[PATCH] add `files-tree' data source

[David Bremner]

This allows the user to conveniently maintain a set of files in their consfig
tree (or elsewhere) for deployment as data.

Signed-off-by: David Bremner <david at tethera.net>
---

I've been using this for a week or so, and the simple version handling
seems good enough for my needs.


 consfigurator.asd        |  3 ++-
 src/data/files-tree.lisp | 52 ++++++++++++++++++++++++++++++++++++++++
 src/package.lisp         |  4 +++-
 3 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 src/data/files-tree.lisp

diff --git a/consfigurator.asd b/consfigurator.asd
index 4ba46b1..61f1208 100644
--- a/consfigurator.asd
+++ b/consfigurator.asd
@@ -92,7 +92,8 @@
 	       (:file "src/data/git-snapshot")
 	       (:file "src/data/gpgpubkeys")
                (:file "src/data/ssh-askpass")
-               (:file "src/data/local-file"))
+               (:file "src/data/local-file")
+               (:file "src/data/files-tree"))
   :in-order-to ((test-op (test-op "consfigurator/tests"))))
 
 (defsystem "consfigurator/tests"
diff --git a/src/data/files-tree.lisp b/src/data/files-tree.lisp
new file mode 100644
index 0000000..5192c39
--- /dev/null
+++ b/src/data/files-tree.lisp
@@ -0,0 +1,52 @@
+;;; Consfigurator -- Lisp declarative configuration management system
+
+;;; Copyright (C) 2021  David Bremner <david at tethera.net>
+
+;;; This file 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, or (at your option)
+;;; any later version.
+
+;;; This file 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+(in-package :consfigurator.data.files-tree)
+(named-readtables:in-readtable :consfigurator)
+
+(defmethod register-data-source ((type (eql :files-tree)) &key location version)
+  "Provide the contents of a local directory on the machine running the root
+Lisp. Register this data source multiple times to provide multiple trees.
+LOCATION, IDEN1 and IDEN2 are joined to generate the path of a data file on
+disk.  The version of the data provided is either VERSION or the file's last
+modification time. This data source treats IDEN1 literally, so e.g. to use
+IDEN1 = `_config', the user should create a subdirectory `_config' under
+LOCATION."
+  (unless (directory-exists-p location)
+    (error 'missing-data-source
+           :text (format nil "~A does not exist, or is not a directory." location)))
+  (labels ((%make-path (iden1 iden2)
+             (let* ((dir (pathname-directory location))
+                    (name (pathname-name location))
+                    (path (if name (append dir (list name)) dir)))
+               (make-pathname :directory (append path (list iden1)) :name iden2)))
+           (check (iden1 iden2)
+             (let ((file-path (%make-path iden1 iden2)))
+               (and (file-exists-p file-path)
+                    (or version (file-write-date file-path)))))
+           (extract (iden1 iden2)
+             (let ((file-path (%make-path iden1 iden2)))
+               (and (file-exists-p file-path)
+                    (make-instance 'file-data
+                                   :file file-path
+                                   :iden1 iden1
+                                   :iden2 iden2
+                                   :version (or version (file-write-date file-path)))))))
+    (cons #'check #'extract)))
+
+
+
diff --git a/src/package.lisp b/src/package.lisp
index 051bfab..dbae766 100644
--- a/src/package.lisp
+++ b/src/package.lisp
@@ -998,4 +998,6 @@
   (package :consfigurator.data.ssh-askpass
            (:local-nicknames (#:re   #:cl-ppcre)))
 
-  (package :consfigurator.data.local-file))
+  (package :consfigurator.data.local-file)
+
+  (package :consfigurator.data.files-tree))
-- 
2.33.0