GraphSimulation/bfs.html at master · harshpalas/GraphSimulation · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <title>BFS Visualizer with Play/Pause & Accumulating Explanation</title>
  <script src="https://cdn.tailwindcss.com"></script>
  <style>
    button:disabled {
      opacity: 0.5;
      cursor: not-allowed;
    }
    #explanationContainer {
      white-space: pre-wrap;
      font-family: monospace;
      font-size: 0.875rem;
      max-height: 220px;
      overflow-y: auto;
      background: #111827;
      padding: 0.75rem;
      border-radius: 0.375rem;
      color: #d1d5db;
    }
  </style>
</head>
<body class="bg-gray-900 text-white min-h-screen flex items-center justify-center">
  <div class="p-6 bg-gray-800 rounded-xl shadow-xl w-[1400px] max-w-full">
    <div class="flex gap-6 flex-wrap">
      <!-- Sidebar -->
      <div class="w-64 flex flex-col gap-4">
        <h2 class="text-2xl font-bold mb-2">BFS Visualizer (Multiple Graphs)</h2>
        <label>
          Start Node:
          <select id="start" class="w-full text-black rounded p-2 mt-1"></select>
        </label>
        <div class="flex gap-2">
          <button id="playPause" class="bg-blue-600 hover:bg-blue-700 text-white py-2 px-4 rounded flex-1">Play</button>
          <button id="reset" class="bg-gray-400 hover:bg-gray-500 text-white py-2 px-4 rounded flex-1">Reset</button>
        </div>
        <button id="changeGraph" class="bg-green-700 hover:bg-green-800 text-white py-2 px-4 rounded">Change Graph</button>

        <p id="orderDisplay" class="text-sm text-gray-300 mt-4">BFS Order: </p>
        <p id="graphName" class="text-gray-400 mt-2"></p>

        <div class="mt-4 flex flex-col gap-2">
          <h3 class="font-semibold">Explanation Steps:</h3>
          <div id="explanationContainer"></div>
        </div>
      </div>

      <!-- Graph Area -->
      <div class="flex-1 overflow-auto max-w-[1100px]">
        <svg id="graph" width="1100" height="700" class="rounded bg-gray-700 shadow"></svg>
      </div>
    </div>
  </div>

<script>
const graphs = [
  {
    name: "Binary Tree (31 nodes)",
    totalNodes: 31,
    positions: (() => {
      const positions = [];
      const levels = 5;
      const width = 1100;
      const verticalSpacing = 110;
      for (let level = 0; level < levels; level++) {
        const nodesInLevel = Math.pow(2, level);
        const horizontalSpacing = width / (nodesInLevel + 1);
        for (let i = 0; i < nodesInLevel; i++) {
          const x = horizontalSpacing * (i + 1);
          const y = verticalSpacing * level + 50;
          positions.push({ x, y });
        }
      }
      return positions;
    })(),
    edges: (() => {
      const edges = [];
      const totalNodes = 31;
      for (let i = 0; i < totalNodes; i++) {
        const left = 2 * i + 1;
        const right = 2 * i + 2;
        if (left < totalNodes) edges.push([i, left]);
        if (right < totalNodes) edges.push([i, right]);
      }
      return edges;
    })()
  },
  {
    name: "Grid Graph (5x5 = 25 nodes)",
    totalNodes: 25,
    positions: (() => {
      const positions = [];
      const rows = 5;
      const cols = 5;
      const spacingX = 180;
      const spacingY = 120;
      const startX = 100;
      const startY = 100;
      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          positions.push({ x: startX + c * spacingX, y: startY + r * spacingY });
        }
      }
      return positions;
    })(),
    edges: (() => {
      const edges = [];
      const rows = 5;
      const cols = 5;
      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          const idx = r * cols + c;
          if (c + 1 < cols) edges.push([idx, idx + 1]);
          if (r + 1 < rows) edges.push([idx, idx + cols]);
        }
      }
      return edges;
    })()
  }
];

let currentGraphIndex = 0;
let graph = graphs[currentGraphIndex];
let adj = [];
let animOrder = [];
let visitedEdges = new Set();

const radius = 18;

let isRunning = false;
let isPaused = true; // initially paused until Play is clicked
let bfsGenerator = null;

let currentTimeout = null;

function buildAdjacency() {
  adj = Array.from({ length: graph.totalNodes }, () => []);
  graph.edges.forEach(([u, v]) => {
    adj[u].push(v);
    adj[v].push(u);
  });
}

function drawGraph() {
  const svg = document.getElementById("graph");
  svg.innerHTML = "";

  // Draw edges
  for (let [u, v] of graph.edges) {
    const p1 = graph.positions[u];
    const p2 = graph.positions[v];
    const edgeId1 = `${u}-${v}`;
    const edgeId2 = `${v}-${u}`;
    const isVisitedEdge = visitedEdges.has(edgeId1) || visitedEdges.has(edgeId2);

    const line = document.createElementNS("http://www.w3.org/2000/svg", "line");
    line.setAttribute("x1", p1.x);
    line.setAttribute("y1", p1.y);
    line.setAttribute("x2", p2.x);
    line.setAttribute("y2", p2.y);
    line.setAttribute("stroke", isVisitedEdge ? "#3b82f6" : "#ccc");
    line.setAttribute("stroke-width", isVisitedEdge ? "5" : "2");
    svg.appendChild(line);
  }

