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| Current File : //proc/self/root/home/saurabh/.npm/_npx/249ca9fcd30c476a/node_modules/dag-map/lib/dag-map.js |
import Vertex from './vertex';
import visit from './visit';
/**
* DAG stands for Directed acyclic graph.
*
* It is used to build a graph of dependencies checking that there isn't circular
* dependencies. p.e Registering initializers with a certain precedence order.
*
* @class DAG
* @constructor
*/
export default function DAG() {
this.names = [];
this.vertices = Object.create(null);
}
/**
* Adds a vertex entry to the graph unless it is already added.
*
* @private
* @method add
* @param {String} name The name of the vertex to add
*/
DAG.prototype.add = function(name) {
if (!name) {
throw new Error("Can't add Vertex without name");
}
if (this.vertices[name] !== undefined) {
return this.vertices[name];
}
var vertex = new Vertex(name);
this.vertices[name] = vertex;
this.names.push(name);
return vertex;
};
/**
* Adds a vertex to the graph and sets its value.
*
* @private
* @method map
* @param {String} name The name of the vertex.
* @param value The value to put in the vertex.
*/
DAG.prototype.map = function(name, value) {
this.add(name).value = value;
};
/**
* Connects the vertices with the given names, adding them to the graph if
* necessary, only if this does not produce is any circular dependency.
*
* @private
* @method addEdge
* @param {String} fromName The name the vertex where the edge starts.
* @param {String} toName The name the vertex where the edge ends.
*/
DAG.prototype.addEdge = function(fromName, toName) {
if (!fromName || !toName || fromName === toName) {
return;
}
var from = this.add(fromName);
var to = this.add(toName);
if (to.incoming.hasOwnProperty(fromName)) {
return;
}
function checkCycle(vertex, path) {
if (vertex.name === toName) {
throw new Error("cycle detected: " + toName + " <- " + path.join(" <- "));
}
}
visit(from, checkCycle);
from.hasOutgoing = true;
to.incoming[fromName] = from;
to.incomingNames.push(fromName);
};
/**
* Visits all the vertex of the graph calling the given function with each one,
* ensuring that the vertices are visited respecting their precedence.
*
* @method topsort
* @param {Function} fn The function to be invoked on each vertex.
*/
DAG.prototype.topsort = function(fn) {
var visited = {};
var vertices = this.vertices;
var names = this.names;
var len = names.length;
var i, vertex;
for (i = 0; i < len; i++) {
vertex = vertices[names[i]];
if (!vertex.hasOutgoing) {
visit(vertex, fn, visited);
}
}
};
/**
* Adds a vertex with the given name and value to the graph and joins it with the
* vertices referenced in _before_ and _after_. If there isn't vertices with those
* names, they are added too.
*
* If either _before_ or _after_ are falsy/empty, the added vertex will not have
* an incoming/outgoing edge.
*
* @method addEdges
* @param {String} name The name of the vertex to be added.
* @param value The value of that vertex.
* @param before An string or array of strings with the names of the vertices before
* which this vertex must be visited.
* @param after An string or array of strings with the names of the vertex after
* which this vertex must be visited.
*
*/
DAG.prototype.addEdges = function(name, value, before, after) {
var i;
this.map(name, value);
if (before) {
if (typeof before === 'string') {
this.addEdge(name, before);
} else {
for (i = 0; i < before.length; i++) {
this.addEdge(name, before[i]);
}
}
}
if (after) {
if (typeof after === 'string') {
this.addEdge(after, name);
} else {
for (i = 0; i < after.length; i++) {
this.addEdge(after[i], name);
}
}
}
};
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