uBlock/src/js/contentscript.js

/*******************************************************************************

    uBlock Origin - a browser extension to block requests.
    Copyright (C) 2014-present Raymond Hill

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://github.com/gorhill/uBlock
*/

'use strict';

/*******************************************************************************

              +--> domCollapser
              |
              |
  domWatcher--+
              |                  +-- domSurveyor
              |                  |
              +--> domFilterer --+-- domLogger
                                 |
                                 +-- domInspector

  domWatcher:
    Watches for changes in the DOM, and notify the other components about these
    changes.

  domCollapser:
    Enforces the collapsing of DOM elements for which a corresponding
    resource was blocked through network filtering.

  domFilterer:
    Enforces the filtering of DOM elements, by feeding it cosmetic filters.

  domSurveyor:
    Surveys the DOM to find new cosmetic filters to apply to the current page.

  domLogger:
    Surveys the page to find and report the injected cosmetic filters blocking
    actual elements on the current page. This component is dynamically loaded
    IF AND ONLY IF uBO's logger is opened.

  If page is whitelisted:
    - domWatcher: off
    - domCollapser: off
    - domFilterer: off
    - domSurveyor: off
    - domLogger: off

  I verified that the code in this file is completely flushed out of memory
  when a page is whitelisted.

  If cosmetic filtering is disabled:
    - domWatcher: on
    - domCollapser: on
    - domFilterer: off
    - domSurveyor: off
    - domLogger: off

  If generic cosmetic filtering is disabled:
    - domWatcher: on
    - domCollapser: on
    - domFilterer: on
    - domSurveyor: off
    - domLogger: on if uBO logger is opened

  If generic cosmetic filtering is enabled:
    - domWatcher: on
    - domCollapser: on
    - domFilterer: on
    - domSurveyor: on
    - domLogger: on if uBO logger is opened

  Additionally, the domSurveyor can turn itself off once it decides that
  it has become pointless (repeatedly not finding new cosmetic filters).

  The domFilterer makes use of platform-dependent user stylesheets[1].

  At time of writing, only modern Firefox provides a custom implementation,
  which makes for solid, reliable and low overhead cosmetic filtering on
  Firefox.

  The generic implementation[2] performs as best as can be, but won't ever be
  as reliable and accurate as real user stylesheets.

  [1] "user stylesheets" refer to local CSS rules which have priority over,
       and can't be overriden by a web page's own CSS rules.
  [2] below, see platformUserCSS / platformHideNode / platformUnhideNode

*/

// Abort execution if our global vAPI object does not exist.
//   https://github.com/chrisaljoudi/uBlock/issues/456
//   https://github.com/gorhill/uBlock/issues/2029

 // >>>>>>>> start of HUGE-IF-BLOCK
if ( typeof vAPI === 'object' && !vAPI.contentScript ) {

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.contentScript = true;

/******************************************************************************/
/******************************************************************************/
/*******************************************************************************

  The purpose of SafeAnimationFrame is to take advantage of the behavior of
  window.requestAnimationFrame[1]. If we use an animation frame as a timer,
  then this timer is described as follow:

  - time events are throttled by the browser when the viewport is not visible --
    there is no point for uBO to play with the DOM if the document is not
    visible.
  - time events are micro tasks[2].
  - time events are synchronized to monitor refresh, meaning that they can fire
    at most 1/60 (typically).

  If a delay value is provided, a plain timer is first used. Plain timers are
  macro-tasks, so this is good when uBO wants to yield to more important tasks
  on a page. Once the plain timer elapse, an animation frame is used to trigger
  the next time at which to execute the job.

  [1] https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame
  [2] https://jakearchibald.com/2015/tasks-microtasks-queues-and-schedules/

*/

// https://github.com/gorhill/uBlock/issues/2147

vAPI.SafeAnimationFrame = function(callback) {
    this.fid = this.tid = undefined;
    this.callback = callback;
};

vAPI.SafeAnimationFrame.prototype = {
    start: function(delay) {
        if ( delay === undefined ) {
            if ( this.fid === undefined ) {
                this.fid = requestAnimationFrame(( ) => { this.onRAF(); } );
            }
            if ( this.tid === undefined ) {
                this.tid = vAPI.setTimeout(( ) => { this.onSTO(); }, 20000);
            }
            return;
        }
        if ( this.fid === undefined && this.tid === undefined ) {
            this.tid = vAPI.setTimeout(( ) => { this.macroToMicro(); }, delay);
        }
    },
    clear: function() {
        if ( this.fid !== undefined ) {
            cancelAnimationFrame(this.fid);
            this.fid = undefined;
        }
        if ( this.tid !== undefined ) {
            clearTimeout(this.tid);
            this.tid = undefined;
        }
    },
    macroToMicro: function() {
        this.tid = undefined;
        this.start();
    },
    onRAF: function() {
        if ( this.tid !== undefined ) {
            clearTimeout(this.tid);
            this.tid = undefined;
        }
        this.fid = undefined;
        this.callback();
    },
    onSTO: function() {
        if ( this.fid !== undefined ) {
            cancelAnimationFrame(this.fid);
            this.fid = undefined;
        }
        this.tid = undefined;
        this.callback();
    },
};

