solverforge_solver/heuristic/move/

list_swap.rs

//! ListSwapMove - swaps two elements within or between list variables.
//!
//! This move exchanges two elements at different positions.
//! Useful for TSP-style improvements and route optimization.
//!
//! # Zero-Erasure Design
//!
//! Uses typed function pointers for list operations. No `dyn Any`, no downcasting.

use std::fmt::Debug;

use solverforge_core::domain::PlanningSolution;
use solverforge_scoring::ScoreDirector;

use super::Move;

/// A move that swaps two elements in list variables.
///
/// Supports both intra-list swaps (within same entity) and inter-list swaps
/// (between different entities). Uses typed function pointers for zero-erasure.
///
/// # Type Parameters
/// * `S` - The planning solution type
/// * `V` - The list element value type
///
/// # Example
///
/// ```
/// use solverforge_solver::heuristic::r#move::ListSwapMove;
/// use solverforge_core::domain::PlanningSolution;
/// use solverforge_core::score::SimpleScore;
///
/// #[derive(Clone, Debug)]
/// struct Vehicle { id: usize, visits: Vec<i32> }
///
/// #[derive(Clone, Debug)]
/// struct Solution { vehicles: Vec<Vehicle>, score: Option<SimpleScore> }
///
/// impl PlanningSolution for Solution {
///     type Score = SimpleScore;
///     fn score(&self) -> Option<Self::Score> { self.score }
///     fn set_score(&mut self, score: Option<Self::Score>) { self.score = score; }
/// }
///
/// fn list_len(s: &Solution, entity_idx: usize) -> usize {
///     s.vehicles.get(entity_idx).map_or(0, |v| v.visits.len())
/// }
/// fn list_get(s: &Solution, entity_idx: usize, pos: usize) -> Option<i32> {
///     s.vehicles.get(entity_idx).and_then(|v| v.visits.get(pos).copied())
/// }
/// fn list_set(s: &mut Solution, entity_idx: usize, pos: usize, val: i32) {
///     if let Some(v) = s.vehicles.get_mut(entity_idx) {
///         if let Some(elem) = v.visits.get_mut(pos) { *elem = val; }
///     }
/// }
///
/// // Swap elements at positions 1 and 3 in vehicle 0
/// let m = ListSwapMove::<Solution, i32>::new(
///     0, 1, 0, 3,
///     list_len, list_get, list_set,
///     "visits", 0,
/// );
/// ```
pub struct ListSwapMove<S, V> {
    /// First entity index
    first_entity_index: usize,
    /// Position in first entity's list
    first_position: usize,
    /// Second entity index
    second_entity_index: usize,
    /// Position in second entity's list
    second_position: usize,
    /// Get list length for an entity
    list_len: fn(&S, usize) -> usize,
    /// Get element at position
    list_get: fn(&S, usize, usize) -> Option<V>,
    /// Set element at position
    list_set: fn(&mut S, usize, usize, V),
    variable_name: &'static str,
    descriptor_index: usize,
    /// Store indices for entity_indices()
    indices: [usize; 2],
}

impl<S, V> Clone for ListSwapMove<S, V> {
    fn clone(&self) -> Self {
        *self
    }
}

impl<S, V> Copy for ListSwapMove<S, V> {}

impl<S, V: Debug> Debug for ListSwapMove<S, V> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ListSwapMove")
            .field("first_entity", &self.first_entity_index)
            .field("first_position", &self.first_position)
            .field("second_entity", &self.second_entity_index)
            .field("second_position", &self.second_position)
            .field("variable_name", &self.variable_name)
            .finish()
    }
}

impl<S, V> ListSwapMove<S, V> {
    /// Creates a new list swap move with typed function pointers.
    ///
    /// # Arguments
    /// * `first_entity_index` - First entity index
    /// * `first_position` - Position in first entity's list
    /// * `second_entity_index` - Second entity index
    /// * `second_position` - Position in second entity's list
    /// * `list_len` - Function to get list length
    /// * `list_get` - Function to get element at position
    /// * `list_set` - Function to set element at position
    /// * `variable_name` - Name of the list variable
    /// * `descriptor_index` - Entity descriptor index
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        first_entity_index: usize,
        first_position: usize,
        second_entity_index: usize,
        second_position: usize,
        list_len: fn(&S, usize) -> usize,
        list_get: fn(&S, usize, usize) -> Option<V>,
        list_set: fn(&mut S, usize, usize, V),
        variable_name: &'static str,
        descriptor_index: usize,
    ) -> Self {
        Self {
            first_entity_index,
            first_position,
            second_entity_index,
            second_position,
            list_len,
            list_get,
            list_set,
            variable_name,
            descriptor_index,
            indices: [first_entity_index, second_entity_index],
        }
    }

