/* holder-app.js — controller for the Hex Holder Designer page.
 *
 * - Loads /api/holder/params for the form schema and builds inputs.
 * - Changing params marks the Render button "dirty"; user must click Render
 *   (or Cancel) to drive POST /api/holder/render → 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)
  rendering: false,
  dirty: false,      // params changed since last successful render
  abortCtrl: null,   // for cancelling in-flight render
  elapsedTimer: null,
  rendererReady: false,
  maxCells: 1000,    // server-published cap; overridden by /api/holder/params
  dimensions: null,  // last ECHO dims dict from X-Holder-Dimensions
  maxBox: null,      // {w, d, h} of assembled-battery bounding box
  enclosure: null,   // {w, d, h} of user-defined case (or null)
  scadEditor: null,    // CodeMirror instance (lazy-initialised on first show)
  bundledSource: null, // text fetched from /api/holder/source
  scadVisible: false,
};

const COLOR_MAX_BOX  = 0x4a9eff;  // blue
const COLOR_ENC_OK   = 0x4ad97a;  // green
const COLOR_ENC_BAD  = 0xd94a4a;  // red

// ----- 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",
  "cap", "box", "insulator",
  "bolts", "wires",
  "stacking", "template", "advanced",
];
const GROUP_LABELS = {
  part:      "Part / pack",
  cell:      "Cell",
  size:      "Pack size",
  holder:    "Holder",
  cap:       "Cap",
  box:       "Box",
  insulator: "Insulator",
  bolts:     "Bolts & zipties",
  wires:     "Wires & clamp",
  stacking:  "Vertical stacking",
  template:  "Busbar template",
  advanced:  "Advanced",
};
// Groups that start collapsed (user opens with a click). Basics stay open.
const GROUPS_COLLAPSED = new Set([
  "cap", "box", "insulator", "bolts", "wires",
  "stacking", "template", "advanced",
]);

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";
    if (GROUPS_COLLAPSED.has(g)) wrap.classList.add("collapsed");

    const title = document.createElement("h3");
    title.className = "param-group-title";
    title.textContent = GROUP_LABELS[g] || g;
    title.addEventListener("click", () => wrap.classList.toggle("collapsed"));
    wrap.appendChild(title);

    const body = document.createElement("div");
    body.className = "param-group-body";
    wrap.appendChild(body);

    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);
      }
      body.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();
  _markDirty();
}

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

function _markDirty() {
  state.dirty = true;
  $("btn-render").classList.add("dirty");
}

function _clearDirty() {
  state.dirty = false;
  $("btn-render").classList.remove("dirty");
}

function _showProgress(show) {
  $("render-progress").hidden = !show;
  $("btn-render").hidden = show;
  $("btn-cancel").hidden = !show;
}

function _classifyError(msg) {
  // Backend RuntimeError messages all carry "openscad" in them. Distinguish:
  if (/not found on PATH/i.test(msg))           return { hint: "OpenSCAD binary not found on the server (apt install openscad)." };
  if (/timed out/i.test(msg))                   return { hint: "Render timed out. Try fewer cells, smaller slot widths, or simpler geometry." };
  if (/produced no STL|geometry empty/i.test(msg)) return { hint: "OpenSCAD produced an empty model — check parameter combinations (e.g. cell_top_overlap too large)." };
  return { hint: "" };
}

async function _doRender() {
  if (state.rendering) return;
  state.rendering = true;
  state.abortCtrl = new AbortController();
  $("render-status").textContent = "rendering…";
  $("warning").textContent = "";
  $("render-time").textContent = "";
  _showProgress(true);

  const t0 = performance.now();
  state.elapsedTimer = setInterval(() => {
    const dt = ((performance.now() - t0) / 1000).toFixed(1);
    $("render-elapsed").textContent = `${dt}s`;
  }, 100);

