const PYODIDE_URL = "https://cdn.jsdelivr.net/pyodide/v0.26.1/full/pyodide.mjs";
const RANGE = { min: -5, max: 5 };
const COLORS = { A: "#2d6cdf", B: "#e86f32" };
const REGION = { A: "rgba(45,108,223,.12)", B: "rgba(232,111,50,.12)" };
const BUILTIN_DATASETS = {
  "easy-linear": [
    { x: -3.2, y: -2.0, label: "A" }, { x: -2.2, y: 0.1, label: "A" }, { x: -3.0, y: 2.3, label: "A" },
    { x: 3.1, y: -2.1, label: "B" }, { x: 2.1, y: 0.2, label: "B" }, { x: 3.2, y: 2.2, label: "B" },
  ],
  "hard-linear": [
    { x: -3.4, y: -1.08, label: "A" }, { x: -0.2, y: 0.80, label: "A" }, { x: 3.2, y: 2.95, label: "A" },
    { x: -3.2, y: -2.30, label: "B" }, { x: 0.2, y: -0.16, label: "B" }, { x: 3.4, y: 1.77, label: "B" },
  ],
  nonlinear: [
    { x: -0.7, y: -0.5, label: "A" }, { x: 0.7, y: -0.5, label: "A" }, { x: 0.0, y: 0.8, label: "A" },
    { x: -3.2, y: -2.4, label: "B" }, { x: 3.2, y: -2.4, label: "B" }, { x: 0.0, y: 3.3, label: "B" },
  ],
};

const state = { points: structuredClone(BUILTIN_DATASETS['easy-linear']), datasetMode: "easy-linear", redoPoints: [], hoveredPoint: -1, label: "A", model: null, pendingUpdate: null, metrics: null, step: 0, permutation: [], cursor: 0, nextBatch: [], rngState: 42, history: [], viewIndex: -1, previewVersion: 0, previewPromise: null, busy: false, animating: false, ready: false };
const canvas = document.querySelector("#plot");
const ctx = canvas.getContext("2d");
const metricsCanvas = document.querySelector("#metrics-chart");
const metricsCtx = metricsCanvas.getContext("2d");
const ui = Object.fromEntries([...document.querySelectorAll("[id]")].map(el => [el.id, el]));

function modelOptions() {
  return {
    loss: ui.loss.value,
    learning_rate: Number(ui["learning-rate"].value),
    batch_size: Math.max(1, Number.parseInt(ui["batch-size"].value, 10) || 1),
    batch_selection: ui["batch-selection"].value,
    random_state: randomSeed(),
  };
}

function randomSeed() { return (Number.parseInt(ui["random-seed"].value, 10) || 0) >>> 0; }

function resetModel(message = "Model reset. Take a step to begin training.") {
  state.model = null; state.pendingUpdate = null; state.metrics = null; state.step = 0; state.permutation = []; state.cursor = 0; state.nextBatch = []; state.history = []; state.viewIndex = -1;
  state.rngState = randomSeed();
  queueNextBatch();
  ui["step-count"].textContent = "Step 0";
  renderView(); setMessage(message); updateControls(); refreshPreview();
}

function setMessage(text, kind = "") { ui.message.textContent = text; ui.message.className = `message ${kind}`; }
function hasBothClasses() { return state.points.some(p => p.label === "A") && state.points.some(p => p.label === "B"); }
function updateControls() {
  ui.undo.disabled = state.points.length === 0 || state.busy || state.animating;
  ui.redo.disabled = state.redoPoints.length === 0 || state.busy || state.animating;
  ui.clear.disabled = state.points.length === 0 || state.busy || state.animating;
  ui["label-a"].disabled = state.busy || state.animating; ui["label-b"].disabled = state.busy || state.animating;
  for (const id of ["dataset-select", "loss", "learning-rate", "batch-size", "random-seed", "animation-speed", "batch-selection"]) ui[id].disabled = state.busy || state.animating;
  ui["history-prev"].disabled = state.viewIndex <= 0 || state.busy || state.animating;
  ui["history-reset"].disabled = state.viewIndex <= 0 || state.busy || state.animating;
  ui["history-next"].disabled = !state.ready || !hasBothClasses() || state.busy || state.animating;
  ui.animate.disabled = !state.ready || !hasBothClasses() || state.busy || state.animating;
  ui.pause.disabled = !state.animating;
  ui["point-count"].textContent = `${state.points.length} point${state.points.length === 1 ? "" : "s"}`;
  ui["empty-hint"].hidden = state.points.length > 0;
  //ui["plot-instructions"].textContent = state.datasetMode === "custom" ? "Click inside the plot to add a point with the selected label." : "Hover over a point to inspect its coordinates.";
  if (!hasBothClasses()) setMessage("Add at least one point from each class to begin.");
}

