class Card {
  constructor(cardString) {
    this.rank = cardString[0];
    this.suit = cardString[1];
  }

  /**
   * Gets the face value of the card, from [0 .. 12].
   * @returns {number} The value.
   */
  get integerValue() {
    return "A23456789TJQK".indexOf(this.rank);
  }

  /**
   * Returns true if the other card has a face value one above or below this card.
   * @param card Another card.
   * @returns {boolean} True if sequential, false otherwise.
   */
  isSequential(card) {
    return (
      (this.integerValue + 13 + 1) % 13 === card.integerValue ||
      (this.integerValue + 13 - 1) % 13 === card.integerValue
    );
  }

  get toString() {
    return this.rank + this.suit;
  }
}

class Pyramid {
  constructor(pyramidArray) {
    this.array = pyramidArray;
  }

  get isCleared() {
    return this.array.every((c) => c === 0);
  }

  get freeCardIndices() {
    let freeIndices = [];
    for (let i = this.array.length - 1; i >= 0; i--) {
      if (this.array[i] === 0) continue;
      const secondOffset = Math.floor((i - 3) / 2);
      // This is the last row
      if (i >= 18) freeIndices.push(i);
      // Third row
      else if (
        i <= 17 &&
        i >= 9 &&
        this.array[i + 9] === 0 &&
        this.array[i + 10] === 0
      )
        freeIndices.push(i);
      // Second row
      else if (
        i <= 8 &&
        i >= 3 &&
        this.array[i + 6 + secondOffset] === 0 &&
        this.array[i + 7 + secondOffset] === 0
      )
        freeIndices.push(i);
      // First row
      else if (
        i <= 2 &&
        i >= 0 &&
        this.array[i + 3 + i] === 0 &&
        this.array[i + 4 + i] === 0
      )
        freeIndices.push(i);
    }
    return freeIndices;
  }
}

class MoveString {
  static gameWon() {
    return "You have won.";
  }
  static gameLost() {
    return "There are no more valid moves.";
  }
  static match(cardA) {
    return "Move " + cardA + " onto the stock.";
  }
  static flipStock() {
    return "Draw a new stock card.";
  }
}

const GameStates = Object.freeze({ won: true, lost: false });

function getBestMoveArray(bestMoveArray, newMoveArray) {
  let bestMoveLength = bestMoveArray.filter((s) => s.startsWith("Move")).length;
  let newMoveLength = newMoveArray.filter((s) => s.startsWith("Move")).length;
  return newMoveLength > bestMoveLength ? newMoveArray : bestMoveArray;
}

/**
 * Solves a Tri Peaks solitaire game.
 * @param pyramidArray The cards in the pyramids, starting in the top-left peak. The cards are in left-to-right, then top-to-bottom order.
 * @param stockArray The cards in the stock.
 * @param stockIndex The index of the top stock card.
 * @param moveArray The list of moves that have been made to get a deck in this configuration.
 * @returns {*[]|([*, *, *]|[*, *, *]|[*, *, *])}
 */
function solve(
  pyramidArray,
  stockArray,
  stockIndex = 0,
  moveArray = [],
  bestMoveArray = []
) {
  let newMoveArray = JSON.parse(JSON.stringify(moveArray));
  let newBestMoveArray = JSON.parse(JSON.stringify(bestMoveArray));
  let pyramid = new Pyramid(pyramidArray);

  // We're in a new game state.
  // Are the moves that brought us here better than the previous best moves we received?
  // If yes, replace the known best move array
  newBestMoveArray = getBestMoveArray(newBestMoveArray, newMoveArray);
  newBestMoveArray = JSON.parse(JSON.stringify(newBestMoveArray));

  // We cleared the pyramid
  if (pyramid.isCleared) {
    newMoveArray.push(MoveString.gameWon());
    return [GameStates.won, newMoveArray, []];
  }

  // We have run out of stock cards
  if (stockIndex >= stockArray.length) {
    newMoveArray.push(MoveString.gameLost());
    return [GameStates.lost, newMoveArray, newBestMoveArray];
  }

  const topStock = new Card(stockArray[stockIndex]);

  let freeCardsIndices = pyramid.freeCardIndices;
  // match free cards with stock
  for (let i = 0; i < freeCardsIndices.length; i++) {
    let cardA = new Card(pyramidArray[freeCardsIndices[i]]);
    if (!cardA.isSequential(topStock)) continue;
    let newStock = JSON.parse(JSON.stringify(stockArray));
    newStock.splice(++stockIndex, 0, cardA.toString);

    newMoveArray = JSON.parse(JSON.stringify(moveArray));
    newMoveArray.push(MoveString.match(cardA.toString));

    let newPyramidArray = JSON.parse(JSON.stringify(pyramidArray));
    newPyramidArray[freeCardsIndices[i]] = 0;

    let result = solve(
      newPyramidArray,
      newStock,
      stockIndex,
      newMoveArray,
      newBestMoveArray
    );
    if (result[0] === GameStates.won) return result;
    // if we didn't win from this move tree, let's grab the best move array
    // if it's better than what we already have
    newBestMoveArray = getBestMoveArray(newBestMoveArray, result[2]);
    newBestMoveArray = JSON.parse(JSON.stringify(newBestMoveArray));
  }

  // Flip over a new card
  newMoveArray = JSON.parse(JSON.stringify(moveArray));
  newMoveArray.push(MoveString.flipStock());
  let result = solve(
    pyramidArray,
    stockArray,
    ++stockIndex,
    newMoveArray,
    newBestMoveArray
  );
  if (result[0] === GameStates.won) return result;
  // if we didn't win from this move tree, let's grab the best move array
  // if it's better than what we already have
  newBestMoveArray = getBestMoveArray(newBestMoveArray, result[2]);
  newBestMoveArray = JSON.parse(JSON.stringify(newBestMoveArray));

  // This node was useless
  return [GameStates.lost, moveArray, newBestMoveArray];
}

module.exports = { Card, solve };