import type { JSXElement } from '../../jsx';
import { Path, Polygon } from '../../jsx';

export const getMidPoint = (points: [number, number][]) => {
  if (points.length === 0) return null;
  if (points.length === 1) return points[0];
  let total = 0;
  const segments: {
    length: number;
    start: [number, number];
    end: [number, number];
  }[] = [];
  for (let i = 0; i < points.length - 1; i += 1) {
    const start = points[i];
    const end = points[i + 1];
    const length = Math.hypot(end[0] - start[0], end[1] - start[1]);
    segments.push({ length, start, end });
    total += length;
  }
  if (total === 0) return points[0];
  let target = total / 2;
  for (let i = 0; i < segments.length; i += 1) {
    const segment = segments[i];
    if (target <= segment.length || i === segments.length - 1) {
      const ratio =
        segment.length === 0
          ? 0
          : Math.max(0, Math.min(1, target / segment.length));
      return [
        segment.start[0] + (segment.end[0] - segment.start[0]) * ratio,
        segment.start[1] + (segment.end[1] - segment.start[1]) * ratio,
      ] as [number, number];
    }
    target -= segment.length;
  }
  return points[Math.floor(points.length / 2)];
};

export const createStraightPath = (
  points: [number, number][],
  dx: number,
  dy: number,
) =>
  points
    .map(([x, y], index) => {
      const prefix = index === 0 ? 'M' : 'L';
      return `${prefix} ${x + dx} ${y + dy}`;
    })
    .join(' ');

export const createRoundedPath = (
  points: [number, number][],
  radius: number,
  dx: number,
  dy: number,
) => {
  if (points.length < 2) return '';
  const clamp = (value: number, min: number, max: number) =>
    Math.min(max, Math.max(min, value));
  const toPoint = ([x, y]: [number, number]) => ({
    x: x + dx,
    y: y + dy,
  });
  const output: string[] = [];
  const first = toPoint(points[0]);
  output.push(`M ${first.x} ${first.y}`);

  if (points.length === 2) {
    const last = toPoint(points[1]);
    output.push(`L ${last.x} ${last.y}`);
    return output.join(' ');
  }

  for (let i = 1; i < points.length - 1; i += 1) {
    const prev = points[i - 1];
    const curr = points[i];
    const next = points[i + 1];
    const v0x = curr[0] - prev[0];
    const v0y = curr[1] - prev[1];
    const v1x = next[0] - curr[0];
    const v1y = next[1] - curr[1];
    const d0 = Math.hypot(v0x, v0y);
    const d1 = Math.hypot(v1x, v1y);
    if (d0 === 0 || d1 === 0) {
      const currPoint = toPoint(curr);
      output.push(`L ${currPoint.x} ${currPoint.y}`);
      continue;
    }
    const r = clamp(radius, 0, Math.min(d0, d1) / 2);
    if (r === 0) {
      const currPoint = toPoint(curr);
      output.push(`L ${currPoint.x} ${currPoint.y}`);
      continue;
    }
    const u0x = v0x / d0;
    const u0y = v0y / d0;
    const u1x = v1x / d1;
    const u1y = v1y / d1;
    const start = toPoint([curr[0] - u0x * r, curr[1] - u0y * r]);
    const end = toPoint([curr[0] + u1x * r, curr[1] + u1y * r]);
    output.push(`L ${start.x} ${start.y}`);
    const currPoint = toPoint(curr);
    output.push(`Q ${currPoint.x} ${currPoint.y} ${end.x} ${end.y}`);
  }

  const last = toPoint(points[points.length - 1]);
  output.push(`L ${last.x} ${last.y}`);
  return output.join(' ');
};

export const createArrowElements = (
  x: number,
  y: number,
  angle: number,
  type: 'arrow' | 'triangle' | 'diamond',
  fillColor: string,
  edgeWidth: number,
  arrowSize: number,
): JSXElement[] => {
  const ux = Math.cos(angle);
  const uy = Math.sin(angle);
  const px = -uy;
  const py = ux;
  const length = arrowSize;
  const halfWidth = arrowSize * 0.55;

  if (type === 'arrow') {
    const leftX = x - ux * length + px * halfWidth;
    const leftY = y - uy * length + py * halfWidth;
    const rightX = x - ux * length - px * halfWidth;
    const rightY = y - uy * length - py * halfWidth;
    return [
      <Path
        d={`M ${leftX} ${leftY} L ${x} ${y} L ${rightX} ${rightY}`}
        stroke={fillColor}
        strokeWidth={Math.max(1.5, edgeWidth)}
        strokeLinecap="round"
        strokeLinejoin="round"
        fill="none"
      />,
    ];
  }

  if (type === 'diamond') {
    const diamondLength = length * 1.25;
    const diamondWidth = halfWidth * 0.75;
    const midX = x - ux * diamondLength * 0.5;
    const midY = y - uy * diamondLength * 0.5;
    const diamondPoints = [
      { x, y },
      { x: midX + px * diamondWidth, y: midY + py * diamondWidth },
      { x: x - ux * diamondLength, y: y - uy * diamondLength },
      { x: midX - px * diamondWidth, y: midY - py * diamondWidth },
    ];
    return [
      <Polygon
        points={diamondPoints}
        fill={fillColor}
        stroke={fillColor}
        strokeWidth={Math.max(1, edgeWidth * 0.8)}
      />,
    ];
  }

  const trianglePoints = [
    { x, y },
    {
      x: x - ux * length + px * halfWidth,
      y: y - uy * length + py * halfWidth,
    },
    {
      x: x - ux * length - px * halfWidth,
      y: y - uy * length - py * halfWidth,
    },
  ];
  return [
    <Polygon
      points={trianglePoints}
      fill={fillColor}
      stroke={fillColor}
      strokeWidth={Math.max(1, edgeWidth * 0.8)}
    />,
  ];
};

