/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { Injectable } from '@angular/core';
import * as i0 from "@angular/core";
/** Injectable that ensures only the most recently enabled FocusTrap is active. */
export class FocusTrapManager {
    constructor() {
        // A stack of the FocusTraps on the page. Only the FocusTrap at the
        // top of the stack is active.
        this._focusTrapStack = [];
    }
    /**
     * Disables the FocusTrap at the top of the stack, and then pushes
     * the new FocusTrap onto the stack.
     */
    register(focusTrap) {
        // Dedupe focusTraps that register multiple times.
        this._focusTrapStack = this._focusTrapStack.filter(ft => ft !== focusTrap);
        let stack = this._focusTrapStack;
        if (stack.length) {
            stack[stack.length - 1]._disable();
        }
        stack.push(focusTrap);
        focusTrap._enable();
    }
    /**
     * Removes the FocusTrap from the stack, and activates the
     * FocusTrap that is the new top of the stack.
     */
    deregister(focusTrap) {
        focusTrap._disable();
        const stack = this._focusTrapStack;
        const i = stack.indexOf(focusTrap);
        if (i !== -1) {
            stack.splice(i, 1);
            if (stack.length) {
                stack[stack.length - 1]._enable();
            }
        }
    }
    static { this.ɵfac = i0.ɵɵngDeclareFactory({ minVersion: "12.0.0", version: "16.1.1", ngImport: i0, type: FocusTrapManager, deps: [], target: i0.ɵɵFactoryTarget.Injectable }); }
    static { this.ɵprov = i0.ɵɵngDeclareInjectable({ minVersion: "12.0.0", version: "16.1.1", ngImport: i0, type: FocusTrapManager, providedIn: 'root' }); }
}
i0.ɵɵngDeclareClassMetadata({ minVersion: "12.0.0", version: "16.1.1", ngImport: i0, type: FocusTrapManager, decorators: [{
            type: Injectable,
            args: [{ providedIn: 'root' }]
        }] });
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