source: node_modules/d3-contour/dist/d3-contour.js@ e4c61dd

// https://d3js.org/d3-contour/ v4.0.2 Copyright 2012-2023 Mike Bostock
(function (global, factory) {
typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('d3-array')) :
typeof define === 'function' && define.amd ? define(['exports', 'd3-array'], factory) :
(global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.d3 = global.d3 || {}, global.d3));
})(this, (function (exports, d3Array) { 'use strict';

var array = Array.prototype;

var slice = array.slice;

function ascending(a, b) {
  return a - b;
}

function area(ring) {
  var i = 0, n = ring.length, area = ring[n - 1][1] * ring[0][0] - ring[n - 1][0] * ring[0][1];
  while (++i < n) area += ring[i - 1][1] * ring[i][0] - ring[i - 1][0] * ring[i][1];
  return area;
}

var constant = x => () => x;

function contains(ring, hole) {
  var i = -1, n = hole.length, c;
  while (++i < n) if (c = ringContains(ring, hole[i])) return c;
  return 0;
}

function ringContains(ring, point) {
  var x = point[0], y = point[1], contains = -1;
  for (var i = 0, n = ring.length, j = n - 1; i < n; j = i++) {
    var pi = ring[i], xi = pi[0], yi = pi[1], pj = ring[j], xj = pj[0], yj = pj[1];
    if (segmentContains(pi, pj, point)) return 0;
    if (((yi > y) !== (yj > y)) && ((x < (xj - xi) * (y - yi) / (yj - yi) + xi))) contains = -contains;
  }
  return contains;
}

function segmentContains(a, b, c) {
  var i; return collinear(a, b, c) && within(a[i = +(a[0] === b[0])], c[i], b[i]);
}

function collinear(a, b, c) {
  return (b[0] - a[0]) * (c[1] - a[1]) === (c[0] - a[0]) * (b[1] - a[1]);
}

function within(p, q, r) {
  return p <= q && q <= r || r <= q && q <= p;
}

function noop() {}

var cases = [
  [],
  [[[1.0, 1.5], [0.5, 1.0]]],
  [[[1.5, 1.0], [1.0, 1.5]]],
  [[[1.5, 1.0], [0.5, 1.0]]],
  [[[1.0, 0.5], [1.5, 1.0]]],
  [[[1.0, 1.5], [0.5, 1.0]], [[1.0, 0.5], [1.5, 1.0]]],
  [[[1.0, 0.5], [1.0, 1.5]]],
  [[[1.0, 0.5], [0.5, 1.0]]],
  [[[0.5, 1.0], [1.0, 0.5]]],
  [[[1.0, 1.5], [1.0, 0.5]]],
  [[[0.5, 1.0], [1.0, 0.5]], [[1.5, 1.0], [1.0, 1.5]]],
  [[[1.5, 1.0], [1.0, 0.5]]],
  [[[0.5, 1.0], [1.5, 1.0]]],
  [[[1.0, 1.5], [1.5, 1.0]]],
  [[[0.5, 1.0], [1.0, 1.5]]],
  []
];

function Contours() {
  var dx = 1,
      dy = 1,
      threshold = d3Array.thresholdSturges,
      smooth = smoothLinear;

  function contours(values) {
    var tz = threshold(values);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      const e = d3Array.extent(values, finite);
      tz = d3Array.ticks(...d3Array.nice(e[0], e[1], tz), tz);
      while (tz[tz.length - 1] >= e[1]) tz.pop();
      while (tz[1] < e[0]) tz.shift();
    } else {
      tz = tz.slice().sort(ascending);
    }

    return tz.map(value => contour(values, value));
  }

  // Accumulate, smooth contour rings, assign holes to exterior rings.
  // Based on https://github.com/mbostock/shapefile/blob/v0.6.2/shp/polygon.js
  function contour(values, value) {
    const v = value == null ? NaN : +value;
    if (isNaN(v)) throw new Error(`invalid value: ${value}`);

    var polygons = [],
        holes = [];

    isorings(values, v, function(ring) {
      smooth(ring, values, v);
      if (area(ring) > 0) polygons.push([ring]);
      else holes.push(ring);
    });

    holes.forEach(function(hole) {
      for (var i = 0, n = polygons.length, polygon; i < n; ++i) {
        if (contains((polygon = polygons[i])[0], hole) !== -1) {
          polygon.push(hole);
          return;
        }
      }
    });

    return {
      type: "MultiPolygon",
      value: value,
      coordinates: polygons
    };
  }

