pons 0.10.0

//! Uncontested openings for every seat

use super::insert_uncontested;
use crate::bidding::constraint::{
    Cons, Constraint, balanced, described, fifths, hcp, len, nth_seat, points, rule_of_20,
};
use crate::bidding::context::Context;
use crate::bidding::{Alert, Rules, Trie};
use contract_bridge::auction::Call;
use contract_bridge::{Bid, Hand, Strain, Suit};
use std::cell::Cell;

/// The strong, artificial `2♣` opening (22+) — the only artificial opening
const STRONG_2C: Alert = Alert("strong-2c");

thread_local! {
    /// Whether our side opens a strong balanced 15-17 with 1NT.  Default `true`.
    static OPEN_ONE_NOTRUMP: Cell<bool> = const { Cell::new(true) };
    /// Restore the fifths gauge (`fifths(14.5..17.5)`, centre-matched to plain HCP
    /// 15-17) for the 1NT opening.  Default `false` — the opening gauges plain HCP.
    static ONE_NOTRUMP_FIFTHS: Cell<bool> = const { Cell::new(false) };
    /// Whether we open sound 10-11 counts that satisfy the Rule of 20 with one
    /// of a suit instead of passing.  Default `true` (shipped default-on).
    static RULE_OF_20: Cell<bool> = const { Cell::new(true) };
}

/// Suppress (`false`) or restore (`true`, the default) our own 1NT opening.
///
/// With it off, a strong balanced 15-17 opens a minor instead of 1NT, so a
/// diagnostic can isolate our *defense* to an opponent's 1NT without our own 1NT
/// openings polluting the duplicate (see `bba-match --no-our-1nt`).
pub fn set_open_one_notrump(on: bool) {
    OPEN_ONE_NOTRUMP.with(|cell| cell.set(on));
}

/// Restore the legacy fifths strength gauge for the 1NT opening (`true`); the
/// default (`false`) gauges plain HCP 15-17, which opens 1NT a touch more often.
pub fn set_one_notrump_fifths(on: bool) {
    ONE_NOTRUMP_FIFTHS.with(|cell| cell.set(on));
}

/// Open sound 10-11 counts satisfying the Rule of 20 (raw HCP + two longest
/// suits ≥ 20) with one of a suit, instead of passing (`true`, the shipped
/// default; `false` restores the 12+-only opener).  Natural: strain priority
/// mirrors the 12+ openings (five-card major first, else the better minor).
/// Shipped default-on after the anchor's Constructive/book/opening bucket
/// traced to sound 11-counts we passed and BBA opened — a plain-DD and
/// sd-lead win both vulnerabilities (the pd loss is the perfect-doubler
/// bracket; see [docs/bba-gap-campaign.md]).
pub fn set_rule_of_20(on: bool) {
    RULE_OF_20.with(|cell| cell.set(on));
}

/// Whether Rule-of-20 light openings are on (read by the opening inference,
/// which drops its one-level suit point floor 12→10 to match).
pub(crate) fn rule_of_20_enabled() -> bool {
    RULE_OF_20.with(Cell::get)
}

/// Which hand shapes the strong 1NT opening admits ([`openings_with`])
///
/// Every variant opens the balanced patterns (4333/4432/5332).  A long *major*
/// always prefers a one-of-a-major opening it can rebid, so the shapely
/// additions are minor-only.  Strength ([`fifths`] 15–17) and the inference side
/// are untouched; this is the shape-only knob for the deferred redesign (see the
/// `nt-shape-abc` and `nt-shape-contested` examples).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum NotrumpShape {
    /// Balanced only — the classic baseline.
    Balanced,
    /// Balanced plus a 5422 with a five-card minor — the shipped default.
    Wide,
    /// [`Wide`][NotrumpShape::Wide] plus a 6322 with a six-card minor
    /// (experimental).
    Wide6322,
}

