// Pure helpers for the OPTIONAL local-LLM (ollama) classifier. The HTTP call lives in
// resolver.js; the prompt builder + reply parser live here so they unit-test with
// `node --test` (no network). The LLM answers one question: "which of these candidate
// substrings are music artists/albums?" — the precision gate when it is configured.

import { norm } from "./lib.js";

// Small, fast, runs comfortably on a 16GB M2 (3.1B params, Q4 ~2GB). Override with OLLAMA_MODEL.
export const DEFAULT_MODEL = "qwen2.5:3b";

// Chat messages for an ollama /api/chat call (used with stream:false, format:"json").
export function buildClassifyMessages(candidates) {
  const system =
    "You are a music-name classifier for a tool that links artist/album mentions in Reddit " +
    "music discussions. You are given a JSON array of candidate text snippets pulled from reddit " +
    "comments. For EACH candidate decide whether it names a music ARTIST/BAND, a music " +
    "ALBUM/release, or NEITHER. The snippets come from music threads, so prefer the music reading " +
    "when a candidate is a plausible band/album even if it is also an ordinary word. Mark ordinary " +
    "words, sentence fragments, generic phrases, place names, and non-music proper nouns as \"none\". " +
    'Reply with ONLY a JSON object of the form {"results":[{"name":<candidate verbatim>,' +
    '"kind":"artist"|"album"|"none"}]}. Use each candidate string VERBATIM as its name.';
  const user = JSON.stringify({ candidates });
  return [
    { role: "system", content: system },
    { role: "user", content: user },
  ];
}

// Parse the model's JSON reply into a Map of norm(name) -> "artist" | "album" for the
// candidates the model marked as music (the kind routes each to the artist or album Spotify
// lookup). Defensive: only names that were actually in the candidate list count (guards
// against the model inventing names); an unparseable reply yields an empty Map, and the
// caller then falls back to the Spotify-exact-match gate. A Map still answers `.has()` like
// the old Set, so a name absent from it is dropped exactly as before.
export function parseClassification(text, candidates) {
  const allowed = new Set(candidates.map(norm));
  const confirmed = new Map();
  let obj;
  try {
    obj = JSON.parse(text);
  } catch {
    return confirmed;
  }
  const rows = Array.isArray(obj?.results) ? obj.results : Array.isArray(obj) ? obj : [];
  for (const row of rows) {
    if (!row || typeof row.name !== "string") continue;
    const k = norm(row.name);
    if (!allowed.has(k)) continue;
    const kind = String(row.kind ?? "").toLowerCase();
    if (kind === "artist" || kind === "album") confirmed.set(k, kind);
  }
  return confirmed;
}