export default class Bowling {
  constructor(rolls) {
    this.rolls = rolls;
  }

  score() {
    const initialState = {
      frameNumber: 1,
      rollNumber: 1,
      pinsRemaining: 10,
      spareLastFrame: false,
      strikeLastFrame: false,
      twoStrikesInARow: false,
      fillBall: false,
      score: 0,
    };

    const finalState = this.rolls.reduce((state, roll) => {
      if (roll < 0 || roll > 10) {
        throw new Error('Pins must have a value from 0 to 10');
      }

      if (roll > state.pinsRemaining) {
        throw new Error('Pin count exceeds pins on the lane');
      }

      if (state.frameNumber > 10) {
        throw new Error('Should not be able to roll after game is over');
      }

      const finalFrame = state.frameNumber === 10;
      const strike = state.rollNumber === 1 && roll === 10;
      const spare = state.rollNumber === 2 && roll === state.pinsRemaining;
      const frameOver = finalFrame
        ? (!state.fillBall && !spare && state.rollNumber === 2) || state.rollNumber === 3
        : strike || spare || state.rollNumber === 2;

      let score = state.score + roll;

      if (state.strikeLastFrame && state.rollNumber < 3) { score += roll; }
      if (state.spareLastFrame && state.rollNumber === 1) { score += roll; }
      if (state.twoStrikesInARow && state.rollNumber === 1) { score += roll; }

      const next = {};

      next.frameNumber = frameOver ? state.frameNumber + 1 : state.frameNumber;
      next.rollNumber = frameOver ? 1 : state.rollNumber + 1;
      next.pinsRemaining = finalFrame
        ? ((strike || spare) ? 10 : state.pinsRemaining - roll)
        : (frameOver ? 10 : state.pinsRemaining - roll);
      next.spareLastFrame = frameOver ? spare : state.spareLastFrame;
      next.strikeLastFrame = frameOver ? strike : state.strikeLastFrame;
      next.twoStrikesInARow = frameOver ? strike && state.strikeLastFrame : state.twoStrikesInARow;
      next.fillBall = next.fillBall || (finalFrame && (strike || spare));
      next.score = score;

      return next;
    }, initialState);

    if (finalState.frameNumber !== 11) {
      throw new Error('Score cannot be taken until the end of the game');
    }

    return finalState.score;
  }
}