linker/extension/content.js

// Reddit -> Spotify/Bandcamp linker (content script).
//
// On a reddit thread page it: pulls candidate artist names out of comment text,
// asks the local resolver service which ones are real artists, and rewrites those
// occurrences in place into links. The resolver does the hard "is this an artist"
// part; this script only handles extraction + DOM rewriting.

(() => {
  "use strict";

  // If you run the resolver on a different host/port, change this AND the matching
  // host entry in manifest.json `permissions`.
  const RESOLVER_URL = "http://localhost:8787";

  // ---- candidate extraction -------------------------------------------------
  // A token is a Capitalized or ALL-CAPS word; a candidate is 1-4 tokens joined by
  // spaces, with a few lowercase connectors allowed inside ("Signs of the Swarm").
  const TOKEN = "[A-Z][A-Za-z0-9'’.&\\-]*";
  const CAND_RE = new RegExp(`${TOKEN}(?:[ ]+(?:${TOKEN}|of|the|and|&|in|on|to|for|a|an)){0,3}`, "g");
  const CONNECTORS = new Set(["of", "the", "and", "&", "in", "on", "to", "for", "a", "an"]);

  // Common capitalized words that are almost never the artist being recommended.
  // Deliberately small: the resolver's exact-name match is the real filter, so we
  // avoid stoplisting plausible one-word band names (Yes, Love, Tool, ...).
  const STOP = new Set([
    "I", "A", "An", "The", "And", "But", "Or", "Nor", "So", "Yet", "For", "If", "As",
    "At", "By", "In", "On", "To", "Of", "Up", "Off", "Out", "It", "He", "She", "We",
    "They", "You", "Me", "Him", "Her", "Us", "Them", "My", "Your", "His", "Its", "Our",
    "Their", "This", "That", "These", "Those", "Is", "Are", "Was", "Were", "Be", "Been",
    "Am", "Do", "Does", "Did", "Has", "Have", "Had", "Will", "Would", "Can", "Could",
    "Should", "Not", "No", "Yeah", "Ok", "Okay", "Lol", "Imo", "Imho", "Tbh", "Edit",
    "Reddit", "Spotify", "Bandcamp", "Youtube", "Google", "Apple", "Album", "Albums",
    "Band", "Bands", "Song", "Songs", "Track", "Tracks", "Ep", "Lp", "Cd", "Op", "Vol",
  ]);

  function matchesIn(text) {
    const out = [];
    CAND_RE.lastIndex = 0;
    let m;
    while ((m = CAND_RE.exec(text))) {
      let str = m[0].replace(/[.,;:!?’'")\]]+$/u, ""); // trim trailing punctuation
      let parts = str.split(/\s+/);
      while (parts.length && CONNECTORS.has(parts[parts.length - 1].toLowerCase())) parts.pop();
      str = parts.join(" ");
      if (!str) continue;
      const single = parts.length === 1;
      if (single && (STOP.has(str) || str.length < 2 || /^\d+$/.test(str))) continue;
      out.push({ name: str, index: m.index, length: str.length }); // only trailing trimmed -> index unchanged
    }
    return out;
  }

  // ---- DOM walking ----------------------------------------------------------
  const SKIP_TAGS = new Set([
    "A", "SCRIPT", "STYLE", "CODE", "PRE", "TEXTAREA", "INPUT", "BUTTON", "TIME", "NOSCRIPT", "SVG", "SELECT",
  ]);

  function inSkippable(node) {
    for (let el = node.parentElement; el; el = el.parentElement) {
      if (SKIP_TAGS.has(el.tagName)) return true;
      if (el.classList && el.classList.contains("rsl-link")) return true;
      if (el.isContentEditable) return true;
    }
    return false;
  }

  function collectTextNodes(root) {
    const nodes = [];
    const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT, {
      acceptNode(node) {
        const v = node.nodeValue;
        if (!v || v.length > 5000 || !/[A-Za-z]/.test(v)) return NodeFilter.FILTER_REJECT;
        if (inSkippable(node)) return NodeFilter.FILTER_REJECT;
        return NodeFilter.FILTER_ACCEPT;
      },
    });
    let n;
    while ((n = walker.nextNode())) nodes.push(n);
    return nodes;
  }