function shuffleIndices(count) {
  const values = Array.from({ length: count }, (_, i) => i);
  for (let i = values.length - 1; i > 0; i--) { const j = Math.floor(seededRandom() * (i + 1)); [values[i], values[j]] = [values[j], values[i]]; }
  return values;
}

function seededRandom() {
  state.rngState = (Math.imul(1664525, state.rngState) + 1013904223) >>> 0;
  return state.rngState / 4294967296;
}

function nextBatch() {
  const { batch_size, batch_selection } = modelOptions();
  const size = Math.min(batch_size, state.points.length);
  if (batch_selection === "random") return shuffleIndices(state.points.length).slice(0, size);
  if (!state.permutation.length || state.cursor >= state.permutation.length) { state.permutation = shuffleIndices(state.points.length); state.cursor = 0; }
  const batch = state.permutation.slice(state.cursor, state.cursor + size); state.cursor += size;
  return batch;
}

function queueNextBatch() {
  state.nextBatch = hasBothClasses() ? nextBatch() : [];
  const count = state.nextBatch.length;
  ui["batch-summary"].textContent = count ? `Next batch: ${count} point${count === 1 ? "" : "s"}` : "No batch selected";
}

function formatNumber(value) {
  if (Math.abs(value) < 0.0000005) return "0.0000";
  if (Math.abs(value) >= 1000 || Math.abs(value) < 0.001) return value.toExponential(3);
  return value.toFixed(4);
}

function formatVector(vector) { return `[${vector.map(formatNumber).join(", ")}]`; }

function visibleSnapshot() {
  return state.history[state.viewIndex] || { model: state.model, pendingUpdate: state.pendingUpdate, metrics: state.metrics, nextBatch: state.nextBatch, step: state.step };
}

function renderParameters(snapshot = visibleSnapshot()) {
  ui["model-parameters"].textContent = snapshot.model
    ? `w_A = ${formatVector(snapshot.model.coef[0])}\nb_A = ${formatNumber(snapshot.model.intercept[0])}`
    : "w_A = —\nb_A = —";
  ui["model-update"].textContent = snapshot.pendingUpdate
    ? `Δw_A = ${formatVector(snapshot.pendingUpdate.coef[0])}\nΔb_A = ${formatNumber(snapshot.pendingUpdate.intercept[0])}`
    : "Δw_A = —\nΔb_A = —";
}

function captureSnapshot() {
  const snapshot = structuredClone({ model: state.model, pendingUpdate: state.pendingUpdate, metrics: state.metrics, nextBatch: state.nextBatch, step: state.step });
  if (state.history.at(-1)?.step === state.step) state.history[state.history.length - 1] = snapshot;
  else state.history.push(snapshot);
  state.viewIndex = state.history.length - 1;
  renderView();
}

function renderView() {
  const snapshot = visibleSnapshot();
  renderParameters(snapshot);
  ui["step-count"].textContent = `Step ${snapshot.step}`;
  ui["history-position"].textContent = `Step ${snapshot.step} of ${Math.max(0, state.history.length - 1)}`;
  const count = snapshot.nextBatch.length;
  ui["batch-summary"].textContent = count ? `Next batch: ${count} point${count === 1 ? "" : "s"}` : "No batch selected";
  updateControls(); draw(); drawMetrics();
}