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.domWatcher = (function() {

    const addedNodeLists = [];
    const removedNodeLists = [];
    const addedNodes = [];
    const ignoreTags = new Set([ 'br', 'head', 'link', 'meta', 'script', 'style' ]);
    const listeners = [];

    let domIsReady = false,
        domLayoutObserver,
        listenerIterator = [], listenerIteratorDirty = false,
        removedNodes = false,
        safeObserverHandlerTimer;

    const safeObserverHandler = function() {
        //console.time('dom watcher/safe observer handler');
        let i = addedNodeLists.length,
            j = addedNodes.length;
        while ( i-- ) {
            const nodeList = addedNodeLists[i];
            let iNode = nodeList.length;
            while ( iNode-- ) {
                const node = nodeList[iNode];
                if ( node.nodeType !== 1 ) { continue; }
                if ( ignoreTags.has(node.localName) ) { continue; }
                if ( node.parentElement === null ) { continue; }
                addedNodes[j++] = node;
            }
        }
        addedNodeLists.length = 0;
        i = removedNodeLists.length;
        while ( i-- && removedNodes === false ) {
            const nodeList = removedNodeLists[i];
            let iNode = nodeList.length;
            while ( iNode-- ) {
                if ( nodeList[iNode].nodeType !== 1 ) { continue; }
                removedNodes = true;
                break;
            }
        }
        removedNodeLists.length = 0;
        //console.timeEnd('dom watcher/safe observer handler');
        if ( addedNodes.length === 0 && removedNodes === false ) { return; }
        for ( const listener of getListenerIterator() ) {
            listener.onDOMChanged(addedNodes, removedNodes);
        }
        addedNodes.length = 0;
        removedNodes = false;
    };

    // https://github.com/chrisaljoudi/uBlock/issues/205
    // Do not handle added node directly from within mutation observer.
    const observerHandler = function(mutations) {
        //console.time('dom watcher/observer handler');
        let i = mutations.length;
        while ( i-- ) {
            const mutation = mutations[i];
            let nodeList = mutation.addedNodes;
            if ( nodeList.length !== 0 ) {
                addedNodeLists.push(nodeList);
            }
            nodeList = mutation.removedNodes;
            if ( nodeList.length !== 0 ) {
                removedNodeLists.push(nodeList);
            }
        }
        if ( addedNodeLists.length !== 0 || removedNodes ) {
            safeObserverHandlerTimer.start(
                addedNodeLists.length < 100 ? 1 : undefined
            );
        }
        //console.timeEnd('dom watcher/observer handler');
    };

    const startMutationObserver = function() {
        if ( domLayoutObserver !== undefined || !domIsReady ) { return; }
        domLayoutObserver = new MutationObserver(observerHandler);
        domLayoutObserver.observe(document.documentElement, {
            //attributeFilter: [ 'class', 'id' ],
            //attributes: true,
            childList: true,
            subtree: true
        });
        safeObserverHandlerTimer = new vAPI.SafeAnimationFrame(safeObserverHandler);
        vAPI.shutdown.add(cleanup);
    };

    const stopMutationObserver = function() {
        if ( domLayoutObserver === undefined ) { return; }
        cleanup();
        vAPI.shutdown.remove(cleanup);
    };

    const getListenerIterator = function() {
        if ( listenerIteratorDirty ) {
            listenerIterator = listeners.slice();
            listenerIteratorDirty = false;
        }
        return listenerIterator;
    };

    const addListener = function(listener) {
        if ( listeners.indexOf(listener) !== -1 ) { return; }
        listeners.push(listener);
        listenerIteratorDirty = true;
        if ( domIsReady !== true ) { return; }
        listener.onDOMCreated();
        startMutationObserver();
    };

    const removeListener = function(listener) {
        const pos = listeners.indexOf(listener);
        if ( pos === -1 ) { return; }
        listeners.splice(pos, 1);
        listenerIteratorDirty = true;
        if ( listeners.length === 0 ) {
            stopMutationObserver();
        }
    };

    const cleanup = function() {
        if ( domLayoutObserver !== undefined ) {
            domLayoutObserver.disconnect();
            domLayoutObserver = null;
        }
        if ( safeObserverHandlerTimer !== undefined ) {
            safeObserverHandlerTimer.clear();
            safeObserverHandlerTimer = undefined;
        }
    };

    const start = function() {
        domIsReady = true;
        for ( const listener of getListenerIterator() ) {
            listener.onDOMCreated();
        }
        startMutationObserver();
    };

    return { start, addListener, removeListener };
})();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.matchesProp = (function() {
    const docElem = document.documentElement;
    if ( typeof docElem.matches !== 'function' ) {
        if ( typeof docElem.mozMatchesSelector === 'function' ) {
            return 'mozMatchesSelector';
        } else if ( typeof docElem.webkitMatchesSelector === 'function' ) {
            return 'webkitMatchesSelector';
        } else if ( typeof docElem.msMatchesSelector === 'function' ) {
            return 'msMatchesSelector';
        }
    }
    return 'matches';
})();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.injectScriptlet = function(doc, text) {
    if ( !doc ) { return; }
    let script;
    try {
        script = doc.createElement('script');
        script.appendChild(doc.createTextNode(text));
        (doc.head || doc.documentElement).appendChild(script);
    } catch (ex) {
    }
    if ( script ) {
        if ( script.parentNode ) {
            script.parentNode.removeChild(script);
        }
        script.textContent = '';
    }
};

/******************************************************************************/
/******************************************************************************/
/*******************************************************************************

  The DOM filterer is the heart of uBO's cosmetic filtering.