  // ---- link building / rewriting --------------------------------------------
  function makeLink(label, links) {
    const frag = document.createDocumentFragment();
    const a = document.createElement("a");
    a.className = "rsl-link";
    a.textContent = label;
    a.href = links.spotify;
    a.target = "_blank";
    a.rel = "noopener noreferrer";
    a.title = "Open on Spotify";
    frag.appendChild(a);
    if (links.bandcamp) {
      const sup = document.createElement("sup");
      sup.className = "rsl-sup";
      const b = document.createElement("a");
      b.className = "rsl-bc";
      b.textContent = "bc";
      b.href = links.bandcamp;
      b.target = "_blank";
      b.rel = "noopener noreferrer";
      b.title = "Search on Bandcamp";
      sup.appendChild(b);
      frag.appendChild(sup);
    }
    return frag;
  }

  function wrapNode(node) {
    const text = node.nodeValue;
    const ms = matchesIn(text).filter((m) => {
      const links = resolved.get(m.name);
      return links && links.spotify;
    });
    if (!ms.length) return;
    const frag = document.createDocumentFragment();
    let last = 0;
    for (const m of ms) {
      if (m.index < last) continue; // skip overlaps
      if (m.index > last) frag.appendChild(document.createTextNode(text.slice(last, m.index)));
      frag.appendChild(makeLink(text.substr(m.index, m.length), resolved.get(m.name)));
      last = m.index + m.length;
    }
    if (last < text.length) frag.appendChild(document.createTextNode(text.slice(last)));
    node.parentNode && node.parentNode.replaceChild(frag, node);
  }

  // ---- resolver client ------------------------------------------------------
  const resolved = new Map(); // candidate string -> { spotify, bandcamp } | null

  async function resolve(names) {
    try {
      const r = await fetch(`${RESOLVER_URL}/resolve`, {
        method: "POST",
        headers: { "content-type": "application/json" },
        body: JSON.stringify({ candidates: names }),
      });
      if (!r.ok) throw new Error(`http ${r.status}`);
      return await r.json();
    } catch (e) {
      console.warn("[rsl] resolver unreachable:", e.message);
      return null;
    }
  }

  // ---- scan orchestration ---------------------------------------------------
  function getRoot() {
    return (
      document.querySelector("main, .content[role='main'], shreddit-comment-tree, .commentarea") ||
      document.body
    );
  }

  async function scan() {
    const nodes = collectTextNodes(getRoot());
    if (!nodes.length) return;

    const seen = new Set();
    for (const node of nodes) for (const m of matchesIn(node.nodeValue)) seen.add(m.name);

    const ask = [...seen].filter((c) => !resolved.has(c));
    if (ask.length) {
      const res = await resolve(ask);
      if (res) for (const c of ask) resolved.set(c, res[c] || null); // negative-cache misses
    }
    for (const node of nodes) if (node.isConnected) wrapNode(node);
  }

  // serialize scans; coalesce overlapping triggers
  let running = false;
  let pending = false;
  function schedule() {
    if (running) { pending = true; return; }
    running = true;
    scan()
      .catch((e) => console.warn("[rsl]", e))
      .finally(() => {
        running = false;
        if (pending) { pending = false; setTimeout(schedule, 300); }
      });
  }

  function debounce(fn, ms) {
    let t;
    return () => { clearTimeout(t); t = setTimeout(fn, ms); };
  }

  const onThread = () => /\/comments\//.test(location.pathname);

  if (onThread()) schedule();
  new MutationObserver(debounce(() => { if (onThread()) schedule(); }, 600))
    .observe(document.documentElement, { childList: true, subtree: true });
})();