365 lines
11 KiB
JavaScript
365 lines
11 KiB
JavaScript
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/**
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* A simple dependency graph
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*/
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/**
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* Helper for creating a Topological Sort using Depth-First-Search on a set of edges.
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*
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* Detects cycles and throws an Error if one is detected (unless the "circular"
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* parameter is "true" in which case it ignores them).
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*
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* @param edges The set of edges to DFS through
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* @param leavesOnly Whether to only return "leaf" nodes (ones who have no edges)
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* @param result An array in which the results will be populated
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* @param circular A boolean to allow circular dependencies
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*/
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function createDFS(edges, leavesOnly, result, circular) {
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var visited = {};
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return function (start) {
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if (visited[start]) {
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return;
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}
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var inCurrentPath = {};
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var currentPath = [];
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var todo = []; // used as a stack
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todo.push({ node: start, processed: false });
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while (todo.length > 0) {
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var current = todo[todo.length - 1]; // peek at the todo stack
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var processed = current.processed;
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var node = current.node;
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if (!processed) {
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// Haven't visited edges yet (visiting phase)
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if (visited[node]) {
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todo.pop();
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continue;
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} else if (inCurrentPath[node]) {
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// It's not a DAG
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if (circular) {
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todo.pop();
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// If we're tolerating cycles, don't revisit the node
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continue;
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}
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currentPath.push(node);
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throw new DepGraphCycleError(currentPath);
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}
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inCurrentPath[node] = true;
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currentPath.push(node);
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var nodeEdges = edges[node];
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// (push edges onto the todo stack in reverse order to be order-compatible with the old DFS implementation)
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for (var i = nodeEdges.length - 1; i >= 0; i--) {
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todo.push({ node: nodeEdges[i], processed: false });
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}
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current.processed = true;
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} else {
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// Have visited edges (stack unrolling phase)
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todo.pop();
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currentPath.pop();
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inCurrentPath[node] = false;
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visited[node] = true;
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if (!leavesOnly || edges[node].length === 0) {
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result.push(node);
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}
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}
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}
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};
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}
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/**
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* Simple Dependency Graph
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*/
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var DepGraph = (exports.DepGraph = function DepGraph(opts) {
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this.nodes = {}; // Node -> Node/Data (treated like a Set)
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this.outgoingEdges = {}; // Node -> [Dependency Node]
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this.incomingEdges = {}; // Node -> [Dependant Node]
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this.circular = opts && !!opts.circular; // Allows circular deps
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});
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DepGraph.prototype = {
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/**
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* The number of nodes in the graph.
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*/
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size: function () {
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return Object.keys(this.nodes).length;
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},
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/**
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* Add a node to the dependency graph. If a node already exists, this method will do nothing.
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*/
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addNode: function (node, data) {
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if (!this.hasNode(node)) {
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// Checking the arguments length allows the user to add a node with undefined data
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if (arguments.length === 2) {
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this.nodes[node] = data;
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} else {
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this.nodes[node] = node;
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}
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this.outgoingEdges[node] = [];
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this.incomingEdges[node] = [];
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}
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},
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/**
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* Remove a node from the dependency graph. If a node does not exist, this method will do nothing.
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*/
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removeNode: function (node) {
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if (this.hasNode(node)) {
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delete this.nodes[node];
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delete this.outgoingEdges[node];
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delete this.incomingEdges[node];
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[this.incomingEdges, this.outgoingEdges].forEach(function (edgeList) {
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Object.keys(edgeList).forEach(function (key) {
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var idx = edgeList[key].indexOf(node);
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if (idx >= 0) {
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edgeList[key].splice(idx, 1);
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}
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}, this);
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});
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}
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},
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/**
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* Check if a node exists in the graph
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*/
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hasNode: function (node) {
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return this.nodes.hasOwnProperty(node);
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},
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/**
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* Get the data associated with a node name
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*/
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getNodeData: function (node) {
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if (this.hasNode(node)) {
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return this.nodes[node];
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* Set the associated data for a given node name. If the node does not exist, this method will throw an error
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*/
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setNodeData: function (node, data) {
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if (this.hasNode(node)) {
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this.nodes[node] = data;
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* Add a dependency between two nodes. If either of the nodes does not exist,
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* an Error will be thrown.
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*/
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addDependency: function (from, to) {
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if (!this.hasNode(from)) {
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throw new Error("Node does not exist: " + from);
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}
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if (!this.hasNode(to)) {
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throw new Error("Node does not exist: " + to);
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}
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if (this.outgoingEdges[from].indexOf(to) === -1) {
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this.outgoingEdges[from].push(to);
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}
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if (this.incomingEdges[to].indexOf(from) === -1) {
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this.incomingEdges[to].push(from);
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}
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return true;
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},
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/**
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* Remove a dependency between two nodes.
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*/
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removeDependency: function (from, to) {
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var idx;
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if (this.hasNode(from)) {
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idx = this.outgoingEdges[from].indexOf(to);
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if (idx >= 0) {
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this.outgoingEdges[from].splice(idx, 1);
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}
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}
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if (this.hasNode(to)) {
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idx = this.incomingEdges[to].indexOf(from);
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if (idx >= 0) {
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this.incomingEdges[to].splice(idx, 1);
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}
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}
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},
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/**
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* Return a clone of the dependency graph. If any custom data is attached
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* to the nodes, it will only be shallow copied.