async function refreshPreview(reportError = true) {
  const version = ++state.previewVersion;
  if (!state.ready || !hasBothClasses() || !state.nextBatch.length) { renderView(); return; }
  state.previewPromise = (async () => {
    try {
      if (!state.model) {
        const pyOptions = state.pyodide.toPy(modelOptions());
        state.pyodide.globals.set("model_options", pyOptions);
        try { state.pyodide.runPython("model = SGDClassifier(**model_options)"); }
        finally { pyOptions.destroy(); state.pyodide.globals.delete("model_options"); }
      }
      const X = state.nextBatch.map(i => [state.points[i].x, state.points[i].y]);
      const y = state.nextBatch.map(i => state.points[i].label);
      const allX = state.points.map(point => [point.x, point.y]);
      const allY = state.points.map(point => point.label);
      const pyX = state.pyodide.toPy(X), pyY = state.pyodide.toPy(y);
      const pyAllX = state.pyodide.toPy(allX), pyAllY = state.pyodide.toPy(allY);
      state.pyodide.globals.set("preview_X", pyX); state.pyodide.globals.set("preview_y", pyY);
      state.pyodide.globals.set("all_X", pyAllX); state.pyodide.globals.set("all_y", pyAllY);
      try {
        const result = state.pyodide.runPython(`
preview_coef, preview_intercept = model.get_update(preview_X, preview_y, classes=["A", "B"])
metrics = model.evaluate(all_X, all_y)
{"coef": model.coef_.tolist(), "intercept": model.intercept_.tolist(),
 "update_coef": preview_coef.tolist(), "update_intercept": preview_intercept.tolist(),
 "loss": metrics["loss"], "accuracy": metrics["accuracy"]}
        `);
        const values = result.toJs({ dict_converter: Object.fromEntries }); result.destroy();
        if (version !== state.previewVersion) return;
        state.model = { coef: values.coef, intercept: values.intercept };
        state.pendingUpdate = { coef: values.update_coef, intercept: values.update_intercept };
        state.metrics = { loss: values.loss, accuracy: values.accuracy };
        captureSnapshot();
      } finally {
        pyX.destroy(); pyY.destroy(); pyAllX.destroy(); pyAllY.destroy();
        for (const name of ["preview_X", "preview_y", "all_X", "all_y"]) state.pyodide.globals.delete(name);
      }
    } catch (error) {
      if (version === state.previewVersion) { state.pendingUpdate = null; renderView(); if (reportError) setMessage(error instanceof Error ? error.message : String(error), "error"); }
    }
  })();
  return state.previewPromise;
}

async function initializeRuntime() {
  try {
    const { loadPyodide } = await import(PYODIDE_URL);
    const pyodide = await loadPyodide({ indexURL: "https://cdn.jsdelivr.net/pyodide/v0.26.1/full/" });
    await pyodide.loadPackage("numpy");
    const classifierUrl = new URL("sgd_classifier.py", window.location.href);
    classifierUrl.searchParams.set("v", Date.now().toString());
    const source = await fetch(classifierUrl, { cache: "no-store" }).then(response => { if (!response.ok) throw new Error("Classifier source could not be loaded."); return response.text(); });
    pyodide.FS.writeFile("sgd_classifier.py", source);
    pyodide.runPython("from sgd_classifier import SGDClassifier");
    state.pyodide = pyodide; state.ready = true;
    ui["runtime-status"].className = "status ready"; ui["runtime-status"].innerHTML = "<span></span>Python runtime ready";
    updateControls(); refreshPreview();
  } catch (error) {
    ui["runtime-status"].className = "status error"; ui["runtime-status"].innerHTML = "<span></span>Runtime failed";
    setMessage(error instanceof Error ? error.message : String(error), "error");
  }
}

async function trainOneStep(fromAnimation = false) {
  if (!fromAnimation && ui["history-next"].disabled) return false;
  if (state.viewIndex < state.history.length - 1) { state.viewIndex += 1; renderView(); return true; }
  state.busy = true; updateControls(); ui["history-next"].querySelector(".button-text").textContent = "Training…";
  try {
    if (state.previewPromise) await state.previewPromise;
    if (!state.model || !state.pendingUpdate) throw new Error("The parameter update is not ready yet.");
    const indices = state.nextBatch.slice();
    const X = indices.map(i => [state.points[i].x, state.points[i].y]);
    const y = indices.map(i => state.points[i].label);
    const pyX = state.pyodide.toPy(X), pyY = state.pyodide.toPy(y);
    state.pyodide.globals.set("batch_X", pyX); state.pyodide.globals.set("batch_y", pyY);
    try {
      const result = state.pyodide.runPython(`
model.train_step(batch_X, batch_y, classes=["A", "B"])
{"coef": model.coef_.tolist(), "intercept": model.intercept_.tolist()}
      `);
      state.model = result.toJs({ dict_converter: Object.fromEntries }); result.destroy();
    } finally { pyX.destroy(); pyY.destroy(); state.pyodide.globals.delete("batch_X"); state.pyodide.globals.delete("batch_y"); }
    state.step += 1;
    queueNextBatch();
    await refreshPreview(false);
    setMessage(`Completed SGD step ${state.step}. The next update is shown.`, "success"); renderView();
    return true;
  } catch (error) { setMessage(error instanceof Error ? error.message : String(error), "error"); return false; }
  finally { state.busy = false; ui["history-next"].querySelector(".button-text").textContent = "Next"; updateControls(); }
}

