import { ConnectedFit, HorizontalAlignment, Point, PositionSettings, Size, Util, VerticalAlignment } from '../utilities';
import { ConnectedPositioningStrategy } from './connected-positioning-strategy';

export abstract class BaseFitPositionStrategy extends ConnectedPositioningStrategy {
    protected _initialSize: Size;
    protected _initialSettings: PositionSettings;

    /**
     * Position the element based on the PositionStrategy implementing this interface.
     *
     * @param contentElement The HTML element to be positioned
     * @param size Size of the element
     * @param document reference to the Document object
     * @param initialCall should be true if this is the initial call to the method
     * @param target attaching target for the component to show
     * ```typescript
     * settings.positionStrategy.position(content, size, document, true);
     * ```
     */
    public override position(
        contentElement: HTMLElement, size: Size, document?: Document, initialCall?: boolean, target?: Point | HTMLElement): void {
        const targetElement = target || this.settings.target;
        const rects = super.calculateElementRectangles(contentElement, targetElement);
        const connectedFit: ConnectedFit = {};
        if (initialCall) {
            connectedFit.targetRect = rects.targetRect;
            connectedFit.contentElementRect = rects.elementRect;
            this._initialSettings = this._initialSettings || Object.assign({}, this.settings);
            this.settings = Object.assign({}, this._initialSettings);
            connectedFit.viewPortRect = Util.getViewportRect(document);
            this.updateViewPortFit(connectedFit);
            if (this.shouldFitInViewPort(connectedFit)) {
                this.fitInViewport(contentElement, connectedFit);
            }
        }
        this.setStyle(contentElement, rects.targetRect, rects.elementRect, connectedFit);
    }

    /**
     * Checks if element can fit in viewport and updates provided connectedFit
     * with the result
     *
     * @param connectedFit connectedFit to update
     */
    protected updateViewPortFit(connectedFit: ConnectedFit) {
        connectedFit.left = this.calculateLeft(
            connectedFit.targetRect,
            connectedFit.contentElementRect,
            this.settings.horizontalStartPoint,
            this.settings.horizontalDirection,
            connectedFit.horizontalOffset ? connectedFit.horizontalOffset : 0);
        connectedFit.right = connectedFit.left + connectedFit.contentElementRect.width;
        connectedFit.fitHorizontal = {
            back: Math.round(connectedFit.left),
            forward: Math.round(connectedFit.viewPortRect.width - connectedFit.right)
        };

        connectedFit.top = this.calculateTop(
            connectedFit.targetRect,
            connectedFit.contentElementRect,
            this.settings.verticalStartPoint,
            this.settings.verticalDirection,
            connectedFit.verticalOffset ? connectedFit.verticalOffset : 0);
        connectedFit.bottom = connectedFit.top + connectedFit.contentElementRect.height;
        connectedFit.fitVertical = {
            back: Math.round(connectedFit.top),
            forward: Math.round(connectedFit.viewPortRect.height - connectedFit.bottom)
        };
    }

    /**
     * Calculates the position of the left border of the element if it gets positioned
     * with provided start point and direction
     *
     * @param targetRect Rectangle of the target where element is attached
     * @param elementRect Rectangle of the element
     * @param startPoint Start point of the target
     * @param direction Direction in which to show the element
     */
    protected calculateLeft(
        targetRect: Partial<DOMRect>,
        elementRect: Partial<DOMRect>,
        startPoint: HorizontalAlignment,
        direction: HorizontalAlignment,
        offset?: number): number {
        return targetRect.right + targetRect.width * startPoint + elementRect.width * direction + offset;
    }

    /**
     * Calculates the position of the top border of the element if it gets positioned
     * with provided position settings related to the target
     *
     * @param targetRect Rectangle of the target where element is attached
     * @param elementRect Rectangle of the element
     * @param startPoint Start point of the target
     * @param direction Direction in which to show the element
     */
    protected calculateTop(
        targetRect: Partial<DOMRect>,
        elementRect: Partial<DOMRect>,
        startPoint: VerticalAlignment,
        direction: VerticalAlignment,
        offset?: number): number {
        return targetRect.bottom + targetRect.height * startPoint + elementRect.height * direction + offset;
    }

    /**
     * Returns whether the element should fit in viewport
     *
     * @param connectedFit connectedFit object containing all necessary parameters
     */
    protected shouldFitInViewPort(connectedFit: ConnectedFit) {
        return connectedFit.fitHorizontal.back < 0 || connectedFit.fitHorizontal.forward < 0 ||
            connectedFit.fitVertical.back < 0 || connectedFit.fitVertical.forward < 0;
    }

    /**
     * Fits the element into viewport according to the position settings
     *
     * @param element element to fit in viewport
     * @param connectedFit connectedFit object containing all necessary parameters
     */
    protected abstract fitInViewport(
        element: HTMLElement,
        connectedFit: ConnectedFit);
}