"use strict";

exports.__esModule = true;

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var privatePool = new WeakMap();

/**
 * Calculates indexes of rows to render OR rows that are visible.
 * To redo the calculation, you need to create a new calculator.
 *
 * @class ViewportRowsCalculator
 */

var ViewportRowsCalculator = function () {
  _createClass(ViewportRowsCalculator, null, [{
    key: "DEFAULT_HEIGHT",

    /**
     * Default row height
     *
     * @type {Number}
     */
    get: function get() {
      return 23;
    }

    /**
     * @param {Number} viewportHeight Height of the viewport
     * @param {Number} scrollOffset Current vertical scroll position of the viewport
     * @param {Number} totalRows Total number of rows
     * @param {Function} rowHeightFn Function that returns the height of the row at a given index (in px)
     * @param {Function} overrideFn Function that changes calculated this.startRow, this.endRow (used by MergeCells plugin)
     * @param {Boolean} onlyFullyVisible if `true`, only startRow and endRow will be indexes of rows that are fully in viewport
     * @param {Number} horizontalScrollbarHeight
     */

  }]);

  function ViewportRowsCalculator(viewportHeight, scrollOffset, totalRows, rowHeightFn, overrideFn, onlyFullyVisible, horizontalScrollbarHeight) {
    _classCallCheck(this, ViewportRowsCalculator);

    privatePool.set(this, {
      viewportHeight: viewportHeight,
      scrollOffset: scrollOffset,
      totalRows: totalRows,
      rowHeightFn: rowHeightFn,
      overrideFn: overrideFn,
      onlyFullyVisible: onlyFullyVisible,
      horizontalScrollbarHeight: horizontalScrollbarHeight
    });

    /**
     * Number of rendered/visible rows
     *
     * @type {Number}
     */
    this.count = 0;

    /**
     * Index of the first rendered/visible row (can be overwritten using overrideFn)
     *
     * @type {Number|null}
     */
    this.startRow = null;

    /**
     * Index of the last rendered/visible row (can be overwritten using overrideFn)
     *
     * @type {null}
     */
    this.endRow = null;

    /**
     * Position of the first rendered/visible row (in px)
     *
     * @type {Number|null}
     */
    this.startPosition = null;

    this.calculate();
  }

  /**
   * Calculates viewport
   */


  _createClass(ViewportRowsCalculator, [{
    key: "calculate",
    value: function calculate() {
      var sum = 0;
      var needReverse = true;
      var startPositions = [];

      var priv = privatePool.get(this);
      var onlyFullyVisible = priv.onlyFullyVisible;
      var overrideFn = priv.overrideFn;
      var rowHeightFn = priv.rowHeightFn;
      var scrollOffset = priv.scrollOffset;
      var totalRows = priv.totalRows;
      var viewportHeight = priv.viewportHeight;
      var horizontalScrollbarHeight = priv.horizontalScrollbarHeight || 0;
      var rowHeight = void 0;

      // Calculate the number (start and end index) of rows needed
      for (var i = 0; i < totalRows; i++) {
        rowHeight = rowHeightFn(i);

        if (rowHeight === undefined) {
          rowHeight = ViewportRowsCalculator.DEFAULT_HEIGHT;
        }
        if (sum <= scrollOffset && !onlyFullyVisible) {
          this.startRow = i;
        }

        // the row is within the "visible range"
        if (sum >= scrollOffset && sum + rowHeight <= scrollOffset + viewportHeight - horizontalScrollbarHeight) {
          if (this.startRow === null) {
            this.startRow = i;
          }
          this.endRow = i;
        }
        startPositions.push(sum);
        sum += rowHeight;

        if (!onlyFullyVisible) {
          this.endRow = i;
        }
        if (sum >= scrollOffset + viewportHeight - horizontalScrollbarHeight) {
          needReverse = false;
          break;
        }
      }

      // If the estimation has reached the last row and there is still some space available in the viewport,
      // we need to render in reverse in order to fill the whole viewport with rows
      if (this.endRow === totalRows - 1 && needReverse) {
        this.startRow = this.endRow;

        while (this.startRow > 0) {
          // rowHeight is the height of the last row
          var viewportSum = startPositions[this.endRow] + rowHeight - startPositions[this.startRow - 1];

          if (viewportSum <= viewportHeight - horizontalScrollbarHeight || !onlyFullyVisible) {
            this.startRow--;
          }
          if (viewportSum >= viewportHeight - horizontalScrollbarHeight) {
            break;
          }
        }
      }

      if (this.startRow !== null && overrideFn) {
        overrideFn(this);
      }
      this.startPosition = startPositions[this.startRow];

      if (this.startPosition == void 0) {
        this.startPosition = null;
      }
      if (this.startRow !== null) {
        this.count = this.endRow - this.startRow + 1;
      }
    }
  }]);

  return ViewportRowsCalculator;
}();

exports.default = ViewportRowsCalculator;