solverforge_scoring/stream/

complemented_stream.rs

/* Zero-erasure complemented constraint stream.

A `ComplementedConstraintStream` adds entities from a complement source
that are not present in grouped results, with default values.
*/

use std::hash::Hash;
use std::marker::PhantomData;

use solverforge_core::score::Score;
use solverforge_core::{ConstraintRef, ImpactType};

use super::collection_extract::CollectionExtract;
use super::collector::UniCollector;
use crate::constraint::complemented::ComplementedGroupConstraint;

/* Zero-erasure constraint stream with complemented groups.

`ComplementedConstraintStream` results from calling `complement` on a
`GroupedConstraintStream`. It ensures all keys from a complement source
are represented, using default values for missing keys.

The key function for A entities returns `Option<K>` to allow skipping
entities without valid keys (e.g., unassigned shifts).

# Type Parameters

- `S` - Solution type
- `A` - Original entity type (e.g., Shift)
- `B` - Complement entity type (e.g., Employee)
- `K` - Group key type
- `EA` - Extractor for A entities
- `EB` - Extractor for B entities (complement source)
- `KA` - Key function for A (returns `Option<K>` to allow filtering)
- `KB` - Key function for B
- `C` - Collector type
- `D` - Default value function
- `Sc` - Score type

# Example

```
use solverforge_scoring::stream::ConstraintFactory;
use solverforge_scoring::stream::collector::count;
use solverforge_scoring::api::constraint_set::IncrementalConstraint;
use solverforge_core::score::SoftScore;

#[derive(Clone, Hash, PartialEq, Eq)]
struct Employee { id: usize }

#[derive(Clone, Hash, PartialEq, Eq)]
struct Shift { employee_id: usize }

#[derive(Clone)]
struct Schedule {
employees: Vec<Employee>,
shifts: Vec<Shift>,
}

// Count shifts per employee, including employees with 0 shifts
let constraint = ConstraintFactory::<Schedule, SoftScore>::new()
.for_each(|s: &Schedule| &s.shifts)
.group_by(|shift: &Shift| shift.employee_id, count())
.complement(
|s: &Schedule| s.employees.as_slice(),
|emp: &Employee| emp.id,
|_emp: &Employee| 0usize,
)
.penalize_with(|count: &usize| SoftScore::of(*count as i64))
.named("Shift count");

let schedule = Schedule {
employees: vec![Employee { id: 0 }, Employee { id: 1 }, Employee { id: 2 }],
shifts: vec![
Shift { employee_id: 0 },
Shift { employee_id: 0 },
// Employee 1 has 0 shifts, Employee 2 has 0 shifts
],
};

// Employee 0: 2, Employee 1: 0, Employee 2: 0 → Total: -2
assert_eq!(constraint.evaluate(&schedule), SoftScore::of(-2));
```
*/
pub struct ComplementedConstraintStream<S, A, B, K, EA, EB, KA, KB, C, D, Sc>
where
    Sc: Score,
{
    extractor_a: EA,
    extractor_b: EB,
    key_a: KA,
    key_b: KB,
    collector: C,
    default_fn: D,
    _phantom: PhantomData<(fn() -> S, fn() -> A, fn() -> B, fn() -> K, fn() -> Sc)>,
}

impl<S, A, B, K, EA, EB, KA, KB, C, D, Sc>
    ComplementedConstraintStream<S, A, B, K, EA, EB, KA, KB, C, D, Sc>
where
    S: Send + Sync + 'static,
    A: Clone + Send + Sync + 'static,
    B: Clone + Send + Sync + 'static,
    K: Clone + Eq + Hash + Send + Sync + 'static,
    EA: CollectionExtract<S, Item = A>,
    EB: CollectionExtract<S, Item = B>,
    KA: Fn(&A) -> Option<K> + Send + Sync,
    KB: Fn(&B) -> K + Send + Sync,
    C: UniCollector<A> + Send + Sync + 'static,
    C::Accumulator: Send + Sync,
    C::Result: Clone + Send + Sync,
    D: Fn(&B) -> C::Result + Send + Sync,
    Sc: Score + 'static,
{
    fn into_weighted_builder<W>(
        self,
        impact_type: ImpactType,
        weight_fn: W,
        is_hard: bool,
    ) -> ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    where
        W: Fn(&C::Result) -> Sc + Send + Sync,
    {
        ComplementedConstraintBuilder {
            extractor_a: self.extractor_a,
            extractor_b: self.extractor_b,
            key_a: self.key_a,
            key_b: self.key_b,
            collector: self.collector,
            default_fn: self.default_fn,
            impact_type,
            weight_fn,
            is_hard,
            _phantom: PhantomData,
        }
    }

    // Creates a new complemented constraint stream.
    pub(crate) fn new(
        extractor_a: EA,
        extractor_b: EB,
        key_a: KA,
        key_b: KB,
        collector: C,
        default_fn: D,
    ) -> Self {
        Self {
            extractor_a,
            extractor_b,
            key_a,
            key_b,
            collector,
            default_fn,
            _phantom: PhantomData,
        }
    }

    // Penalizes each complemented group with a weight based on the result.
    pub fn penalize_with<W>(
        self,
        weight_fn: W,
    ) -> ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    where
        W: Fn(&C::Result) -> Sc + Send + Sync,
    {
        self.into_weighted_builder(ImpactType::Penalty, weight_fn, false)
    }