async function startAnimation() {
  if (ui.animate.disabled) return;
  state.animating = true; updateControls(); setMessage("Animation running…", "success");
  while (state.animating) {
    const succeeded = await trainOneStep(true);
    if (!succeeded) { state.animating = false; break; }
    await new Promise(resolve => setTimeout(resolve, Number(ui["animation-speed"].value)));
  }
  updateControls();
  if (!state.animating && !ui.message.classList.contains("error")) setMessage("Animation paused.");
}

function pauseAnimation() { state.animating = false; updateControls(); }

function drawMetrics() {
  const rect = metricsCanvas.getBoundingClientRect();
  if (!rect.width || !rect.height) return;
  const ratio = window.devicePixelRatio || 1;
  metricsCanvas.width = Math.round(rect.width * ratio); metricsCanvas.height = Math.round(rect.height * ratio);
  metricsCtx.setTransform(ratio, 0, 0, ratio, 0, 0); metricsCtx.clearRect(0, 0, rect.width, rect.height);
  const data = state.history.filter(snapshot => snapshot.metrics);
  const pad = { left: 34, right: 34, top: 10, bottom: 22 };
  const width = rect.width - pad.left - pad.right, height = rect.height - pad.top - pad.bottom;
  const bottom = pad.top + height;
  metricsCtx.font = "9px system-ui"; metricsCtx.fillStyle = "#77847d"; metricsCtx.strokeStyle = "#e4e9e5"; metricsCtx.lineWidth = 1;
  for (let fraction = 0; fraction <= 1; fraction += 0.5) {
    const y = pad.top + height * fraction; metricsCtx.beginPath(); metricsCtx.moveTo(pad.left,y); metricsCtx.lineTo(pad.left+width,y); metricsCtx.stroke();
  }
  if (!data.length) { metricsCtx.textAlign="center"; metricsCtx.fillText("Metrics appear after initialization",rect.width/2,rect.height/2); return; }
  const maxLoss = Math.max(...data.map(snapshot => snapshot.metrics.loss), 1e-9) * 1.08;
  const pointX = index => data.length === 1 ? pad.left + width / 2 : pad.left + index / (data.length - 1) * width;
  const lossY = value => bottom - value / maxLoss * height;
  const accuracyY = value => bottom - value * height;
  metricsCtx.textAlign="right"; metricsCtx.fillStyle="#8b5cf6"; metricsCtx.fillText(maxLoss.toFixed(2),pad.left-5,pad.top+3); metricsCtx.fillText("0",pad.left-5,bottom+3);
  metricsCtx.textAlign="left"; metricsCtx.fillStyle="#159267"; metricsCtx.fillText("100%",pad.left+width+5,pad.top+3); metricsCtx.fillText("0%",pad.left+width+5,bottom+3);
  metricsCtx.textAlign="center"; metricsCtx.fillStyle="#77847d"; metricsCtx.fillText("step",pad.left+width/2,rect.height-3);
  const drawSeries = (color, getY) => {
    metricsCtx.strokeStyle=color; metricsCtx.lineWidth=2; metricsCtx.beginPath();
    data.forEach((snapshot,index)=>{const x=pointX(index),y=getY(snapshot.metrics);if(index)metricsCtx.lineTo(x,y);else metricsCtx.moveTo(x,y);}); metricsCtx.stroke();
    data.forEach((snapshot,index)=>{const x=pointX(index),y=getY(snapshot.metrics),active=index===state.viewIndex;metricsCtx.beginPath();metricsCtx.arc(x,y,active?5:2.5,0,Math.PI*2);metricsCtx.fillStyle=active?"white":color;metricsCtx.fill();metricsCtx.strokeStyle=color;metricsCtx.lineWidth=active?2.5:1;metricsCtx.stroke();});
  };
  drawSeries("#8b5cf6", metrics => lossY(metrics.loss));
  drawSeries("#159267", metrics => accuracyY(metrics.accuracy));
}

