import { warn } from '../utils';
class ZIndexManager {
    constructor() {
        this.elementZIndex = new Map();
        this.nextZIndex = 2000;
    }
    get elementCount() {
        return this.elementZIndex.size;
    }
    ensureZIndex(el, zIndex) {
        const { elementZIndex } = this;
        if (zIndex !== undefined) {
            el.style.zIndex = `${zIndex}`;
            elementZIndex.delete(el);
            return;
        }
        const { nextZIndex } = this;
        if (elementZIndex.has(el)) {
            const currentZIndex = elementZIndex.get(el);
            if (currentZIndex + 1 === this.nextZIndex)
                return;
        }
        el.style.zIndex = `${nextZIndex}`;
        elementZIndex.set(el, nextZIndex);
        this.nextZIndex = nextZIndex + 1;
        this.squashState();
    }
    unregister(el, zIndex) {
        const { elementZIndex } = this;
        if (elementZIndex.has(el)) {
            elementZIndex.delete(el);
        }
        else if (zIndex === undefined) {
            warn('z-index-manager/unregister-element', 'Element not found when unregistering.');
        }
        this.squashState();
    }
    squashState() {
        const { elementCount } = this;
        if (!elementCount) {
            this.nextZIndex = 2000;
        }
        if (this.nextZIndex - elementCount > 2500)
            this.rearrange();
    }
    rearrange() {
        const elementZIndexPair = Array.from(this.elementZIndex.entries());
        elementZIndexPair.sort((pair1, pair2) => {
            return pair1[1] - pair2[1];
        });
        this.nextZIndex = 2000;
        elementZIndexPair.forEach((pair) => {
            const el = pair[0];
            const zIndex = this.nextZIndex++;
            if (`${zIndex}` !== el.style.zIndex)
                el.style.zIndex = `${zIndex}`;
        });
    }
}
export default new ZIndexManager();