AlexAegis/advent-of-code

export interface SpringLog {
    log: string;
    criteria: number[];
}

export const parse = (input: string): SpringLog[] => {
    return input.lines(false).map<SpringLog>((line) => {
        const [log, critRaw] = line.splitIntoStringPair(' ');
        const criteria = critRaw.splitToInt({ delimiter: /,/ });
        return {
            log,
            criteria,
        };
    });
};

export interface State {
    rebuiltLog: string;
    currentCriteria: number;
    currentOriginalCriteria: number;
    remainingDamagedLog: string;
    remainingCriteria: number[];
}

export const calculateVariations = (
    state: State,
    cache: Map<string, number> = new Map(),
): number => {
    const key = `${state.remainingCriteria.join(',')};${state.remainingDamagedLog};${state.remainingDamagedLog};${state.currentOriginalCriteria};${state.currentCriteria}`;

    const cachedResult = cache.get(key);
    if (cachedResult !== undefined) {
        return cachedResult;
    }

    let result = cachedResult ?? 0;

    while (state.currentCriteria > 0 && state.remainingDamagedLog.startsWith('#')) {
        state.currentCriteria = state.currentCriteria - 1;
        state.remainingDamagedLog = state.remainingDamagedLog.slice(1);
        state.rebuiltLog = state.rebuiltLog + '#';
    }

    if (
        state.currentCriteria === 0 &&
        state.remainingCriteria.length === 0 &&
        !state.remainingDamagedLog.includes('#')
    ) {
        state.rebuiltLog += state.remainingDamagedLog.replaceAll('?', '.');
        return 1;
    }

    while (
        state.currentCriteria === state.currentOriginalCriteria &&
        state.remainingDamagedLog.startsWith('.')
    ) {
        state.remainingDamagedLog = state.remainingDamagedLog.slice(1);
        state.rebuiltLog = state.rebuiltLog + '.';
    }

    if (state.currentCriteria > 0 && state.remainingDamagedLog.startsWith('.')) {
        return 0;
    }

    if (state.currentCriteria === 0 && state.remainingDamagedLog.startsWith('#')) {
        return 0;
    }

    if (
        state.currentCriteria === 0 &&
        (state.remainingDamagedLog.startsWith('.') || state.remainingDamagedLog.startsWith('?'))
    ) {
        const nextCriteria = state.remainingCriteria.shift();

        if (nextCriteria === undefined) {
            state.currentOriginalCriteria = 0;
        } else {
            state.currentCriteria = nextCriteria;
            state.currentOriginalCriteria = nextCriteria;
        }

        state.rebuiltLog = state.rebuiltLog + '.';
        state.remainingDamagedLog = state.remainingDamagedLog.slice(1);
    }

    while (
        state.currentCriteria === state.currentOriginalCriteria &&
        state.remainingDamagedLog.startsWith('.')
    ) {
        state.remainingDamagedLog = state.remainingDamagedLog.slice(1);
        state.rebuiltLog = state.rebuiltLog + '.';
    }

    if (
        state.currentCriteria === 0 &&
        state.remainingDamagedLog.length === 0 &&
        state.remainingCriteria.length === 0
    ) {
        return 1;
    }

    if (state.remainingDamagedLog.startsWith('?')) {
        result += calculateVariations(
            {
                ...state,
                remainingCriteria: [...state.remainingCriteria],
                remainingDamagedLog: '#' + state.remainingDamagedLog.slice(1),
            },
            cache,
        );

        result += calculateVariations(
            {
                ...state,
                remainingCriteria: [...state.remainingCriteria],
                remainingDamagedLog: '.' + state.remainingDamagedLog.slice(1),
            },
            cache,
        );
    } else if (state.currentCriteria > 0 && state.remainingDamagedLog.length > 0) {
        result += calculateVariations(state, cache);
    }
    cache.set(key, result);
    return result;
};