document.addEventListener("DOMContentLoaded", () => {
  // DOM Elements
  const video = document.getElementById("camera-stream");
  const canvas = document.getElementById("overlay-canvas");
  const ctx = canvas.getContext("2d", { willReadFrequently: true });
  const sourceImage = document.getElementById("source-image");

  // Controls
  const opacitySlider = document.getElementById("opacity-slider");
  const opacityVal = document.getElementById("opacity-val");
  const scaleSlider = document.getElementById("scale-slider");
  const scaleVal = document.getElementById("scale-val");
  const colorPicker = document.getElementById("color-picker");
  const toleranceSlider = document.getElementById("tolerance-slider");
  const toleranceVal = document.getElementById("tolerance-val");
  const imageUpload = document.getElementById("image-upload");
  const lockBtn = document.getElementById("lock-btn");
  const unlockBtn = document.getElementById("unlock-btn");
  const resetBtn = document.getElementById("reset-btn");

  // State
  let isLocked = false;
  let imgX = 0;
  let imgY = 0;
  let scale = 1.0;

  // Touch & Drag State
  let isDragging = false;
  let startDragX = 0;
  let startDragY = 0;
  let initialPinchDistance = null;
  let initialScale = 1.0;
  let initialPinchCenter = { x: 0, y: 0 };

  // Original image data for processing
  let originalImageData = null;

  // --- Camera Setup ---
  async function setupCamera() {
    try {
      const stream = await navigator.mediaDevices.getUserMedia({
        video: { facingMode: "environment" }, // Prefer rear camera
      });
      video.srcObject = stream;
    } catch (err) {
      console.error("Error accessing camera:", err);
      alert(
        "Could not access the camera. Please ensure you have granted permission.",
      );
    }
  }

  // --- Image Processing ---
  function hexToRgb(hex) {
    const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result
      ? {
          r: parseInt(result[1], 16),
          g: parseInt(result[2], 16),
          b: parseInt(result[3], 16),
        }
      : { r: 255, g: 255, b: 255 };
  }

  function processImageColor() {
    if (!originalImageData) return;

    const targetColor = hexToRgb(colorPicker.value);
    const tolerance = parseInt(toleranceSlider.value, 10);

    // Create a copy of the original data to modify
    const processedData = new ImageData(
      new Uint8ClampedArray(originalImageData.data),
      originalImageData.width,
      originalImageData.height,
    );

    const data = processedData.data;

    for (let i = 0; i < data.length; i += 4) {
      const r = data[i];
      const g = data[i + 1];
      const b = data[i + 2];

      // Calculate color distance (simple Manhattan distance for speed)
      const rDiff = Math.abs(r - targetColor.r);
      const gDiff = Math.abs(g - targetColor.g);
      const bDiff = Math.abs(b - targetColor.b);

      // If the pixel is within tolerance of the target color, make it transparent
      if (rDiff <= tolerance && gDiff <= tolerance && bDiff <= tolerance) {
        data[i + 3] = 0; // Set alpha to 0
      }
    }

    ctx.putImageData(processedData, 0, 0);
  }

  function initImage() {
    // Set canvas size to match image
    canvas.width = sourceImage.naturalWidth;
    canvas.height = sourceImage.naturalHeight;

    // Draw initial image
    ctx.drawImage(sourceImage, 0, 0);

    // Store original data for color processing
    originalImageData = ctx.getImageData(0, 0, canvas.width, canvas.height);

    // Center the image initially
    resetPosition();

    // Apply initial transparency if needed
    processImageColor();
  }

  // --- Interactions & Controls ---
  function updateTransform() {
    canvas.style.transform = `translate(${imgX}px, ${imgY}px) scale(${scale})`;
    canvas.style.opacity = opacitySlider.value;

    // Sync slider with scale
    scaleSlider.value = scale;
    scaleVal.textContent = scale.toFixed(1) + "x";
  }

  function resetPosition() {
    scale = 1.0;

