Factor watch implementations into their own modules.

This should also hopefully resolve some issues that Christine
Lemmer-Webber reported with the old code when resolving all of those
inotify bindings at runtime.

1 files changed, 58 insertions, 0 deletions

diff --git a/haunt/watch/fallback.scm b/haunt/watch/fallback.scm
new file mode 100644
index 0000000..c001776
--- /dev/null
+++ b/haunt/watch/fallback.scm
@@ -0,0 +1,58 @@
+;;; Haunt --- Static site generator for GNU Guile
+;;; Copyright © 2022 David Thompson <davet@gnu.org>
+;;;
+;;; This file is part of Haunt.
+;;;
+;;; Haunt is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; Haunt is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with Haunt.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Fallback file update watcher that uses a naive tree walking
+;; implementation.
+;;
+;;; Code:
+
+(define-module (haunt watch fallback)
+  #:use-module (haunt site)
+  #:use-module (ice-9 ftw)
+  #:export (watch))
+
+(define (watch thunk check-dir? check-file?)
+  (define cwd (getcwd))
+
+  (define (any-files-changed? time)
+    (define (enter? name stat result)
+      ;; Don't bother descending if we already know that a file has
+      ;; changed.
+      (and (not result) (check-dir? name)))
+
+    (define (leaf name stat result)
+      ;; Test if file has been modified since the last time we
+      ;; checked.
+      (or result
+          (and (check-file? name)
+               (or (>= (stat:mtime stat) time)
+                   (>= (stat:ctime stat) time)))))
+
+    (define (no-op name stat result) result)
+
+    (file-system-fold enter? leaf no-op no-op no-op no-op #f cwd))
+
+  (let loop ((time (current-time)))
+    (when (any-files-changed? time)
+      (display "watch: file changes detected")
+      (thunk))
+    (let ((next-time (current-time)))
+      (sleep 1)
+      (loop next-time))))