    /// Returns the first entity index.
    pub fn first_entity_index(&self) -> usize {
        self.first_entity_index
    }

    /// Returns the first position.
    pub fn first_position(&self) -> usize {
        self.first_position
    }

    /// Returns the second entity index.
    pub fn second_entity_index(&self) -> usize {
        self.second_entity_index
    }

    /// Returns the second position.
    pub fn second_position(&self) -> usize {
        self.second_position
    }

    /// Returns true if this is an intra-list swap (same entity).
    pub fn is_intra_list(&self) -> bool {
        self.first_entity_index == self.second_entity_index
    }
}

impl<S, V> Move<S> for ListSwapMove<S, V>
where
    S: PlanningSolution,
    V: Clone + PartialEq + Send + Sync + Debug + 'static,
{
    fn is_doable<D: ScoreDirector<S>>(&self, score_director: &D) -> bool {
        let solution = score_director.working_solution();

        // Check first position is valid
        let first_len = (self.list_len)(solution, self.first_entity_index);
        if self.first_position >= first_len {
            return false;
        }

        // Check second position is valid
        let second_len = (self.list_len)(solution, self.second_entity_index);
        if self.second_position >= second_len {
            return false;
        }

        // For intra-list, can't swap with self
        if self.is_intra_list() && self.first_position == self.second_position {
            return false;
        }

        // Get values and check they're different
        let first_val = (self.list_get)(solution, self.first_entity_index, self.first_position);
        let second_val = (self.list_get)(solution, self.second_entity_index, self.second_position);

        first_val != second_val
    }

    fn do_move<D: ScoreDirector<S>>(&self, score_director: &mut D) {
        // Get both values
        let first_val = (self.list_get)(
            score_director.working_solution(),
            self.first_entity_index,
            self.first_position,
        )
        .expect("first position should be valid");

        let second_val = (self.list_get)(
            score_director.working_solution(),
            self.second_entity_index,
            self.second_position,
        )
        .expect("second position should be valid");

        // Notify before changes
        score_director.before_variable_changed(
            self.descriptor_index,
            self.first_entity_index,
            self.variable_name,
        );
        if !self.is_intra_list() {
            score_director.before_variable_changed(
                self.descriptor_index,
                self.second_entity_index,
                self.variable_name,
            );
        }

        // Swap: first gets second's value, second gets first's value
        (self.list_set)(
            score_director.working_solution_mut(),
            self.first_entity_index,
            self.first_position,
            second_val.clone(),
        );
        (self.list_set)(
            score_director.working_solution_mut(),
            self.second_entity_index,
            self.second_position,
            first_val.clone(),
        );

        // Notify after changes
        score_director.after_variable_changed(
            self.descriptor_index,
            self.first_entity_index,
            self.variable_name,
        );
        if !self.is_intra_list() {
            score_director.after_variable_changed(
                self.descriptor_index,
                self.second_entity_index,
                self.variable_name,
            );
        }

        // Register undo - swap back
        let list_set = self.list_set;
        let first_entity = self.first_entity_index;
        let first_pos = self.first_position;
        let second_entity = self.second_entity_index;
        let second_pos = self.second_position;

        score_director.register_undo(Box::new(move |s: &mut S| {
            // Restore original values
            list_set(s, first_entity, first_pos, first_val);
            list_set(s, second_entity, second_pos, second_val);
        }));
    }

    fn descriptor_index(&self) -> usize {
        self.descriptor_index
    }

    fn entity_indices(&self) -> &[usize] {
        if self.is_intra_list() {
            &self.indices[0..1]
        } else {
            &self.indices
        }
    }

    fn variable_name(&self) -> &str {
        self.variable_name
    }
}