import { Position } from '@reactflow/system';

export type GetBezierPathParams = {
  sourceX: number;
  sourceY: number;
  sourcePosition?: Position;
  targetX: number;
  targetY: number;
  targetPosition?: Position;
  curvature?: number;
};

export type GetControlWithCurvatureParams = {
  pos: Position;
  x1: number;
  y1: number;
  x2: number;
  y2: number;
  c: number;
};

export function getBezierEdgeCenter({
  sourceX,
  sourceY,
  targetX,
  targetY,
  sourceControlX,
  sourceControlY,
  targetControlX,
  targetControlY,
}: {
  sourceX: number;
  sourceY: number;
  targetX: number;
  targetY: number;
  sourceControlX: number;
  sourceControlY: number;
  targetControlX: number;
  targetControlY: number;
}): [number, number, number, number] {
  // 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 offsetX = Math.abs(centerX - sourceX);
  const offsetY = Math.abs(centerY - sourceY);

  return [centerX, centerY, offsetX, offsetY];
}

function calculateControlOffset(distance: number, curvature: number): number {
  if (distance >= 0) {
    return 0.5 * distance;
  }

  return curvature * 25 * Math.sqrt(-distance);
}

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

export function getBezierPath({
  sourceX,
  sourceY,
  sourcePosition = Position.Bottom,
  targetX,
  targetY,
  targetPosition = Position.Top,
  curvature = 0.25,
}: GetBezierPathParams): [path: string, labelX: number, labelY: number, offsetX: number, offsetY: 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,
  });
  const [labelX, labelY, offsetX, offsetY] = getBezierEdgeCenter({
    sourceX,
    sourceY,
    targetX,
    targetY,
    sourceControlX,
    sourceControlY,
    targetControlX,
    targetControlY,
  });

  return [
    `M${sourceX},${sourceY} C${sourceControlX},${sourceControlY} ${targetControlX},${targetControlY} ${targetX},${targetY}`,
    labelX,
    labelY,
    offsetX,
    offsetY,
  ];
}