// previous version:
// https://github.com/angular-ui/bootstrap/blob/07c31d0731f7cb068a1932b8e01d2312b796b4ec/src/position/position.js
export class Positioning {
  private getStyle(element: HTMLElement, prop: string): string { return window.getComputedStyle(element)[prop]; }

  private isStaticPositioned(element: HTMLElement): boolean {
    return (this.getStyle(element, 'position') || 'static') === 'static';
  }

  private offsetParent(element: HTMLElement): HTMLElement {
    let offsetParentEl = <HTMLElement>element.offsetParent || document.documentElement;

    while (offsetParentEl && offsetParentEl !== document.documentElement && this.isStaticPositioned(offsetParentEl)) {
      offsetParentEl = <HTMLElement>offsetParentEl.offsetParent;
    }

    return offsetParentEl || document.documentElement;
  }

  public position(element: HTMLElement, round = true): ClientRect {
    let elPosition: ClientRect;
    let parentOffset: ClientRect = {width: 0, height: 0, top: 0, bottom: 0, left: 0, right: 0};

    if (this.getStyle(element, 'position') === 'fixed') {
      elPosition = element.getBoundingClientRect();
    } else {
      const offsetParentEl = this.offsetParent(element);

      elPosition = this.offset(element, false);

      if (offsetParentEl !== document.documentElement) {
        parentOffset = this.offset(offsetParentEl, false);
      }

      parentOffset.top += offsetParentEl.clientTop;
      parentOffset.left += offsetParentEl.clientLeft;
    }

    elPosition.top -= parentOffset.top;
    elPosition.bottom -= parentOffset.top;
    elPosition.left -= parentOffset.left;
    elPosition.right -= parentOffset.left;

    if (round) {
      elPosition.top = Math.round(elPosition.top);
      elPosition.bottom = Math.round(elPosition.bottom);
      elPosition.left = Math.round(elPosition.left);
      elPosition.right = Math.round(elPosition.right);
    }

    return elPosition;
  }

  public offset(element: HTMLElement, round = true): ClientRect {
    const elBcr = element.getBoundingClientRect();
    const viewportOffset = {
      top: window.pageYOffset - document.documentElement.clientTop,
      left: window.pageXOffset - document.documentElement.clientLeft
    };

    let elOffset = {
      height: elBcr.height || element.offsetHeight,
      width: elBcr.width || element.offsetWidth,
      top: elBcr.top + viewportOffset.top,
      bottom: elBcr.bottom + viewportOffset.top,
      left: elBcr.left + viewportOffset.left,
      right: elBcr.right + viewportOffset.left
    };

    if (round) {
      elOffset.height = Math.round(elOffset.height);
      elOffset.width = Math.round(elOffset.width);
      elOffset.top = Math.round(elOffset.top);
      elOffset.bottom = Math.round(elOffset.bottom);
      elOffset.left = Math.round(elOffset.left);
      elOffset.right = Math.round(elOffset.right);
    }

    return elOffset;
  }

  public positionElements(hostElement: HTMLElement, targetElement: HTMLElement, placement: string, appendToBody?: boolean):
      ClientRect {
    const hostElPosition = appendToBody ? this.offset(hostElement, false) : this.position(hostElement, false);
    const shiftWidth: any = {
      left: hostElPosition.left,
      left2: (hostElPosition.left - 85),
      center: hostElPosition.left + hostElPosition.width / 2 - targetElement.offsetWidth / 2,
      right: hostElPosition.left + hostElPosition.width
    };
    const shiftHeight: any = {
      top: hostElPosition.top,
      center: hostElPosition.top + hostElPosition.height / 2 - targetElement.offsetHeight / 2,
      bottom: hostElPosition.top + hostElPosition.height
    };
    const targetElBCR = targetElement.getBoundingClientRect();
    const placementPrimary = placement.split('-')[0] || 'top';
    const placementSecondary = placement.split('-')[1] || 'center';

    let targetElPosition: ClientRect = {
      height: targetElBCR.height || targetElement.offsetHeight,
      width: targetElBCR.width || targetElement.offsetWidth,
      top: 0,
      bottom: targetElBCR.height || targetElement.offsetHeight,
      left: 0,
      right: targetElBCR.width || targetElement.offsetWidth
    };

    switch (placementPrimary) {
      case 'top':
        targetElPosition.top = hostElPosition.top - targetElement.offsetHeight;
        targetElPosition.bottom += hostElPosition.top - targetElement.offsetHeight;
        targetElPosition.left = shiftWidth[placementSecondary];
        targetElPosition.right += shiftWidth[placementSecondary];
        break;
      case 'bottom':
        targetElPosition.top = shiftHeight[placementPrimary];
        targetElPosition.bottom += shiftHeight[placementPrimary];
        targetElPosition.left = shiftWidth[placementSecondary];
        targetElPosition.right += shiftWidth[placementSecondary];
        break;
      case 'left':
        targetElPosition.top = shiftHeight[placementSecondary];
        targetElPosition.bottom += shiftHeight[placementSecondary];
        targetElPosition.left = hostElPosition.left - targetElement.offsetWidth;
        targetElPosition.right += hostElPosition.left - targetElement.offsetWidth;
        break;
      case 'right':
        targetElPosition.top = shiftHeight[placementSecondary];
        targetElPosition.bottom += shiftHeight[placementSecondary];
        targetElPosition.left = shiftWidth[placementPrimary];
        targetElPosition.right += shiftWidth[placementPrimary];
        break;

    }

    targetElPosition.top = Math.round(targetElPosition.top);
    targetElPosition.bottom = Math.round(targetElPosition.bottom);
    targetElPosition.left = Math.round(targetElPosition.left);
    targetElPosition.right = Math.round(targetElPosition.right);

    return targetElPosition;
  }
}

const positionService = new Positioning();
export function positionElements(
    hostElement: HTMLElement, targetElement: HTMLElement, placement: string, appendToBody?: boolean): void {
  const pos = positionService.positionElements(hostElement, targetElement, placement, appendToBody);

  targetElement.style.top = `${pos.top}px`;
  targetElement.style.left = `${pos.left}px`;
}