chartjs/chartjs-plugin-datalabels

function orient(point, origin) {
  var x0 = origin.x;
  var y0 = origin.y;

  if (x0 === null) {
    return {x: 0, y: -1};
  }
  if (y0 === null) {
    return {x: 1, y: 0};
  }

  var dx = point.x - x0;
  var dy = point.y - y0;
  var ln = Math.sqrt(dx * dx + dy * dy);

  return {
    x: ln ? dx / ln : 0,
    y: ln ? dy / ln : -1
  };
}

function aligned(x, y, vx, vy, align) {
  switch (align) {
  case 'center':
    vx = vy = 0;
    break;
  case 'bottom':
    vx = 0;
    vy = 1;
    break;
  case 'right':
    vx = 1;
    vy = 0;
    break;
  case 'left':
    vx = -1;
    vy = 0;
    break;
  case 'top':
    vx = 0;
    vy = -1;
    break;
  case 'start':
    vx = -vx;
    vy = -vy;
    break;
  case 'end':
    // keep natural orientation
    break;
  default:
    // clockwise rotation (in degree)
    align *= (Math.PI / 180);
    vx = Math.cos(align);
    vy = Math.sin(align);
    break;
  }

  return {
    x: x,
    y: y,
    vx: vx,
    vy: vy
  };
}

// Line clipping (Cohen–Sutherland algorithm)
// https://en.wikipedia.org/wiki/Cohen–Sutherland_algorithm

var R_INSIDE = 0;
var R_LEFT = 1;
var R_RIGHT = 2;
var R_BOTTOM = 4;
var R_TOP = 8;

function region(x, y, rect) {
  var res = R_INSIDE;

  if (x < rect.left) {
    res |= R_LEFT;
  } else if (x > rect.right) {
    res |= R_RIGHT;
  }
  if (y < rect.top) {
    res |= R_TOP;
  } else if (y > rect.bottom) {
    res |= R_BOTTOM;
  }

  return res;
}

function clipped(segment, area) {
  var x0 = segment.x0;
  var y0 = segment.y0;
  var x1 = segment.x1;
  var y1 = segment.y1;
  var r0 = region(x0, y0, area);
  var r1 = region(x1, y1, area);
  var r, x, y;

  // eslint-disable-next-line no-constant-condition
  while (true) {
    if (!(r0 | r1) || (r0 & r1)) {
      // both points inside or on the same side: no clipping
      break;
    }

    // at least one point is outside
    r = r0 || r1;

    if (r & R_TOP) {
      x = x0 + (x1 - x0) * (area.top - y0) / (y1 - y0);
      y = area.top;
    } else if (r & R_BOTTOM) {
      x = x0 + (x1 - x0) * (area.bottom - y0) / (y1 - y0);
      y = area.bottom;
    } else if (r & R_RIGHT) {
      y = y0 + (y1 - y0) * (area.right - x0) / (x1 - x0);
      x = area.right;
    } else if (r & R_LEFT) {
      y = y0 + (y1 - y0) * (area.left - x0) / (x1 - x0);
      x = area.left;
    }

    if (r === r0) {
      x0 = x;
      y0 = y;
      r0 = region(x0, y0, area);
    } else {
      x1 = x;
      y1 = y;
      r1 = region(x1, y1, area);
    }
  }

  return {
    x0: x0,
    x1: x1,
    y0: y0,
    y1: y1
  };
}

function compute(range, config) {
  var anchor = config.anchor;
  var segment = range;
  var x, y;

  if (config.clamp) {
    segment = clipped(segment, config.area);
  }

  if (anchor === 'start') {
    x = segment.x0;
    y = segment.y0;
  } else if (anchor === 'end') {
    x = segment.x1;
    y = segment.y1;
  } else {
    x = (segment.x0 + segment.x1) / 2;
    y = (segment.y0 + segment.y1) / 2;
  }

  return aligned(x, y, range.vx, range.vy, config.align);
}

export default {
  arc: function(el, config) {
    var angle = (el.startAngle + el.endAngle) / 2;
    var vx = Math.cos(angle);
    var vy = Math.sin(angle);
    var r0 = el.innerRadius;
    var r1 = el.outerRadius;

    return compute({
      x0: el.x + vx * r0,
      y0: el.y + vy * r0,
      x1: el.x + vx * r1,
      y1: el.y + vy * r1,
      vx: vx,
      vy: vy
    }, config);
  },

  point: function(el, config) {
    var v = orient(el, config.origin);
    var rx = v.x * el.options.radius;
    var ry = v.y * el.options.radius;

    return compute({
      x0: el.x - rx,
      y0: el.y - ry,
      x1: el.x + rx,
      y1: el.y + ry,
      vx: v.x,
      vy: v.y
    }, config);
  },

  bar: function(el, config) {
    var v = orient(el, config.origin);
    var x = el.x;
    var y = el.y;
    var sx = 0;
    var sy = 0;

    if (el.horizontal) {
      x = Math.min(el.x, el.base);
      sx = Math.abs(el.base - el.x);
    } else {
      y = Math.min(el.y, el.base);
      sy = Math.abs(el.base - el.y);
    }

    return compute({
      x0: x,
      y0: y + sy,
      x1: x + sx,
      y1: y,
      vx: v.x,
      vy: v.y
    }, config);
  },

  fallback: function(el, config) {
    var v = orient(el, config.origin);

    return compute({
      x0: el.x,
      y0: el.y,
      x1: el.x + (el.width || 0),
      y1: el.y + (el.height || 0),
      vx: v.x,
      vy: v.y
    }, config);
  }
};