/* The block protocol — how 선생님 drives the UI.
   The tutor writes prose plus fenced blocks; the client renders them
   as real interface and sends structured answers back. */

const RE = {
  task:     /::task\s+(translate|recall|match|build|choice)\s*\n([\s\S]*?)(?:\n::|$)/,
  words:    /::words\s*\n([\s\S]*?)(?:\n::|$)/,
  gloss:    /::gloss\s*\n([\s\S]*?)(?:\n::|$)/,
  progress: /::progress\s+(\d{1,3})\s*(?:\|\s*([^\n]*))?/,
  result:   /::result\s*\n([\s\S]*?)(?:\n::|$)/,
  confirmed:/::confirmed\s*\n([\s\S]*?)(?:\n::|$)/,
};
const rows = s => s.split("\n").map(l => l.trim()).filter(l => l && !/^::/.test(l));
const cols = l => l.split("|").map(x => x.trim());

/* 선생님 sometimes writes an exercise, notices mid-message that it broke the
   gate, and rewrites it below. Matching the FIRST block served the draft it
   had just retracted — a real bug seen in production, where the student was
   handed and answered an exercise the tutor had already withdrawn.
   So: collect every block; the LAST task, words and progress win, and gloss
   blocks accumulate (a message may legitimately gloss several sentences). */
const all = (text, re) => {
  const r = new RegExp(re.source, "g");
  const out = [];
  let m;
  while ((m = r.exec(text)) !== null) {
    out.push(m);
    if (m.index === r.lastIndex) r.lastIndex++;
  }
  return out;
};

export function parse(text) {
  const ws = all(text, RE.words), ts = all(text, RE.task);
  const gs = all(text, RE.gloss), ps = all(text, RE.progress);
  const t = ts.length ? ts[ts.length - 1] : null;
  const p = ps.length ? ps[ps.length - 1] : null;

  /* keep every word listed anywhere, first gloss of a term wins */
  let words = null;
  if (ws.length) {
    const seen = new Set(), acc = [];
    ws.forEach(w => rows(w[1]).forEach(l => {
      const c = cols(l);
      if (!c[0] || seen.has(c[0])) return;
      seen.add(c[0]);
      acc.push({ ko: c[0], gloss: c[1] || "", note: c[2] || "" });
    }));
    if (acc.length) words = acc;
  }

  let task = null;
  if (t) {
    const r = rows(t[2]);
    if (t[1] === "translate") task = { type: "translate", items: r.map(q => ({ q })) };
    /* recall: English prompt, the student WRITES the 한글. The one task type
       that proves memory rather than recognition — and the only one whose
       answers need letter-level marking, see hangul.js letterCheck(). */
    if (t[1] === "recall")    task = { type: "recall", items: r.map(l => { const c = cols(l);
                                        return { q: c[0], hint: c[1] || "" }; }).filter(x => x.q) };
    if (t[1] === "match")     task = { type: "match", pairs: r.map(l => { const c = cols(l);
                                        return { ko: c[0], gloss: c[1] }; }).filter(x => x.ko && x.gloss) };
    if (t[1] === "build")     task = { type: "build", items: r.map(l => { const c = cols(l);
                                        return { en: c[0], chips: c.slice(1).filter(Boolean) }; }).filter(x => x.en && x.chips.length) };
    if (t[1] === "choice")    task = { type: "choice", items: r.map(l => { const c = cols(l);
                                        return { q: c[0], options: c.slice(1).filter(Boolean) }; }).filter(x => x.q && x.options.length > 1) };
    if (task) { task.retracted = ts.length - 1;   /* >0 means a draft was withdrawn */
                task.rows = r; }                  /* raw rows, for the gate to read */
  }

  let gloss = null;
  if (gs.length) {
    const blocks = [];
    gs.forEach(g => {
      let cur = null;
      g[1].split("\n").forEach(line => {
        const l = line.trim();
        if (!l || /^::/.test(l)) return;
        if (l.startsWith("=")) { if (cur) { cur.en = l.slice(1).trim(); cur = null; } return; }
        const c = cols(l);
        if (!cur) { cur = { parts: [], en: "" }; blocks.push(cur); }
        cur.parts.push({ ko: c[0], role: (c[1] || "N").toUpperCase()[0], gloss: c[2] || "", highlight: c[3] || "" });
      });
    });
    const keep = blocks.filter(b => b.parts.length);
    if (keep.length) gloss = keep;
  }

  /* marking the tutor sends back: per-item outcomes, and words he certifies */
  const rs = all(text, RE.result), cs = all(text, RE.confirmed);
  const results = rs.length ? rows(rs[rs.length - 1][1]).map(l => {
    const c = cols(l);
    return { item: c[0], ok: /^ok$/i.test(c[1] || ""), mistakenFor: c[2] || "" };
  }).filter(x => x.item) : null;
  const confirmed = cs.length ? rows(cs[cs.length - 1][1]).map(l => cols(l)[0]).filter(Boolean) : null;

  /* strip every block, not only the matched one */
  let body = text;
  [RE.progress, RE.gloss, RE.task, RE.words, RE.result, RE.confirmed].forEach(re => {
    body = body.replace(new RegExp(re.source, "g"), "");
  });
  body = body.replace(/^[ \t]*::[ \t]*$/gm, "");

  return {
    body: body.replace(/\n{3,}/g, "\n\n").trim(),
    words, task, gloss, results, confirmed,
    progress: p ? { score: Math.max(0, Math.min(100, +p[1])), note: (p[2] || "").trim() } : null,
  };
}

/** Roles a gloss part can carry, and what the UI should do with each. */
export const ROLES = {
  S: "주어 subject",      T: "주제 topic",       O: "목적어 object",
  V: "서술어 predicate",  P: "자리·때 place/time", C: "이음 connective",
  Q: "인용 quotation",    M: "수식 modifier",    N: "",
};

/**
 * Turn a completed task back into the message the student sends.
 *
 * `letterBlock` is the output of hangul.js letterCheck() for a recall task —
 * pass it, always. The tutor cannot see inside a Hangul syllable and will
 * invent a diagnosis if you leave him to it.
 */
export function answerText(task, state, lookups = [], letterBlock = "") {
  let body;
  if (task.type === "recall")
    body = "My written answers:\n" + task.items.map((it, i) =>
      `${it.q} → ${(state[i] || "").trim() || "(not sure)"}`).join("\n")
      + (letterBlock ? "\n\n" + letterBlock : "");
  else if (task.type === "translate")
    body = "My answers:\n" + task.items.map((it, i) =>
      `${it.q} → ${(state[i] || "").trim() || "(not sure)"}`).join("\n");
  else if (task.type === "match")
    body = "My pairings:\n" + (state.pairs.map(p => `${p.ko} = ${p.gloss}`).join("\n") || "(none)");
  else if (task.type === "build")
    body = "My sentences:\n" + task.items.map((it, i) =>
      `${it.en} → ${(state[i] || []).join(" ") || "(not sure)"}`).join("\n");
  else
    body = "My choices:\n" + task.items.map((it, i) =>
      `${it.q} → ${state[i] == null ? "(not sure)" : it.options[state[i]]}`).join("\n");

  return body + (lookups.length
    ? `\n\n(I had to look up: ${lookups.join(", ")})`
    : "\n\n(No lookups.)");
}