  DOMBaseFilterer: platform-specific
  |
  |
  +---- DOMFilterer: adds procedural cosmetic filtering

*/

vAPI.DOMFilterer = (function() {

    // 'P' stands for 'Procedural'

    const PSelectorHasTextTask = function(task) {
        let arg0 = task[1], arg1;
        if ( Array.isArray(task[1]) ) {
            arg1 = arg0[1]; arg0 = arg0[0];
        }
        this.needle = new RegExp(arg0, arg1);
    };
    PSelectorHasTextTask.prototype.exec = function(input) {
        const output = [];
        for ( const node of input ) {
            if ( this.needle.test(node.textContent) ) {
                output.push(node);
            }
        }
        return output;
    };

    const PSelectorIfTask = function(task) {
        this.pselector = new PSelector(task[1]);
    };
    PSelectorIfTask.prototype.target = true;
    PSelectorIfTask.prototype.exec = function(input) {
        const output = [];
        for ( const node of input ) {
            if ( this.pselector.test(node) === this.target ) {
                output.push(node);
            }
        }
        return output;
    };

    const PSelectorIfNotTask = function(task) {
        PSelectorIfTask.call(this, task);
        this.target = false;
    };
    PSelectorIfNotTask.prototype = Object.create(PSelectorIfTask.prototype);
    PSelectorIfNotTask.prototype.constructor = PSelectorIfNotTask;

    const PSelectorMatchesCSSTask = function(task) {
        this.name = task[1].name;
        let arg0 = task[1].value, arg1;
        if ( Array.isArray(arg0) ) {
            arg1 = arg0[1]; arg0 = arg0[0];
        }
        this.value = new RegExp(arg0, arg1);
    };
    PSelectorMatchesCSSTask.prototype.pseudo = null;
    PSelectorMatchesCSSTask.prototype.exec = function(input) {
        const output = [];
        for ( const node of input ) {
            const style = window.getComputedStyle(node, this.pseudo);
            if ( style === null ) { return null; } /* FF */
            if ( this.value.test(style[this.name]) ) {
                output.push(node);
            }
        }
        return output;
    };

    const PSelectorMatchesCSSAfterTask = function(task) {
        PSelectorMatchesCSSTask.call(this, task);
        this.pseudo = ':after';
    };
    PSelectorMatchesCSSAfterTask.prototype = Object.create(PSelectorMatchesCSSTask.prototype);
    PSelectorMatchesCSSAfterTask.prototype.constructor = PSelectorMatchesCSSAfterTask;

    const PSelectorMatchesCSSBeforeTask = function(task) {
        PSelectorMatchesCSSTask.call(this, task);
        this.pseudo = ':before';
    };
    PSelectorMatchesCSSBeforeTask.prototype = Object.create(PSelectorMatchesCSSTask.prototype);
    PSelectorMatchesCSSBeforeTask.prototype.constructor = PSelectorMatchesCSSBeforeTask;

    const PSelectorSpathTask = function(task) {
        this.spath = task[1];
    };
    PSelectorSpathTask.prototype.exec = function(input) {
        const output = [];
        for ( let node of input ) {
            const parent = node.parentElement;
            if ( parent === null ) { continue; }
            let pos = 1;
            for (;;) {
                node = node.previousElementSibling;
                if ( node === null ) { break; }
                pos += 1;
            }
            const nodes = parent.querySelectorAll(
                ':scope > :nth-child(' + pos + ')' + this.spath
            );
            for ( const node of nodes ) {
                output.push(node);
            }
        }
        return output;
    };

    const PSelectorWatchAttrs = function(task) {
        this.observer = null;
        this.observed = new WeakSet();
        this.observerOptions = {
            attributes: true,
            subtree: true,
        };
        const attrs = task[1];
        if ( Array.isArray(attrs) && attrs.length !== 0 ) {
            this.observerOptions.attributeFilter = task[1];
        }
    };
    // TODO: Is it worth trying to re-apply only the current selector?
    PSelectorWatchAttrs.prototype.handler = function() {
        const filterer =
            vAPI.domFilterer && vAPI.domFilterer.proceduralFilterer;
        if ( filterer instanceof Object ) {
            filterer.onDOMChanged([ null ]);
        }
    };
    PSelectorWatchAttrs.prototype.exec = function(input) {
        if ( input.length === 0 ) { return input; }
        if ( this.observer === null ) {
            this.observer = new MutationObserver(this.handler);
        }
        for ( const node of input ) {
            if ( this.observed.has(node) ) { continue; }
            this.observer.observe(node, this.observerOptions);
            this.observed.add(node);
        }
        return input;
    };

    const PSelectorXpathTask = function(task) {
        this.xpe = document.createExpression(task[1], null);
        this.xpr = null;
    };
    PSelectorXpathTask.prototype.exec = function(input) {
        const output = [];
        for ( const node of input ) {
            this.xpr = this.xpe.evaluate(
                node,
                XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
                this.xpr
            );
            let j = this.xpr.snapshotLength;
            while ( j-- ) {
                const node = this.xpr.snapshotItem(j);
                if ( node.nodeType === 1 ) {
                    output.push(node);
                }
            }
        }
        return output;
    };

