/* holder-app.js — controller for the Hex Holder Designer page.
 *
 * - Loads /api/holder/params for the form schema and builds inputs.
 * - On any param change, debounces 400 ms then POSTs /api/holder/render and
 *   pushes the returned STL ArrayBuffer into the Three.js viewer.
 * - "Download STL" re-uses the last rendered blob (no double trip).
 * - "Design busbars →" computes cells via /api/holder/cells, creates a new
 *   busbar-designer project via /api/projects, redirects to /?p=<id>.
 */

const $ = (id) => document.getElementById(id);

const state = {
  params: {},        // current values, name → value
  schema: [],        // [{name, label, kind, ...}]
  lastBlob: null,    // last rendered STL blob (for download)
  renderTimer: null,
  rendering: false,
  rendererReady: false,
};

// ----- viewer init ----------------------------------------------------------
// HolderViewer is set up by holder-viewer.js (loaded as ES module) and
// attached to window. We wait briefly for it to be ready.

function _whenViewerReady(cb) {
  if (window.HolderViewer) {
    cb();
    return;
  }
  let tries = 0;
  const t = setInterval(() => {
    tries++;
    if (window.HolderViewer) {
      clearInterval(t);
      cb();
    } else if (tries > 50) {
      clearInterval(t);
      console.error("HolderViewer never loaded");
    }
  }, 60);
}

// ----- form generation ------------------------------------------------------

const GROUP_ORDER = ["part", "cell", "size", "holder"];
const GROUP_LABELS = {
  part:   "Part / pack",
  cell:   "Cell",
  size:   "Pack size",
  holder: "Holder",
};

function _renderForm(schema, defaults) {
  const root = $("param-form");
  root.innerHTML = "";

  // Group params.
  const byGroup = new Map();
  for (const p of schema) {
    if (!byGroup.has(p.group)) byGroup.set(p.group, []);
    byGroup.get(p.group).push(p);
  }
  const groups = GROUP_ORDER.filter((g) => byGroup.has(g))
    .concat([...byGroup.keys()].filter((g) => !GROUP_ORDER.includes(g)));

  for (const g of groups) {
    const wrap = document.createElement("div");
    wrap.className = "param-group";
    const title = document.createElement("h3");
    title.className = "param-group-title";
    title.textContent = GROUP_LABELS[g] || g;
    wrap.appendChild(title);

    for (const p of byGroup.get(g)) {
      const row = document.createElement("div");
      row.className = "param-row";

      const label = document.createElement("label");
      label.textContent = p.label;
      row.appendChild(label);

      let inp;
      if (p.kind === "select") {
        inp = document.createElement("select");
        for (const opt of p.options || []) {
          const o = document.createElement("option");
          o.value = opt; o.textContent = opt;
          if (opt === state.params[p.name]) o.selected = true;
          inp.appendChild(o);
        }
      } else if (p.kind === "bool") {
        inp = document.createElement("input");
        inp.type = "checkbox";
        inp.checked = !!state.params[p.name];
      } else {
        inp = document.createElement("input");
        inp.type = "number";
        if (p.min  != null) inp.min  = p.min;
        if (p.max  != null) inp.max  = p.max;
        if (p.step != null) inp.step = p.step;
        inp.value = state.params[p.name] ?? p.default;
      }
      inp.name = p.name;
      inp.dataset.kind = p.kind;
      inp.addEventListener("change", _onParamChange);
      inp.addEventListener("input",  _onParamChange);
      row.appendChild(inp);

      if (p.help) {
        const h = document.createElement("div");
        h.className = "param-help";
        h.textContent = p.help;
        row.appendChild(h);
      }
      wrap.appendChild(row);
    }
    root.appendChild(wrap);
  }
}

function _onParamChange(e) {
  const el = e.target;
  const k = el.name;
  const kind = el.dataset.kind;
  let v;
  if (kind === "bool") v = el.checked;
  else if (kind === "number") v = el.value === "" ? null : Number(el.value);
  else v = el.value;
  state.params[k] = v;
  _updateStatus();
  _scheduleRender();
}

