add package CONSFIGURATOR.DATA.UTIL

This package is intended to provide a home for utility functions used by
multiple data sources.  Initially move a local function from
CONSFIGURATOR.DATA.FILES-TREE, and slightly generalize it to support an
extension or TYPE argument.

Note that the goal of LITERAL-DATA-PATHNAME is to map (IDEN1 IDEN2) to
existing paths in a user-maintained file hierarchy.  This is quite different
from DATA-PATHNAME, which escapes various characters to map to a safe internal
filename, effectively flattening a directory hierarchy into a single level.

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

2 files changed, 43 insertions, 11 deletions

diff --git a/src/data/files-tree.lisp b/src/data/files-tree.lisp
index 993d9aa..8418a80 100644
--- a/src/data/files-tree.lisp
+++ b/src/data/files-tree.lisp
@@ -37,20 +37,12 @@ IDEN2 an an absolute or relative path are all supported."
     (unless (directory-exists-p base-path)
       (missing-data-source
        "~A does not exist, or is not a directory." base-path))
-    (labels ((%make-path (iden1 iden2)
-               (merge-pathnames
-                (uiop:relativize-pathname-directory
-                 iden2)
-                (merge-pathnames
-                 (uiop:relativize-pathname-directory
-                  (ensure-directory-pathname iden1))
-                 base-path)))
-             (check (iden1 iden2)
-               (let ((file-path (%make-path iden1 iden2)))
+    (labels ((check (iden1 iden2)
+               (let ((file-path (literal-data-pathname base-path iden1 iden2)))
                  (and (file-exists-p file-path)
                       (file-write-date file-path))))
              (extract (iden1 iden2)
-               (let ((file-path (%make-path iden1 iden2)))
+               (let ((file-path (literal-data-pathname base-path iden1 iden2)))
                  (and (file-exists-p file-path)
                       (make-instance 'file-data
                                      :file file-path
diff --git a/src/data/util.lisp b/src/data/util.lisp
new file mode 100644
index 0000000..3fd8895
--- /dev/null
+++ b/src/data/util.lisp
@@ -0,0 +1,40 @@
+;;; Consfigurator -- Lisp declarative configuration management system
+
+;;; Copyright (C) 2022  David Bremner <david@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.util)
+(named-readtables:in-readtable :consfigurator)
+
+(defun literal-data-pathname (base-path iden1 iden2 &key type)
+  "Generate a path from BASE-PATH, IDEN1 and IDEN2 by concatentation,
+optionally adding extension TYPE.
+
+No escaping of special characters is done, but extra '/' characters between
+pathname components are removed.
+
+The intended use case is to map IDEN1 and IDEN2 to files in a user-maintained
+hierarchy under BASE-PATH.  In particular IDEN2 and (if prefixed by '_') IDEN1
+may contain '/' characters to map into multiple levels of directory."
+  (let ((base-dir (uiop:parse-unix-namestring base-path :ensure-directory t)))
+    (unless (uiop:directory-pathname-p base-dir)
+      (simple-program-error "~A does not specify a directory" base-dir))
+    (merge-pathnames
+     (uiop:relativize-pathname-directory
+      (uiop:parse-unix-namestring iden2 :type type))
+     (merge-pathnames
+      (uiop:relativize-pathname-directory
+       (ensure-directory-pathname iden1))
+      base-dir))))