sitegen/framework/watch.ts

// File watcher and live reloading site generator

const debounceMilliseconds = 25;

let subprocess: child_process.ChildProcess | null = null;
process.on("beforeExit", () => {
  subprocess?.removeListener("close", onSubprocessClose);
});

let watch: Watch;

export async function main() {
  // Catch up state by running a main build.
  await incr.restore();
  watch = new Watch(rebuild);
  rebuild([]);
}

function serve() {
  if (subprocess) {
    subprocess.removeListener("close", onSubprocessClose);
    subprocess.kill();
  }
  subprocess = child_process.fork(".clover/o/backend.js", [
    "--development",
  ], {
    stdio: "inherit",
  });
  subprocess.on("close", onSubprocessClose);
}

function onSubprocessClose(code: number | null, signal: string | null) {
  subprocess = null;
  const status = code != null ? `code ${code}` : `signal ${signal}`;
  console.error(`Backend process exited with ${status}`);
}

async function rebuild(files: string[]) {
  const hasInvalidated = files.length === 0
    || (await Promise.all(files.map(incr.invalidate))).some(Boolean);
  if (!hasInvalidated) return;
  incr.compile(generate.generate).then(({
    watchFiles,
    newOutputs,
    newAssets
  }) => {
    const removeWatch = [...watch.files].filter(x => !watchFiles.has(x))
    for (const file of removeWatch) watch.remove(file);
    watch.add(...watchFiles);
    // Restart the server if it was changed or not running.
    if (!subprocess || newOutputs.includes("backend.js")) {
      serve();
    } else if (subprocess && newAssets) {
      subprocess.send({ type: "clover.assets.reload" });
    }
  }).catch((err) => {
    console.error(util.inspect(err));
  }).finally(statusLine);
}

function statusLine() {
  console.info(
    `Watching ${watch.files.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();
  }

  #getFiles(absPath: string, event: fs.WatchEventType) {
    const files = [];
    if (this.files.has(absPath)) files.push(absPath);
    if (event === 'rename') {
      const dir = path.dirname(absPath);
      if (this.files.has(dir)) files.push(dir);
    }
    return files;
  }

  #handleEvent(root: string, event: fs.WatchEventType, subPath: string | null) {
    if (!subPath) return;
    const files = this.#getFiles(path.join(root, subPath), event);
    if (files.length === 0) return;
    for(const file of files) 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 * as fs from "node:fs";
import { withSpinner } from "@paperclover/console/Spinner";
import * as generate from "./generate.ts";
import * as incr from "./incremental.ts";
import * as path from "node:path";
import * as util from "node:util";
import * as hot from "./hot.ts";
import * as child_process from "node:child_process";