// LT: Left Top (radio), LC: Left Center (1/2), LB: Left Bottom (1 - radio)
// RT: Right Top (radio), RC: Right Center (1/2), RB: Right Bottom (1 - radio)
export const getNodesAnchors = (node: {
  x: number;
  y: number;
  width: number;
  height: number;
  radio?: number;
}) => {
  const { x, y, width, height, radio = 0.25 } = node;
  const q1H = height * radio;
  const halfH = height * 0.5;
  const q3H = height * (1 - radio);

  return {
    LT: { x, y: y + q1H },
    LC: { x, y: y + halfH },
    LB: { x, y: y + q3H },
    RT: { x: x + width, y: y + q1H },
    RC: { x: x + width, y: y + halfH },
    RB: { x: x + width, y: y + q3H },
  };
};

export const getTangentAngle = (points: [number, number][], t: 0 | 1) => {
  const len = points.length;
  // Cubic Bezier (Self loop)
  if (len === 4) {
    const p0 = points[0],
      p1 = points[1],
      p2 = points[2],
      p3 = points[3];
    if (t === 0) {
      return Math.atan2(p1[1] - p0[1], p1[0] - p0[0]);
    } else {
      return Math.atan2(p3[1] - p2[1], p3[0] - p2[0]);
    }
  }
  // Quad Bezier (Curved)
  if (len === 3) {
    const p0 = points[0],
      p1 = points[1],
      p2 = points[2];
    if (t === 0) {
      return Math.atan2(p1[1] - p0[1], p1[0] - p0[0]);
    } else {
      return Math.atan2(p2[1] - p1[1], p2[0] - p1[0]);
    }
  }
  // Line
  if (len === 2) {
    const p0 = points[0],
      p1 = points[1];
    const angle = Math.atan2(p1[1] - p0[1], p1[0] - p0[0]);
    return angle;
  }
  return 0;
};

/**
 * 计算贝塞尔曲线上任意 t (0-1) 位置的点
 */
export const getPointAtT = (
  points: [number, number][],
  t = 0.5,
): [number, number] => {
  const len = points.length;
  if (len === 4) {
    const [p0, p1, p2, p3] = points;
    const mt = 1 - t;
    // B(t) = (1-t)^3*P0 + 3(1-t)^2*t*P1 + 3(1-t)*t^2*P2 + t^3*P3
    return [
      mt ** 3 * p0[0] +
        3 * mt ** 2 * t * p1[0] +
        3 * mt * t ** 2 * p2[0] +
        t ** 3 * p3[0],
      mt ** 3 * p0[1] +
        3 * mt ** 2 * t * p1[1] +
        3 * mt * t ** 2 * p2[1] +
        t ** 3 * p3[1],
    ];
  }
  if (len === 3) {
    const [p0, p1, p2] = points;
    const mt = 1 - t;
    // B(t) = (1-t)^2*P0 + 2(1-t)*t*P1 + t^2*P2
    return [
      mt ** 2 * p0[0] + 2 * mt * t * p1[0] + t ** 2 * p2[0],
      mt ** 2 * p0[1] + 2 * mt * t * p1[1] + t ** 2 * p2[1],
    ];
  }
  if (len === 2) {
    const [p0, p1] = points;
    return [p0[0] + (p1[0] - p0[0]) * t, p0[1] + (p1[1] - p0[1]) * t];
  }
  return points[0] || [0, 0];
};

export const getLabelPosition = (
  points: [number, number][],
  selfLoopOffset = 10,
) => {
  const len = points.length;
  // 默认取中点
  const labelPoint = getPointAtT(points);

  if (len === 4) {
    // 针对自连接(len=4)的特殊偏移处理
    labelPoint[0] += selfLoopOffset;
  }

  return labelPoint as [number, number];
};

export const getEdgePathD = (points: [number, number][]) => {
  const len = points.length;
  if (len === 4) {
    const [p0, p1, p2, p3] = points;
    return `M ${p0[0]} ${p0[1]} C ${p1[0]} ${p1[1]} ${p2[0]} ${p2[1]} ${p3[0]} ${p3[1]}`;
  }
  if (len === 3) {
    const [p0, p1, p2] = points;
    return `M ${p0[0]} ${p0[1]} Q ${p1[0]} ${p1[1]} ${p2[0]} ${p2[1]}`;
  }
  if (len === 2) {
    const [p0, p1] = points;
    return `M ${p0[0]} ${p0[1]} L ${p1[0]} ${p1[1]}`;
  }
  return '';
};