;;; Consfigurator -- Lisp declarative configuration management system

;;; Copyright (C) 2021  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.files-tree)
(named-readtables:in-readtable :consfigurator)

(defmethod register-data-source ((type (eql :files-tree)) &key location)
  "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 is either a designator for a pathname representing the root of the
tree of files or a symbol which designates an ASDF package where the tree is
contained in the subdirectory 'data/'.

LOCATION, IDEN1 and IDEN2 are concatenated to locate files.  Thus, IDEN1
specifies a (possibly nested) subdirectory under LOCATION and IDEN2 a relative
path within that subdirectory.  For convenience IDEN1 and IDEN2 may be passed
as absolute and will be converted to relative paths.  The usual cases of IDEN1
as a hostname, IDEN1 as an underscore-prefixed identifier, and IDEN2 an an
absolute or relative path are all supported."
  (let ((base-path (if (symbolp location)
                        (asdf:system-relative-pathname location "data/")
                        (ensure-directory-pathname location))))
    (unless (directory-exists-p base-path)
      (missing-data-source
       "~A does not exist, or is not a directory." base-path))
    (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 (literal-data-pathname base-path iden1 iden2)))
                 (and (file-exists-p file-path)
                      (make-instance 'file-data
                                     :file file-path
                                     :iden1 iden1
                                     :iden2 iden2
                                     :version (file-write-date file-path))))))
      (cons #'check #'extract))))