import { Card } from '../cards/Card';
import { Action, Actions } from './Action';
import { GameState, Phase, PlayerId } from './GameState';
import { beats, currentActor, legalActions, unbeatenSlots } from './DurakRules';

/**
 * What tapping a card means for a player right now, or null if that card cannot
 * be played.
 *
 * This lives in the core rather than in the game screen so it can be tested
 * without the engine: it is the one piece of interface logic that can silently
 * turn a legal move into a rejected tap, and it is far too easy to get wrong by
 * eye. The screen just calls it and submits whatever comes back.
 *
 * One tap is the whole interaction. When defending, the attack to beat is worked
 * out here instead of being chosen separately — the serialised rules leave only
 * one unanswered attack at a time, and where several somehow exist the lowest
 * slot this card can beat is taken.
 */
export function intentFor(state: GameState, player: PlayerId, card: Card): Action | null {
    if (currentActor(state) !== player) {
        return null;
    }

    if (state.phase === Phase.Defence) {
        const slot = unbeatenSlots(state)
            .find((i) => beats(card, state.table[i].attack, state.trumpSuit));
        return slot === undefined ? null : Actions.defend(player, card, slot);
    }

    const wanted = Actions.attack(player, card);
    const legal = legalActions(state, player)
        .some((a) => a.type === wanted.type && (a as { card?: Card }).card === card);
    return legal ? wanted : null;
}