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*/
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clone: function () {
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var source = this;
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var result = new DepGraph();
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var keys = Object.keys(source.nodes);
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keys.forEach(function (n) {
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result.nodes[n] = source.nodes[n];
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result.outgoingEdges[n] = source.outgoingEdges[n].slice(0);
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result.incomingEdges[n] = source.incomingEdges[n].slice(0);
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});
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return result;
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},
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/**
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* Get an array containing the direct dependencies of the specified node.
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*
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* Throws an Error if the specified node does not exist.
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*/
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directDependenciesOf: function (node) {
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if (this.hasNode(node)) {
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return this.outgoingEdges[node].slice(0);
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* Get an array containing the nodes that directly depend on the specified node.
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*
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* Throws an Error if the specified node does not exist.
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*/
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directDependantsOf: function (node) {
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if (this.hasNode(node)) {
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return this.incomingEdges[node].slice(0);
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* Get an array containing the nodes that the specified node depends on (transitively).
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*
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* Throws an Error if the graph has a cycle, or the specified node does not exist.
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*
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* If `leavesOnly` is true, only nodes that do not depend on any other nodes will be returned
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* in the array.
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*/
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dependenciesOf: function (node, leavesOnly) {
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if (this.hasNode(node)) {
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var result = [];
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var DFS = createDFS(
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this.outgoingEdges,
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leavesOnly,
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result,
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this.circular
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);
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DFS(node);
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var idx = result.indexOf(node);
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if (idx >= 0) {
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result.splice(idx, 1);
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}
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return result;
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* get an array containing the nodes that depend on the specified node (transitively).
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*
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* Throws an Error if the graph has a cycle, or the specified node does not exist.
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*
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* If `leavesOnly` is true, only nodes that do not have any dependants will be returned in the array.
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*/
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dependantsOf: function (node, leavesOnly) {
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if (this.hasNode(node)) {
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var result = [];
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var DFS = createDFS(
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this.incomingEdges,
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leavesOnly,
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result,
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this.circular
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);
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DFS(node);
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var idx = result.indexOf(node);
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if (idx >= 0) {
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result.splice(idx, 1);
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}
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return result;
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} else {
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throw new Error("Node does not exist: " + node);
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}
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},
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/**
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* Construct the overall processing order for the dependency graph.
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*
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* Throws an Error if the graph has a cycle.
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*
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* If `leavesOnly` is true, only nodes that do not depend on any other nodes will be returned.
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*/
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overallOrder: function (leavesOnly) {
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var self = this;
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var result = [];
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var keys = Object.keys(this.nodes);
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if (keys.length === 0) {
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return result; // Empty graph
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} else {
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if (!this.circular) {
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// Look for cycles - we run the DFS starting at all the nodes in case there
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// are several disconnected subgraphs inside this dependency graph.
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var CycleDFS = createDFS(this.outgoingEdges, false, [], this.circular);
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keys.forEach(function (n) {
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CycleDFS(n);
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});
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}
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var DFS = createDFS(
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this.outgoingEdges,
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leavesOnly,
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result,
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this.circular
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);
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// Find all potential starting points (nodes with nothing depending on them) an
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// run a DFS starting at these points to get the order
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keys
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.filter(function (node) {
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return self.incomingEdges[node].length === 0;
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})
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.forEach(function (n) {
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DFS(n);
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});
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// If we're allowing cycles - we need to run the DFS against any remaining
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// nodes that did not end up in the initial result (as they are part of a
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// subgraph that does not have a clear starting point)
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if (this.circular) {
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keys
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.filter(function (node) {
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return result.indexOf(node) === -1;
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})
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.forEach(function (n) {
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DFS(n);
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});
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}
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return result;
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}
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},
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/**
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* Get an array of nodes that have no dependants (i.e. nothing depends on them).
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*/
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entryNodes: function () {
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var self = this;
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return Object.keys(this.nodes).filter(function (node) {
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return self.incomingEdges[node].length === 0;
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});
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}
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};
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// Create some aliases
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DepGraph.prototype.directDependentsOf = DepGraph.prototype.directDependantsOf;
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DepGraph.prototype.dependentsOf = DepGraph.prototype.dependantsOf;
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/**
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* Cycle error, including the path of the cycle.
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*/
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var DepGraphCycleError = (exports.DepGraphCycleError = function (cyclePath) {
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var message = "Dependency Cycle Found: " + cyclePath.join(" -> ");
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var instance = new Error(message);
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instance.cyclePath = cyclePath;
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Object.setPrototypeOf(instance, Object.getPrototypeOf(this));
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if (Error.captureStackTrace) {
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Error.captureStackTrace(instance, DepGraphCycleError);
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}
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return instance;
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});
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DepGraphCycleError.prototype = Object.create(Error.prototype, {
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constructor: {
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value: Error,
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enumerable: false,
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writable: true,
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configurable: true
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}
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});
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Object.setPrototypeOf(DepGraphCycleError, Error);
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