// ==UserScript==
// @name         Inline Reddit images and Comment Redirect
// @namespace    https://www.reddit.com
// @version      2026-08-28.1
// @description  Embed images and videos posted as comments and redirect post links to comments
// @author       luxick
// @updateURL    https://git.luxick.de/luxick/scripts/raw/branch/master/js/reddit-image-inline.user.js
// @downloadURL  https://git.luxick.de/luxick/scripts/raw/branch/master/js/reddit-image-inline.user.js
// @match        https://old.reddit.com/r/*
// @match        https://www.reddit.com/r/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=reddit.com
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // Collect the placeholder links Reddit renders for media comments,
    // e.g. "<image>" or "<video>" as the link text.
    function collectLinks(placeholder) {
        let xpath = "//a[text()='" + placeholder + "']";
        var element;
        var result = document.evaluate(xpath, document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
        let links = [];
        while(element = result.iterateNext()){
            if (element.href) {
                links.push(element);
            }
        }
        return links;
    }

    // Comment media is linked through Reddit's viewer:
    // "https://reddit.com/media?url=<media url>"
    function unwrapMediaUrl(href) {
        let match = href.match(/[?&]url=([^&]+)/);
        if (!match) {
            return href;
        }
        try {
            return decodeURIComponent(match[1]);
        } catch (e) {
            return match[1];
        }
    }

    // Video comments point at an HLS playlist, which only Safari plays without
    // a library. The same upload is also served as standalone MP4 renditions,
    // so use those instead.
    //
    // Newer uploads name them CMAF_<height>.mp4, older ones DASH_<height>.mp4,
    // and no upload has every height. Missing names return 403, so just walk
    // the list until one loads. 720 first as a sane default for a 300px embed;
    // 1080 last, only worth fetching when nothing smaller exists.
    const HEIGHTS = [720, 480, 360, 270, 240, 220, 1080];
    const FAMILIES = ['CMAF', 'DASH'];
    const AUDIO_NAMES = [
        'CMAF_AUDIO_128', 'CMAF_AUDIO_64',
        'DASH_AUDIO_128', 'DASH_AUDIO_64', 'DASH_audio',
    ];

    function mediaUrls(id, names) {
        return names.map(name => 'https://v.redd.it/' + id + '/' + name + '.mp4');
    }

    function videoNames() {
        let names = [];
        for (let family of FAMILIES) {
            for (let height of HEIGHTS) {
                names.push(family + '_' + height);
            }
        }
        return names;
    }

    function vredditId(url) {
        let match = url.match(/^https?:\/\/v\.redd\.it\/([A-Za-z0-9]+)/i);
        return match ? match[1] : null;
    }

    // Move to the next candidate URL whenever the current one fails to load.
    function chainSources(media, sources, onExhausted) {
        let index = 0;
        media.src = sources[0];
        media.addEventListener('error', function() {
            index += 1;
            if (index < sources.length) {
                media.src = sources[index];
                media.load();
            } else if (onExhausted) {
                onExhausted();
            }
        });
    }

    // The MP4 renditions carry the video track only; the audio is a separate
    // file that has to be kept in step with the video element by hand.
    function buildAudio(video, id) {
        let audio = document.createElement('audio');
        audio.preload = 'metadata';
        chainSources(audio, mediaUrls(id, AUDIO_NAMES));

        video.addEventListener('play', function() {
            audio.currentTime = video.currentTime;
            audio.play().catch(() => {});
        });
        video.addEventListener('pause', () => audio.pause());
        video.addEventListener('seeking', () => { audio.currentTime = video.currentTime; });
        video.addEventListener('ratechange', () => { audio.playbackRate = video.playbackRate; });
        video.addEventListener('volumechange', function() {
            audio.volume = video.volume;
            audio.muted = video.muted;
        });
        return audio;
    }

    function buildVideo(href) {
        let container = document.createElement('span');
        let mediaUrl = unwrapMediaUrl(href);
        let id = vredditId(mediaUrl);

        let video = document.createElement('video');
        video.controls = true;
        video.preload = 'metadata';
        video.style = "max-width: 300px";

        let sources = id ? mediaUrls(id, videoNames()) : [mediaUrl];

        chainSources(video, sources, function() {
            console.log("no playable source for " + href);
            let anchor = document.createElement('a');
            anchor.href = href;
            anchor.target = '_blank';
            anchor.textContent = '<video>';
            container.replaceChildren(anchor);
        });

        container.appendChild(video);
        if (id) {
            container.appendChild(buildAudio(video, id));
        }
        return container;
    }

    // Handle image inlining
    for (var elem of collectLinks('<image>')) {
        console.log("inlining image " + elem.href);
        let image = new Image();
        image.src = elem.href;
        image.style = "max-width: 300px";

        // Create a new anchor element
        let anchor = document.createElement('a');
        anchor.href = elem.href;
        anchor.target = '_blank'; // Opens in new tab

        // Append the image to the anchor
        anchor.appendChild(image);

        // Add the anchor (containing the image) to the parent
        elem.parentElement.appendChild(anchor);
        elem.remove();
    }

    // Handle video inlining
    for (var videoElem of collectLinks('<video>')) {
        console.log("inlining video " + videoElem.href);
        videoElem.parentElement.appendChild(buildVideo(videoElem.href));
        videoElem.remove();
    }

    // Only proceed with link rewriting if we're not already in a comments section
    if (!window.location.pathname.includes('/comments/')) {
        // Handle post link redirection
        const postLinks = document.querySelectorAll('a.title');
        postLinks.forEach(link => {
            // Find the comments link for this post
            const thing = link.closest('.thing');
            if (thing) {
                const commentsLink = thing.querySelector('a.comments');
                if (commentsLink) {
                    link.href = commentsLink.href;
                }
            }
        });
    }
})();