneArgs> Default for RuneScriptHost<A> {
    fn default() -> Self {
        Self {
            _ph: Default::default(),
        }
    }
}

impl<A: RuneArgs> RuneScriptHost<A> {
    /// Helper function to handle errors from a Rune virtual machine.
    ///
    #[cold]
    fn handle_rune_error(world: WorldPointer, error: VmError, script_data: &ScriptData<'_>) {
        let mut world = world.write();
        let mut state: CachedScriptState<Self> = world.remove_resource().unwrap();

        let (_, mut error_wrt, _) = state.event_state.get_mut(&mut world);

        let error = ScriptError::RuntimeError {
            script: script_data.name.to_owned(),
            msg: error.to_string(),
        };

        error!("{}", error);

        error_wrt.send(ScriptErrorEvent { error });
        world.insert_resource(state);
    }
}

impl<A: RuneArgs> ScriptHost for RuneScriptHost<A> {
    type ScriptContext = RuneScriptContext;

    type ScriptEvent = RuneEvent<A>;

    type ScriptAsset = RuneFile;

    type APITarget = Context;

    type DocTarget = RuneDocFragment;

    fn register_with_app_in_set(
        app: &mut App,
        schedule: impl bevy::ecs::schedule::ScheduleLabel,
        set: impl SystemSet,
    ) {
        app.add_priority_event::<Self::ScriptEvent>()
            .init_asset::<RuneFile>()
            .init_asset_loader::<RuneLoader>()
            .init_resource::<CachedScriptState<Self>>()
            .init_resource::<ScriptContexts<Self::ScriptContext>>()
            .init_resource::<APIProviders<Self>>()
            .register_type::<ScriptCollection<Self::ScriptAsset>>()
            .register_type::<Script<Self::ScriptAsset>>()
            .register_type::<Handle<RuneFile>>()
            // Add a cached Vm as a non-send resource.
            .insert_non_send_resource(RuneVm::default())
            // handle script insertions removal first
            // then update their contexts later on script asset changes
            .add_systems(
                schedule,
                (
                    systems::script_add_synchronizer::<Self>,
                    systems::script_remove_synchronizer::<Self>,
                    systems::script_hot_reload_handler::<Self>,
                )
                    .chain()
                    .in_set(set),
            );
    }

    fn load_script(
        &mut self,
        script: &[u8],
        script_data: &ScriptData,
        providers: &mut APIProviders<Self>,
    ) -> Result<Self::ScriptContext, ScriptError> {
        let mut context = rune_modules::default_context().map_err(ScriptError::new_other)?;

        // Rune requires that we tell it what modules and types we'll be using before
        // it compiles a file.
        providers.attach_all(&mut context).unwrap();

        let mut diagnostics = Diagnostics::new();

        let mut sources = Sources::new();
        sources
            .insert(
                Source::new(
                    script_data.name,
                    std::str::from_utf8(script).expect("Slice is not UTF-8"),
                )
                .map_err(|msg| ScriptError::FailedToLoad {
                    script: script_data.name.into(),
                    msg: msg.to_string(),
                })?,
            )
            .map_err(|msg| ScriptError::FailedToLoad {
                script: script_data.name.into(),
                msg: msg.to_string(),
            })?;

        let result = rune::prepare(&mut sources)
            .with_context(&context)
            .with_diagnostics(&mut diagnostics)
            .build();

        if !diagnostics.is_empty() {
            let mut writer = rune::termcolor::Buffer::no_color();

            diagnostics
                .emit(&mut writer, &sources)
                .expect("Failed to write diagnostics to buffer");

            return Err(ScriptError::SyntaxError {
                script: script_data.name.into(),
                msg: std::str::from_utf8(writer.as_slice())
                    .expect("Slice was not UTF-8")
                    .to_owned(),
            });
        }

        let unit = result.expect("Failed to build Rune unit.");

        let runtime_ctx = context
            .runtime()
            .expect("Failed to create Rune runtime context.");

        Ok(RuneScriptContext {
            unit: Arc::new(unit),
            runtime_context: Arc::new(runtime_ctx),
        })
    }

    fn setup_script(
        &mut self,
        script_data: &ScriptData,
        ctx: &mut Self::ScriptContext,
        providers: &mut APIProviders<Self>,
    ) -> Result<(), ScriptError> {
        providers.setup_all(script_data, ctx)
    }

    fn handle_events<'a>(
        &mut self,
        world: &mut World,
        events: &[Self::ScriptEvent],
        ctxs: impl Iterator<Item = (ScriptData<'a>, &'a mut Self::ScriptContext)>,
        providers: &mut APIProviders<Self>,
    ) {
        // Grab the cached Vm.
        let RuneVm(mut vm) = world.remove_non_send_resource::<RuneVm>().unwrap(/* invariant */);

        {
            // Safety:
            // - we have &mut World access
            // - we do not use the original reference again anywhere in this block.
            // - the guard is dropped at the end of this block.
            let world = unsafe { WorldPointerGuard::new(world) };

            ctxs.for_each(|(script_data, ctx)| {
                providers
                    .setup_runtime_all(world.clone(), &script_data, ctx)
                    .expect("Could not setup script runtime");

                for event in events {
                    if !event.recipients().is_recipient(&script_data) {
                        continue;
                    }

                    // Swap out the old context and old unit with the new ones.
                    *vm.context_mut() = Arc::clone(&ctx.runtime_context);
                    *vm.unit_mut() = Arc::clone(&ctx.unit);

                    let mut exec = match vm.execute([event.hook_name.as_str()], event.args.clone())
                    {
                        Ok(exec) => exec,
                        Err(error) => {
                            Self::handle_rune_error(world.clone(), error, &script_data);
                            continue;
                        }
                    };

                    if let VmResult::Err(error) = exec.complete() {
                        Self::handle_rune_error(world.clone(), error, &script_data);
                    }
                }
            });

            // explictly release the pointer to world.
            drop(world);
        }

        world.insert_non_send_resource(RuneVm(vm));
    }
}