import {_limitValue} from './helpers.math';
import {_lookupByKey} from './helpers.collection';

export function fontString(pixelSize, fontStyle, fontFamily) {
  return fontStyle + ' ' + pixelSize + 'px ' + fontFamily;
}

/**
* Request animation polyfill
*/
export const requestAnimFrame = (function() {
  if (typeof window === 'undefined') {
    return function(callback) {
      return callback();
    };
  }
  return window.requestAnimationFrame;
}());

/**
 * Throttles calling `fn` once per animation frame
 * Latest arguments are used on the actual call
 * @param {function} fn
 * @param {*} thisArg
 * @param {function} [updateFn]
 */
export function throttled(fn, thisArg, updateFn) {
  const updateArgs = updateFn || ((args) => Array.prototype.slice.call(args));
  let ticking = false;
  let args = [];

  return function(...rest) {
    args = updateArgs(rest);

    if (!ticking) {
      ticking = true;
      requestAnimFrame.call(window, () => {
        ticking = false;
        fn.apply(thisArg, args);
      });
    }
  };
}

/**
 * Debounces calling `fn` for `delay` ms
 * @param {function} fn - Function to call.
 * @param {number} delay - Delay in ms. 0 = immediate invocation.
 * @returns {function}
 */
export function debounce(fn, delay) {
  let timeout;
  return function(...args) {
    if (delay) {
      clearTimeout(timeout);
      timeout = setTimeout(fn, delay, args);
    } else {
      fn.apply(this, args);
    }
    return delay;
  };
}

/**
 * Converts 'start' to 'left', 'end' to 'right' and others to 'center'
 * @param {string} align start, end, center
 * @private
 */
export const _toLeftRightCenter = (align) => align === 'start' ? 'left' : align === 'end' ? 'right' : 'center';

/**
 * Returns `start`, `end` or `(start + end) / 2` depending on `align`. Defaults to `center`
 * @param {string} align start, end, center
 * @param {number} start value for start
 * @param {number} end value for end
 * @private
 */
export const _alignStartEnd = (align, start, end) => align === 'start' ? start : align === 'end' ? end : (start + end) / 2;

/**
 * Returns `left`, `right` or `(left + right) / 2` depending on `align`. Defaults to `left`
 * @param {string} align start, end, center
 * @param {number} left value for start
 * @param {number} right value for end
 * @param {boolean} rtl Is this an RTL draw
 * @private
 */
export const _textX = (align, left, right, rtl) => {
  const check = rtl ? 'left' : 'right';
  return align === check ? right : align === 'center' ? (left + right) / 2 : left;
};

/**
 * Return start and count of visible points.
 * @param {object} meta - dataset meta.
 * @param {array} points - array of point elements.
 * @param {boolean} animationsDisabled - if true animation is disabled.
 * @returns {{start: number; count: number}}
 * @private
 */
export function _getStartAndCountOfVisiblePoints(meta, points, animationsDisabled) {
  const pointCount = points.length;

  let start = 0;
  let count = pointCount;

  if (meta._sorted) {
    const {iScale, _parsed} = meta;
    const axis = iScale.axis;
    const {min, max, minDefined, maxDefined} = iScale.getUserBounds();

    if (minDefined) {
      start = _limitValue(Math.min(
        _lookupByKey(_parsed, iScale.axis, min).lo,
        animationsDisabled ? pointCount : _lookupByKey(points, axis, iScale.getPixelForValue(min)).lo),
      0, pointCount - 1);
    }
    if (maxDefined) {
      count = _limitValue(Math.max(
        _lookupByKey(_parsed, iScale.axis, max, true).hi + 1,
        animationsDisabled ? 0 : _lookupByKey(points, axis, iScale.getPixelForValue(max), true).hi + 1),
      start, pointCount) - start;
    } else {
      count = pointCount - start;
    }
  }

  return {start, count};
}

/**
 * Checks if the scale ranges have changed.
 * @param {object} meta - dataset meta.
 * @returns {boolean}
 * @private
 */
export function _scaleRangesChanged(meta) {
  const {xScale, yScale, _scaleRanges} = meta;
  const newRanges = {
    xmin: xScale.min,
    xmax: xScale.max,
    ymin: yScale.min,
    ymax: yScale.max
  };
  if (!_scaleRanges) {
    meta._scaleRanges = newRanges;
    return true;
  }
  const changed = _scaleRanges.xmin !== xScale.min
		|| _scaleRanges.xmax !== xScale.max
		|| _scaleRanges.ymin !== yScale.min
		|| _scaleRanges.ymax !== yScale.max;

  Object.assign(_scaleRanges, newRanges);
  return changed;
}