import * as THREE from 'three';

/** Rounded capture footprint; the underlying survey grid remains untouched. */
export function roundedTerrainPlanes(axis: THREE.Vector3, start: number, end: number, halfWidth: number, radius: number) {
  const lateral = new THREE.Vector3(-axis.z, 0, axis.x);
  const corners = [[end-radius,halfWidth-radius,0],[start+radius,halfWidth-radius,90],[start+radius,-halfWidth+radius,180],[end-radius,-halfWidth+radius,270]];
  const points: [number,number][]=[];
  for(const [s,t,angle] of corners) for(let i=0;i<=8;i++) {
    const a=(angle+i*90/8)*Math.PI/180;
    points.push([s+radius*Math.cos(a),t+radius*Math.sin(a)]);
  }
  return points.map((p,i)=>{
    const q=points[(i+1)%points.length],ds=q[0]-p[0],dt=q[1]-p[1];
    const normal=axis.clone().multiplyScalar(-dt).addScaledVector(lateral,ds).normalize();
    const origin=axis.clone().multiplyScalar(p[0]).addScaledVector(lateral,p[1]);
    return new THREE.Plane(normal,-normal.dot(origin));
  });
}

/** Landing-only road ribbons, joining the photographed road to ground at each abutment. */
export function buildRoadExtensions(terrain: THREE.Mesh, anchors: {name:string;kind:string;point:THREE.Vector3}[], axis: THREE.Vector3, top: number) {
  const piers=anchors.filter(a=>a.kind==='pier').toSorted((a,b)=>a.point.dot(axis)-b.point.dot(axis));
  const abuts=anchors.filter(a=>a.kind==='abutment').toSorted((a,b)=>a.point.dot(axis)-b.point.dot(axis));
  if(piers.length<2||abuts.length!==2)throw new Error('Road extensions require two abutments and at least two piers');
  const group=new THREE.Group();group.name='landing-road-extensions';
  const ray=new THREE.Raycaster(),down=new THREE.Vector3(0,-1,0),widthM=8;
  const sample=(x:number,z:number)=>{
    ray.set(new THREE.Vector3(x,top+100,z),down);
    return ray.intersectObject(terrain,false)[0]?.point;
  };
  const descriptions=[];
  const ends=[{name:'A1–P1',points:[abuts[0].point,piers[0].point,piers[1].point],from:0,to:.58},
    {name:'P6–A2',points:[piers.at(-2)!.point,piers.at(-1)!.point,abuts[1].point],from:.42,to:1}];
  for(const end of ends){
    const curve=new THREE.CatmullRomCurve3(end.points.map(p=>new THREE.Vector3(p.x,0,p.z)),false,'catmullrom',.2);
    const steps=80,positions:number[]=[],colors:number[]=[],indices:number[]=[];
    let previous=-1,validSections=0,missingSections=0;
    for(let i=0;i<=steps;i++){
      const t=i/steps,u=end.from+(end.to-end.from)*t,p=curve.getPoint(u),tangent=curve.getTangent(u).normalize();
      const cross=new THREE.Vector3(-tangent.z,0,tangent.x);
      const offsets=Array.from({length:17},(_,j)=>-widthM/2+widthM*j/16);
      const hits=offsets.map(o=>sample(p.x+cross.x*o,p.z+cross.z*o));
      if(hits.some(h=>!h)){previous=-1;missingSections++;continue;}
      const first=positions.length/3;
      const blend=end.from===0?1-THREE.MathUtils.smoothstep(t,.72,1):THREE.MathUtils.smoothstep(t,0,.28);
      const color=new THREE.Color('#dcd8c7').multiplyScalar(1+Math.sin(i*2.33)*.018);
      hits.forEach((hit,j)=>{positions.push(hit!.x,hit!.y+.15,hit!.z);colors.push(color.r,color.g,color.b,blend*(j===0||j===offsets.length-1?0:.96));});
      if(previous>=0)for(let j=0;j<offsets.length-1;j++)indices.push(previous+j,first+j,previous+j+1,previous+j+1,first+j,first+j+1);
      previous=first;validSections++;
    }
    const geometry=new THREE.BufferGeometry();geometry.setAttribute('position',new THREE.Float32BufferAttribute(positions,3));geometry.setAttribute('color',new THREE.Float32BufferAttribute(colors,4));geometry.setIndex(indices);geometry.computeVertexNormals();
    const mesh=new THREE.Mesh(geometry,new THREE.MeshBasicMaterial({vertexColors:true,side:THREE.DoubleSide,transparent:true,depthWrite:false,polygonOffset:true,polygonOffsetFactor:-2,polygonOffsetUnits:-2}));
    mesh.name=end.name;mesh.renderOrder=2;group.add(mesh);
    descriptions.push({name:end.name,widthM,validSections,missingSections,triangles:indices.length/3,visualizationOnly:true});
  }
  return {group,descriptions};
}