    // Center based on window size and canvas size
    imgX = (window.innerWidth - canvas.width) / 2;
    // Place it slightly higher than center to leave room for controls
    imgY = (window.innerHeight - canvas.height) / 3;

    updateTransform();
  }

  // --- Multi-Touch Gesture Logic ---
  function getPinchDistance(touches) {
    const dx = touches[0].clientX - touches[1].clientX;
    const dy = touches[0].clientY - touches[1].clientY;
    return Math.sqrt(dx * dx + dy * dy);
  }

  function getPinchCenter(touches) {
    return {
      x: (touches[0].clientX + touches[1].clientX) / 2,
      y: (touches[0].clientY + touches[1].clientY) / 2,
    };
  }

  function startDrag(e) {
    if (isLocked) return;
    e.preventDefault(); // Prevent default touch actions like scrolling

    if (e.touches) {
      if (e.touches.length === 1) {
        // Single finger: Pan
        isDragging = true;
        startDragX = e.touches[0].clientX - imgX;
        startDragY = e.touches[0].clientY - imgY;
      } else if (e.touches.length === 2) {
        // Two fingers: Zoom & Pan
        isDragging = true;
        initialPinchDistance = getPinchDistance(e.touches);
        initialScale = scale;

        const center = getPinchCenter(e.touches);
        startDragX = center.x - imgX;
        startDragY = center.y - imgY;
      }
    } else {
      // Mouse drag
      isDragging = true;
      startDragX = e.clientX - imgX;
      startDragY = e.clientY - imgY;
    }
  }

  function doDrag(e) {
    if (!isDragging || isLocked) return;
    e.preventDefault();

    if (e.touches) {
      if (e.touches.length === 1) {
        // Single finger: Pan
        imgX = e.touches[0].clientX - startDragX;
        imgY = e.touches[0].clientY - startDragY;
      } else if (e.touches.length === 2) {
        // Two fingers: Zoom & Pan

        // 1. Handle Pan (using midpoint)
        const center = getPinchCenter(e.touches);
        imgX = center.x - startDragX;
        imgY = center.y - startDragY;

        // 2. Handle Zoom
        if (initialPinchDistance) {
          const currentDistance = getPinchDistance(e.touches);
          const distanceRatio = currentDistance / initialPinchDistance;
          let newScale = initialScale * distanceRatio;

          // Constrain scale to reasonable limits
          newScale = Math.max(0.1, Math.min(newScale, 5.0));
          scale = newScale;
        }
      }
    } else {
      // Mouse drag
      imgX = e.clientX - startDragX;
      imgY = e.clientY - startDragY;
    }

    updateTransform();
  }

  function endDrag(e) {
    if (e.touches && e.touches.length > 0) {
      // If one finger remains after a pinch, reset the drag starting point so it doesn't jump
      isDragging = true;
      startDragX = e.touches[0].clientX - imgX;
      startDragY = e.touches[0].clientY - imgY;
      initialPinchDistance = null;
    } else {
      isDragging = false;
      initialPinchDistance = null;
    }
  }

  // Event Listeners for Dragging & Gestures
  canvas.addEventListener("mousedown", startDrag);
  window.addEventListener("mousemove", doDrag);
  window.addEventListener("mouseup", endDrag);

  // Use passive: false so we can call e.preventDefault() to stop page scroll
  canvas.addEventListener("touchstart", startDrag, { passive: false });
  window.addEventListener("touchmove", doDrag, { passive: false });
  window.addEventListener("touchend", endDrag);
  window.addEventListener("touchcancel", endDrag);

  // Controls Listeners
  opacitySlider.addEventListener("input", (e) => {
    opacityVal.textContent = Math.round(e.target.value * 100) + "%";
    canvas.style.opacity = e.target.value;
  });

  scaleSlider.addEventListener("input", (e) => {
    scale = parseFloat(e.target.value);
    updateTransform();
  });

  colorPicker.addEventListener("input", processImageColor);

  toleranceSlider.addEventListener("input", (e) => {
    toleranceVal.textContent = e.target.value;
    processImageColor();
  });

  resetBtn.addEventListener("click", resetPosition);

  // Lock logic
  lockBtn.addEventListener("click", () => {
    isLocked = true;
    document.body.classList.add("locked");
    lockBtn.style.display = "none";
    unlockBtn.style.display = "block"; // Explicitly show the unlock button
  });

  unlockBtn.addEventListener("click", () => {
    isLocked = false;
    document.body.classList.remove("locked");
    lockBtn.style.display = "inline-block";
    unlockBtn.style.display = "none"; // Hide unlock button
  });

  imageUpload.addEventListener("change", (e) => {
    const file = e.target.files[0];
    if (!file) return;

    const reader = new FileReader();
    reader.onload = (event) => {
      sourceImage.onload = () => {
        initImage();
      };
      sourceImage.src = event.target.result;
    };
    reader.readAsDataURL(file);
  });

  // --- Initialization ---
  // Ensure image loads (especially useful for local dev or cached images)
  if (sourceImage.complete) {
    initImage();
  } else {
    sourceImage.onload = initImage;
  }

  setupCamera();
});