// VV compare frontend
(() => {
  const $ = (id) => document.getElementById(id);
  const sections = {
    upload: $("s-upload"),
    processing: $("s-processing"),
    result: $("s-result"),
  };
  const show = (n) => {
    for (const [k, el] of Object.entries(sections)) el.classList.toggle("hidden", k !== n);
  };

  let state = { jobId: null, result: null, origFile: null, newFile: null };

  function attachDrop(zoneId, inputId, textId, which) {
    const zone = $(zoneId);
    const input = $(inputId);
    const text = $(textId);
    zone.addEventListener("click", () => input.click());
    input.addEventListener("change", (e) => {
      if (e.target.files[0]) setFile(which, e.target.files[0], zone, text);
    });
    ["dragenter", "dragover"].forEach((ev) =>
      zone.addEventListener(ev, (e) => { e.preventDefault(); zone.classList.add("drag-over"); }));
    ["dragleave", "drop"].forEach((ev) =>
      zone.addEventListener(ev, (e) => { e.preventDefault(); zone.classList.remove("drag-over"); }));
    zone.addEventListener("drop", (e) => {
      if (e.dataTransfer.files[0]) setFile(which, e.dataTransfer.files[0], zone, text);
    });
  }

  function setFile(which, file, zone, textEl) {
    if (which === "orig") state.origFile = file;
    else state.newFile = file;
    zone.classList.add("has-file");
    const size = file.size > 1024 * 1024
      ? `${(file.size / 1024 / 1024).toFixed(1)} MB`
      : `${(file.size / 1024).toFixed(0)} kB`;
    textEl.innerHTML = `<strong>${escapeHtml(file.name)}</strong><br><span style="color:var(--text-tertiary);font-size:12px">${size}</span>`;
    updateRunBtn();
  }

  attachDrop("drop-original", "orig-input", "orig-text", "orig");
  attachDrop("drop-new", "new-input", "new-text", "new");

  function updateRunBtn() {
    const btn = $("compare-btn");
    const hint = $("compare-hint");
    if (!state.origFile && !state.newFile) {
      btn.disabled = true; hint.textContent = "Nahrajte oba soubory.";
    } else if (!state.origFile) {
      btn.disabled = true; hint.textContent = "Chybí původní VV.";
    } else if (!state.newFile) {
      btn.disabled = true; hint.textContent = "Chybí nový VV.";
    } else {
      btn.disabled = false; hint.textContent = "Připraveno k porovnání.";
    }
  }

  $("compare-btn").addEventListener("click", async () => {
    if (!state.origFile || !state.newFile) return;
    show("processing");
    try {
      const fd = new FormData();
      fd.append("original", state.origFile);
      fd.append("new", state.newFile);
      const r = await fetch("/api/compare", { method: "POST", body: fd });
      if (!r.ok) throw new Error((await r.json()).detail || r.statusText);
      const json = await r.json();
      state.jobId = json.job_id;
      state.result = json.result;
      renderResult();
      show("result");
    } catch (err) {
      alert("Chyba: " + err.message);
      show("upload");
    }
  });

  function renderResult() {
    const r = state.result;
    const c = r.changes.length, a = r.added.length, d = r.removed.length;
    $("cnt-changed").textContent = c;
    $("cnt-added").textContent = a;
    $("cnt-removed").textContent = d;
    $("results-meta").textContent =
      `Porovnání ${r.per_sheet.length} listů — ${c + a + d} celkových rozdílů.`;

    const psHtml = r.per_sheet.map((ps) => `
      <tr>
        <td>${escapeHtml(ps.sheet)}</td>
        <td>${escapeHtml(ps.hala || "")}</td>
        <td class="num">${ps.orig_count}</td>
        <td class="num">${ps.new_count}</td>
        <td class="num"><span class="pill ${ps.changes ? "changed" : "zero"}">${ps.changes}</span></td>
        <td class="num"><span class="pill ${ps.added ? "added" : "zero"}">${ps.added}</span></td>
        <td class="num"><span class="pill ${ps.removed ? "removed" : "zero"}">${ps.removed}</span></td>
      </tr>`).join("");
    $("per-sheet").innerHTML = r.per_sheet.length ? `
      <table>
        <thead>
          <tr>
            <th>List</th><th>Hala</th>
            <th>Pol. původní</th><th>Pol. nový</th>
            <th>Změněné</th><th>Přidané</th><th>Odebrané</th>
          </tr>
        </thead>
        <tbody>${psHtml}</tbody>
      </table>` : `<p style="color:var(--text-tertiary)">Nepodařilo se najít listy VV v žádném ze souborů.</p>`;
  }

  $("download-btn").addEventListener("click", () => {
    if (state.jobId) window.location.href = `/api/report/${state.jobId}`;
  });
  $("restart-btn").addEventListener("click", () => {
    state = { jobId: null, result: null, origFile: null, newFile: null };
    $("orig-input").value = ""; $("new-input").value = "";
    $("drop-original").classList.remove("has-file");
    $("drop-new").classList.remove("has-file");
    $("orig-text").textContent = "Přetáhněte soubor sem nebo klikněte";
    $("new-text").textContent = "Přetáhněte soubor sem nebo klikněte";
    updateRunBtn();
    show("upload");
  });

  function escapeHtml(s) {
    return String(s ?? "").replace(/[&<>"']/g, (c) =>
      ({"&":"&amp;","<":"&lt;",">":"&gt;",'"':"&quot;","'":"&#39;"}[c]));
  }
})();