fool-cardgame/tests/core/rules/intent.spec.ts

import { describe, expect, it } from 'vitest';
import { Card } from '@core/cards/Card';
import { ActionType } from '@core/rules/Action';
import { Phase } from '@core/rules/GameState';
import { apply, currentActor, legalActions } from '@core/rules/DurakRules';
import { intentFor } from '@core/rules/intent';
import { makeState } from '../../support/fixtures';

const YOU = 'you';
const BOT = 'bot';

const tap = (state: Parameters<typeof intentFor>[0], code: string) =>
    intentFor(state, YOU, Card.parse(code));

describe('intentFor when opening a turn', () => {
    const position = () => makeState({
        hands: { [YOU]: '6C 7D KH', [BOT]: '8C 9D QH' },
        trump: 'S',
        deck: '10C 10D',
        attacker: YOU,
    });

    it('plays any card from hand', () => {
        expect(tap(position(), '6C')).toMatchObject({ type: ActionType.Attack });
        expect(tap(position(), 'KH')).toMatchObject({ type: ActionType.Attack });
    });

    it('refuses a card that is not in hand', () => {
        expect(tap(position(), 'AS')).toBeNull();
    });

    it('refuses everything when it is not your move', () => {
        const state = position();
        expect(intentFor(state, BOT, Card.parse('8C'))).toBeNull();
    });
});

describe('intentFor when defending', () => {
    const position = () => makeState({
        hands: { [YOU]: '8D 6S KC', [BOT]: 'AH AD' },
        trump: 'S',
        deck: '10C 10D',
        attacker: BOT,
        defender: YOU,
        table: [{ attack: '7D' }],
        phase: Phase.Defence,
    });

    it('works out which attack the card beats, with no second tap', () => {
        expect(tap(position(), '8D')).toMatchObject({ type: ActionType.Defend, slot: 0 });
    });

    it('allows a trump', () => {
        expect(tap(position(), '6S')).toMatchObject({ type: ActionType.Defend, slot: 0 });
    });

    it('refuses a card that beats nothing', () => {
        expect(tap(position(), 'KC')).toBeNull();
    });

    it('picks the lowest slot the card can answer', () => {
        const state = makeState({
            hands: { [YOU]: 'AD', [BOT]: 'AH AC' },
            trump: 'S',
            deck: '10C 10D',
            attacker: BOT,
            defender: YOU,
            table: [{ attack: '7C' }, { attack: '7D' }],
            phase: Phase.Defence,
        });
        // The ace of diamonds cannot answer the clubs, so slot 1 is the answer.
        expect(tap(state, 'AD')).toMatchObject({ slot: 1 });
    });
});

describe('intentFor when adding to an attack', () => {
    const position = () => makeState({
        hands: { [YOU]: '7H 9C KD', [BOT]: 'AH AD' },
        trump: 'S',
        deck: '10C 10D',
        attacker: YOU,
        table: [{ attack: '7D', defence: '9D' }],
        phase: Phase.Reinforce,
    });

    it('adds a card whose rank is on the table', () => {
        expect(tap(position(), '7H')).toMatchObject({ type: ActionType.Attack });
        expect(tap(position(), '9C')).toMatchObject({ type: ActionType.Attack });
    });

    it('refuses a rank that is not on the table', () => {
        expect(tap(position(), 'KD')).toBeNull();
    });
});

describe('intentFor agrees with the rules', () => {
    it('never proposes an action the rules would reject', () => {
        // Play many matches by tapping cards, and check every proposal is legal.
        for (let seed = 0; seed < 400; seed++) {
            let state = makeState({
                hands: { [YOU]: '6C 7D 8H 9S 10C JD', [BOT]: '6D 7H 8S 9C 10D JH' },
                trump: 'S',
                deck: 'QC QD QH QS KC KD KH KS AC AD AH',
                attacker: seed % 2 === 0 ? YOU : BOT,
                turnNumber: 1 + (seed % 3),
            });

            for (let step = 0; step < 40 && state.phase !== Phase.Finished; step++) {
                const actor = currentActor(state);
                if (actor === null) break;

                if (actor === YOU) {
                    const hand = state.players[0].hand;
                    for (const card of hand) {
                        const action = intentFor(state, YOU, card);
                        if (!action) continue;
                        // Whatever it proposes, the rules must accept it.
                        expect(() => apply(state, action)).not.toThrow();
                    }
                }

                const options = legalActions(state, actor);
                state = apply(state, options[seed % options.length]).state;
            }
        }
    });

    it('proposes something for every card the rules would accept', () => {
        const state = makeState({
            hands: { [YOU]: '6C 7D 8H 9S 10C JD', [BOT]: '6D 7H 8S' },
            trump: 'S',
            deck: 'QC QD QH',
            attacker: YOU,
        });

        const playable = state.players[0].hand.filter((c) => intentFor(state, YOU, c) !== null);
        const legalCards = legalActions(state, YOU)
            .filter((a) => a.type === ActionType.Attack)
            .map((a) => (a as { card: Card }).card);

        expect(new Set(playable)).toEqual(new Set(legalCards));
    });
});