import * as I from 'immutable';

import {compose} from '@avocado/core';
import {Rectangle, Vector} from '@avocado/math';

const decorate = compose(
  Vector.Mixin('size', 'width', 'height', {
    default: [0, 0],
  }),
);

class TilesBase {

  constructor() {
    this._sizeState = I.List();
    this._state = I.Map();
  }

  acceptStateChange(change) {
    if (change.size) {
      this.size = change.size;
    }
    if (change.data) {
      this.data = change.data;
    }
  }

  fromJSON(json) {
    if (json.size) {
      this.size = json.size;
    }
    if (json.data) {
      this.data = json.data;
    }
    return this;
  }

  get rectangle() {
    return Rectangle.compose([0, 0], this.size);
  }

  setTileAt(x, y, tile) {
    const index = y * this.width + x;
    if (index < 0 || index >= this.data.length) {
      return;
    }
    this.data[index] = tile;
  }

  slice(rectangle) {
    const tilesRectangle = this.rectangle;
    // Get intersection.
    if (!Rectangle.intersects(rectangle, tilesRectangle)) {
      return [];
    }
    let [x, y, sliceWidth, sliceHeight] = Rectangle.intersection(
      rectangle,
      tilesRectangle,
    );
    // No muls in the loop.
    let sliceRow = y * sliceWidth;
    const dataWidth = this.width;
    let dataRow = y * dataWidth;
    // Copy slice.
    const slice = new Array(sliceWidth * sliceHeight);
    for (let j = 0; j < sliceHeight; ++j) {
      for (let i = 0; i < sliceWidth; ++i) {
        slice[sliceRow + x] = this.data[dataRow + x];
        x++;
      }
      sliceRow += sliceWidth;
      dataRow += dataWidth;
      x -= sliceWidth;
    }
    return slice;
  }

  get state() {
    return this._state;
  }

  tick(elapsed) {
    this._sizeState = this._sizeState.set(0, this.width);
    this._sizeState = this._sizeState.set(1, this.height);
    this._state = this._state.set('size', this._sizeState);
    this._state = this._state.set('data', this.data);
  }

  tileAt(x, y) {
    return this.data[y * this.width + x];
  }

  toJSON() {
    return {
      size: [...this.size],
      data: [...this.data],
    };
  }

}

export class Tiles extends decorate(TilesBase) {}