'use strict';

/**
 *  `callWhenHrefChanges(callback)`
 *
 *  Schedules a callback to be called whenever the browser's URL
 *  (`window.location.href`) changes.
 *
 */
let callWhenHrefChanges = (() => {

    // =========================================================================

    // Stores previous href location.
    let prev = '';

    // Stores functions to be called
    let functions = new Array();

    // =========================================================================

    /** Checks if the URL has changed. Updates the `prev` if so. */
    function hasHrefChanged() {
        let hasChanged = false;
        const href = window.location.href;

        if ( href != prev ) {
            prev = href;
            hasChanged = true;
        }

        return hasChanged;
    }

    /** Call every function scheduled to be called on URL changes. */
    function callFunctions() {
        functions.forEach( f => f() );
    }

    /** Schedule a function to be called when the browsers URL changes. */
    function callWhenHrefChanges(callback) {
        functions.push(callback);
    }

    // == Main Async Loop ======================================================

    setInterval(() => {

        if ( hasHrefChanged() ) {
            callFunctions();
        }

    }, 250);

    // =========================================================================

    return callWhenHrefChanges;

})();