/**
 * @fileOverview convert the line to curve
 * @author dxq613@gmail.com
 */
import { vec2 } from 'gl-matrix';

function getPoint(v) {
  return [v.x, v.y];
}

function smoothBezier(points, smooth, isLoop, constraint) {
  const cps = [];

  let prevPoint;
  let nextPoint;
  const hasConstraint = !!constraint;
  let min;
  let max;
  let point;
  let len;
  let l;
  let i;
  if (hasConstraint) {
    min = [Infinity, Infinity];
    max = [-Infinity, -Infinity];

    for (i = 0, l = points.length; i < l; i++) {
      point = getPoint(points[i]);
      vec2.min(min, min, point);
      vec2.max(max, max, point);
    }
    vec2.min(min, min, constraint[0]);
    vec2.max(max, max, constraint[1]);
  }

  for (i = 0, len = points.length; i < len; i++) {
    point = getPoint(points[i]);
    if (isLoop) {
      prevPoint = getPoint(points[i ? i - 1 : len - 1]);
      nextPoint = getPoint(points[(i + 1) % len]);
    } else {
      if (i === 0 || i === len - 1) {
        cps.push([point[0], point[1]]);
        continue;
      } else {
        prevPoint = getPoint(points[i - 1]);
        nextPoint = getPoint(points[i + 1]);
      }
    }

    const v = vec2.sub(([] as unknown) as vec2, nextPoint, prevPoint);
    vec2.scale(v, v, smooth);
    let d0 = vec2.distance(point, prevPoint);
    let d1 = vec2.distance(point, nextPoint);

    const sum = d0 + d1;
    if (sum !== 0) {
      d0 /= sum;
      d1 /= sum;
    }

    const v1 = vec2.scale(([] as unknown) as vec2, v, -d0);
    const v2 = vec2.scale(([] as unknown) as vec2, v, d1);

    const cp0 = vec2.add(([] as unknown) as vec2, point, v1);
    const cp1 = vec2.add(([] as unknown) as vec2, point, v2);

    if (hasConstraint) {
      vec2.max(cp0, cp0, min);
      vec2.min(cp0, cp0, max);
      vec2.max(cp1, cp1, min);
      vec2.min(cp1, cp1, max);
    }

    cps.push([cp0[0], cp0[1]]);
    cps.push([cp1[0], cp1[1]]);
  }

  if (isLoop) {
    cps.push(cps.shift());
  }
  return cps;
}

function catmullRom2bezier(pointList, z, constraint) {
  const isLoop = !!z;

  const controlPointList = smoothBezier(pointList, 0.4, isLoop, constraint);
  const len = pointList.length;
  const d1 = [];

  let cp1;
  let cp2;
  let p;

  for (let i = 0; i < len - 1; i++) {
    cp1 = controlPointList[i * 2];
    cp2 = controlPointList[i * 2 + 1];
    p = pointList[i + 1];
    d1.push(['C', cp1[0], cp1[1], cp2[0], cp2[1], p.x, p.y]);
  }

  if (isLoop) {
    cp1 = controlPointList[len];
    cp2 = controlPointList[len + 1];
    p = pointList[0];

    d1.push(['C', cp1[0], cp1[1], cp2[0], cp2[1], p.x, p.y]);
  }
  return d1;
}

export { catmullRom2bezier as smooth };