// ----- render orchestration -------------------------------------------------

function _scheduleRender() {
  clearTimeout(state.renderTimer);
  state.renderTimer = setTimeout(_doRender, 400);
}

async function _doRender() {
  if (state.rendering) {
    // Re-schedule once current finishes.
    state.renderTimer = setTimeout(_doRender, 200);
    return;
  }
  state.rendering = true;
  $("render-status").textContent = "rendering…";
  $("warning").textContent = "";
  const t0 = performance.now();
  try {
    const res = await fetch("/api/holder/render", {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ params: state.params }),
    });
    if (!res.ok) {
      let msg = res.statusText;
      try { msg = (await res.json()).error || msg; } catch {}
      throw new Error(msg);
    }
    state.lastBlob = await res.blob();
    const buf = await state.lastBlob.arrayBuffer();
    window.HolderViewer.loadSTL(buf);
    const dt = ((performance.now() - t0) / 1000).toFixed(1);
    $("render-status").textContent = `✓ rendered in ${dt}s · ${(state.lastBlob.size/1024).toFixed(0)} kB`;
    $("render-time").textContent = "";
  } catch (e) {
    $("render-status").textContent = `✗ ${e.message}`;
    if (/openscad/i.test(e.message)) {
      $("warning").textContent =
        "Make sure OpenSCAD is installed on the server (apt install openscad).";
    }
  } finally {
    state.rendering = false;
  }
}

function _updateStatus() {
  // Quick cell count without hitting the server — uses the same formulas
  // server-side but we cheap-out here for instant feedback.
  const rows = +state.params.num_rows || 0;
  const cols = +state.params.num_cols || 0;
  const style = state.params.pack_style;
  let n;
  if (style === "tria") n = rows * (rows + 1) / 2;
  else n = rows * cols;
  $("status").textContent = `${n} cells`;
}

// ----- buttons --------------------------------------------------------------

$("btn-download-stl").addEventListener("click", () => {
  if (!state.lastBlob) { alert("Nothing rendered yet."); return; }
  const url = URL.createObjectURL(state.lastBlob);
  const a = document.createElement("a");
  a.href = url;
  a.download = `hex_holder_${state.params.pack_style}_${state.params.num_rows}x${state.params.num_cols}.stl`;
  document.body.appendChild(a); a.click();
  setTimeout(() => { URL.revokeObjectURL(url); a.remove(); }, 100);
});

$("btn-download-scad").addEventListener("click", async () => {
  // Reuse the bundled SCAD plus a header that pins current values, so the
  // downloaded file reproduces the same model when opened in OpenSCAD.
  const overrides = Object.entries(state.params)
    .map(([k, v]) => `${k} = ${JSON.stringify(v)};`)
    .join("\n");
  // We don't have a backend endpoint for the .scad source yet; fetch it
  // directly (deploy/install.sh puts it under /scad/hex_cell.scad — for the
  // local Flask app it's not exposed under /static. So inline a banner that
  // points the user to copy the params manually for now.)
  const banner = `// Generated by Hex Holder Designer\n// Drop these overrides into hex_cell.scad (or pass via OpenSCAD -D):\n//\n${
    overrides.split("\n").map((l) => "//   " + l).join("\n")
  }\n//\n// Or run: openscad -o out.stl ${
    Object.entries(state.params).map(([k,v]) => `-D ${k}=${JSON.stringify(v)}`).join(" ")
  } hex_cell.scad\n`;
  const blob = new Blob([banner + "\n" + overrides + "\n"], { type: "text/plain" });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = "hex_holder_params.scad";
  document.body.appendChild(a); a.click();
  setTimeout(() => { URL.revokeObjectURL(url); a.remove(); }, 100);
});

$("btn-to-busbar").addEventListener("click", async () => {
  $("render-status").textContent = "exporting cells…";
  try {
    const r = await fetch("/api/holder/cells", {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ params: state.params }),
    });
    if (!r.ok) throw new Error((await r.json()).error || r.statusText);
    const { cells } = await r.json();
    if (!cells || !cells.length) throw new Error("no cells produced");

    const partLabel = `${state.params.pack_style} ${state.params.num_rows}×${state.params.num_cols} (${state.params.cell_dia}mm)`;
    const proj = await Api.createProject(`Holder · ${partLabel}`, {
      params: {
        cellDia:    state.params.cell_dia,
        openingDia: state.params.cell_dia - 2 * state.params.cell_top_overlap,
      },
      cells,
      busbars: [],
      activeBusbarId: null,
    });
    location.href = `/?p=${proj.id}`;
  } catch (e) {
    $("render-status").textContent = `✗ ${e.message}`;
  }
});

// ----- bootstrap ------------------------------------------------------------

async function init() {
  try {
    const r = await fetch("/api/holder/params");
    if (!r.ok) throw new Error(r.statusText);
    const { params: schema, defaults } = await r.json();
    state.schema = schema;
    state.params = { ...defaults };
    _renderForm(schema, defaults);
    _updateStatus();
  } catch (e) {
    $("param-form").innerHTML =
      `<div class="step-preview-err">Couldn't load param schema: ${e.message}</div>`;
    return;
  }

  _whenViewerReady(() => {
    window.HolderViewer.init($("viewer3d"));
    state.rendererReady = true;
    _doRender();   // initial render with defaults
  });
}

init();