// ==UserScript==
// @name         北大树洞去水印
// @namespace    http://tampermonkey.net/
// @version      1.0.0
// @description  北大树洞去水印
// @match        *://treehole.pku.edu.cn/*
// @run-at       document-start
// @grant        GM_addStyle
// @grant        unsafeWindow
// ==/UserScript==

(function() {
    'use strict';
    const W = unsafeWindow, B = atob("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAC0lEQVQIW2NkAAIAAAoAAggV38AAAAAASUVORK5CYII="),
          A = new Uint8Array(B.length);
    for(let i=0;i<B.length;i++) A[i] = B.charCodeAt(i);
    const Z = new Blob([A], {type: 'image/png'});

    const isBad = u => u && (u.includes('mangshuiyin') || (u.includes('getImageBinary') && /[?&](texturedBgColor|id=[12](&|$))/.test(u)));

    const oF = W.fetch;
    W.fetch = (i, c) => isBad(i instanceof Request ? i.url : i) ?
        new Response(Z, {status: 200, headers: {'Content-Type': 'image/png'}}) : oF.apply(W, [i, c]);

    const X = W.XMLHttpRequest.prototype, oO = X.open, oS = X.send;
    X.open = function(m, u) { this._k = isBad(u); return oO.apply(this, arguments); };
    X.send = function(b) {
        if (this._k) {
            ['status','statusText','response','responseText','responseType','readyState'].forEach((k,i)=>
                Object.defineProperty(this, k, {value: [200,'OK',Z,'','blob',4][i]}));
            return setTimeout(()=>['onreadystatechange','onload','onloadend'].forEach(e=>this[e]&&this[e]()), 1);
        }
        return oS.apply(this, arguments);
    };

    GM_addStyle('canvas{display:none!important;opacity:0!important;width:0!important;height:0!important}.replyItem{background-color:var(--theme_bgc_color,#f5f5f5)!important}html.dark .replyItem{background-color:#2c2c2c!important}');

    new MutationObserver(ms => ms.forEach(m => m.addedNodes.forEach(n => n.tagName === 'CANVAS' && (n.style.display = 'none'))))
        .observe(document, {childList: true, subtree: true});
})();