    const PSelector = function(o) {
        if ( PSelector.prototype.operatorToTaskMap === undefined ) {
            PSelector.prototype.operatorToTaskMap = new Map([
                [ ':has', PSelectorIfTask ],
                [ ':has-text', PSelectorHasTextTask ],
                [ ':if', PSelectorIfTask ],
                [ ':if-not', PSelectorIfNotTask ],
                [ ':matches-css', PSelectorMatchesCSSTask ],
                [ ':matches-css-after', PSelectorMatchesCSSAfterTask ],
                [ ':matches-css-before', PSelectorMatchesCSSBeforeTask ],
                [ ':not', PSelectorIfNotTask ],
                [ ':spath', PSelectorSpathTask ],
                [ ':watch-attrs', PSelectorWatchAttrs ],
                [ ':xpath', PSelectorXpathTask ],
            ]);
        }
        this.budget = 200; // I arbitrary picked a 1/5 second
        this.raw = o.raw;
        this.cost = 0;
        this.lastAllowanceTime = 0;
        this.selector = o.selector;
        this.tasks = [];
        const tasks = o.tasks;
        if ( !tasks ) { return; }
        for ( const task of tasks ) {
            this.tasks.push(new (this.operatorToTaskMap.get(task[0]))(task));
        }
    };
    PSelector.prototype.operatorToTaskMap = undefined;
    PSelector.prototype.prime = function(input) {
        const root = input || document;
        if ( this.selector !== '' ) {
            return root.querySelectorAll(this.selector);
        }
        return [ root ];
    };
    PSelector.prototype.exec = function(input) {
        let nodes = this.prime(input);
        for ( const task of this.tasks ) {
            if ( nodes.length === 0 ) { break; }
            nodes = task.exec(nodes);
        }
        return nodes;
    };
    PSelector.prototype.test = function(input) {
        const nodes = this.prime(input);
        const AA = [ null ];
        for ( const node of nodes ) {
            AA[0] = node;
            let aa = AA;
            for ( const task of this.tasks ) {
                aa = task.exec(aa);
                if ( aa.length === 0 ) { break; }
            }
            if ( aa.length !== 0 ) { return true; }
        }
        return false;
    };

    const DOMProceduralFilterer = function(domFilterer) {
        this.domFilterer = domFilterer;
        this.domIsReady = false;
        this.domIsWatched = false;
        this.mustApplySelectors = false;
        this.selectors = new Map();
        this.hiddenNodes = new Set();
    };

    DOMProceduralFilterer.prototype = {

        addProceduralSelectors: function(aa) {
            const addedSelectors = [];
            let mustCommit = this.domIsWatched;
            for ( let i = 0, n = aa.length; i < n; i++ ) {
                const raw = aa[i];
                const o = JSON.parse(raw);
                if ( o.style ) {
                    this.domFilterer.addCSSRule(o.style[0], o.style[1]);
                    mustCommit = true;
                    continue;
                }
                if ( o.pseudoclass ) {
                    this.domFilterer.addCSSRule(
                        o.raw,
                        'display:none!important;'
                    );
                    mustCommit = true;
                    continue;
                }
                if ( o.tasks ) {
                    if ( this.selectors.has(raw) === false ) {
                        const pselector = new PSelector(o);
                        this.selectors.set(raw, pselector);
                        addedSelectors.push(pselector);
                        mustCommit = true;
                    }
                    continue;
                }
            }
            if ( mustCommit === false ) { return; }
            this.mustApplySelectors = this.selectors.size !== 0;
            this.domFilterer.commit();
            if ( this.domFilterer.hasListeners() ) {
                this.domFilterer.triggerListeners({
                    procedural: addedSelectors
                });
            }
        },

        commitNow: function() {
            if ( this.selectors.size === 0 || this.domIsReady === false ) {
                return;
            }

            this.mustApplySelectors = false;

            //console.time('procedural selectors/dom layout changed');

            // https://github.com/uBlockOrigin/uBlock-issues/issues/341
            //   Be ready to unhide nodes which no longer matches any of
            //   the procedural selectors.
            const toRemove = this.hiddenNodes;
            this.hiddenNodes = new Set();

            let t0 = Date.now();

            for ( const entry of this.selectors ) {
                const pselector = entry[1];
                const allowance = Math.floor((t0 - pselector.lastAllowanceTime) / 2000);
                if ( allowance >= 1 ) {
                    pselector.budget += allowance * 50;
                    if ( pselector.budget > 200 ) { pselector.budget = 200; }
                    pselector.lastAllowanceTime = t0;
                }
                if ( pselector.budget <= 0 ) { continue; }
                const nodes = pselector.exec();
                const t1 = Date.now();
                pselector.budget += t0 - t1;
                if ( pselector.budget < -500 ) {
                    console.info('uBO: disabling %s', pselector.raw);
                    pselector.budget = -0x7FFFFFFF;
                }
                t0 = t1;
                for ( const node of nodes ) {
                    this.domFilterer.hideNode(node);
                    this.hiddenNodes.add(node);
                }
            }

            for ( const node of toRemove ) {
                if ( this.hiddenNodes.has(node) ) { continue; }
                this.domFilterer.unhideNode(node);
            }
            //console.timeEnd('procedural selectors/dom layout changed');
        },

        createProceduralFilter: function(o) {
            return new PSelector(o);
        },

        onDOMCreated: function() {
            this.domIsReady = true;
            this.domFilterer.commitNow();
        },

        onDOMChanged: function(addedNodes, removedNodes) {
            if ( this.selectors.size === 0 ) { return; }
            this.mustApplySelectors =
                this.mustApplySelectors ||
                addedNodes.length !== 0 ||
                removedNodes;
            this.domFilterer.commit();
        }
    };

    const DOMFiltererBase = vAPI.DOMFilterer;

    const domFilterer = function() {
        DOMFiltererBase.call(this);
        this.exceptions = [];
        this.proceduralFilterer = new DOMProceduralFilterer(this);
        this.hideNodeAttr = undefined;
        this.hideNodeStyleSheetInjected = false;

