import Module from "./module.js";
import {
  registerCaller,
  unregisterCaller,
  startLoop,
  stopLoop,
  subscribeKeyPressed,
  unsubscribeKeyPressed
} from "./game.js";

const MODULE_NAME = "SNAKE";
const DEFAULT_GRID_SIZE = 16;

const initialState = {
  grid: createGrid(DEFAULT_GRID_SIZE),
  size: DEFAULT_GRID_SIZE,
  paused: false,
  vX: 1,
  vY: 0,
  snake: [],
  score: 0,
  previousScore: 0,
  apple: randomPosition(DEFAULT_GRID_SIZE)
};

/* === Snake Helper Functions ================================================================== */

export const directions = {
  UP: "UP",
  DOWN: "DOWN",
  LEFT: "LEFT",
  RIGHT: "RIGHT"
};

export const keys = {
  UP: "ArrowUp",
  RIGHT: "ArrowRight",
  DOWN: "ArrowDown",
  LEFT: "ArrowLeft",

  h: "h",
  j: "j",
  k: "k",
  l: "l",

  p: "p",
  s: "s",
  r: "r"
};

function randomPosition(size) {
  return [Math.round(Math.random() * (size - 1)), Math.round(Math.random() * (size - 1))];
}
const comparePositions = (pos1, pos2) => pos1[0] === pos2[0] && pos1[1] === pos2[1];

function createGrid(size) {
  const rows = [];
  for (let y = 0; y < size; y += 1) {
    const columns = [];
    for (let x = 0; x < size; x += 1) {
      if (Math.random() > 9) {
        columns[x] = "x";
      } else {
        columns[x] = " ";
      }
    }
    rows[y] = columns;
  }
  return rows;
}

const markCell = (grid, [x, y], mark) => {
  grid[y][x] = mark;
  return grid;
};

const moveSnakePart = ([x, y], vX, vY, size) => {
  let newX = x + vX;
  let newY = y + vY;
  if (newX > size - 1) {
    newX = 0;
  }
  if (newX < 0) {
    newX = size - 1;
  }
  if (newY > size - 1) {
    newY = 0;
  }
  if (newY < 0) {
    newY = size - 1;
  }
  return [newX, newY];
};

export const module = new Module(MODULE_NAME, initialState);

/* === Actions ================================================================================== */

export const [START_SNAKE, startSnake] = module.action("START_SNAKE");
export const [RESET_SNAKE, resetSnake] = module.action("RESET_SNAKE", options => ({ ...options }));
export const [STOP_SNAKE, stopSnake] = module.action("STOP_SNAKE");
export const [PAUSE_SNAKE, pauseSnake] = module.action("PAUSE_SNAKE");
export const [UPDATE_FRAME_SNAKE, updateFrameSnake] = module.action("UPDATE_FRAME_SNAKE");
export const [CHANGE_DIRECTION, changeDirection] = module.action("CHANGE_DIRECTION", direction => ({ direction }));
export const [KEY_PRESSED_SNAKE, keyPressedSnake] = module.action("KEY_PRESSED_SNAKE", key => ({ key }));
export const [UPDATE_STATE, updateState] = module.action("UPDATE_STATE", (newState, fullUpdate = false) => ({
  newState,
  fullUpdate
}));

/* === Reducers ================================================================================= */

module.reducer(UPDATE_STATE, (state, { newState, fullUpdate }) => (fullUpdate ? newState : { ...state, ...newState }));
module.reducer(RESET_SNAKE, (state, options) => {
  const grid = createGrid(state.size);
  const { apple } = initialState;
  const snake = options.started ? [[0, 0]] : [];

  markCell(grid, apple, "a");
  snake.forEach(p => markCell(grid, p, "s"));
  return { ...state, ...initialState, grid, snake, ...options };
});

module.reducer(CHANGE_DIRECTION, (state, { direction }) => {
  const { vX, vY } = state;

  if (direction === directions.UP && vY !== 1) {
    return { ...state, vX: 0, vY: -1 };
  }
  if (direction === directions.DOWN && vY !== -1) {
    return { ...state, vX: 0, vY: 1 };
  }
  if (direction === directions.LEFT && vX !== 1) {
    return { ...state, vX: -1, vY: 0 };
  }
  if (direction === directions.RIGHT && vX !== -1) {
    return { ...state, vX: 1, vY: 0 };
  }

  return state;
});

module.reducer(UPDATE_FRAME_SNAKE, state => {
  const { snake, vX, vY, size } = state;
  let { apple, started, died, previousScore, score } = state;
  const grid = createGrid(size);
  const newSnake = [...snake];
  const nextPosition = moveSnakePart(newSnake[newSnake.length - 1], vX, vY, size);
  previousScore = score;
  if (comparePositions(nextPosition, apple)) {
    apple = randomPosition(size);
    // eslint-disable-next-line no-loop-func
    while (newSnake.filter(p => comparePositions(p, apple)).length) {
      apple = randomPosition(size);
    }
  } else {
    newSnake.shift();
  }
  if (newSnake.filter(p => comparePositions(p, nextPosition)).length) {
    started = false;
    died = true;
  }
  newSnake.push(nextPosition);
  markCell(grid, apple, "a");
  const brightness = (l, i) => 20 + Math.round(0.8 * ((i + 1) / l) * 100);
  newSnake.forEach((p, i) => markCell(grid, p, "s" + brightness(newSnake.length, i)));
  score = newSnake.length;
  return { ...state, grid, vX, vY, snake: newSnake, apple, started, died, previousScore, score };
});

/* === Middleware =============================================================================== */

module.after(UPDATE_FRAME_SNAKE, (dispatch, { died }) => {
  if (died) {
    dispatch(unregisterCaller(UPDATE_FRAME_SNAKE));
    dispatch(stopLoop());
  }
});

module.middleware(START_SNAKE, (dispatch, { started }) => {
  dispatch(resetSnake({ started: true, died: false }));
  dispatch(registerCaller(UPDATE_FRAME_SNAKE));
  dispatch(subscribeKeyPressed(KEY_PRESSED_SNAKE));
  dispatch(startLoop());
});

module.middleware(STOP_SNAKE, (dispatch, { started }) => {
  dispatch(unregisterCaller(UPDATE_FRAME_SNAKE));
  dispatch(unsubscribeKeyPressed(KEY_PRESSED_SNAKE));
  dispatch(stopLoop());
  dispatch(resetSnake({ started: false }));
});

module.middleware(PAUSE_SNAKE, (dispatch, { paused }) => {
  dispatch(updateState({ paused: !paused }));
  if (paused) {
    dispatch(registerCaller(UPDATE_FRAME_SNAKE));
  } else {
    dispatch(unregisterCaller(UPDATE_FRAME_SNAKE));
  }
});

module.middleware(KEY_PRESSED_SNAKE, (dispatch, _, { key }) => {
  if (key === keys.UP || key === keys.k) {
    dispatch(changeDirection(directions.UP));
  }
  if (key === keys.DOWN || key === keys.j) {
    dispatch(changeDirection(directions.DOWN));
  }
  if (key === keys.LEFT || key === keys.h) {
    dispatch(changeDirection(directions.LEFT));
  }
  if (key === keys.RIGHT || key === keys.l) {
    dispatch(changeDirection(directions.RIGHT));
  }
  if (key === keys.s) {
    dispatch(stopSnake());
  }
  if (key === keys.p) {
    dispatch(pauseSnake());
  }
  if (key === keys.r) {
    dispatch(startSnake());
  }
});