function dimensions() {
  const rect = canvas.getBoundingClientRect(), ratio = window.devicePixelRatio || 1;
  if (canvas.width !== Math.round(rect.width * ratio) || canvas.height !== Math.round(rect.height * ratio)) { canvas.width = Math.round(rect.width * ratio); canvas.height = Math.round(rect.height * ratio); }
  ctx.setTransform(ratio, 0, 0, ratio, 0, 0); return { width: rect.width, height: rect.height, pad: 40 };
}
function toPixel(x, y, d) { const sizeX = d.width - d.pad * 2, sizeY = d.height - d.pad * 2; return [d.pad + (x - RANGE.min) / 10 * sizeX, d.height - d.pad - (y - RANGE.min) / 10 * sizeY]; }
function fromPixel(px, py, d) { return [RANGE.min + (px - d.pad) / (d.width - d.pad * 2) * 10, RANGE.min + (d.height - d.pad - py) / (d.height - d.pad * 2) * 10]; }
function predictedClass(x, y, model) {
  if (!model) return null;
  const scoreA = model.coef[0][0] * x + model.coef[0][1] * y + model.intercept[0];
  const scoreB = model.coef[1][0] * x + model.coef[1][1] * y + model.intercept[1];
  return scoreA >= scoreB ? "A" : "B";
}
function draw() {
  const snapshot = visibleSnapshot(), model = snapshot.model, step = snapshot.step;
  const d = dimensions(); ctx.clearRect(0, 0, d.width, d.height);
  const [left, bottom] = toPixel(RANGE.min, RANGE.min, d), [right, top] = toPixel(RANGE.max, RANGE.max, d);
  ctx.fillStyle = "#fbfcfa"; ctx.fillRect(left, top, right - left, bottom - top);
  if (model && step > 0) { const cells = 55, cellW = (right-left)/cells, cellH = (bottom-top)/cells; for (let row=0; row<cells; row++) for (let col=0; col<cells; col++) { const [x,y] = fromPixel(left+(col+.5)*cellW, top+(row+.5)*cellH,d); ctx.fillStyle=REGION[predictedClass(x,y,model)]; ctx.fillRect(left+col*cellW,top+row*cellH,cellW+1,cellH+1); } }
  ctx.strokeStyle = "#e3e8e4"; ctx.lineWidth = 1; ctx.fillStyle = "#7b8881"; ctx.font = "10px system-ui";
  for (let value=-4; value<=4; value+=2) { const [x] = toPixel(value,0,d), [,y]=toPixel(0,value,d); ctx.beginPath(); ctx.moveTo(x,top);ctx.lineTo(x,bottom);ctx.moveTo(left,y);ctx.lineTo(right,y);ctx.stroke(); ctx.fillText(String(value),x-5,bottom+17); ctx.fillText(String(value),left-23,y+3); }
  const [axisX, axisY] = toPixel(0, 0, d);
  ctx.strokeStyle="#718078"; ctx.fillStyle="#526159"; ctx.lineWidth=1.4;
  ctx.beginPath(); ctx.moveTo(left,axisY); ctx.lineTo(right-1,axisY); ctx.moveTo(axisX,bottom); ctx.lineTo(axisX,top+1); ctx.stroke();
  ctx.beginPath(); ctx.moveTo(right-1,axisY); ctx.lineTo(right-8,axisY-4); ctx.lineTo(right-8,axisY+4); ctx.closePath(); ctx.fill();