  try {
    const useCustomSource = state.scadVisible && state.scadEditor &&
                            state.scadEditor.getValue() !== state.bundledSource;
    const url  = useCustomSource ? "/api/scad/render"   : "/api/holder/render";
    const body = useCustomSource
      ? { source: state.scadEditor.getValue(), params: state.params }
      : { params: state.params };
    const res = await fetch(url, {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify(body),
      signal: state.abortCtrl.signal,
    });
    if (!res.ok) {
      let msg = res.statusText;
      try { msg = (await res.json()).error || msg; } catch {}
      throw new Error(msg);
    }
    // Pick up the ECHO dimensions header before we read the body (whichever
    // order is fine, but keep header access close to the response).
    const dimHdr = res.headers.get("X-Holder-Dimensions");
    state.dimensions = dimHdr ? _safeParseJSON(dimHdr) : null;

    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`;
    _clearDirty();
    _updateFitCheck();
  } catch (e) {
    if (e.name === "AbortError") {
      $("render-status").textContent = "✗ cancelled";
    } else {
      $("render-status").textContent = `✗ ${e.message}`;
      const { hint } = _classifyError(e.message);
      if (hint) $("warning").textContent = hint;
    }
  } finally {
    state.rendering = false;
    state.abortCtrl = null;
    clearInterval(state.elapsedTimer);
    _showProgress(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;
  const status = $("status");
  const overLimit = n > state.maxCells;
  status.textContent = overLimit
    ? `${n} cells · over limit (${state.maxCells})`
    : `${n} cells`;
  status.classList.toggle("over-limit", overLimit);
  // Block render when over the cap. Also blocks "Design busbars →"
  // since it'd hit the same limit on the server.
  $("btn-render").disabled = overLimit;
  $("btn-to-busbar").disabled = overLimit;
}

// ----- fit check ------------------------------------------------------------

function _safeParseJSON(s) {
  try { return JSON.parse(s); } catch { return null; }
}

function _extractMaxBox(dims) {
  if (!dims) return null;
  // Prefer the fully-assembled-case dims; fall back to plain-holder dims.
  const w = dims.box_total_length ?? dims.total_length_holder;
  const d = dims.box_total_width  ?? dims.total_width_holder;
  const h = dims.box_total_height ?? dims.pack_height_holder;
  if (!(w > 0) || !(d > 0) || !(h > 0)) return null;
  return { w, d, h };
}

function _readEnclosureInputs() {
  const w = +$("enc-w").value;
  const d = +$("enc-d").value;
  const h = +$("enc-h").value;
  if (!(w > 0) || !(d > 0) || !(h > 0)) return null;
  return { w, d, h };
}

function _checkFit(maxBox, enc) {
  // Compare orientation-independently in the XY plane (rotating the battery
  // 90° around Z is usually free), but keep Z (height) fixed.
  if (!maxBox || !enc) return null;
  const mxxy = [maxBox.w, maxBox.d].sort((a, b) => a - b);
  const exxy = [enc.w, enc.d].sort((a, b) => a - b);
  return exxy[0] + 1e-6 >= mxxy[0]
      && exxy[1] + 1e-6 >= mxxy[1]
      && enc.h + 1e-6 >= maxBox.h;
}

function _fmt(n) { return (Math.round(n * 10) / 10).toFixed(1); }

function _updateFitCheck() {
  state.maxBox = _extractMaxBox(state.dimensions);
  state.enclosure = _readEnclosureInputs();

  // Max-box ghost + label
  if (state.maxBox) {
    $("max-box-dims").textContent =
      `${_fmt(state.maxBox.w)} × ${_fmt(state.maxBox.d)} × ${_fmt(state.maxBox.h)} mm`;
    window.HolderViewer.setGhostBox("max", state.maxBox, {
      visible: $("show-max-box").checked,
      color: COLOR_MAX_BOX,
    });
  } else {
    $("max-box-dims").textContent = "— render first";
    window.HolderViewer.clearGhostBox("max");
  }