        // May or may not exist: cache locally since this may be called often.
        this.baseOnDOMChanged = DOMFiltererBase.prototype.onDOMChanged;

        if ( vAPI.domWatcher instanceof Object ) {
            vAPI.domWatcher.addListener(this);
        }
    };
    domFilterer.prototype = Object.create(DOMFiltererBase.prototype);
    domFilterer.prototype.constructor = domFilterer;

    domFilterer.prototype.commitNow = function() {
        DOMFiltererBase.prototype.commitNow.call(this);
        this.proceduralFilterer.commitNow();
    };

    domFilterer.prototype.addProceduralSelectors = function(aa) {
        this.proceduralFilterer.addProceduralSelectors(aa);
    };

    domFilterer.prototype.createProceduralFilter = function(o) {
        return this.proceduralFilterer.createProceduralFilter(o);
    };

    domFilterer.prototype.getAllSelectors = function() {
        const out = DOMFiltererBase.prototype.getAllSelectors.call(this);
        out.procedural = Array.from(this.proceduralFilterer.selectors.values());
        return out;
    };

    domFilterer.prototype.getAllExceptionSelectors = function() {
        return this.exceptions.join(',\n');
    };

    domFilterer.prototype.onDOMCreated = function() {
        if ( DOMFiltererBase.prototype.onDOMCreated !== undefined ) {
            DOMFiltererBase.prototype.onDOMCreated.call(this);
        }
        this.proceduralFilterer.onDOMCreated();
    };

    domFilterer.prototype.onDOMChanged = function() {
        if ( this.baseOnDOMChanged !== undefined ) {
            this.baseOnDOMChanged.apply(this, arguments);
        }
        this.proceduralFilterer.onDOMChanged.apply(
            this.proceduralFilterer,
            arguments
        );
    };

    return domFilterer;
})();

vAPI.domFilterer = new vAPI.DOMFilterer();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.domCollapser = (function() {
    const messaging = vAPI.messaging;
    const toCollapse = new Map();
    const src1stProps = {
        embed: 'src',
        iframe: 'src',
        img: 'src',
        object: 'data'
    };
    const src2ndProps = {
        img: 'srcset'
    };
    const tagToTypeMap = {
        embed: 'object',
        iframe: 'sub_frame',
        img: 'image',
        object: 'object'
    };

    let resquestIdGenerator = 1,
        processTimer,
        cachedBlockedSet,
        cachedBlockedSetHash,
        cachedBlockedSetTimer,
        toProcess = [],
        toFilter = [],
        netSelectorCacheCount = 0;

    const cachedBlockedSetClear = function() {
        cachedBlockedSet =
        cachedBlockedSetHash =
        cachedBlockedSetTimer = undefined;
    };

    // https://github.com/chrisaljoudi/uBlock/issues/174
    //   Do not remove fragment from src URL
    const onProcessed = function(response) {
        if ( !response ) { // This happens if uBO is disabled or restarted.
            toCollapse.clear();
            return;
        }

        const targets = toCollapse.get(response.id);
        if ( targets === undefined ) { return; }
        toCollapse.delete(response.id);
        if ( cachedBlockedSetHash !== response.hash ) {
            cachedBlockedSet = new Set(response.blockedResources);
            cachedBlockedSetHash = response.hash;
            if ( cachedBlockedSetTimer !== undefined ) {
                clearTimeout(cachedBlockedSetTimer);
            }
            cachedBlockedSetTimer = vAPI.setTimeout(cachedBlockedSetClear, 30000);
        }
        if ( cachedBlockedSet === undefined || cachedBlockedSet.size === 0 ) {
            return;
        }
        const selectors = [];
        const iframeLoadEventPatch = vAPI.iframeLoadEventPatch;
        let netSelectorCacheCountMax = response.netSelectorCacheCountMax;

        for ( const target of targets ) {
            const tag = target.localName;
            let prop = src1stProps[tag];
            if ( prop === undefined ) { continue; }
            let src = target[prop];
            if ( typeof src !== 'string' || src.length === 0 ) {
                prop = src2ndProps[tag];
                if ( prop === undefined ) { continue; }
                src = target[prop];
                if ( typeof src !== 'string' || src.length === 0 ) { continue; }
            }
            if ( cachedBlockedSet.has(tagToTypeMap[tag] + ' ' + src) === false ) {
                continue;
            }
            // https://github.com/chrisaljoudi/uBlock/issues/399
            // Never remove elements from the DOM, just hide them
            target.style.setProperty('display', 'none', 'important');
            target.hidden = true;
            // https://github.com/chrisaljoudi/uBlock/issues/1048
            // Use attribute to construct CSS rule
            if ( netSelectorCacheCount <= netSelectorCacheCountMax ) {
                const value = target.getAttribute(prop);
                if ( value ) {
                    selectors.push(tag + '[' + prop + '="' + value + '"]');
                    netSelectorCacheCount += 1;
                }
            }
            if ( iframeLoadEventPatch !== undefined ) {
                iframeLoadEventPatch(target);
            }
        }

        if ( selectors.length !== 0 ) {
            messaging.send(
                'contentscript',
                {
                    what: 'cosmeticFiltersInjected',
                    type: 'net',
                    hostname: window.location.hostname,
                    selectors: selectors
                }
            );
        }
    };

    const send = function() {
        processTimer = undefined;
        toCollapse.set(resquestIdGenerator, toProcess);
        const msg = {
            what: 'getCollapsibleBlockedRequests',
            id: resquestIdGenerator,
            frameURL: window.location.href,
            resources: toFilter,
            hash: cachedBlockedSetHash
        };
        messaging.send('contentscript', msg, onProcessed);
        toProcess = [];
        toFilter = [];
        resquestIdGenerator += 1;
    };

    const process = function(delay) {
        if ( toProcess.length === 0 ) { return; }
        if ( delay === 0 ) {
            if ( processTimer !== undefined ) {
                clearTimeout(processTimer);
            }
            send();
        } else if ( processTimer === undefined ) {
            processTimer = vAPI.setTimeout(send, delay || 20);
        }
    };

    const add = function(target) {
        toProcess[toProcess.length] = target;
    };

    const addMany = function(targets) {
        for ( const target of targets ) {
            add(target);
        }
    };

    const iframeSourceModified = function(mutations) {
        for ( const mutation of mutations ) {
            addIFrame(mutation.target, true);
        }
        process();
    };
    const iframeSourceObserver = new MutationObserver(iframeSourceModified);
    const iframeSourceObserverOptions = {
        attributes: true,
        attributeFilter: [ 'src' ]
    };

