/**
 * AKSRT Page Loader
 *
 * Lightweight top progress bar for page transitions and AJAX requests.
 * No external dependencies — pure vanilla JS.
 *
 * @package AKSRT
 */

(function () {
  'use strict';

  var STYLE_ID = 'aksrt-loader-style';
  var BAR_ID = 'aksrt-loader-bar';
  var CSS =
    '#' + BAR_ID + '{' +
      'position:fixed;top:0;left:0;width:0;height:3px;z-index:99999;' +
      'background:linear-gradient(90deg,#1890ff,#36cfc9);' +
      'transition:width 0.3s ease,opacity 0.3s ease;' +
      'pointer-events:none;opacity:0;' +
    '}' +
    '#' + BAR_ID + '.is-active{opacity:1;}' +
    '#' + BAR_ID + '.is-done{' +
      'width:100%!important;opacity:0;' +
    '}';

  var bar = null;
  var timer = null;
  var progress = 0;

  function injectStyle() {
    if (document.getElementById(STYLE_ID)) return;
    var style = document.createElement('style');
    style.id = STYLE_ID;
    style.textContent = CSS;
    document.head.appendChild(style);
  }

  function createBar() {
    if (bar) return;
    bar = document.createElement('div');
    bar.id = BAR_ID;
    document.body.appendChild(bar);
  }

  function start() {
    if (!bar) createBar();
    clearTimeout(timer);
    bar.classList.remove('is-done');
    bar.classList.add('is-active');
    progress = 0;
    bar.style.width = '0%';
    trickle();
  }

  function trickle() {
    if (progress >= 90) return;
    var increment = progress < 30 ? 8 : progress < 60 ? 4 : 2;
    progress = Math.min(90, progress + increment * (0.8 + Math.random() * 0.4));
    bar.style.width = progress + '%';
    timer = setTimeout(trickle, 200 + Math.random() * 300);
  }

  function done() {
    if (!bar) return;
    clearTimeout(timer);
    bar.style.width = '100%';
    bar.classList.add('is-done');
    setTimeout(function () {
      bar.classList.remove('is-active', 'is-done');
      bar.style.width = '0%';
      progress = 0;
    }, 400);
  }

  // Intercept link clicks for same-origin page transitions
  function onLinkClick(e) {
    if (e.defaultPrevented) return;
    if (e.button !== 0) return; // left click only
    if (e.metaKey || e.ctrlKey || e.shiftKey || e.altKey) return;

    var link = e.target.closest('a');
    if (!link || !link.href) return;
    if (link.target === '_blank') return;
    if (link.hasAttribute('download')) return;
    if (link.href.indexOf('#') === 0) return;

    // Same-origin only
    try {
      var url = new URL(link.href);
      if (url.origin !== window.location.origin) return;
      if (url.protocol !== "http:" && url.protocol !== "https:") return;
      if (url.pathname === window.location.pathname && url.search === window.location.search) return;
    } catch (ex) { return; }

    start();
  }

  // Intercept form submissions
  function onFormSubmit(e) {
    var form = e.target;
    if (!form || form.tagName !== 'FORM') return;
    if (form.target === '_blank') return;
    start();
  }

  // Hook into AJAX (fetch) if available
  function hookFetch() {
    if (!window.fetch) return;
    var origFetch = window.fetch;
    window.fetch = function () {
      start();
      return origFetch.apply(this, arguments).then(function (response) {
        done();
        return response;
      }).catch(function (err) {
        done();
        throw err;
      });
    };
  }

  // Hook into XMLHttpRequest
  function hookXHR() {
    if (!window.XMLHttpRequest) return;
    var origOpen = XMLHttpRequest.prototype.open;
    var origSend = XMLHttpRequest.prototype.send;

    XMLHttpRequest.prototype.open = function () {
      this._aksrtLoader = true;
      return origOpen.apply(this, arguments);
    };

    XMLHttpRequest.prototype.send = function () {
      if (this._aksrtLoader) {
        start();
        var self = this;
        this.addEventListener('loadend', function () { done(); });
      }
      return origSend.apply(this, arguments);
    };
  }

  function init() {
    injectStyle();
    createBar();

    document.addEventListener('click', onLinkClick, true);
    document.addEventListener('submit', onFormSubmit, true);

    // Done on page load (handles bfcache)
    window.addEventListener('pageshow', function (e) {
      if (e.persisted) done();
    });
    window.addEventListener('load', done);

    hookFetch();
    hookXHR();
  }

  // Public API
  window.AksrtLoader = {
    start: start,
    done: done
  };

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', init);
  } else {
    init();
  }
})();