  // Marching squares with isolines stitched into rings.
  // Based on https://github.com/topojson/topojson-client/blob/v3.0.0/src/stitch.js
  function isorings(values, value, callback) {
    var fragmentByStart = new Array,
        fragmentByEnd = new Array,
        x, y, t0, t1, t2, t3;

    // Special case for the first row (y = -1, t2 = t3 = 0).
    x = y = -1;
    t1 = above(values[0], value);
    cases[t1 << 1].forEach(stitch);
    while (++x < dx - 1) {
      t0 = t1, t1 = above(values[x + 1], value);
      cases[t0 | t1 << 1].forEach(stitch);
    }
    cases[t1 << 0].forEach(stitch);

    // General case for the intermediate rows.
    while (++y < dy - 1) {
      x = -1;
      t1 = above(values[y * dx + dx], value);
      t2 = above(values[y * dx], value);
      cases[t1 << 1 | t2 << 2].forEach(stitch);
      while (++x < dx - 1) {
        t0 = t1, t1 = above(values[y * dx + dx + x + 1], value);
        t3 = t2, t2 = above(values[y * dx + x + 1], value);
        cases[t0 | t1 << 1 | t2 << 2 | t3 << 3].forEach(stitch);
      }
      cases[t1 | t2 << 3].forEach(stitch);
    }

    // Special case for the last row (y = dy - 1, t0 = t1 = 0).
    x = -1;
    t2 = values[y * dx] >= value;
    cases[t2 << 2].forEach(stitch);
    while (++x < dx - 1) {
      t3 = t2, t2 = above(values[y * dx + x + 1], value);
      cases[t2 << 2 | t3 << 3].forEach(stitch);
    }
    cases[t2 << 3].forEach(stitch);

    function stitch(line) {
      var start = [line[0][0] + x, line[0][1] + y],
          end = [line[1][0] + x, line[1][1] + y],
          startIndex = index(start),
          endIndex = index(end),
          f, g;
      if (f = fragmentByEnd[startIndex]) {
        if (g = fragmentByStart[endIndex]) {
          delete fragmentByEnd[f.end];
          delete fragmentByStart[g.start];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[f.start] = fragmentByEnd[g.end] = {start: f.start, end: g.end, ring: f.ring.concat(g.ring)};
          }
        } else {
          delete fragmentByEnd[f.end];
          f.ring.push(end);
          fragmentByEnd[f.end = endIndex] = f;
        }
      } else if (f = fragmentByStart[endIndex]) {
        if (g = fragmentByEnd[startIndex]) {
          delete fragmentByStart[f.start];
          delete fragmentByEnd[g.end];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[g.start] = fragmentByEnd[f.end] = {start: g.start, end: f.end, ring: g.ring.concat(f.ring)};
          }
        } else {
          delete fragmentByStart[f.start];
          f.ring.unshift(start);
          fragmentByStart[f.start = startIndex] = f;
        }
      } else {
        fragmentByStart[startIndex] = fragmentByEnd[endIndex] = {start: startIndex, end: endIndex, ring: [start, end]};
      }
    }
  }

  function index(point) {
    return point[0] * 2 + point[1] * (dx + 1) * 4;
  }

  function smoothLinear(ring, values, value) {
    ring.forEach(function(point) {
      var x = point[0],
          y = point[1],
          xt = x | 0,
          yt = y | 0,
          v1 = valid(values[yt * dx + xt]);
      if (x > 0 && x < dx && xt === x) {
        point[0] = smooth1(x, valid(values[yt * dx + xt - 1]), v1, value);
      }
      if (y > 0 && y < dy && yt === y) {
        point[1] = smooth1(y, valid(values[(yt - 1) * dx + xt]), v1, value);
      }
    });
  }

  contours.contour = contour;

  contours.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.floor(_[0]), _1 = Math.floor(_[1]);
    if (!(_0 >= 0 && _1 >= 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, contours;
  };

  contours.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), contours) : threshold;
  };

  contours.smooth = function(_) {
    return arguments.length ? (smooth = _ ? smoothLinear : noop, contours) : smooth === smoothLinear;
  };

  return contours;
}

// When computing the extent, ignore infinite values (as well as invalid ones).
function finite(x) {
  return isFinite(x) ? x : NaN;
}

// Is the (possibly invalid) x greater than or equal to the (known valid) value?
// Treat any invalid value as below negative infinity.
function above(x, value) {
  return x == null ? false : +x >= value;
}

