(() => {
  const canvas = document.querySelector('#model-canvas');
  const stage = document.querySelector('.rov-stage');
  const ctx = canvas.getContext('2d');
  let vertices = null, frame = 0;
  const renderScale = .62;

  function parseStl(buffer) {
    const view = new DataView(buffer);
    let raw = [];
    const binaryCount = buffer.byteLength >= 84 ? view.getUint32(80, true) : 0;
    const isBinary = binaryCount > 0 && 84 + binaryCount * 50 <= buffer.byteLength;
    if (isBinary) {
      const stride = Math.max(1, Math.ceil(binaryCount / 14000));
      for (let t = 0; t < binaryCount; t += stride) {
        const offset = 84 + t * 50 + 12;
        for (let v = 0; v < 3; v++) {
          raw.push(view.getFloat32(offset + v * 12, true));
          raw.push(view.getFloat32(offset + v * 12 + 4, true));
          raw.push(view.getFloat32(offset + v * 12 + 8, true));
        }
      }
    } else {
      const text = new TextDecoder().decode(buffer);
      const matches = [...text.matchAll(/vertex\s+([-+\deE.]+)\s+([-+\deE.]+)\s+([-+\deE.]+)/gi)];
      if (matches.length < 3) throw new Error('This file does not contain a readable STL mesh');
      const stride = Math.max(1, Math.ceil(matches.length / 42000));
      for (let i = 0; i + 2 < matches.length; i += 3 * stride) {
        for (let j = 0; j < 3; j++) raw.push(+matches[i+j][1], +matches[i+j][2], +matches[i+j][3]);
      }
    }
    if (raw.length < 9) throw new Error('The STL mesh is empty');
    let minX=Infinity,minY=Infinity,minZ=Infinity,maxX=-Infinity,maxY=-Infinity,maxZ=-Infinity;
    for(let i=0;i<raw.length;i+=3){minX=Math.min(minX,raw[i]);maxX=Math.max(maxX,raw[i]);minY=Math.min(minY,raw[i+1]);maxY=Math.max(maxY,raw[i+1]);minZ=Math.min(minZ,raw[i+2]);maxZ=Math.max(maxZ,raw[i+2])}
    const cx=(minX+maxX)/2,cy=(minY+maxY)/2,cz=(minZ+maxZ)/2,scale=2/Math.max(maxX-minX,maxY-minY,maxZ-minZ,1e-9);
    for(let i=0;i<raw.length;i+=3){raw[i]=(raw[i]-cx)*scale;raw[i+1]=(raw[i+1]-cy)*scale;raw[i+2]=(raw[i+2]-cz)*scale}
    return new Float32Array(raw);
  }

  function draw() {
    frame=0;if(!vertices)return;
    const rect=canvas.getBoundingClientRect();
    const width=Math.max(1,Math.round(rect.width*renderScale)),height=Math.max(1,Math.round(rect.height*renderScale));
    if(canvas.width!==width||canvas.height!==height){canvas.width=width;canvas.height=height}
    ctx.setTransform(1,0,0,1,0,0);ctx.clearRect(0,0,width,height);
    const mask=document.createElement('canvas'),maskCtx=mask.getContext('2d');
    mask.width=width;mask.height=height;
    const size=Math.min(width,height)*.43,cx=width/2,cy=height/2;
    maskCtx.fillStyle='#fff';
    for(let i=0;i<vertices.length;i+=9){
      maskCtx.beginPath();
      maskCtx.moveTo(cx+vertices[i]*size,cy-vertices[i+1]*size);
      maskCtx.lineTo(cx+vertices[i+3]*size,cy-vertices[i+4]*size);
      maskCtx.lineTo(cx+vertices[i+6]*size,cy-vertices[i+7]*size);
      maskCtx.closePath();maskCtx.fill();
    }
    // A filtered copy creates only the exterior contour; triangle boundaries
    // never enter the final image because the source is a single solid mask.
    ctx.save();
    ctx.filter='drop-shadow(0 0 1.2px rgba(8,15,17,.9)) drop-shadow(0 4px 5px rgba(0,0,0,.28))';
    ctx.drawImage(mask,0,0);ctx.restore();
    const surface=document.createElement('canvas'),surfaceCtx=surface.getContext('2d');
    surface.width=width;surface.height=height;
    const gradient=surfaceCtx.createLinearGradient(0,0,width,height);
    gradient.addColorStop(0,'#ffffff');gradient.addColorStop(.58,'#f4f5f2');gradient.addColorStop(1,'#dfe2de');
    surfaceCtx.fillStyle=gradient;surfaceCtx.fillRect(0,0,width,height);
    surfaceCtx.globalCompositeOperation='destination-in';surfaceCtx.drawImage(mask,0,0);
    ctx.drawImage(surface,0,0);
  }
  function requestDraw(){if(!frame)frame=requestAnimationFrame(draw)}
  addEventListener('resize',requestDraw);

  window.rovModel = {
    loadBuffer(buffer, name) {
      vertices=parseStl(buffer);stage.classList.add('model-loaded');
      document.querySelector('#model-file-name').textContent=name;
      requestDraw();
      return {name,triangles:vertices.length/9};
    },
    load(payload) {
      if (!payload?.data) throw new Error('The selected STL returned no mesh data');
      const binary=atob(payload.data),bytes=new Uint8Array(binary.length);
      for(let i=0;i<binary.length;i++)bytes[i]=binary.charCodeAt(i);
      return this.loadBuffer(bytes.buffer,payload.name);
    }
  };
})();