e621 Temp Sticky Blacklist Prototype Extension

// Create folder e621-extension, then put the following files inside it.
// Go to chrome://extensions/ put yourself in developer mode (top right), then "Load Unpacked Extension"; the _folder_ you created is the extension.

// manifest.json
{
    "manifest_version": 3,
    "name": "e621 Blacklist Toggle",
    "version": "0.1",
    "content_scripts": [{
        "matches": ["https://e621.net/*", "https://e926.net/*"],
        "js": ["content-script.js"]
    }],
    "web_accessible_resources": [{
        "resources": ["e621.user.js"],
        "matches": ["https://e621.net/*", "https://e926.net/*"],
        "use_dynamic_url": true
    }]
}

// content-script.js
// Credit: https://stackoverflow.com/a/9517879
var s = document.createElement('script');
s.src = chrome.runtime.getURL('e621.user.js');
s.onload = function() {
        this.remove();
};
(document.head || document.documentElement).appendChild(s);

// e621.user.js
// ==UserScript==
// @name Blacklist Toggle
// @match https://e621.net/*
// @match https://e926.net/*
// ==/UserScript==

(function() {
    function runWhenReady(run) {
        if (document.readyState != 'loading')
            run();
        else
            document.addEventListener('DOMContentLoaded', run);
    }
    runWhenReady(function() {
        function toggle(set, key) {
            set.delete(key) || set.add(key);
        }
        let off;
        function setOff(keys) {
            off = new Set(keys);
            off.forEach(key => {
                Danbooru.Blacklist.lineSet(key, false);
            })
            if (off.size)
                Danbooru.Blacklist.apply();
        }

        // Expire after six hours
        let expire = new Date(
            new Date(
                window.localStorage.getItem('blacklist_last')
            ).getTime()
            + 6 * 60 * 60 * 1000
        );
        if (expire < new Date())
            window.localStorage.removeItem('blacklist_off');

        setOff(JSON.parse(window.localStorage.getItem('blacklist_off')) || []);
        addEventListener('storage', e => {
            // wipe on Disable/Re-enable all blacklist entries
            if (e.key === 'dab') {
                window.localStorage.removeItem('blacklist_off');
                Danbooru.Blacklist.entries.forEach(entry => {
                    entry.disabled = !!JSON.parse(e.newValue);
                })
                Danbooru.Blacklist.apply();
                return;
            }

            if (e.key !== 'blacklist_off')
                return;

            // re-enable all, then disable from local storage
            Danbooru.Blacklist.entries.forEach(entry => {
                entry.disabled = false;
            })
            setOff(JSON.parse(e.newValue) || []);
        });

        let lineToggle = Danbooru.Blacklist.lineToggle; // monkey patch it
        Danbooru.Blacklist.lineToggle = (t) => {
            lineToggle(t);
            window.localStorage.setItem('blacklist_last', new Date().toJSON());
            toggle(off, t);
            window.localStorage.setItem('blacklist_off', JSON.stringify(Array.from(off.keys())));
        };
    });
})();