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'use strict';
const Assert = require('@hapi/hoek/lib/assert');
const internals = {};
module.exports = class Topo {
constructor() {
this._items = [];
this.nodes = [];
}
add(nodes, options) {
options = options || {};
// Validate rules
const before = [].concat(options.before || []);
const after = [].concat(options.after || []);
const group = options.group || '?';
const sort = options.sort || 0; // Used for merging only
Assert(!before.includes(group), `Item cannot come before itself: ${group}`);
Assert(!before.includes('?'), 'Item cannot come before unassociated items');
Assert(!after.includes(group), `Item cannot come after itself: ${group}`);
Assert(!after.includes('?'), 'Item cannot come after unassociated items');
if (!Array.isArray(nodes)) {
nodes = [nodes];
}
for (const node of nodes) {
const item = {
seq: this._items.length,
sort,
before,
after,
group,
node
};
this._items.push(item);
}
// Insert event
const valid = this._sort();
Assert(valid, 'item', group !== '?' ? `added into group ${group}` : '', 'created a dependencies error');
return this.nodes;
}
merge(others) {
if (!Array.isArray(others)) {
others = [others];
}
for (const other of others) {
if (other) {
for (const item of other._items) {
this._items.push(Object.assign({}, item)); // Shallow cloned
}
}
}
// Sort items
this._items.sort(internals.mergeSort);
for (let i = 0; i < this._items.length; ++i) {
this._items[i].seq = i;
}
const valid = this._sort();
Assert(valid, 'merge created a dependencies error');
return this.nodes;
}
_sort() {
// Construct graph
const graph = {};
const graphAfters = Object.create(null); // A prototype can bungle lookups w/ false positives
const groups = Object.create(null);
for (const item of this._items) {
const seq = item.seq; // Unique across all items
const group = item.group;
// Determine Groups
groups[group] = groups[group] || [];
groups[group].push(seq);
// Build intermediary graph using 'before'
graph[seq] = item.before;
// Build second intermediary graph with 'after'
for (const after of item.after) {
graphAfters[after] = graphAfters[after] || [];
graphAfters[after].push(seq);
}
}
// Expand intermediary graph
for (const node in graph) {
const expandedGroups = [];
for (const graphNodeItem in graph[node]) {
const group = graph[node][graphNodeItem];
groups[group] = groups[group] || [];
expandedGroups.push(...groups[group]);
}
graph[node] = expandedGroups;
}
// Merge intermediary graph using graphAfters into final graph
for (const group in graphAfters) {
if (groups[group]) {
for (const node of groups[group]) {
graph[node].push(...graphAfters[group]);
}
}
}
// Compile ancestors
const ancestors = {};
for (const node in graph) {
const children = graph[node];
for (const child of children) {
ancestors[child] = ancestors[child] || [];
ancestors[child].push(node);
}
}
// Topo sort
const visited = {};
const sorted = [];
for (let i = 0; i < this._items.length; ++i) { // Looping through item.seq values out of order
let next = i;
if (ancestors[i]) {
next = null;
for (let j = 0; j < this._items.length; ++j) { // As above, these are item.seq values
if (visited[j] === true) {
continue;
}
if (!ancestors[j]) {
ancestors[j] = [];
}
const shouldSeeCount = ancestors[j].length;
let seenCount = 0;
for (let k = 0; k < shouldSeeCount; ++k) {
if (visited[ancestors[j][k]]) {
++seenCount;
}
}
if (seenCount === shouldSeeCount) {
next = j;
break;
}
}
}
if (next !== null) {
visited[next] = true;
sorted.push(next);
}
}
if (sorted.length !== this._items.length) {
return false;
}
const seqIndex = {};
for (const item of this._items) {
seqIndex[item.seq] = item;
}
this._items = [];
this.nodes = [];
for (const value of sorted) {
const sortedItem = seqIndex[value];
this.nodes.push(sortedItem.node);
this._items.push(sortedItem);
}
return true;
}
};
internals.mergeSort = (a, b) => {
return a.sort === b.sort ? 0 : (a.sort < b.sort ? -1 : 1);
};
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