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import {Adder} from "d3-array";
import {asin, atan2, cos, degrees, epsilon, epsilon2, hypot, radians, sin, sqrt} from "./math.js";
import noop from "./noop.js";
import stream from "./stream.js";
var W0, W1,
X0, Y0, Z0,
X1, Y1, Z1,
X2, Y2, Z2,
lambda00, phi00, // first point
x0, y0, z0; // previous point
var centroidStream = {
sphere: noop,
point: centroidPoint,
lineStart: centroidLineStart,
lineEnd: centroidLineEnd,
polygonStart: function() {
centroidStream.lineStart = centroidRingStart;
centroidStream.lineEnd = centroidRingEnd;
},
polygonEnd: function() {
centroidStream.lineStart = centroidLineStart;
centroidStream.lineEnd = centroidLineEnd;
}
};
// Arithmetic mean of Cartesian vectors.
function centroidPoint(lambda, phi) {
lambda *= radians, phi *= radians;
var cosPhi = cos(phi);
centroidPointCartesian(cosPhi * cos(lambda), cosPhi * sin(lambda), sin(phi));
}
function centroidPointCartesian(x, y, z) {
++W0;
X0 += (x - X0) / W0;
Y0 += (y - Y0) / W0;
Z0 += (z - Z0) / W0;
}
function centroidLineStart() {
centroidStream.point = centroidLinePointFirst;
}
function centroidLinePointFirst(lambda, phi) {
lambda *= radians, phi *= radians;
var cosPhi = cos(phi);
x0 = cosPhi * cos(lambda);
y0 = cosPhi * sin(lambda);
z0 = sin(phi);
centroidStream.point = centroidLinePoint;
centroidPointCartesian(x0, y0, z0);
}
function centroidLinePoint(lambda, phi) {
lambda *= radians, phi *= radians;
var cosPhi = cos(phi),
x = cosPhi * cos(lambda),
y = cosPhi * sin(lambda),
z = sin(phi),
w = atan2(sqrt((w = y0 * z - z0 * y) * w + (w = z0 * x - x0 * z) * w + (w = x0 * y - y0 * x) * w), x0 * x + y0 * y + z0 * z);
W1 += w;
X1 += w * (x0 + (x0 = x));
Y1 += w * (y0 + (y0 = y));
Z1 += w * (z0 + (z0 = z));
centroidPointCartesian(x0, y0, z0);
}
function centroidLineEnd() {
centroidStream.point = centroidPoint;
}
// See J. E. Brock, The Inertia Tensor for a Spherical Triangle,
// J. Applied Mechanics 42, 239 (1975).
function centroidRingStart() {
centroidStream.point = centroidRingPointFirst;
}
function centroidRingEnd() {
centroidRingPoint(lambda00, phi00);
centroidStream.point = centroidPoint;
}
function centroidRingPointFirst(lambda, phi) {
lambda00 = lambda, phi00 = phi;
lambda *= radians, phi *= radians;
centroidStream.point = centroidRingPoint;
var cosPhi = cos(phi);
x0 = cosPhi * cos(lambda);
y0 = cosPhi * sin(lambda);
z0 = sin(phi);
centroidPointCartesian(x0, y0, z0);
}
function centroidRingPoint(lambda, phi) {
lambda *= radians, phi *= radians;
var cosPhi = cos(phi),
x = cosPhi * cos(lambda),
y = cosPhi * sin(lambda),
z = sin(phi),
cx = y0 * z - z0 * y,
cy = z0 * x - x0 * z,
cz = x0 * y - y0 * x,
m = hypot(cx, cy, cz),
w = asin(m), // line weight = angle
v = m && -w / m; // area weight multiplier
X2.add(v * cx);
Y2.add(v * cy);
Z2.add(v * cz);
W1 += w;
X1 += w * (x0 + (x0 = x));
Y1 += w * (y0 + (y0 = y));
Z1 += w * (z0 + (z0 = z));
centroidPointCartesian(x0, y0, z0);
}
export default function(object) {
W0 = W1 =
X0 = Y0 = Z0 =
X1 = Y1 = Z1 = 0;
X2 = new Adder();
Y2 = new Adder();
Z2 = new Adder();
stream(object, centroidStream);
var x = +X2,
y = +Y2,
z = +Z2,
m = hypot(x, y, z);
// If the area-weighted ccentroid is undefined, fall back to length-weighted ccentroid.
if (m < epsilon2) {
x = X1, y = Y1, z = Z1;
// If the feature has zero length, fall back to arithmetic mean of point vectors.
if (W1 < epsilon) x = X0, y = Y0, z = Z0;
m = hypot(x, y, z);
// If the feature still has an undefined ccentroid, then return.
if (m < epsilon2) return [NaN, NaN];
}
return [atan2(y, x) * degrees, asin(z / m) * degrees];
}