the home site for me: also iteration 3 or 4 of my site
dunkirk.sh
1// Taken from Vale's 404 Guesser
2// https://vale.rocks/assets/scripts/404-guesser.js
3// which was based on Gwern's 404 Error Page URL Suggester
4// https://gwern.net/static/js/404-guesser.js
5
6class URLSuggester {
7 constructor() {
8 this.maxDistance = 8;
9 this.urls = [];
10 }
11
12 async initialize() {
13 try {
14 const sitemapText = await this.fetchSitemap();
15 if (sitemapText) {
16 this.urls = this.parseUrls(sitemapText);
17 const currentPath = window.location.pathname;
18 if (!currentPath.endsWith("/404")) {
19 const suggestions = this.findSimilarUrls(currentPath);
20 this.injectSuggestions(currentPath, suggestions);
21 }
22 }
23 } catch (error) {
24 console.error("Error initializing URL suggester:", error);
25 }
26 }
27
28 async fetchSitemap() {
29 try {
30 const response = await fetch("/sitemap.xml");
31 return await response.text();
32 } catch (error) {
33 console.error("Error fetching sitemap:", error);
34 return null;
35 }
36 }
37
38 parseUrls(sitemapText) {
39 const parser = new DOMParser();
40 const xmlDoc = parser.parseFromString(sitemapText, "text/xml");
41 const urlNodes = xmlDoc.getElementsByTagName("url");
42 return Array.from(urlNodes).map(
43 (node) =>
44 new URL(node.getElementsByTagName("loc")[0].textContent).pathname,
45 );
46 }
47
48 boundedLevenshteinDistance(a, b, maxDistance) {
49 if (Math.abs(a.length - b.length) > maxDistance) return maxDistance + 1;
50 const matrix = Array(b.length + 1)
51 .fill(null)
52 .map((_, i) => [i]);
53 for (let j = 1; j <= a.length; j++) {
54 matrix[0][j] = j;
55 }
56 for (let i = 1; i <= b.length; i++) {
57 let minDistance = maxDistance + 1;
58 for (let j = 1; j <= a.length; j++) {
59 if (b.charAt(i - 1) === a.charAt(j - 1)) {
60 matrix[i][j] = matrix[i - 1][j - 1];
61 } else {
62 matrix[i][j] = Math.min(
63 matrix[i - 1][j - 1] + 1,
64 matrix[i][j - 1] + 1,
65 matrix[i - 1][j] + 1,
66 );
67 }
68 minDistance = Math.min(minDistance, matrix[i][j]);
69 }
70 if (minDistance > maxDistance) {
71 return maxDistance + 1;
72 }
73 }
74 return matrix[b.length][a.length];
75 }
76
77 findSimilarUrls(targetUrl) {
78 const targetPath = new URL(targetUrl, location.origin).pathname;
79
80 if (targetPath.startsWith("/posts/")) {
81 const exactMatch = this.urls.find((url) => url === targetPath);
82 if (exactMatch) {
83 return [location.origin + exactMatch];
84 }
85 }
86
87 const potentialMatches = this.urls.filter(
88 (url) =>
89 Math.abs(url.length - targetPath.length) <= this.maxDistance &&
90 !url.endsWith("/404.html"),
91 );
92
93 const similarUrls = potentialMatches
94 .map((url) => ({
95 url,
96 distance: this.boundedLevenshteinDistance(
97 url,
98 targetPath,
99 this.maxDistance,
100 ),
101 }))
102 .filter((item) => item.distance <= this.maxDistance)
103 .sort((a, b) => a.distance - b.distance);
104
105 const seenUrls = new Set();
106 const uniqueSimilarUrls = similarUrls
107 .filter((item) => {
108 if (seenUrls.has(item.url)) return false;
109 seenUrls.add(item.url);
110 return true;
111 })
112 .slice(0, 10);
113
114 return uniqueSimilarUrls.map((item) => location.origin + item.url);
115 }
116
117 injectSuggestions(currentPath, suggestions) {
118 const app = document.querySelector("#suggestions");
119 if (!app) return;
120
121 if (suggestions.length > 0) {
122 const p = document.createElement("p");
123
124 p.innerHTML = "I did however find some URLs that might be relevant?";
125 app.appendChild(p);
126
127 for (const url of suggestions) {
128 const a = document.createElement("a");
129 const cleanUrl = url.replace(/\.html$/, "");
130 a.href = cleanUrl;
131 a.textContent = cleanUrl;
132 app.appendChild(a);
133 }
134
135 const endText = document.createElement("p");
136 app.appendChild(endText);
137 } else {
138 const p = document.createElement("p");
139 p.innerHTML = `Couldn't find any URLs similar to <code>${currentPath}</code>. I guess it's time to find something new`;
140 app.appendChild(p);
141 }
142
143 app.className = "url-suggestions";
144 }
145}
146
147document.addEventListener("DOMContentLoaded", () => {
148 new URLSuggester().initialize();
149});