    // Penalizes each complemented group, explicitly marked as hard constraint.
    pub fn penalize_hard_with<W>(
        self,
        weight_fn: W,
    ) -> ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    where
        W: Fn(&C::Result) -> Sc + Send + Sync,
    {
        self.into_weighted_builder(ImpactType::Penalty, weight_fn, true)
    }

    // Rewards each complemented group with a weight based on the result.
    pub fn reward_with<W>(
        self,
        weight_fn: W,
    ) -> ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    where
        W: Fn(&C::Result) -> Sc + Send + Sync,
    {
        self.into_weighted_builder(ImpactType::Reward, weight_fn, false)
    }

    // Rewards each complemented group, explicitly marked as hard constraint.
    pub fn reward_hard_with<W>(
        self,
        weight_fn: W,
    ) -> ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    where
        W: Fn(&C::Result) -> Sc + Send + Sync,
    {
        self.into_weighted_builder(ImpactType::Reward, weight_fn, true)
    }

    // Penalizes each complemented group with one hard score unit.
    pub fn penalize_hard(
        self,
    ) -> ComplementedConstraintBuilder<
        S,
        A,
        B,
        K,
        EA,
        EB,
        KA,
        KB,
        C,
        D,
        impl Fn(&C::Result) -> Sc + Send + Sync,
        Sc,
    >
    where
        Sc: Copy,
    {
        let w = Sc::one_hard();
        self.penalize_hard_with(move |_: &C::Result| w)
    }

    // Penalizes each complemented group with one soft score unit.
    pub fn penalize_soft(
        self,
    ) -> ComplementedConstraintBuilder<
        S,
        A,
        B,
        K,
        EA,
        EB,
        KA,
        KB,
        C,
        D,
        impl Fn(&C::Result) -> Sc + Send + Sync,
        Sc,
    >
    where
        Sc: Copy,
    {
        let w = Sc::one_soft();
        self.penalize_with(move |_: &C::Result| w)
    }

    // Rewards each complemented group with one hard score unit.
    pub fn reward_hard(
        self,
    ) -> ComplementedConstraintBuilder<
        S,
        A,
        B,
        K,
        EA,
        EB,
        KA,
        KB,
        C,
        D,
        impl Fn(&C::Result) -> Sc + Send + Sync,
        Sc,
    >
    where
        Sc: Copy,
    {
        let w = Sc::one_hard();
        self.reward_hard_with(move |_: &C::Result| w)
    }

    // Rewards each complemented group with one soft score unit.
    pub fn reward_soft(
        self,
    ) -> ComplementedConstraintBuilder<
        S,
        A,
        B,
        K,
        EA,
        EB,
        KA,
        KB,
        C,
        D,
        impl Fn(&C::Result) -> Sc + Send + Sync,
        Sc,
    >
    where
        Sc: Copy,
    {
        let w = Sc::one_soft();
        self.reward_with(move |_: &C::Result| w)
    }
}

impl<S, A, B, K, EA, EB, KA, KB, C, D, Sc: Score> std::fmt::Debug
    for ComplementedConstraintStream<S, A, B, K, EA, EB, KA, KB, C, D, Sc>
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ComplementedConstraintStream").finish()
    }
}

// Zero-erasure builder for finalizing a complemented constraint.
pub struct ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
where
    Sc: Score,
{
    extractor_a: EA,
    extractor_b: EB,
    key_a: KA,
    key_b: KB,
    collector: C,
    default_fn: D,
    impact_type: ImpactType,
    weight_fn: W,
    is_hard: bool,
    _phantom: PhantomData<(fn() -> S, fn() -> A, fn() -> B, fn() -> K, fn() -> Sc)>,
}

impl<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
    ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
where
    S: Send + Sync + 'static,
    A: Clone + Send + Sync + 'static,
    B: Clone + Send + Sync + 'static,
    K: Clone + Eq + Hash + Send + Sync + 'static,
    EA: CollectionExtract<S, Item = A>,
    EB: CollectionExtract<S, Item = B>,
    KA: Fn(&A) -> Option<K> + Send + Sync,
    KB: Fn(&B) -> K + Send + Sync,
    C: UniCollector<A> + Send + Sync + 'static,
    C::Accumulator: Send + Sync,
    C::Result: Clone + Send + Sync,
    D: Fn(&B) -> C::Result + Send + Sync,
    W: Fn(&C::Result) -> Sc + Send + Sync,
    Sc: Score + 'static,
{
    pub fn named(
        self,
        name: &str,
    ) -> ComplementedGroupConstraint<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc> {
        ComplementedGroupConstraint::new(
            ConstraintRef::new("", name),
            self.impact_type,
            self.extractor_a,
            self.extractor_b,
            self.key_a,
            self.key_b,
            self.collector,
            self.default_fn,
            self.weight_fn,
            self.is_hard,
        )
    }

    // Finalizes the builder into a `ComplementedGroupConstraint`.
}

impl<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc: Score> std::fmt::Debug
    for ComplementedConstraintBuilder<S, A, B, K, EA, EB, KA, KB, C, D, W, Sc>
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ComplementedConstraintBuilder")
            .field("impact_type", &self.impact_type)
            .finish()
    }
}