[6a3a178] | 1 | /*
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| 2 | MIT License http://www.opensource.org/licenses/mit-license.php
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| 3 | Author Tobias Koppers @sokra
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| 4 | */
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| 5 |
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| 6 | "use strict";
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| 7 |
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| 8 | const NO_MARKER = 0;
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| 9 | const IN_PROGRESS_MARKER = 1;
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| 10 | const DONE_MARKER = 2;
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| 11 | const DONE_MAYBE_ROOT_CYCLE_MARKER = 3;
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| 12 | const DONE_AND_ROOT_MARKER = 4;
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| 13 |
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| 14 | /**
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| 15 | * @template T
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| 16 | */
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| 17 | class Node {
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| 18 | /**
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| 19 | * @param {T} item the value of the node
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| 20 | */
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| 21 | constructor(item) {
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| 22 | this.item = item;
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| 23 | /** @type {Set<Node<T>>} */
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| 24 | this.dependencies = new Set();
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| 25 | this.marker = NO_MARKER;
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| 26 | /** @type {Cycle<T> | undefined} */
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| 27 | this.cycle = undefined;
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| 28 | this.incoming = 0;
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| 29 | }
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| 30 | }
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| 31 |
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| 32 | /**
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| 33 | * @template T
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| 34 | */
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| 35 | class Cycle {
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| 36 | constructor() {
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| 37 | /** @type {Set<Node<T>>} */
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| 38 | this.nodes = new Set();
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| 39 | }
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| 40 | }
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| 41 |
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| 42 | /**
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| 43 | * @template T
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| 44 | * @typedef {Object} StackEntry
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| 45 | * @property {Node<T>} node
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| 46 | * @property {Node<T>[]} openEdges
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| 47 | */
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| 48 |
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| 49 | /**
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| 50 | * @template T
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| 51 | * @param {Iterable<T>} items list of items
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| 52 | * @param {function(T): Iterable<T>} getDependencies function to get dependencies of an item (items that are not in list are ignored)
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| 53 | * @returns {Iterable<T>} graph roots of the items
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| 54 | */
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| 55 | module.exports = (items, getDependencies) => {
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| 56 | /** @type {Map<T, Node<T>>} */
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| 57 | const itemToNode = new Map();
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| 58 | for (const item of items) {
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| 59 | const node = new Node(item);
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| 60 | itemToNode.set(item, node);
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| 61 | }
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| 62 |
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| 63 | // early exit when there is only a single item
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| 64 | if (itemToNode.size <= 1) return items;
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| 65 |
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| 66 | // grab all the dependencies
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| 67 | for (const node of itemToNode.values()) {
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| 68 | for (const dep of getDependencies(node.item)) {
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| 69 | const depNode = itemToNode.get(dep);
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| 70 | if (depNode !== undefined) {
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| 71 | node.dependencies.add(depNode);
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| 72 | }
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| 73 | }
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| 74 | }
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| 75 |
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| 76 | // Set of current root modules
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| 77 | // items will be removed if a new reference to it has been found
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| 78 | /** @type {Set<Node<T>>} */
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| 79 | const roots = new Set();
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| 80 |
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| 81 | // Set of current cycles without references to it
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| 82 | // cycles will be removed if a new reference to it has been found
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| 83 | // that is not part of the cycle
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| 84 | /** @type {Set<Cycle<T>>} */
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| 85 | const rootCycles = new Set();
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| 86 |
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| 87 | // For all non-marked nodes
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| 88 | for (const selectedNode of itemToNode.values()) {
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| 89 | if (selectedNode.marker === NO_MARKER) {
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| 90 | // deep-walk all referenced modules
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| 91 | // in a non-recursive way
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| 92 |
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| 93 | // start by entering the selected node
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| 94 | selectedNode.marker = IN_PROGRESS_MARKER;
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| 95 |
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| 96 | // keep a stack to avoid recursive walk
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| 97 | /** @type {StackEntry<T>[]} */
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| 98 | const stack = [
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| 99 | {
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| 100 | node: selectedNode,
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| 101 | openEdges: Array.from(selectedNode.dependencies)
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| 102 | }
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| 103 | ];
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| 104 |
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| 105 | // process the top item until stack is empty
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| 106 | while (stack.length > 0) {
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| 107 | const topOfStack = stack[stack.length - 1];
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| 108 |
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| 109 | // Are there still edges unprocessed in the current node?