/// Shapes eligible for a 1NT opening, per the [`NotrumpShape`] policy
fn notrump_shape(shape: NotrumpShape) -> Cons<impl Constraint + Clone> {
    balanced()
        | described("wide 1NT shape", move |hand: Hand, _: &Context<'_>| {
            let mut lengths = Suit::ASC.map(|suit| hand[suit].len());
            lengths.sort_unstable();
            let long = match (shape, lengths) {
                (NotrumpShape::Balanced, _) => return false,
                (_, [2, 2, 4, 5]) => 5,
                (NotrumpShape::Wide6322, [2, 2, 3, 6]) => 6,
                _ => return false,
            };
            hand[Suit::Clubs].len() == long || hand[Suit::Diamonds].len() == long
        })
}

/// Better-minor selector: open 1♦ rather than 1♣
///
/// Open the longer minor; with equal length open 1♦ on four-or-more (the
/// standard 4-4 → 1♦, 3-3 → 1♣ split).
fn prefers_diamonds() -> Cons<impl Constraint + Clone> {
    described("prefers diamonds", |hand: Hand, _: &Context<'_>| {
        let clubs = hand[Suit::Clubs].len();
        let diamonds = hand[Suit::Diamonds].len();
        diamonds > clubs || (diamonds == clubs && diamonds >= 4)
    })
}

/// The opening table, shared by every seat
///
/// Strong notrumps (15–17 / 20–21), the artificial 2♣ (22+), five-card majors,
/// better-minor one-of-a-minor openings, weak twos, and three-level preempts.
/// A lighter five-card major is allowed in third and fourth seat.  The 1NT also
/// opens a 5422 with a five-card minor (`wide`; see [`openings_with`]).
///
/// Sharp on shape, fuzzy on strength: suit openings gauge upgraded
/// [`points`], notrump ranges gauge [`fifths`].  A clean shapely maximum
/// upgrades out of a weak two — it is too good for one.
#[must_use]
pub fn openings() -> Rules {
    openings_with(NotrumpShape::Wide)
}

/// [`openings`] with the 1NT [`NotrumpShape`] policy selectable
///
/// `openings()` ships [`NotrumpShape::Wide`] (a 5422 with a five-card minor also
/// opens 1NT); [`NotrumpShape::Balanced`] is the classic baseline and
/// [`NotrumpShape::Wide6322`] the experimental superset.
#[must_use]
pub fn openings_with(shape: NotrumpShape) -> Rules {
    let mut rules = Rules::new()
        // Strong, artificial 2♣ — top priority.
        .rule(Bid::new(2, Strain::Clubs), 3.0, points(22..))
        .alert(STRONG_2C);
    // Strong 1NT — gated so a diagnostic can suppress our own 1NT opening
    // (`set_open_one_notrump`); the 15-17 balanced hands then open a minor.
    if OPEN_ONE_NOTRUMP.with(Cell::get) {
        // Strength gauged by plain HCP 15-17 by default; `set_one_notrump_fifths`
        // restores the legacy Andrews' fifths gauge.  Each arm reissues `.rule()`
        // so the differing constraint types unify to `Rules`.
        rules = if ONE_NOTRUMP_FIFTHS.with(Cell::get) {
            // 14.5..17.5 (centre 16), not 15..18 (centre 16.5): fifths sums to 40
            // over the deck like HCP, so an unbiased "15-17 HCP" gate shares the
            // plain-HCP band's centre — the old 15..18 was half a point too high.
            rules.rule(
                Bid::new(1, Strain::Notrump),
                2.0,
                fifths(14.5..17.5) & notrump_shape(shape),
            )
        } else {
            rules.rule(
                Bid::new(1, Strain::Notrump),
                2.0,
                hcp(15..=17) & notrump_shape(shape),
            )
        };
    }
    rules = rules
        // Strong 2NT.
        .rule(
            Bid::new(2, Strain::Notrump),
            2.0,
            fifths(20.0..22.0) & balanced(),
        )
        // Five-card majors; 1♠ ranks just above 1♥ so 5-5 opens the higher.
        .rule(
            Bid::new(1, Strain::Spades),
            1.6,
            points(12..=21) & len(Suit::Spades, 5..),
        )
        .rule(
            Bid::new(1, Strain::Hearts),
            1.5,
            points(12..=21) & len(Suit::Hearts, 5..),
        )
        // Lighter five-card majors in third/fourth seat.
        .rule(
            Bid::new(1, Strain::Spades),
            2.6,
            points(9..=11) & len(Suit::Spades, 5..) & (nth_seat(3) | nth_seat(4)),
        )
        .rule(
            Bid::new(1, Strain::Hearts),
            2.5,
            points(9..=11) & len(Suit::Hearts, 5..) & (nth_seat(3) | nth_seat(4)),
        )
        // Better-minor openings (deny a five-card major).
        .rule(
            Bid::new(1, Strain::Diamonds),
            1.0,
            points(12..=21) & prefers_diamonds() & len(Suit::Hearts, ..5) & len(Suit::Spades, ..5),
        )
        .rule(
            Bid::new(1, Strain::Clubs),
            1.0,
            points(12..=21)
                & len(Suit::Clubs, 3..)
                & !prefers_diamonds()
                & len(Suit::Hearts, ..5)
                & len(Suit::Spades, ..5),
        );