// During smoothing, treat any invalid value as negative infinity.
function valid(v) {
  return v == null || isNaN(v = +v) ? -Infinity : v;
}

function smooth1(x, v0, v1, value) {
  const a = value - v0;
  const b = v1 - v0;
  const d = isFinite(a) || isFinite(b) ? a / b : Math.sign(a) / Math.sign(b);
  return isNaN(d) ? x : x + d - 0.5;
}

function defaultX(d) {
  return d[0];
}

function defaultY(d) {
  return d[1];
}

function defaultWeight() {
  return 1;
}

function density() {
  var x = defaultX,
      y = defaultY,
      weight = defaultWeight,
      dx = 960,
      dy = 500,
      r = 20, // blur radius
      k = 2, // log2(grid cell size)
      o = r * 3, // grid offset, to pad for blur
      n = (dx + o * 2) >> k, // grid width
      m = (dy + o * 2) >> k, // grid height
      threshold = constant(20);

  function grid(data) {
    var values = new Float32Array(n * m),
        pow2k = Math.pow(2, -k),
        i = -1;

    for (const d of data) {
      var xi = (x(d, ++i, data) + o) * pow2k,
          yi = (y(d, i, data) + o) * pow2k,
          wi = +weight(d, i, data);
      if (wi && xi >= 0 && xi < n && yi >= 0 && yi < m) {
        var x0 = Math.floor(xi),
            y0 = Math.floor(yi),
            xt = xi - x0 - 0.5,
            yt = yi - y0 - 0.5;
        values[x0 + y0 * n] += (1 - xt) * (1 - yt) * wi;
        values[x0 + 1 + y0 * n] += xt * (1 - yt) * wi;
        values[x0 + 1 + (y0 + 1) * n] += xt * yt * wi;
        values[x0 + (y0 + 1) * n] += (1 - xt) * yt * wi;
      }
    }

    d3Array.blur2({data: values, width: n, height: m}, r * pow2k);
    return values;
  }

  function density(data) {
    var values = grid(data),
        tz = threshold(values),
        pow4k = Math.pow(2, 2 * k);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      tz = d3Array.ticks(Number.MIN_VALUE, d3Array.max(values) / pow4k, tz);
    }

    return Contours()
        .size([n, m])
        .thresholds(tz.map(d => d * pow4k))
      (values)
        .map((c, i) => (c.value = +tz[i], transform(c)));
  }

  density.contours = function(data) {
    var values = grid(data),
        contours = Contours().size([n, m]),
        pow4k = Math.pow(2, 2 * k),
        contour = value => {
          value = +value;
          var c = transform(contours.contour(values, value * pow4k));
          c.value = value; // preserve exact threshold value
          return c;
        };
    Object.defineProperty(contour, "max", {get: () => d3Array.max(values) / pow4k});
    return contour;
  };

  function transform(geometry) {
    geometry.coordinates.forEach(transformPolygon);
    return geometry;
  }

  function transformPolygon(coordinates) {
    coordinates.forEach(transformRing);
  }

  function transformRing(coordinates) {
    coordinates.forEach(transformPoint);
  }

  // TODO Optimize.
  function transformPoint(coordinates) {
    coordinates[0] = coordinates[0] * Math.pow(2, k) - o;
    coordinates[1] = coordinates[1] * Math.pow(2, k) - o;
  }

  function resize() {
    o = r * 3;
    n = (dx + o * 2) >> k;
    m = (dy + o * 2) >> k;
    return density;
  }

  density.x = function(_) {
    return arguments.length ? (x = typeof _ === "function" ? _ : constant(+_), density) : x;
  };

  density.y = function(_) {
    return arguments.length ? (y = typeof _ === "function" ? _ : constant(+_), density) : y;
  };

  density.weight = function(_) {
    return arguments.length ? (weight = typeof _ === "function" ? _ : constant(+_), density) : weight;
  };

  density.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = +_[0], _1 = +_[1];
    if (!(_0 >= 0 && _1 >= 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, resize();
  };

  density.cellSize = function(_) {
    if (!arguments.length) return 1 << k;
    if (!((_ = +_) >= 1)) throw new Error("invalid cell size");
    return k = Math.floor(Math.log(_) / Math.LN2), resize();
  };

  density.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), density) : threshold;
  };

  density.bandwidth = function(_) {
    if (!arguments.length) return Math.sqrt(r * (r + 1));
    if (!((_ = +_) >= 0)) throw new Error("invalid bandwidth");
    return r = (Math.sqrt(4 * _ * _ + 1) - 1) / 2, resize();
  };

  return density;
}

exports.contourDensity = density;
exports.contours = Contours;

}));