  // Draw nodes
  for (let i = 0; i < graph.totalNodes; i++) {
    const { x, y } = graph.positions[i];
    const circle = document.createElementNS("http://www.w3.org/2000/svg", "circle");
    circle.setAttribute("cx", x);
    circle.setAttribute("cy", y);
    circle.setAttribute("r", radius);
    circle.setAttribute("fill", animOrder.includes(i) ? "#3b82f6" : "#e2e8f0");
    circle.setAttribute("stroke", "#1e293b");
    circle.setAttribute("stroke-width", "2");
    svg.appendChild(circle);

    const text = document.createElementNS("http://www.w3.org/2000/svg", "text");
    text.setAttribute("x", x);
    text.setAttribute("y", y + 6);
    text.setAttribute("text-anchor", "middle");
    text.setAttribute("font-size", "16");
    text.setAttribute("font-weight", "bold");
    text.setAttribute("fill", animOrder.includes(i) ? "#fff" : "#000");
    text.textContent = i;
    svg.appendChild(text);
  }
}

function fillSelects() {
  const startSel = document.getElementById("start");
  startSel.innerHTML = "";
  for (let i = 0; i < graph.totalNodes; i++) {
    const opt = document.createElement("option");
    opt.value = i;
    opt.textContent = i;
    startSel.appendChild(opt);
  }
}

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

// Typewriter effect: appends text char-by-char to the explanation container with abort support
async function typeWriter(text, container, delay = 40, abortSignal) {
  return new Promise(async (resolve, reject) => {
    if (!text) {
      resolve();
      return;
    }
    let i = 0;
    const chars = text.split("");
    while (i < chars.length) {
      if (abortSignal.aborted) {
        reject(new Error("Cancelled"));
        return;
      }
      container.textContent += chars[i];
      container.scrollTop = container.scrollHeight;
      i++;
      await sleep(delay);
    }
    container.textContent += "\n";
    container.scrollTop = container.scrollHeight;
    resolve();
  });
}

// BFS generator yields explanation steps
function* bfsGen(start) {
  const visited = Array(graph.totalNodes).fill(false);
  const queue = [];
  animOrder = [];
  visitedEdges.clear();

  yield `Starting BFS from node ${start}.`;

  queue.push(start);
  visited[start] = true;

  while (queue.length > 0) {
    const u = queue.shift();
    yield `Dequeued node ${u} for processing.`;

    animOrder.push(u);
    yield null; // redraw step indicator (no explanation text)

    for (const v of adj[u]) {
      if (!visited[v]) {
        visitedEdges.add(`${u}-${v}`);
        yield `Visiting node ${v} from node ${u}, marking it as visited and adding to queue.`;
        visited[v] = true;
        queue.push(v);
        animOrder.push(v);
        yield null; // redraw
      } else {
        yield `Node ${v} already visited, skipping.`;
      }
    }
  }
  yield "BFS traversal completed.";
}

function updateOrderDisplay() {
  document.getElementById("orderDisplay").textContent = `BFS Order: ${animOrder.join(" → ")}`;
  document.getElementById("graphName").textContent = `Current Graph: ${graph.name}`;
}

function resetSimulation() {
  isRunning = false;
  isPaused = true;
  animOrder = [];
  visitedEdges.clear();
  bfsGenerator = null;

  clearTimeout(currentTimeout);
  currentTimeout = null;

  // Reset UI states
  document.getElementById("playPause").textContent = "Play";
  document.getElementById("explanationContainer").textContent = "";
  drawGraph();
  updateOrderDisplay();
}

async function animateBFS(start) {
  isRunning = true;
  isPaused = false;
  document.getElementById("playPause").textContent = "Pause";

  bfsGenerator = bfsGen(start);
  const explanationContainer = document.getElementById("explanationContainer");
  const abortController = new AbortController();

  async function step() {
    if (!isRunning || isPaused) {
      // Wait a bit and re-check if resumed
      currentTimeout = setTimeout(step, 200);
      return;
    }

    const { value, done } = bfsGenerator.next();
    if (done) {
      isRunning = false;
      document.getElementById("playPause").textContent = "Play";
      return;
    }

    if (value !== null) {
      try {
        await typeWriter(value.trim(), explanationContainer, 40, abortController.signal);
      } catch {
        // Cancelled - stop further animation
        return;
      }
    }

    drawGraph();
    updateOrderDisplay();

    // Next step after delay (shorter if no text)
    const delay = (value === null) ? 600 : 1000;
    currentTimeout = setTimeout(step, delay);
  }

  step();

  // Return abortController to cancel if needed
  return abortController;
}

let currentAbortController = null;

document.addEventListener("DOMContentLoaded", () => {
  buildAdjacency();
  fillSelects();
  drawGraph();
  updateOrderDisplay();

  const playPauseBtn = document.getElementById("playPause");
  const resetBtn = document.getElementById("reset");
  const changeGraphBtn = document.getElementById("changeGraph");

  playPauseBtn.onclick = () => {
    if (!isRunning) {
      // Start animation
      const start = +document.getElementById("start").value;
      animateBFS(start).then(controller => {
        currentAbortController = controller;
      });
    } else if (isPaused) {
      // Resume
      isPaused = false;
      playPauseBtn.textContent = "Pause";
    } else {
      // Pause
      isPaused = true;
      playPauseBtn.textContent = "Play";
    }
  };

  resetBtn.onclick = () => {
    if (isRunning) {
      isRunning = false;
      isPaused = true;
      if (currentAbortController) currentAbortController.abort();
      currentAbortController = null;
      clearTimeout(currentTimeout);
      currentTimeout = null;
    }
    resetSimulation();
  };

  changeGraphBtn.onclick = () => {
    if (isRunning) {
      isRunning = false;
      isPaused = true;
      if (currentAbortController) currentAbortController.abort();
      currentAbortController = null;
      clearTimeout(currentTimeout);
      currentTimeout = null;
    }
    currentGraphIndex = (currentGraphIndex + 1) % graphs.length;
    graph = graphs[currentGraphIndex];
    buildAdjacency();
    fillSelects();
    resetSimulation();
  };
});
</script>
</body>
</html>