    // The injected scriptlets are those which were injected in the current
    // document, from within `bootstrapPhase1`, and which scriptlets are
    // selectively looked-up from:
    // https://github.com/uBlockOrigin/uAssets/blob/master/filters/resources.txt
    const primeLocalIFrame = function(iframe) {
        if ( vAPI.injectedScripts ) {
            vAPI.injectScriptlet(iframe.contentDocument, vAPI.injectedScripts);
        }
    };

    // https://github.com/gorhill/uBlock/issues/162
    // Be prepared to deal with possible change of src attribute.
    const addIFrame = function(iframe, dontObserve) {
        if ( dontObserve !== true ) {
            iframeSourceObserver.observe(iframe, iframeSourceObserverOptions);
        }
        const src = iframe.src;
        if ( src === '' || typeof src !== 'string' ) {
            primeLocalIFrame(iframe);
            return;
        }
        if ( src.startsWith('http') === false ) { return; }
        toFilter.push({ type: 'sub_frame', url: iframe.src });
        add(iframe);
    };

    const addIFrames = function(iframes) {
        for ( const iframe of iframes ) {
            addIFrame(iframe);
        }
    };

    const onResourceFailed = function(ev) {
        if ( tagToTypeMap[ev.target.localName] !== undefined ) {
            add(ev.target);
            process();
        }
    };

    const domWatcherInterface = {
        onDOMCreated: function() {
            if ( vAPI instanceof Object === false ) { return; }
            if ( vAPI.domCollapser instanceof Object === false ) {
                if ( vAPI.domWatcher instanceof Object ) {
                    vAPI.domWatcher.removeListener(domWatcherInterface);
                }
                return;
            }
            // Listener to collapse blocked resources.
            // - Future requests not blocked yet
            // - Elements dynamically added to the page
            // - Elements which resource URL changes
            // https://github.com/chrisaljoudi/uBlock/issues/7
            // Preferring getElementsByTagName over querySelectorAll:
            //   http://jsperf.com/queryselectorall-vs-getelementsbytagname/145
            const elems = document.images ||
                          document.getElementsByTagName('img');
            for ( const elem of elems ) {
                if ( elem.complete ) {
                    add(elem);
                }
            }
            addMany(document.embeds || document.getElementsByTagName('embed'));
            addMany(document.getElementsByTagName('object'));
            addIFrames(document.getElementsByTagName('iframe'));
            process(0);

            document.addEventListener('error', onResourceFailed, true);

            vAPI.shutdown.add(function() {
                document.removeEventListener('error', onResourceFailed, true);
                if ( processTimer !== undefined ) {
                    clearTimeout(processTimer);
                }
            });
        },
        onDOMChanged: function(addedNodes) {
            if ( addedNodes.length === 0 ) { return; }
            for ( const node of addedNodes ) {
                if ( node.localName === 'iframe' ) {
                    addIFrame(node);
                }
                if ( node.childElementCount === 0 ) { continue; }
                const iframes = node.getElementsByTagName('iframe');
                if ( iframes.length !== 0 ) {
                    addIFrames(iframes);
                }
            }
            process();
        }
    };

    if ( vAPI.domWatcher instanceof Object ) {
        vAPI.domWatcher.addListener(domWatcherInterface);
    }

    return { add, addMany, addIFrame, addIFrames, process };
})();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

vAPI.domSurveyor = (function() {
    const messaging = vAPI.messaging;
    const queriedIds = new Set();
    const queriedClasses = new Set();
    const maxSurveyNodes = 65536;
    const maxSurveyTimeSlice = 4;
    const maxSurveyBuffer = 64;

    let domFilterer,
        hostname = '',
        surveyCost = 0;

    const pendingNodes = {
        nodeLists: [],
        buffer: [
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
            null, null, null, null, null, null, null, null,
        ],
        j: 0,
        accepted: 0,
        iterated: 0,
        stopped: false,
        add: function(nodes) {
            if ( nodes.length === 0 || this.accepted >= maxSurveyNodes ) {
                return;
            }
            this.nodeLists.push(nodes);
            this.accepted += nodes.length;
        },
        next: function() {
            if ( this.nodeLists.length === 0 || this.stopped ) { return 0; }
            const nodeLists = this.nodeLists;
            let ib = 0;
            do {
                const nodeList = nodeLists[0];
                let j = this.j;
                let n = j + maxSurveyBuffer - ib;
                if ( n > nodeList.length ) {
                    n = nodeList.length;
                }
                for ( let i = j; i < n; i++ ) {
                    this.buffer[ib++] = nodeList[j++];
                }
                if ( j !== nodeList.length ) {
                    this.j = j;
                    break;
                }
                this.j = 0;
                this.nodeLists.shift();
            } while ( ib < maxSurveyBuffer && nodeLists.length !== 0 );
            this.iterated += ib;
            if ( this.iterated >= maxSurveyNodes ) {
                this.nodeLists = [];
                this.stopped = true;
                //console.info(`domSurveyor> Surveyed a total of ${this.iterated} nodes. Enough.`);
            }
            return ib;
        },
        hasNodes: function() {
            return this.nodeLists.length !== 0;
        },
    };

