From 3b770c69507ef139cd07f5335aefba33217d43ad Mon Sep 17 00:00:00 2001
From: "(quasar) nebula" <qznebula@protonmail.com>
Date: Thu, 12 May 2022 23:23:17 -0300
Subject: preload, map and format sizes of additional files

---
 src/file-size-preloader.js | 100 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 src/file-size-preloader.js

(limited to 'src/file-size-preloader.js')

diff --git a/src/file-size-preloader.js b/src/file-size-preloader.js
new file mode 100644
index 0000000..d0807cc
--- /dev/null
+++ b/src/file-size-preloader.js
@@ -0,0 +1,100 @@
+// Very simple, bare-bones file size loader which takes a bunch of file
+// paths, gets their filesizes, and resolves a promise when it's done.
+//
+// Once the size of a path has been loaded, it's available synchronously -
+// so this may be provided to code areas which don't support async code!
+//
+// This class also supports loading more paths after the initial batch is
+// done (it uses a queue system) - but make sure you pause any sync code
+// depending on the results until it's finished. waitUntilDoneLoading will
+// always hold until the queue is completely emptied, including waiting for
+// any entries to finish which were added after the wait function itself was
+// called. (Same if you decide to await loadPaths. Sorry that function won't
+// resolve as soon as just the paths it provided are finished - that's not
+// really a worthwhile feature to support for its complexity here, since
+// basically all this should process almost instantaneously anyway!)
+//
+// This only processes files one at a time because I'm lazy and stat calls
+// are very, very fast.
+
+import { stat } from 'fs/promises';
+import { logWarn } from './util/cli.js';
+
+export default class FileSizePreloader {
+    #paths = [];
+    #sizes = [];
+    #loadedPathIndex = -1;
+
+    #loadingPromise = null;
+    #resolveLoadingPromise = null;
+
+    loadPaths(...paths) {
+        this.#paths.push(...paths.filter(p => !this.#paths.includes(p)));
+        return this.#startLoadingPaths();
+    }
+
+    waitUntilDoneLoading() {
+        return this.#loadingPromise ?? Promise.resolve();
+    }
+
+    #startLoadingPaths() {
+        if (this.#loadingPromise) {
+            return this.#loadingPromise;
+        }
+
+        this.#loadingPromise = new Promise((resolve => {
+            this.#resolveLoadingPromise = resolve;
+        }));
+
+        this.#loadNextPath();
+
+        return this.#loadingPromise;
+    }
+
+    async #loadNextPath() {
+        if (this.#loadedPathIndex === this.#paths.length - 1) {
+            return this.#doneLoadingPaths();
+        }
+
+        let size;
+
+        const path = this.#paths[this.#loadedPathIndex + 1];
+
+        try {
+            size = await this.readFileSize(path);
+        } catch (error) {
+            // Oops! Discard that path, and don't increment the index before
+            // moving on, since the next path will now be in its place.
+            this.#paths.splice(this.#loadedPathIndex + 1, 1);
+            logWarn`Failed to process file size for ${path}: ${error.message}`;
+            return this.#loadNextPath();
+        }
+
+        this.#sizes.push(size);
+        this.#loadedPathIndex++;
+        return this.#loadNextPath();
+    }
+
+    #doneLoadingPaths() {
+        this.#resolveLoadingPromise();
+        this.#loadingPromise = null;
+        this.#resolveLoadingPromise = null;
+    }
+
+    // Override me if you want?
+    // The rest of the code here is literally just a queue system, so you could
+    // pretty much repurpose it for anything... but there are probably cleaner
+    // ways than making an instance or subclass of this and overriding this one
+    // method!
+    async readFileSize(path) {
+        const stats = await stat(path);
+        return stats.size;
+    }
+
+    getSizeOfPath(path) {
+        const index = this.#paths.indexOf(path);
+        if (index === -1) return null;
+        if (index > this.#loadedPathIndex) return null;
+        return this.#sizes[index];
+    }
+}
-- 
cgit 1.3.0-6-gf8a5