mapf 0.3.0

Base traits and utilities for multi-agent planning
Documentation 
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/*
 * Copyright (C) 2022 Open Source Robotics Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
*/

use crate::{
    domain::{Extrapolator, Informed, Key, KeyedSpace, Reversible, SelfKey, Weighted},
    graph::Graph,
    motion::r2::{DiscreteSpaceTimeR2, LineFollow, LineFollowError, Position, StateR2, WaypointR2},
};
use arrayvec::ArrayVec;
use std::borrow::Borrow;
use thiserror::Error as ThisError;

#[derive(Debug, Clone)]
pub struct DirectTravelHeuristic<G: Graph, W> {
    pub space: DiscreteSpaceTimeR2<G::Key>,
    pub graph: G,
    pub weight: W,
    pub extrapolator: LineFollow,
}

impl<G, W, Goal> Informed<StateR2<G::Key>, Goal> for DirectTravelHeuristic<G, W>
where
    G: Graph,
    G::Key: Key + Clone,
    G::Vertex: Borrow<Position>,
    W: Weighted<StateR2<G::Key>, ArrayVec<WaypointR2, 1>>,
    Goal: SelfKey<Key = G::Key>,
{
    type CostEstimate = W::Cost;
    type InformedError = DirectTravelError<W::WeightedError>;

    fn estimate_remaining_cost(
        &self,
        from_state: &StateR2<G::Key>,
        to_goal: &Goal,
    ) -> Result<Option<Self::CostEstimate>, Self::InformedError> {
        let p_target = {
            if let Some(p) = self.graph.vertex(to_goal.key().borrow()) {
                p
            } else {
                return Ok(None);
            }
        };

        self.extrapolator
            .extrapolate(
                &from_state.waypoint,
                p_target.borrow().borrow(),
                &(),
                (Some(&from_state.key), Some(to_goal.key().borrow())),
            )
            .transpose()
            .map_err(DirectTravelError::Extrapolator)
            .map(|action| {
                action
                    .map(|(action, child_wp)| {
                        let child_state = self
                            .space
                            .make_keyed_state(to_goal.key().borrow().clone(), child_wp);
                        self.weight
                            .cost(from_state, &action, &child_state)
                            .map_err(DirectTravelError::Weighted)
                    })
                    .transpose()
                    .map(|x| x.flatten())
            })
            .and_then(|x| x)
    }
}

// NOTE(MXG): With this implementation, we assume that the reverse graph's
// vertices are in the same locations as the forward graph's vertices. We could
// consider loosening this assumption in the future.
impl<G: Graph + Reversible, W: Reversible> Reversible for DirectTravelHeuristic<G, W> {
    type ReversalError = DirectTravelReversalError<
        G::ReversalError,
        W::ReversalError,
        <LineFollow as Reversible>::ReversalError,
    >;

    fn reversed(&self) -> Result<Self, Self::ReversalError> {
        Ok(DirectTravelHeuristic {
            space: DiscreteSpaceTimeR2::new(),
            graph: self
                .graph
                .reversed()
                .map_err(DirectTravelReversalError::Graph)?,
            weight: self
                .weight
                .reversed()
                .map_err(DirectTravelReversalError::Weighted)?,
            extrapolator: self
                .extrapolator
                .reversed()
                .map_err(DirectTravelReversalError::Extrapolator)?,
        })
    }
}

#[derive(ThisError, Debug, Clone)]
pub enum DirectTravelError<W> {
    #[error("The cost calculator had an error:\n{0}")]
    Weighted(W),
    #[error("The extrapolator had an error:\n{0}")]
    Extrapolator(LineFollowError),
}

#[derive(ThisError, Debug, Clone)]
pub enum DirectTravelReversalError<G, W, E> {
    #[error("The graph had an error while reversing:\n{0}")]
    Graph(G),
    #[error("The cost calculator had an error while reversing:\n{0}")]
    Weighted(W),
    #[error("The extrapolator had an error while reversing:\n{0}")]
    Extrapolator(E),
}