script.js

function simulate() {
  const refString = document.getElementById('refString').value.split(',').map(n => parseInt(n.trim()));
  const numFrames = parseInt(document.getElementById('numFrames').value);
  const algorithm = document.getElementById('algorithm').value;
  let output = '';

  if (algorithm === 'FIFO') {
    output = fifo(refString, numFrames);
  } else if (algorithm === 'LRU') {
    output = lru(refString, numFrames);
  } else if (algorithm === 'Optimal') {
    output = optimal(refString, numFrames);
  }

  document.getElementById('output').innerText = output;
}

function fifo(pages, frames) {
  let queue = [];
  let pageFaults = 0;
  let result = '';

  for (let page of pages) {
    if (!queue.includes(page)) {
      if (queue.length >= frames) queue.shift();
      queue.push(page);
      pageFaults++;
    }
    result += `Page: ${page} | Frames: [${queue.join(', ')}]\n`;
  }

  result += `\nTotal Page Faults (FIFO): ${pageFaults}`;
  return result;
}

function lru(pages, frames) {
  let stack = [];
  let pageFaults = 0;
  let result = '';

  for (let page of pages) {
    let idx = stack.indexOf(page);
    if (idx !== -1) stack.splice(idx, 1);
    else {
      if (stack.length >= frames) stack.shift();
      pageFaults++;
    }
    stack.push(page);
    result += `Page: ${page} | Frames: [${stack.join(', ')}]\n`;
  }

  result += `\nTotal Page Faults (LRU): ${pageFaults}`;
  return result;
}

function optimal(pages, frames) {
  let memory = [];
  let pageFaults = 0;
  let result = '';

  for (let i = 0; i < pages.length; i++) {
    let page = pages[i];
    if (!memory.includes(page)) {
      if (memory.length < frames) {
        memory.push(page);
      } else {
        let future = pages.slice(i + 1);
        let indexes = memory.map(p => future.indexOf(p));
        let replaceIndex = indexes.indexOf(-1) !== -1 ? indexes.indexOf(-1) : indexes.indexOf(Math.max(...indexes));
        memory[replaceIndex] = page;
      }
      pageFaults++;
    }
    result += `Page: ${page} | Frames: [${memory.join(', ')}]\n`;
  }

  result += `\nTotal Page Faults (Optimal): ${pageFaults}`;
  return result;
}

document.addEventListener('DOMContentLoaded', (event) => {
  // Get the algorithm from the URL query parameters
  const params = new URLSearchParams(window.location.search);
  const algorithmFromURL = params.get('algorithm');

  if (algorithmFromURL) {
    const algorithmSelect = document.getElementById('algorithm');
    if (algorithmSelect) {
      // Set the dropdown value to the algorithm from the URL
      algorithmSelect.value = algorithmFromURL;

      // You could optionally disable or hide the dropdown here if needed
      // E.g., algorithmSelect.disabled = true;
      // E.g., algorithmSelect.style.display = 'none';
      // const algorithmLabel = document.querySelector('label[for="algorithm"]');
      // if (algorithmLabel) algorithmLabel.style.display = 'none';
    }
  }
});