    // Weak twos (six-card suit, not in fourth seat).
    for suit in [Suit::Diamonds, Suit::Hearts, Suit::Spades] {
        rules = rules.rule(
            Bid::new(2, Strain::from(suit)),
            1.0,
            len(suit, 6..=6) & points(5..=10) & !nth_seat(4),
        );
    }
    // Three-level preempts (seven-card suit, not in fourth seat).
    for suit in [Suit::Clubs, Suit::Diamonds, Suit::Hearts, Suit::Spades] {
        rules = rules.rule(
            Bid::new(3, Strain::from(suit)),
            0.9,
            len(suit, 7..) & points(..12) & !nth_seat(4),
        );
    }
    // Rule-of-20 light openers (sound 10-11 counts) — behind `set_rule_of_20`.
    // Natural; same weights and strain priority as the 12+ suit openings, so a
    // five-card major opens ahead of the better minor and these outrank the
    // weak two / preempt a shapely light hand would otherwise reach.
    if RULE_OF_20.with(Cell::get) {
        rules = rules
            .rule(
                Bid::new(1, Strain::Spades),
                1.6,
                hcp(10..=11) & rule_of_20() & len(Suit::Spades, 5..),
            )
            .rule(
                Bid::new(1, Strain::Hearts),
                1.5,
                hcp(10..=11) & rule_of_20() & len(Suit::Hearts, 5..),
            )
            .rule(
                Bid::new(1, Strain::Diamonds),
                1.0,
                hcp(10..=11)
                    & rule_of_20()
                    & prefers_diamonds()
                    & len(Suit::Hearts, ..5)
                    & len(Suit::Spades, ..5),
            )
            .rule(
                Bid::new(1, Strain::Clubs),
                1.0,
                hcp(10..=11)
                    & rule_of_20()
                    & len(Suit::Clubs, 3..)
                    & !prefers_diamonds()
                    & len(Suit::Hearts, ..5)
                    & len(Suit::Spades, ..5),
            );
    }
    rules.rule(Call::Pass, 0.0, points(..12))
}

/// Register the opening table in the constructive book
pub(super) fn register(book: &mut Trie, shape: NotrumpShape) {
    insert_uncontested(book, &[], openings_with(shape));
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::bidding::context::Context;
    use crate::bidding::trie::Classifier;
    use contract_bridge::auction::RelativeVulnerability;

