JoshHeaps.Net/tests/holdem/potCalculator.test.js

const { test, describe } = require("node:test");
const assert = require("node:assert/strict");
const { PotCalculator } = require("./load");

const p = (id, contribution, folded = false) => ({ id, contribution, folded });

describe("PotCalculator.layers", () => {
    test("one pot when everyone put in the same", () => {
        const layers = PotCalculator.layers([p("a", 50), p("b", 50), p("c", 50)]);
        assert.equal(layers.length, 1);
        assert.equal(layers[0].amount, 150);
        assert.equal(layers[0].label, "Main pot");
        assert.deepEqual(layers[0].eligible.sort(), ["a", "b", "c"]);
    });

    test("a short all-in opens a side pot only the deeper players can win", () => {
        // a is all-in for 20, b and c keep betting to 60.
        const layers = PotCalculator.layers([p("a", 20), p("b", 60), p("c", 60)]);
        assert.equal(layers.length, 2);

        assert.equal(layers[0].amount, 60); // 20 x 3
        assert.deepEqual(layers[0].eligible.sort(), ["a", "b", "c"]);

        assert.equal(layers[1].amount, 80); // 40 x 2
        assert.deepEqual(layers[1].eligible.sort(), ["b", "c"]);
        assert.equal(layers[1].label, "Side pot 1");
    });

    test("folded money stays in the pot as dead money but wins nothing", () => {
        const layers = PotCalculator.layers([p("a", 50), p("b", 50), p("folder", 50, true)]);
        assert.equal(layers.length, 1);
        assert.equal(layers[0].amount, 150, "the folder's chips are still in the middle");
        assert.ok(!layers[0].eligible.includes("folder"));
    });

    test("layers with the same eligible players are announced as one pot", () => {
        // Two folders at different heights would each open a band, but a dealer
        // announces one pot between the two players who can actually win it.
        const layers = PotCalculator.layers([
            p("a", 100),
            p("b", 100),
            p("f1", 20, true),
            p("f2", 40, true),
        ]);
        const eligibleSets = layers.map(l => l.eligible.slice().sort().join(","));
        assert.deepEqual(eligibleSets, ["a,b"], "one announceable pot, not three");
        assert.equal(layers[0].amount, 260);
    });

    test("layer amounts always sum to the contested money", () => {
        const players = [p("a", 12.5), p("b", 33.25), p("c", 33.25), p("d", 5, true)];
        const total = players.reduce((s, x) => s + x.contribution, 0);
        const uncalled = PotCalculator.uncalledReturns(players).reduce((s, r) => s + r.amount, 0);
        const layered = PotCalculator.layers(players).reduce((s, l) => s + l.amount, 0);
        assert.equal(Math.round((layered + uncalled) * 100), Math.round(total * 100));
    });

    test("nobody contributed means no pots, not an empty main pot", () => {
        assert.deepEqual(PotCalculator.layers([p("a", 0), p("b", 0)]), []);
    });
});

describe("PotCalculator.uncalledReturns", () => {
    test("an overbet nobody called goes back to whoever bet it", () => {
        // b shoves 200, a calls only 50 and everyone else folds.
        const returns = PotCalculator.uncalledReturns([p("a", 50), p("b", 200)]);
        assert.deepEqual(returns, [{ id: "b", amount: 150 }]);
    });

    test("a called bet leaves nothing to return", () => {
        assert.deepEqual(PotCalculator.uncalledReturns([p("a", 50), p("b", 50)]), []);
    });

    test("the cap is the biggest live contribution, so a folder's overbet comes back", () => {
        const returns = PotCalculator.uncalledReturns([p("live", 30), p("bully", 90, true)]);
        assert.deepEqual(returns, [{ id: "bully", amount: 60 }]);
    });

    test("with nobody live it stays quiet rather than refunding the table", () => {
        // Every fold flag set is a dealer mistake to correct, not a signal that
        // every chip on the felt was uncalled.
        assert.deepEqual(PotCalculator.uncalledReturns([p("a", 10, true), p("b", 20, true)]), []);
    });
});

describe("PotCalculator.resolveRound", () => {
    test("a single winner takes the layer they were matched for", () => {
        const entries = PotCalculator.buildEntries([p("a", 50), p("b", 50)]);
        const result = PotCalculator.resolveRound(entries, ["a"]);
        assert.equal(result.payoutPool, 100);
        assert.deepEqual(result.perWinner, [{ id: "a", amount: 100 }]);
        assert.equal(result.remainingContenders.length, 0);
    });

