export function getDistance2D(point1, point2) {
  return Math.sqrt(
    Math.pow(Number(point1.x) - Number(point2.x), 2) +
    Math.pow(Number(point1.y) - Number(point2.y), 2)
  )
}

// 斜率slope：指的是点位阵列排列的每行斜率。计算方法：取考察点“上下左右”（注意与x轴、y轴方向无必然关系）的邻居，即与它最近的四个邻居，分别计算邻居与它的连线的斜率，限定斜率范围是[0, +Infinity),不符合则计算其负倒数。
export function computePointDistanceAndRowSlope(rawWholeData) {
  // return 0.36
  const sampleNumber = Math.min(1000, rawWholeData.length)
  let pointDistance = null
  let rowSlope = null
  while((pointDistance === null) || (rowSlope === null)) {
    const distanceList = []
    const rowSlopeList = []
    for (let index = 0; index < sampleNumber; index++) {
      const sampleIdx = Math.floor(Math.random() * rawWholeData.length)
      const sample = rawWholeData[sampleIdx]
      for (const neighbourId of sample.ids.slice(0, 4)) {
        if (neighbourId !== "-1") {
          distanceList.push(getDistance2D(sample, rawWholeData[neighbourId - 1]))
          let rowSlopeTemp = null
          if (Math.abs(Number(sample.x) - Number(rawWholeData[neighbourId - 1].x)) <= Number.EPSILON) {
            rowSlopeTemp = 0
          } else if ((Number(sample.x) - Number(rawWholeData[neighbourId - 1].x)) < 0) {
            rowSlopeTemp = -1 / (Number(sample.x) - Number(rawWholeData[neighbourId - 1].x))
          } else {
            rowSlopeTemp = (Number(sample.y) - Number(rawWholeData[neighbourId - 1].y)) / (Number(sample.x) - Number(rawWholeData[neighbourId - 1].x))
          }
          rowSlopeList.push(rowSlopeTemp)
        }
      }
    }
    if (distanceList.length) {
      let sum = 0
      for (const distItem of distanceList) {
        sum += distItem
      }
      pointDistance = sum / distanceList.length
    }
    if (rowSlopeList.length) {
      let sum = 0
      for (const rowSlopeItem of rowSlopeList) {
        sum += rowSlopeItem
      }
      rowSlope = sum / rowSlopeList.length
    }
  }
  console.log('pointDistance: ', pointDistance, 'rowSlope: ', rowSlope)
  return [pointDistance, rowSlope]
}

export function getNeighbourLocations(centerPointPos, pointDistance, rowSlope) {
  // 返回的位置列表中位置顺序：
  // posRight
  // posBottom
  // posLeft
  // posTop
  // posTopRight
  // posBottomRight
  // posBottomLeft
  // posTopLeft
  // 注意，方位的确定与x轴、y轴无直接关联，而是由点位阵列中的行列（或者说行的斜率）决定的。
  const alpha = Math.atan(rowSlope)
  const posRight = {
    x: centerPointPos.x + pointDistance * Math.cos(alpha),
    y: centerPointPos.y + pointDistance * Math.sin(alpha),
  }
  const posBottom = {
    x: centerPointPos.x + pointDistance * Math.cos(Math.PI / 2 - alpha),
    y: centerPointPos.y - pointDistance * Math.sin(Math.PI / 2 - alpha),
  }
  const posLeft = {
    x: centerPointPos.x - pointDistance * Math.cos(alpha),
    y: centerPointPos.y - pointDistance * Math.sin(alpha),
  }
  const posTop = {
    x: centerPointPos.x - pointDistance * Math.cos(Math.PI / 2 - alpha),
    y: centerPointPos.y + pointDistance * Math.sin(Math.PI / 2 - alpha),
  }
  // 相当于right的top
  const posTopRight = {
    x: posRight.x - pointDistance * Math.cos(Math.PI / 2 - alpha),
    y: posRight.y + pointDistance * Math.sin(Math.PI / 2 - alpha),
  }
  // 相当于right的bottom
  const posBottomRight = {
    x: posRight.x + pointDistance * Math.cos(Math.PI / 2 - alpha),
    y: posRight.y - pointDistance * Math.sin(Math.PI / 2 - alpha),
  }
  // 相当于left的bottom
  const posBottomLeft = {
    x: posLeft.x + pointDistance * Math.cos(Math.PI / 2 - alpha),
    y: posLeft.y - pointDistance * Math.sin(Math.PI / 2 - alpha),
  }
  // 相当于left的top
  const posTopLeft = {
    x: posLeft.x + pointDistance * Math.cos(alpha),
    y: posLeft.y + pointDistance * Math.sin(alpha),
  }
  return {
    posRight,
    posBottom,
    posLeft,
    posTop,
    posTopRight,
    posBottomRight,
    posBottomLeft,
    posTopLeft,
  }
}