  ctx.beginPath(); ctx.moveTo(axisX,top+1); ctx.lineTo(axisX-4,top+8); ctx.lineTo(axisX+4,top+8); ctx.closePath(); ctx.fill();
  ctx.font="italic 12px Georgia, serif"; ctx.fillText("x₁",right-13,axisY-9); ctx.fillText("x₂",axisX+9,top+14);
  ctx.strokeStyle="#aebbb3"; ctx.strokeRect(left,top,right-left,bottom-top);
  if (step === 0 && hasBothClasses()) {
    // Zero initialization has no unique separating hyperplane; use x = 0 as
    // the visible reference boundary until the first gradient update.
    const [x] = toPixel(0, 0, d);
    ctx.save(); ctx.setLineDash([6, 6]); ctx.strokeStyle="#68766e"; ctx.lineWidth=2;
    ctx.beginPath(); ctx.moveTo(x,top); ctx.lineTo(x,bottom); ctx.stroke(); ctx.restore();
  }
  else if (model) { const w0=model.coef[0][0]-model.coef[1][0], w1=model.coef[0][1]-model.coef[1][1], b=model.intercept[0]-model.intercept[1]; if (Math.abs(w1)>1e-10) { const y1=-(w0*RANGE.min+b)/w1,y2=-(w0*RANGE.max+b)/w1,[px1,py1]=toPixel(RANGE.min,y1,d),[px2,py2]=toPixel(RANGE.max,y2,d); ctx.save();ctx.beginPath();ctx.rect(left,top,right-left,bottom-top);ctx.clip();ctx.strokeStyle="#26342c";ctx.lineWidth=2;ctx.beginPath();ctx.moveTo(px1,py1);ctx.lineTo(px2,py2);ctx.stroke();ctx.restore(); } else if(Math.abs(w0)>1e-10) { const x=-b/w0,[px]=toPixel(x,0,d);ctx.strokeStyle="#26342c";ctx.lineWidth=2;ctx.beginPath();ctx.moveTo(px,top);ctx.lineTo(px,bottom);ctx.stroke(); } }
  const selected = new Set(snapshot.nextBatch);
  state.points.forEach((point, index) => {
    const [x,y]=toPixel(point.x,point.y,d);
    if (selected.has(index)) {
      ctx.beginPath(); ctx.arc(x,y,11,0,Math.PI*2);
      ctx.fillStyle="rgba(255, 202, 58, .28)"; ctx.fill();
      ctx.strokeStyle="#d29400"; ctx.lineWidth=2; ctx.stroke();
    }
    ctx.beginPath();ctx.arc(x,y,6,0,Math.PI*2);ctx.fillStyle=COLORS[point.label];ctx.fill();ctx.strokeStyle="white";ctx.lineWidth=2;ctx.stroke();
  });
  if (state.hoveredPoint >= 0 && state.points[state.hoveredPoint]) {
    const point = state.points[state.hoveredPoint], [x,y] = toPixel(point.x,point.y,d);
    const text = `Class ${point.label} · (${point.x.toFixed(2)}, ${point.y.toFixed(2)})`;
    ctx.font = "11px system-ui"; const width = ctx.measureText(text).width + 16;
    const boxX = Math.min(Math.max(left + 4, x + 12), right - width - 4);
    const boxY = y - 35 < top ? y + 13 : y - 35;
    ctx.fillStyle = "rgba(31, 43, 36, .94)"; ctx.beginPath(); ctx.roundRect(boxX, boxY, width, 27, 5); ctx.fill();
    ctx.fillStyle = "white"; ctx.fillText(text, boxX + 8, boxY + 18);
  }
}