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| 110 | if (topOfStack.openEdges.length > 0) {
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| 111 | // Process one dependency
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| 112 | const dependency = topOfStack.openEdges.pop();
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| 113 | switch (dependency.marker) {
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| 114 | case NO_MARKER:
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| 115 | // dependency has not be visited yet
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| 116 | // mark it as in-progress and recurse
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| 117 | stack.push({
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| 118 | node: dependency,
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| 119 | openEdges: Array.from(dependency.dependencies)
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| 120 | });
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| 121 | dependency.marker = IN_PROGRESS_MARKER;
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| 122 | break;
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| 123 | case IN_PROGRESS_MARKER: {
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| 124 | // It's a in-progress cycle
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| 125 | let cycle = dependency.cycle;
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| 126 | if (!cycle) {
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| 127 | cycle = new Cycle();
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| 128 | cycle.nodes.add(dependency);
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| 129 | dependency.cycle = cycle;
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| 130 | }
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| 131 | // set cycle property for each node in the cycle
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| 132 | // if nodes are already part of a cycle
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| 133 | // we merge the cycles to a shared cycle
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| 134 | for (
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| 135 | let i = stack.length - 1;
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| 136 | stack[i].node !== dependency;
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| 137 | i--
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| 138 | ) {
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| 139 | const node = stack[i].node;
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| 140 | if (node.cycle) {
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| 141 | if (node.cycle !== cycle) {
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| 142 | // merge cycles
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| 143 | for (const cycleNode of node.cycle.nodes) {
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| 144 | cycleNode.cycle = cycle;
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| 145 | cycle.nodes.add(cycleNode);
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| 146 | }
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| 147 | }
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| 148 | } else {
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| 149 | node.cycle = cycle;
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| 150 | cycle.nodes.add(node);
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| 151 | }
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| 152 | }
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| 153 | // don't recurse into dependencies
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| 154 | // these are already on the stack
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| 155 | break;
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| 156 | }
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| 157 | case DONE_AND_ROOT_MARKER:
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| 158 | // This node has be visited yet and is currently a root node
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| 159 | // But as this is a new reference to the node
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| 160 | // it's not really a root
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| 161 | // so we have to convert it to a normal node
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| 162 | dependency.marker = DONE_MARKER;
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| 163 | roots.delete(dependency);
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| 164 | break;
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| 165 | case DONE_MAYBE_ROOT_CYCLE_MARKER:
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| 166 | // This node has be visited yet and
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| 167 | // is maybe currently part of a completed root cycle
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| 168 | // we found a new reference to the cycle
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| 169 | // so it's not really a root cycle
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| 170 | // remove the cycle from the root cycles
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| 171 | // and convert it to a normal node
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| 172 | rootCycles.delete(dependency.cycle);
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| 173 | dependency.marker = DONE_MARKER;
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| 174 | break;
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| 175 | // DONE_MARKER: nothing to do, don't recurse into dependencies
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| 176 | }
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| 177 | } else {
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| 178 | // All dependencies of the current node has been visited
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| 179 | // we leave the node
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| 180 | stack.pop();
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| 181 | topOfStack.node.marker = DONE_MARKER;
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| 182 | }
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| 183 | }
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| 184 | const cycle = selectedNode.cycle;
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| 185 | if (cycle) {
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| 186 | for (const node of cycle.nodes) {
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| 187 | node.marker = DONE_MAYBE_ROOT_CYCLE_MARKER;
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| 188 | }
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| 189 | rootCycles.add(cycle);
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| 190 | } else {
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| 191 | selectedNode.marker = DONE_AND_ROOT_MARKER;
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| 192 | roots.add(selectedNode);
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| 193 | }
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| 194 | }
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| 195 | }
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| 196 |
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| 197 | // Extract roots from root cycles
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| 198 | // We take the nodes with most incoming edges
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| 199 | // inside of the cycle
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| 200 | for (const cycle of rootCycles) {
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| 201 | let max = 0;
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| 202 | /** @type {Set<Node<T>>} */
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| 203 | const cycleRoots = new Set();
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| 204 | const nodes = cycle.nodes;
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| 205 | for (const node of nodes) {
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| 206 | for (const dep of node.dependencies) {
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| 207 | if (nodes.has(dep)) {
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| 208 | dep.incoming++;
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| 209 | if (dep.incoming < max) continue;
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| 210 | if (dep.incoming > max) {
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| 211 | cycleRoots.clear();
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| 212 | max = dep.incoming;
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| 213 | }
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| 214 | cycleRoots.add(dep);
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| 215 | }
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| 216 | }
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| 217 | }
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| 218 | for (const cycleRoot of cycleRoots) {
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| 219 | roots.add(cycleRoot);
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| 220 | }
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| 221 | }
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| 222 |
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| 223 | // When roots were found, return them
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| 224 | if (roots.size > 0) {
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| 225 | return Array.from(roots, r => r.item);
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| 226 | } else {
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| 227 | throw new Error("Implementation of findGraphRoots is broken");
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| 228 | }
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| 229 | };
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