    // Extract all classes/ids: these will be passed to the cosmetic
    // filtering engine, and in return we will obtain only the relevant
    // CSS selectors.
    const reWhitespace = /\s/;

    // https://github.com/gorhill/uBlock/issues/672
    // http://www.w3.org/TR/2014/REC-html5-20141028/infrastructure.html#space-separated-tokens
    // http://jsperf.com/enumerate-classes/6

    const surveyPhase1 = function() {
        //console.time('dom surveyor/surveying');
        const t0 = performance.now();
        const rews = reWhitespace;
        const ids = [];
        const classes = [];
        const nodes = pendingNodes.buffer;
        const deadline = t0 + maxSurveyTimeSlice;
        let qids = queriedIds;
        let qcls = queriedClasses;
        let processed = 0;
        for (;;) {
            const n = pendingNodes.next();
            if ( n === 0 ) { break; }
            for ( let i = 0; i < n; i++ ) {
                const node = nodes[i]; nodes[i] = null;
                let v = node.id;
                if ( typeof v === 'string' && v.length !== 0 ) {
                    v = v.trim();
                    if ( qids.has(v) === false && v.length !== 0 ) {
                        ids.push(v); qids.add(v);
                    }
                }
                let vv = node.className;
                if ( typeof vv === 'string' && vv.length !== 0 ) {
                    if ( rews.test(vv) === false ) {
                        if ( qcls.has(vv) === false ) {
                            classes.push(vv); qcls.add(vv);
                        }
                    } else {
                        vv = node.classList;
                        let j = vv.length;
                        while ( j-- ) {
                            const v = vv[j];
                            if ( qcls.has(v) === false ) {
                                classes.push(v); qcls.add(v);
                            }
                        }
                    }
                }
            }
            processed += n;
            if ( performance.now() >= deadline ) { break; }
        }
        const t1 = performance.now();
        surveyCost += t1 - t0;
        //console.info(`domSurveyor> Surveyed ${processed} nodes in ${(t1-t0).toFixed(2)} ms`);
        // Phase 2: Ask main process to lookup relevant cosmetic filters.
        if ( ids.length !== 0 || classes.length !== 0 ) {
            messaging.send(
                'contentscript',
                {
                    what: 'retrieveGenericCosmeticSelectors',
                    hostname: hostname,
                    ids: ids,
                    classes: classes,
                    exceptions: domFilterer.exceptions,
                    cost: surveyCost
                },
                surveyPhase3
            );
        } else {
            surveyPhase3(null);
        }
        //console.timeEnd('dom surveyor/surveying');
    };

    const surveyTimer = new vAPI.SafeAnimationFrame(surveyPhase1);

    // This is to shutdown the surveyor if result of surveying keeps being
    // fruitless. This is useful on long-lived web page. I arbitrarily
    // picked 5 minutes before the surveyor is allowed to shutdown. I also
    // arbitrarily picked 256 misses before the surveyor is allowed to
    // shutdown.
    let canShutdownAfter = Date.now() + 300000,
        surveyingMissCount = 0;

    // Handle main process' response.

    const surveyPhase3 = function(response) {
        const result = response && response.result;
        let mustCommit = false;

        if ( result ) {
            let selectors = result.simple;
            if ( Array.isArray(selectors) && selectors.length !== 0 ) {
                domFilterer.addCSSRule(
                    selectors,
                    'display:none!important;',
                    { type: 'simple' }
                );
                mustCommit = true;
            }
            selectors = result.complex;
            if ( Array.isArray(selectors) && selectors.length !== 0 ) {
                domFilterer.addCSSRule(
                    selectors,
                    'display:none!important;',
                    { type: 'complex' }
                );
                mustCommit = true;
            }
            selectors = result.injected;
            if ( typeof selectors === 'string' && selectors.length !== 0 ) {
                domFilterer.addCSSRule(
                    selectors,
                    'display:none!important;',
                    { injected: true }
                );
                mustCommit = true;
            }
        }

        if ( pendingNodes.stopped === false ) {
            if ( pendingNodes.hasNodes() ) {
                surveyTimer.start(1);
            }
            if ( mustCommit ) {
                surveyingMissCount = 0;
                canShutdownAfter = Date.now() + 300000;
                return;
            }
            surveyingMissCount += 1;
            if ( surveyingMissCount < 256 || Date.now() < canShutdownAfter ) {
                return;
            }
        }

        //console.info('dom surveyor shutting down: too many misses');

        surveyTimer.clear();
        vAPI.domWatcher.removeListener(domWatcherInterface);
        vAPI.domSurveyor = null;
    };

    const domWatcherInterface = {
        onDOMCreated: function() {
            if (
                vAPI instanceof Object === false ||
                vAPI.domSurveyor instanceof Object === false ||
                vAPI.domFilterer instanceof Object === false
            ) {
                if ( vAPI instanceof Object ) {
                    if ( vAPI.domWatcher instanceof Object ) {
                        vAPI.domWatcher.removeListener(domWatcherInterface);
                    }
                    vAPI.domSurveyor = null;
                }
                return;
            }
            //console.time('dom surveyor/dom layout created');
            domFilterer = vAPI.domFilterer;
            pendingNodes.add(document.querySelectorAll('[id],[class]'));
            surveyTimer.start();
            //console.timeEnd('dom surveyor/dom layout created');
        },
        onDOMChanged: function(addedNodes) {
            if ( addedNodes.length === 0 ) { return; }
            //console.time('dom surveyor/dom layout changed');
            let i = addedNodes.length;
            while ( i-- ) {
                const node = addedNodes[i];
                pendingNodes.add([ node ]);
                if ( node.childElementCount === 0 ) { continue; }
                pendingNodes.add(node.querySelectorAll('[id],[class]'));
            }
            if ( pendingNodes.hasNodes() ) {
                surveyTimer.start(1);
            }
            //console.timeEnd('dom surveyor/dom layout changed');
        }
    };

    const start = function(details) {
        if ( vAPI.domWatcher instanceof Object === false ) { return; }
        hostname = details.hostname;
        vAPI.domWatcher.addListener(domWatcherInterface);
    };

    return { start };
})();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

// Bootstrapping allows all components of the content script to be launched
// if/when needed.