    test("an all-in winner only takes what everyone matched, the rest rolls forward", () => {
        const entries = PotCalculator.buildEntries([p("short", 20), p("b", 60), p("c", 60)]);
        const result = PotCalculator.resolveRound(entries, ["short"]);
        assert.equal(result.capApplied, 20);
        assert.equal(result.payoutPool, 60, "20 from each of three players");
        // b and c still have 40 each left to play for.
        assert.deepEqual(result.remainingContenders.map(e => e.id).sort(), ["b", "c"]);
        assert.equal(PotCalculator.totalPot(result.updatedEntries), 80);
    });

    test("a chopped pot splits evenly", () => {
        const entries = PotCalculator.buildEntries([p("a", 30), p("b", 30)]);
        const result = PotCalculator.resolveRound(entries, ["a", "b"]);
        assert.deepEqual(result.perWinner, [{ id: "a", amount: 30 }, { id: "b", amount: 30 }]);
    });

    test("odd cents go to the winners in selection order and nothing is lost", () => {
        // A $10.01 pot three ways doesn't divide: 3.34 / 3.34 / 3.33.
        const entries = PotCalculator.buildEntries([p("a", 3.34), p("b", 3.34), p("c", 3.33)]);
        const result = PotCalculator.resolveRound(entries, ["a", "b", "c"]);
        const paid = result.perWinner.reduce((s, w) => s + w.amount, 0);
        assert.equal(Math.round(paid * 100), Math.round(result.payoutPool * 100), "no chips lost to rounding");
        assert.ok(result.perWinner[0].amount >= result.perWinner[2].amount, "odd cent goes to the first selected");
    });

    test("selecting nobody who can win is an error, not a silent no-op", () => {
        const entries = PotCalculator.buildEntries([p("a", 50), p("b", 50)]);
        assert.throws(() => PotCalculator.resolveRound(entries, ["ghost"]), /No valid winners/);
    });
});

// The pots come out of layers() in one order and with one relationship between them,
// and the action bar's wording now depends on both. If eligibility were not nested,
// "8 in, not Mike and Bob" would be a lie — there would be someone eligible for a side
// pot who was never eligible for the main one, and naming the complement would hide
// them. It is a property of how the layers are built rather than an accident of the
// examples above, so it is checked as one.
describe("pot eligibility is nested", () => {
    function rng(seed) {
        let s = seed >>> 0;
        return () => {
            s = (s * 1664525 + 1013904223) >>> 0;
            return s / 4294967296;
        };
    }

    test("every side pot's players are a strict subset of the pot below it", () => {
        const random = rng(20260905);
        let multiPotTables = 0;
        let pairs = 0;

        for (let table = 0; table < 20000; table++) {
            const n = 2 + Math.floor(random() * 11);
            const players = Array.from({ length: n }, (_, i) => p(
                `p${i}`,
                // A sixth of the table never puts anything in, which is a table mid-deal.
                random() < 1 / 6 ? 0 : (1 + Math.floor(random() * 8)) * 25,
                random() < 0.2));

            const layers = PotCalculator.layers(players);
            if (layers.length > 1) multiPotTables++;

            for (let i = 1; i < layers.length; i++) {
                const below = layers[i - 1].eligible;
                const belowSet = new Set(below);
                const here = layers[i].eligible;
                pairs++;
                assert.ok(here.every(id => belowSet.has(id)),
                    `table ${table}: ${layers[i].label} has a player ${layers[i - 1].label} does not\n` +
                    JSON.stringify(players));
                assert.ok(here.length < below.length,
                    `table ${table}: ${layers[i].label} is no smaller than ${layers[i - 1].label} — ` +
                    `layers with the same eligibility are supposed to be merged into one pot\n` +
                    JSON.stringify(players));
            }
        }

        // Guards the generator rather than the code: a shape that stopped producing side
        // pots would make every assertion above vacuous and the test would still pass.
        assert.ok(multiPotTables > 10000, `only ${multiPotTables} tables had a side pot`);
        assert.ok(pairs > 20000, `only ${pairs} adjacent pairs to check`);
    });

    test("so the main pot is everyone still live, and it is the widest", () => {
        const layers = PotCalculator.layers([p("a", 100), p("b", 40), p("c", 100), p("d", 25)]);
        assert.deepEqual(layers[0].eligible.sort(), ["a", "b", "c", "d"]);
        layers.slice(1).forEach(layer =>
            assert.ok(layer.eligible.length < layers[0].eligible.length));
    });
});