    /// The highest-logit opening `rules` makes for a hand
    fn opens(rules: &Rules, hand: &str) -> Call {
        let hand: Hand = hand.parse().expect("valid test hand");
        let context = Context::new(RelativeVulnerability::NONE, &[]);
        let logits = rules.classify(hand, &context);
        (&logits.0)
            .into_iter()
            .max_by(|(_, a): &(Call, &f32), (_, b)| a.partial_cmp(b).expect("logits are never NaN"))
            .map(|(call, _)| call)
            .expect("array is never empty")
    }

    #[test]
    fn wide_notrump_shape_gate() {
        let one_nt = Call::Bid(Bid::new(1, Strain::Notrump));
        let one_s = Call::Bid(Bid::new(1, Strain::Spades));
        let one_c = Call::Bid(Bid::new(1, Strain::Clubs));
        // 5422 / 6322, ~15–17 fifths, long suit a minor (joins the wide 1NT) or a
        // major (stays a suit); the long-minor 6322 also stays a suit.
        let five422_minor = "Q432.KQ.K2.AK432";
        let five422_major = "AK432.KQ.Q432.K2";
        let six322_minor = "Q2.K3.AQ4.KQ8765";
        let six322_major = "KQ8765.K3.AQ4.Q2";
        let balanced16 = "AQ32.K53.QJ4.A92";

        // Classic: only the balanced hand opens 1NT; the shapely ones open a suit.
        let narrow = openings_with(NotrumpShape::Balanced);
        assert_eq!(opens(&narrow, balanced16), one_nt);
        assert_eq!(opens(&narrow, five422_minor), one_c);
        assert_eq!(opens(&narrow, five422_major), one_s);
        assert_eq!(opens(&narrow, six322_minor), one_c);
        assert_eq!(opens(&narrow, six322_major), one_s);

        // Wide (default): the long-minor 5422 joins 1NT; majors and 6322 stay suits.
        let wide = openings_with(NotrumpShape::Wide);
        assert_eq!(opens(&wide, balanced16), one_nt);
        assert_eq!(opens(&wide, five422_minor), one_nt);
        assert_eq!(opens(&wide, five422_major), one_s);
        assert_eq!(opens(&wide, six322_minor), one_c);
        assert_eq!(opens(&wide, six322_major), one_s);

        // Wide6322: the long-minor 6322 also joins 1NT; majors still stay suits.
        let wide6322 = openings_with(NotrumpShape::Wide6322);
        assert_eq!(opens(&wide6322, five422_minor), one_nt);
        assert_eq!(opens(&wide6322, five422_major), one_s);
        assert_eq!(opens(&wide6322, six322_minor), one_nt);
        assert_eq!(opens(&wide6322, six322_major), one_s);
    }

    #[test]
    fn suppress_one_notrump_opens_a_minor() {
        let one_nt = Call::Bid(Bid::new(1, Strain::Notrump));
        let one_c = Call::Bid(Bid::new(1, Strain::Clubs));
        let balanced16 = "AQ32.K53.QJ4.A92"; // 4333, 16 HCP — a textbook 1NT opener

        // Default: opens 1NT.
        assert_eq!(opens(&openings(), balanced16), one_nt);

        // Suppressed: the same hand opens its minor — never 1NT, never Pass.
        set_open_one_notrump(false);
        let call = opens(&openings(), balanced16);
        set_open_one_notrump(true);
        assert_eq!(call, one_c);
    }

    #[test]
    fn rule_of_20_opens_sound_eleven_counts() {
        let one_s = Call::Bid(Bid::new(1, Strain::Spades));
        // 11 HCP, 5-2-4-2, Rule of 20 (11 + 9).  The wasted J9 voids the points
        // upgrade, so the 12+ opener would pass; by default (Rule of 20 on) we
        // open the five-card major.
        let sound_11 = "AK986.J9.QJT6.64";
        assert_eq!(opens(&openings(), sound_11), one_s);

        // Turning it off restores the 12+-only opener, which passes this hand.
        set_rule_of_20(false);
        let call = opens(&openings(), sound_11);
        set_rule_of_20(true);
        assert_eq!(call, Call::Pass);
    }
}