(function bootstrap() {

    const bootstrapPhase2 = function() {
        // This can happen on Firefox. For instance:
        // https://github.com/gorhill/uBlock/issues/1893
        if ( window.location === null ) { return; }
        if ( vAPI instanceof Object === false ) { return; }

        vAPI.messaging.send(
            'contentscript',
            { what: 'shouldRenderNoscriptTags' }
        );

        if ( vAPI.domWatcher instanceof Object ) {
            vAPI.domWatcher.start();
        }

        // Element picker works only in top window for now.
        if (
            window !== window.top ||
            vAPI.domFilterer instanceof Object === false
        ) {
            return;
        }

        // To send mouse coordinates to main process, as the chrome API fails
        // to provide the mouse position to context menu listeners.
        // https://github.com/chrisaljoudi/uBlock/issues/1143
        // Also, find a link under the mouse, to try to avoid confusing new tabs
        // as nuisance popups.
        // Ref.: https://developer.mozilla.org/en-US/docs/Web/Events/contextmenu

        const onMouseClick = function(ev) {
            let elem = ev.target;
            while ( elem !== null && elem.localName !== 'a' ) {
                elem = elem.parentElement;
            }
            vAPI.messaging.send(
                'contentscript',
                {
                    what: 'mouseClick',
                    x: ev.clientX,
                    y: ev.clientY,
                    url: elem !== null && ev.isTrusted !== false ? elem.href : ''
                }
            );
        };

        document.addEventListener('mousedown', onMouseClick, true);

        // https://github.com/gorhill/uMatrix/issues/144
        vAPI.shutdown.add(function() {
            document.removeEventListener('mousedown', onMouseClick, true);
        });
    };

    const bootstrapPhase1 = function(response) {
        // cosmetic filtering engine aka 'cfe'
        const cfeDetails = response && response.specificCosmeticFilters;
        if ( !cfeDetails || !cfeDetails.ready ) {
            vAPI.domWatcher = vAPI.domCollapser = vAPI.domFilterer =
            vAPI.domSurveyor = vAPI.domIsLoaded = null;
            return;
        }

        if ( response.noCosmeticFiltering ) {
            vAPI.domFilterer = null;
            vAPI.domSurveyor = null;
        } else {
            const domFilterer = vAPI.domFilterer;
            if ( response.noGenericCosmeticFiltering || cfeDetails.noDOMSurveying ) {
                vAPI.domSurveyor = null;
            }
            domFilterer.exceptions = cfeDetails.exceptionFilters;
            domFilterer.hideNodeAttr = cfeDetails.hideNodeAttr;
            domFilterer.hideNodeStyleSheetInjected =
                cfeDetails.hideNodeStyleSheetInjected === true;
            domFilterer.addCSSRule(
                cfeDetails.declarativeFilters,
                'display:none!important;'
            );
            domFilterer.addCSSRule(
                cfeDetails.highGenericHideSimple,
                'display:none!important;',
                { type: 'simple', lazy: true }
            );
            domFilterer.addCSSRule(
                cfeDetails.highGenericHideComplex,
                'display:none!important;',
                { type: 'complex', lazy: true }
            );
            domFilterer.addCSSRule(
                cfeDetails.injectedHideFilters,
                'display:none!important;',
                { injected: true }
            );
            domFilterer.addProceduralSelectors(cfeDetails.proceduralFilters);
        }

        if ( cfeDetails.networkFilters.length !== 0 ) {
            vAPI.userStylesheet.add(
                cfeDetails.networkFilters + '\n{display:none!important;}');
        }

        vAPI.userStylesheet.apply();

        // Library of resources is located at:
        // https://github.com/gorhill/uBlock/blob/master/assets/ublock/resources.txt
        if ( response.scriptlets ) {
            vAPI.injectScriptlet(document, response.scriptlets);
            vAPI.injectedScripts = response.scriptlets;
        }

        if ( vAPI.domSurveyor instanceof Object ) {
            vAPI.domSurveyor.start(cfeDetails);
        }

        // https://github.com/chrisaljoudi/uBlock/issues/587
        // If no filters were found, maybe the script was injected before
        // uBlock's process was fully initialized. When this happens, pages
        // won't be cleaned right after browser launch.
        if (
            typeof document.readyState === 'string' &&
            document.readyState !== 'loading'
        ) {
            bootstrapPhase2();
        } else {
            document.addEventListener(
                'DOMContentLoaded',
                bootstrapPhase2,
                { once: true }
            );
        }
    };

    // This starts bootstrap process.
    vAPI.messaging.send(
        'contentscript',
        {
            what: 'retrieveContentScriptParameters',
            url: window.location.href,
            isRootFrame: window === window.top,
            charset: document.characterSet
        },
        bootstrapPhase1
    );
})();

/******************************************************************************/
/******************************************************************************/
/******************************************************************************/

}
// <<<<<<<< end of HUGE-IF-BLOCK