Drafting stuff to share with Tadhg

lib/related-posts.js

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+const { DateTime } = require('luxon')
+
+// Builds the file path for a related posts cache, using the current time.
+//   Optionally pass in timestamp for a deterministic result.
+// @param ts [number, string, undefined] Timestamp to assign to the filename
+// @return [string] Filepath to a related posts cache
+// @example With no given timestamp, uses current time
+//   filepath() => `.cache/related-posts-1720796065028`
+// @example With a given timestamp
+//   filepath(1737392400000) => `.cache/related-posts-1737392400000`
+const filepath = (ts=undefined) => {
+  return `.cache/related-posts-${ ts || DateTime.now().ts }.json`
+}
+
+// Creates a related posts cache file for the current time (or given timestamp)
+//   and writes the given object to the file as JSON data
+// @param ts [number, string, undefined] Timestamp to assign to the filename
+// @param data [object] data to write to the file
+// @return [undefined]
+const createFile = (data={}, ts=undefined) => {
+  return fs.writeFileSync(filepath(ts), JSON.stringify(data))
+}
+
+// @return [Array<string>] List of filepaths to related posts caches
+const cacheFiles = () => {
+  return fs.readdirSync('.cache').filter(file => file.startsWith('related-posts-')).sort().reverse()
+}
+
+// @return [object] JSON data from the most recent cache
+const currentCache = () => {
+  return JSON.parse(fs.readFileSync(`.cache/${cacheFiles()[0]}`))
+}
+
+// Deletes all caches except the cache with the most future date
+// @return [undefined]
+const deleteOldCaches = () => {
+  cacheFiles().slice(1,).forEach(file => fs.unlinkSync(`.cache/${file}`))
+}
+
+// Deletes all caches
+// @return [undefined]
+const deleteAllCaches = () => {
+  cacheFiles().forEach(file => fs.unlinkSync(`.cache/${file}`))
+}
+
+
+
+/*
+usage:
+
+Create a bunch of related posts files
+
+createFile()
+createFile()
+createFile()
+createFile({hi: "tadhg"})
+
+
+Get the data from the file with the latest date (it should have content).
+
+currentCache()
+
+
+Delete all the caches except the latest one
+
+deleteOldCaches()
+
+
+The current cache should still be there
+
+currentCache()
+
+
+Delete all the caches except the latest one
+
+deleteAllCaches()
+
+
+The current cache shouldn't exit
+
+currentCache()
+
+
+*/
+
+// Compares two files' frontmatter for similar authors and similar tags and returns
+//   a similarity score
+// Current algorithm:
+//   - Each author in common is +1
+//   - Each tag in common is +1
+//   - If there are both authors and tags in common, multiply the base score x2
+// @param file [object] JSON data representing front matter of the current file
+// @param other [object] JSON data representing front matter of the file being compared
+// @return [number]
+const similarity = (file, other) => {
+  const commonAuthors = intersection(new Set(file.authors), new Set(other.authors)).length
+  const commonTags = intersection(new Set(file.tags), new Set(other.tags)).length
+  const multiplier = (commonAuthors > 0 && commonTags > 0) ? 2 : 1
+  return (commonTags + commonAuthors) * multiplier
+}
+
+function intersection(setA, setB) {
+  const result = new Set();
+  setA.forEach((value) => {
+    if (setB.has(value)) {
+      result.add(value)
+    }
+  });
+  return result
+}
+
+
+
+
+