sitegen/framework/watch.ts

// File watcher and live reloading site generator

const debounceMilliseconds = 25;

export async function main() {
  // Catch up state by running a main build.
  const { incr } = await generate.main();
  // ...and watch the files that cause invals.
  const watch = new Watch(rebuild);
  watch.add(...incr.invals.keys());
  statusLine();

  function rebuild(files: string[]) {
    files = files.map((file) => path.relative(hot.projectRoot, file));
    const changed: string[] = [];
    for (const file of files) {
      if (incr.updateStat(file, fs.statSync(file).mtimeMs)) changed.push(file);
    }
    if (changed.length === 0) {
      console.warn("Files were modified but the 'modify' time did not change.");
      return;
    }
    withSpinner<Record<string, unknown>, any>({
      text: "Rebuilding",
      successText: generate.successText,
      failureText: () => "sitegen FAIL",
    }, async (spinner) => {
      console.clear();
      console.log(
        "Updated" +
          (changed.length === 1
            ? " " + changed[0]
            : changed.map((file) => "\n- " + file)),
      );
      const result = await generate.sitegen(spinner, incr);
      incr.toDisk(); // Allows picking up this state again
      for (const file of watch.files) {
        const relative = path.relative(hot.projectRoot, file);
        if (!incr.invals.has(file)) watch.remove(file);
      }
      return result;
    }).catch((err) => {
      console.error(util.inspect(err));
    }).finally(statusLine);
  }

  function statusLine() {
    console.info(
      `Watching ${incr.invals.size} files \x1b[36m[last change: ${
        new Date().toLocaleTimeString()
      }]\x1b[39m`,
    );
  }
}

class Watch {
  files = new Set<string>();
  stale = new Set<string>();
  onChange: (files: string[]) => void;
  watchers: fs.FSWatcher[] = [];
  /** Has a trailing slash */
  roots: string[] = [];
  debounce: ReturnType<typeof setTimeout> | null = null;

  constructor(onChange: Watch["onChange"]) {
    this.onChange = onChange;
  }

  add(...files: string[]) {
    const { roots, watchers } = this;
    let newRoots: string[] = [];
    for (let file of files) {
      file = path.resolve(file);
      if (this.files.has(file)) continue;
      this.files.add(file);
      // Find an existing watcher
      if (roots.some((root) => file.startsWith(root))) continue;
      if (newRoots.some((root) => file.startsWith(root))) continue;
      newRoots.push(path.dirname(file) + path.sep);
    }
    if (newRoots.length === 0) return;
    // Filter out directories that are already specified
    newRoots = newRoots
      .sort((a, b) => a.length - b.length)
      .filter((dir, i, a) => {
        for (let j = 0; j < i; j++) if (dir.startsWith(a[j])) return false;
        return true;
      });
    // Append Watches
    let i = roots.length;
    for (const root of newRoots) {
      this.watchers.push(fs.watch(
        root,
        { recursive: true, encoding: "utf-8" },
        this.#handleEvent.bind(this, root),
      ));
      this.roots.push(root);
    }
    // If any new roots shadow over and old one, delete it!
    while (i > 0) {
      i -= 1;
      const root = roots[i];
      if (newRoots.some((newRoot) => root.startsWith(newRoot))) {
        watchers.splice(i, 1)[0].close();
        roots.splice(i, 1);
      }
    }
  }

  remove(...files: string[]) {
    for (const file of files) this.files.delete(path.resolve(file));
    // Find watches that are covering no files
    const { roots, watchers } = this;
    const existingFiles = Array.from(this.files);
    let i = roots.length;
    while (i > 0) {
      i -= 1;
      const root = roots[i];
      if (!existingFiles.some((file) => file.startsWith(root))) {
        watchers.splice(i, 1)[0].close();
        roots.splice(i, 1);
      }
    }
  }

  stop() {
    for (const w of this.watchers) w.close();
  }

  #handleEvent(root: string, event: fs.WatchEventType, subPath: string | null) {
    if (!subPath) return;
    const file = path.join(root, subPath);
    if (!this.files.has(file)) return;
    this.stale.add(file);
    const { debounce } = this;
    if (debounce !== null) clearTimeout(debounce);
    this.debounce = setTimeout(() => {
      this.debounce = null;
      this.onChange(Array.from(this.stale));
      this.stale.clear();
    }, debounceMilliseconds);
  }
}

import { Incremental } from "./incremental.ts";
import * as fs from "node:fs";
import { Spinner, withSpinner } from "@paperclover/console/Spinner";
import * as generate from "./generate.ts";
import * as path from "node:path";
import * as util from "node:util";
import * as hot from "./hot.ts";