Section.js

/** @rlow */
import type { Index, SizeAndPositionInfo } from './types'

/**
 * A section of the Window.
 * Window Sections are used to group nearby cells.
 * This enables us to more quickly determine which cells to display in a given region of the Window.
 * Sections have a fixed size and contain 0 to many cells (tracked by their indices).
 */
export default class Section {
  constructor ({
    height,
    width,
    x,
    y
  }: SizeAndPositionInfo) {
    this.height = height
    this.width = width
    this.x = x
    this.y = y

    this._indexMap = {}
    this._indices = []
  }

  /** Add a cell to this section. */
  addCellIndex ({
    index
  }: Index) {
    if (!this._indexMap[index]) {
      this._indexMap[index] = true
      this._indices.push(index)
    }
  }

  /** Get all cell indices that have been added to this section. */
  getCellIndices (): Array<number> {
    return this._indices
  }

  /** Intended for debugger/test purposes only */
  toString () {
    return `${this.x},${this.y} ${this.width}x${this.height}`
  }
}