import { Position } from '~/types'

interface GetControlWithCurvatureParams {
  pos: Position
  x1: number
  y1: number
  x2: number
  y2: number
  c: number
}

export interface GetBezierPathParams {
  sourceX: number
  sourceY: number
  sourcePosition?: Position
  targetX: number
  targetY: number
  targetPosition?: Position
  curvature?: number
  centerX?: number
  centerY?: number
}

function calculateControlOffset(distance: number, curvature: number): number {
  if (distance >= 0) {
    return 0.5 * distance
  } else {
    return curvature * 25 * Math.sqrt(-distance)
  }
}

function getControlWithCurvature({ pos, x1, y1, x2, y2, c }: GetControlWithCurvatureParams): [number, number] {
  let ctX: number, ctY: number
  switch (pos) {
    case Position.Left:
      ctX = x1 - calculateControlOffset(x1 - x2, c)
      ctY = y1
      break
    case Position.Right:
      ctX = x1 + calculateControlOffset(x2 - x1, c)
      ctY = y1
      break
    case Position.Top:
      ctX = x1
      ctY = y1 - calculateControlOffset(y1 - y2, c)
      break
    case Position.Bottom:
      ctX = x1
      ctY = y1 + calculateControlOffset(y2 - y1, c)
      break
  }
  return [ctX, ctY]
}

export function getBezierPath({
  sourceX,
  sourceY,
  sourcePosition = Position.Bottom,
  targetX,
  targetY,
  targetPosition = Position.Top,
  curvature = 0.25,
}: GetBezierPathParams): string {
  const [sourceControlX, sourceControlY] = getControlWithCurvature({
    pos: sourcePosition,
    x1: sourceX,
    y1: sourceY,
    x2: targetX,
    y2: targetY,
    c: curvature,
  })
  const [targetControlX, targetControlY] = getControlWithCurvature({
    pos: targetPosition,
    x1: targetX,
    y1: targetY,
    x2: sourceX,
    y2: sourceY,
    c: curvature,
  })
  return `M${sourceX},${sourceY} C${sourceControlX},${sourceControlY} ${targetControlX},${targetControlY} ${targetX},${targetY}`
}

export function getBezierCenter({
  sourceX,
  sourceY,
  sourcePosition = Position.Bottom,
  targetX,
  targetY,
  targetPosition = Position.Top,
  curvature = 0.25,
}: GetBezierPathParams): [number, number, number, number] {
  const [sourceControlX, sourceControlY] = getControlWithCurvature({
    pos: sourcePosition,
    x1: sourceX,
    y1: sourceY,
    x2: targetX,
    y2: targetY,
    c: curvature,
  })
  const [targetControlX, targetControlY] = getControlWithCurvature({
    pos: targetPosition,
    x1: targetX,
    y1: targetY,
    x2: sourceX,
    y2: sourceY,
    c: curvature,
  })
  // cubic bezier t=0.5 mid point, not the actual mid point, but easy to calculate
  // https://stackoverflow.com/questions/67516101/how-to-find-distance-mid-point-of-bezier-curve
  const centerX = sourceX * 0.125 + sourceControlX * 0.375 + targetControlX * 0.375 + targetX * 0.125
  const centerY = sourceY * 0.125 + sourceControlY * 0.375 + targetControlY * 0.375 + targetY * 0.125
  const xOffset = Math.abs(centerX - sourceX)
  const yOffset = Math.abs(centerY - sourceY)
  return [centerX, centerY, xOffset, yOffset]
}