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import constant from "./constant.js";
import jiggle from "./jiggle.js";
function index(d) {
return d.index;
}
function find(nodeById, nodeId) {
var node = nodeById.get(nodeId);
if (!node) throw new Error("node not found: " + nodeId);
return node;
}
export default function(links) {
var id = index,
strength = defaultStrength,
strengths,
distance = constant(30),
distances,
nodes,
count,
bias,
random,
iterations = 1;
if (links == null) links = [];
function defaultStrength(link) {
return 1 / Math.min(count[link.source.index], count[link.target.index]);
}
function force(alpha) {
for (var k = 0, n = links.length; k < iterations; ++k) {
for (var i = 0, link, source, target, x, y, l, b; i < n; ++i) {
link = links[i], source = link.source, target = link.target;
x = target.x + target.vx - source.x - source.vx || jiggle(random);
y = target.y + target.vy - source.y - source.vy || jiggle(random);
l = Math.sqrt(x * x + y * y);
l = (l - distances[i]) / l * alpha * strengths[i];
x *= l, y *= l;
target.vx -= x * (b = bias[i]);
target.vy -= y * b;
source.vx += x * (b = 1 - b);
source.vy += y * b;
}
}
}
function initialize() {
if (!nodes) return;
var i,
n = nodes.length,
m = links.length,
nodeById = new Map(nodes.map((d, i) => [id(d, i, nodes), d])),
link;
for (i = 0, count = new Array(n); i < m; ++i) {
link = links[i], link.index = i;
if (typeof link.source !== "object") link.source = find(nodeById, link.source);
if (typeof link.target !== "object") link.target = find(nodeById, link.target);
count[link.source.index] = (count[link.source.index] || 0) + 1;
count[link.target.index] = (count[link.target.index] || 0) + 1;
}
for (i = 0, bias = new Array(m); i < m; ++i) {
link = links[i], bias[i] = count[link.source.index] / (count[link.source.index] + count[link.target.index]);
}
strengths = new Array(m), initializeStrength();
distances = new Array(m), initializeDistance();
}
function initializeStrength() {
if (!nodes) return;
for (var i = 0, n = links.length; i < n; ++i) {
strengths[i] = +strength(links[i], i, links);
}
}
function initializeDistance() {
if (!nodes) return;
for (var i = 0, n = links.length; i < n; ++i) {
distances[i] = +distance(links[i], i, links);
}
}
force.initialize = function(_nodes, _random) {
nodes = _nodes;
random = _random;
initialize();
};
force.links = function(_) {
return arguments.length ? (links = _, initialize(), force) : links;
};
force.id = function(_) {
return arguments.length ? (id = _, force) : id;
};
force.iterations = function(_) {
return arguments.length ? (iterations = +_, force) : iterations;
};
force.strength = function(_) {
return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initializeStrength(), force) : strength;
};
force.distance = function(_) {
return arguments.length ? (distance = typeof _ === "function" ? _ : constant(+_), initializeDistance(), force) : distance;
};
return force;
}