canvas.addEventListener("mousemove", event => {
  const d=dimensions(), rect=canvas.getBoundingClientRect(), px=event.clientX-rect.left, py=event.clientY-rect.top;
  let nearest=-1, distance=10;
  state.points.forEach((point,index)=>{const [x,y]=toPixel(point.x,point.y,d), current=Math.hypot(px-x,py-y);if(current<distance){nearest=index;distance=current;}});
  if (nearest !== state.hoveredPoint) { state.hoveredPoint=nearest; canvas.style.cursor=nearest>=0?"pointer":state.datasetMode==="custom"?"crosshair":"default"; draw(); }
});
canvas.addEventListener("mouseleave",()=>{if(state.hoveredPoint>=0){state.hoveredPoint=-1;canvas.style.cursor=state.datasetMode==="custom"?"crosshair":"default";draw();}});
canvas.addEventListener("click", event => { if (state.busy || state.animating || state.datasetMode !== "custom") return; const d=dimensions(), rect=canvas.getBoundingClientRect(), px=event.clientX-rect.left,py=event.clientY-rect.top; if(px<d.pad||px>d.width-d.pad||py<d.pad||py>d.height-d.pad)return; const [x,y]=fromPixel(px,py,d);state.points.push({x,y,label:state.label});state.redoPoints=[];state.hoveredPoint=-1;resetModel("Dataset changed. The model was reset."); });
ui["label-a"].addEventListener("click",()=>{state.label="A";ui["label-a"].classList.add("active");ui["label-b"].classList.remove("active");});
ui["label-b"].addEventListener("click",()=>{state.label="B";ui["label-b"].classList.add("active");ui["label-a"].classList.remove("active");});
ui.undo.addEventListener("click",()=>{const point=state.points.pop();if(point)state.redoPoints.push(point);state.hoveredPoint=-1;resetModel("Dataset changed. The model was reset.");});
ui.redo.addEventListener("click",()=>{const point=state.redoPoints.pop();if(point)state.points.push(point);resetModel("Point restored. The model was reset.");});
ui.clear.addEventListener("click",()=>{state.points=[];state.redoPoints=[];state.hoveredPoint=-1;resetModel("Dataset cleared.");});
function loadDataset(mode, message) {
  ui["dataset-select"].value = mode;
  state.datasetMode = mode;
  ui["custom-data-controls"].hidden = state.datasetMode !== "custom";
  state.points = state.datasetMode === "custom" ? [] : structuredClone(BUILTIN_DATASETS[state.datasetMode]);
  state.redoPoints = []; state.hoveredPoint = -1;
  canvas.style.cursor = state.datasetMode === "custom" ? "crosshair" : "default";
  resetModel(message || (state.datasetMode === "custom" ? "Click the plot to create a custom dataset." : "Builtin dataset loaded. The model was reset."));
}
ui["dataset-select"].addEventListener("change", () => loadDataset(ui["dataset-select"].value));
function selectTab(name) {
  for (const tab of ["configure", "train", "examples", "usage"]) {
    const active = tab === name;
    ui[`${tab}-tab`].classList.toggle("active", active);
    ui[`${tab}-panel`].classList.toggle("active", active);
  }
  if (name === "train") requestAnimationFrame(drawMetrics);
}
ui["configure-tab"].addEventListener("click", () => selectTab("configure"));
ui["train-tab"].addEventListener("click", () => selectTab("train"));
ui["examples-tab"].addEventListener("click", () => selectTab("examples"));
ui["usage-tab"].addEventListener("click", () => selectTab("usage"));
for (const button of document.querySelectorAll(".example-button")) {
  button.addEventListener("click", () => {
    pauseAnimation();
    ui.loss.value = button.dataset.loss || "perceptron";
    ui["learning-rate"].value = button.dataset.learningRate || "1";
    ui["batch-size"].value = "1";
    ui["batch-selection"].value = "random"; ui["random-seed"].value = "42"; ui["animation-speed"].value = "200";
    ui["sampling-help"].textContent = "Each point is used once before the dataset is shuffled again.";
    loadDataset(button.dataset.dataset, `${button.textContent.trim()} example loaded.`);
    selectTab("train");
  });
}
ui["history-next"].addEventListener("click", trainOneStep);
ui["history-prev"].addEventListener("click", () => { if (state.viewIndex > 0) { state.viewIndex -= 1; renderView(); } });
ui["history-reset"].addEventListener("click", () => { if (state.history.length) { state.viewIndex = 0; renderView(); } });
ui.animate.addEventListener("click", startAnimation); ui.pause.addEventListener("click", pauseAnimation);
for (const id of ["loss","learning-rate","batch-size","random-seed","batch-selection"]) ui[id].addEventListener("change",()=>{if(id==="batch-selection")ui["sampling-help"].textContent=ui[id].value==="random"?"Each step independently samples a subset without replacement.":"Each point is used once before the dataset is shuffled again.";resetModel("Configuration changed. The model was reset.");});
window.addEventListener("keydown",event=>{if(event.code==="Space"&&!event.repeat&&!/INPUT|SELECT|TEXTAREA/.test(document.activeElement.tagName)){event.preventDefault();trainOneStep();}});
new ResizeObserver(draw).observe(canvas.parentElement); new ResizeObserver(drawMetrics).observe(metricsCanvas); queueNextBatch(); updateControls(); draw(); initializeRuntime();