  // Enclosure ghost + verdict
  const verdict = $("fit-verdict");
  verdict.className = "hint";
  if (state.enclosure) {
    const fits = _checkFit(state.maxBox, state.enclosure);
    const color = fits === false ? COLOR_ENC_BAD : COLOR_ENC_OK;
    window.HolderViewer.setGhostBox("enc", state.enclosure, {
      visible: $("show-enclosure").checked,
      color,
    });
    if (fits === true) {
      verdict.textContent = "✓ fits";
      verdict.classList.add("fit-ok");
    } else if (fits === false) {
      verdict.textContent = "✗ too small — battery won't fit";
      verdict.classList.add("fit-bad");
    } else {
      verdict.textContent = "render to compare";
    }
  } else {
    window.HolderViewer.clearGhostBox("enc");
    verdict.textContent = "";
  }
}

// ----- SCAD editor ----------------------------------------------------------

async function _ensureBundledSource() {
  if (state.bundledSource !== null) return;
  const r = await fetch("/api/holder/source");
  if (!r.ok) throw new Error(`source fetch failed: ${r.statusText}`);
  state.bundledSource = await r.text();
}

function _updateScadDirtyTag() {
  if (!state.scadEditor) return;
  const dirty = state.scadEditor.getValue() !== state.bundledSource;
  $("scad-dirty-tag").hidden = !dirty;
}

async function _showScadEditor() {
  await _ensureBundledSource();
  $("scad-panel").hidden = false;
  state.scadVisible = true;
  if (!state.scadEditor) {
    state.scadEditor = window.CodeMirror($("scad-editor"), {
      value: state.bundledSource,
      mode: "text/x-csrc",      // closest built-in mode for OpenSCAD
      theme: "dracula",
      lineNumbers: true,
      indentUnit: 4,
      tabSize: 4,
      lineWrapping: false,
      viewportMargin: Infinity, // render whole document so CM fills the panel
    });
    state.scadEditor.on("change", _updateScadDirtyTag);
  } else {
    state.scadEditor.refresh();
  }
  _updateScadDirtyTag();
}

function _hideScadEditor() {
  $("scad-panel").hidden = true;
  state.scadVisible = false;
}

$("btn-scad-toggle").addEventListener("click", () => {
  if (state.scadVisible) _hideScadEditor();
  else _showScadEditor().catch((e) => alert("Couldn't load SCAD: " + e.message));
});
$("btn-scad-close").addEventListener("click", _hideScadEditor);
$("btn-scad-reset").addEventListener("click", () => {
  if (!state.scadEditor || state.bundledSource == null) return;
  state.scadEditor.setValue(state.bundledSource);
  _updateScadDirtyTag();
});

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

$("show-max-box").addEventListener("change", _updateFitCheck);
$("show-enclosure").addEventListener("change", _updateFitCheck);
for (const id of ["enc-w", "enc-d", "enc-h"]) {
  $(id).addEventListener("input", () => {
    // Auto-enable the toggle when the user starts typing dims.
    if (_readEnclosureInputs()) $("show-enclosure").checked = true;
    _updateFitCheck();
  });
}

$("btn-render").addEventListener("click", () => {
  if (state.rendererReady) _doRender();
});

$("btn-cancel").addEventListener("click", () => {
  if (state.abortCtrl) state.abortCtrl.abort();
});

$("btn-download-stl").addEventListener("click", () => {
  if (!state.lastBlob) { alert("Nothing rendered yet."); return; }
  const url = URL.createObjectURL(state.lastBlob);
  const a = document.createElement("a");
  a.href = url;
  a.download = `hex_holder_${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, max_cells } = await r.json();
    state.schema = schema;
    state.params = { ...defaults };
    if (typeof max_cells === "number") state.maxCells = max_cells;
    _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;
    // Auto-render once on load so the user sees something immediately.
    // After that, rendering is explicit (Render button).
    _doRender();
  });
}

init();