1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150

use legion::prelude::*;
use std::sync::atomic::{AtomicBool, Ordering};

/// An ephemeral component that needs access to `Data` to run some task. Will be run by `run_tasks`
/// in a system with access to `task_runner_query` and `Data`.
pub trait TaskComponent<'a>: Send + Sync {
    type Data;

    /// Returns `true` iff the task is complete.
    fn run(&mut self, data: &mut Self::Data) -> bool;
}

#[doc(hidden)]
#[derive(Default)]
pub struct TaskProgress {
    pub(crate) is_complete: AtomicBool,
    pub(crate) is_unblocked: bool,
}

impl TaskProgress {
    pub(crate) fn is_complete(&self) -> bool {
        self.is_complete.load(Ordering::Relaxed)
    }

    pub(crate) fn complete(&self) {
        self.is_complete.store(true, Ordering::Relaxed);
    }

    pub(crate) fn unblock(&mut self) {
        self.is_unblocked = true;
    }
}

#[doc(hidden)]
#[derive(Clone)]
pub struct SingleEdge {
    pub(crate) child: Entity,
}

#[doc(hidden)]
#[derive(Clone, Default)]
pub struct MultiEdge {
    pub(crate) children: Vec<Entity>,
}

impl MultiEdge {
    fn add_child(&mut self, entity: Entity) {
        self.children.push(entity);
    }
}

#[doc(hidden)]
#[derive(Clone, Copy, Default)]
pub struct FinalTag {
    pub(crate) on_completion: OnCompletion,
}

/// What to do to a final task and its descendents when they complete.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum OnCompletion {
    None,
    Delete,
}

impl Default for OnCompletion {
    fn default() -> Self {
        OnCompletion::None
    }
}

/// Gives read-only access to the task meta-components in order to query the state of task entities.
pub fn with_task_components(builder: SystemBuilder) -> SystemBuilder {
    builder
        .read_component::<TaskProgress>()
        .read_component::<SingleEdge>()
        .read_component::<MultiEdge>()
}

/// Create a new task entity.
pub fn make_task<'a, T: 'static + TaskComponent<'a>>(
    cmd: &mut CommandBuffer,
    task_component: T,
) -> Entity {
    let entity = cmd
        .start_entity()
        .with_component(TaskProgress::default())
        .with_component(task_component)
        .build();
    log::debug!("Created task {:?}", entity);

    entity
}

/// Mark `entity` as "final," i.e. a task with no parent.
pub fn finalize(cmd: &CommandBuffer, entity: Entity, on_completion: OnCompletion) {
    cmd.add_component(entity, FinalTag { on_completion });
    log::debug!("Finalized task {:?}", entity);
}

/// Create a new fork entity with no children.
pub fn make_fork(cmd: &mut CommandBuffer) -> Entity {
    let entity = cmd
        .start_entity()
        .with_component(MultiEdge::default())
        // BUG: builder seems to require at least 2 components
        .with_component(())
        .build();
    log::debug!("Created fork {:?}", entity);

    entity
}

/// Add `prong` as a child on the `MultiEdge` of `fork_entity`.
pub fn add_prong(cmd: &CommandBuffer, fork_entity: Entity, prong: Entity) {
    cmd.exec_mut(move |world| {
        let mut multi_edge = world
            .get_component_mut::<MultiEdge>(fork_entity)
            .unwrap_or_else(|| {
                panic!(
                    "Tried to add prong {} to non-fork entity {}",
                    prong, fork_entity
                )
            });
        multi_edge.add_child(prong);
    });
    log::debug!(
        "Submitted command to add prong {} to fork {}",
        prong,
        fork_entity
    );
}

/// Creates a `SingleEdge` from `parent` to `child`. Creates a fork-join if `parent` is a fork.
pub fn join(cmd: &CommandBuffer, parent: Entity, child: Entity) {
    cmd.exec_mut(move |world| {
        if let Some(edge) = world
            .get_component::<SingleEdge>(parent)
            .map(|e| (*e).clone())
        {
            panic!(
                "Attempted to make task {} child of {}, but task {} already has child {}",
                child, parent, parent, edge.child
            );
        } else {
            // PERF: avoid this?
            world.add_component(parent, SingleEdge { child }).unwrap();
        }
    });
    log::debug!("Submitted command to make {} parent of {}", parent, child);
}