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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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.
;;;
;;; GNU Guix 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu home-services symlink-manager)
#:use-module (gnu home-services)
#:use-module (guix gexp)
#:export (home-symlink-manager-service-type))
;;; Comment:
;;;
;;; symlink-manager cares about configuration files: it backs up files
;;; created by user, removes symlinks and directories created by a
;;; previous generation, and creates new directories and symlinks to
;;; configuration files according to the content of files/ directory
;;; (created by home-files-service) of the current home environment
;;; generation.
;;;
;;; Code:
(define (update-symlinks-script)
(program-file
"update-symlinks"
#~(begin
(use-modules (ice-9 ftw)
(ice-9 curried-definitions)
(ice-9 match)
(srfi srfi-1))
(define ((simplify-file-tree parent) file)
"Convert the result produced by `file-system-tree' to less
verbose and more suitable for further processing format.
Extract dir/file info from stat and compose a relative path to the
root of the file tree.
Sample output:
((dir . \".\")
((dir . \"config\")
((dir . \"config/fontconfig\")
(file . \"config/fontconfig/fonts.conf\"))
((dir . \"config/isync\")
(file . \"config/isync/mbsyncrc\"))))
"
(match file
((name stat) `(file . ,(string-append parent name)))
((name stat children ...)
(cons `(dir . ,(string-append parent name))
(map (simplify-file-tree
(if (equal? name ".")
""
(string-append parent name "/")))
children)))))
(define ((file-tree-traverse preordering) node)
"Traverses the file tree in different orders, depending on PREORDERING.
if PREORDERING is @code{#t} resulting list will contain directories
before files located in those directories, otherwise directory will
appear only after all nested items already listed."
(let ((prepend (lambda (a b) (append b a))))
(match node
(('file . path) (list node))
((('dir . path) . rest)
((if preordering append prepend)
(list (cons 'dir path))
(append-map (file-tree-traverse preordering) rest))))))
(use-modules (guix build utils))
(let* ((config-home (or (getenv "XDG_CONFIG_HOME")
(string-append (getenv "HOME") "/.config")))
(he-path (string-append (getenv "HOME") "/.guix-home"))
(new-he-path (string-append he-path ".new"))
(new-home (getenv "GUIX_NEW_HOME"))
(old-home (getenv "GUIX_OLD_HOME"))
(new-files-path (string-append new-home "/files"))
;; Trailing dot is required, because files itself is symlink and
;; to make file-system-tree works it should be a directory.
(new-files-dir-path (string-append new-files-path "/."))
(home-path (getenv "HOME"))
(backup-dir (string-append home-path "/"
(number->string (current-time))
"-guix-home-legacy-configs-backup"))
(old-tree (if (file-exists? old-home)
((simplify-file-tree "")
(file-system-tree
(string-append old-home "/files/.")))
#f))
(new-tree ((simplify-file-tree "")
(file-system-tree new-files-dir-path)))
(get-source-path
(lambda (path)
(readlink (string-append new-files-path "/" path))))
(get-target-path
(lambda (path)
(string-append home-path "/." path)))
(get-backup-path
(lambda (path)
(string-append backup-dir "/." path)))
(directory?
(lambda (path)
(equal? (stat:type (stat path)) 'directory)))
(empty-directory?
(lambda (dir)
(equal? (scandir dir) '("." ".."))))
(symlink-to-store?
(lambda (path)
(and
(equal? (stat:type (lstat path)) 'symlink)
(store-file-name? (readlink path)))))
(backup-file
(lambda (path)
(mkdir-p backup-dir)
(format #t "Backing up ~a..." (get-target-path path))
(mkdir-p (dirname (get-backup-path path)))
(rename-file (get-target-path path) (get-backup-path path))
(display " done\n")))
(cleanup-symlinks
(lambda ()
(let ((to-delete ((file-tree-traverse #f) old-tree)))
(display
"Cleaning up symlinks from previous home-environment.\n\n")
(map
(match-lambda
(('dir . ".")
(display "Cleanup finished.\n\n"))
(('dir . path)
(if (and
(file-exists? (get-target-path path))
(directory? (get-target-path path))
(empty-directory? (get-target-path path)))
(begin
(format #t "Removing ~a..."
(get-target-path path))
(rmdir (get-target-path path))
(display " done\n"))
(format
#t "Skipping ~a (not an empty directory)... done\n"
(get-target-path path))))
(('file . path)
(when (file-exists? (get-target-path path))
;; DO NOT remove the file if it is no longer
;; a symlink to the store, it will be backed
;; up later during create-symlinks phase.
(if (symlink-to-store? (get-target-path path))
(begin
(format #t "Removing ~a..." (get-target-path path))
(delete-file (get-target-path path))
(display " done\n"))
(format
#t
"Skipping ~a (not a symlink to store)... done\n"
(get-target-path path))))))
to-delete))))
(create-symlinks
(lambda ()
(let ((to-create ((file-tree-traverse #t) new-tree)))
(map
(match-lambda
(('dir . ".")
(display
"New symlinks to home-environment will be created soon.\n")
(format
#t "All conflicting files will go to ~a.\n\n" backup-dir))
(('dir . path)
(let ((target-path (get-target-path path)))
(when (and (file-exists? target-path)
(not (directory? target-path)))
(backup-file path))
(if (file-exists? target-path)
(format
#t "Skipping ~a (directory already exists)... done\n"
target-path)
(begin
(format #t "Creating ~a..." target-path)
(mkdir target-path)
(display " done\n")))))
(('file . path)
(when (file-exists? (get-target-path path))
(backup-file path))
(format #t "Symlinking ~a -> ~a..."
(get-target-path path) (get-source-path path))
(symlink (get-source-path path) (get-target-path path))
(display " done\n")))
to-create)))))
(when old-tree
(cleanup-symlinks))
(create-symlinks)
(symlink new-home new-he-path)
(rename-file new-he-path he-path)
(display " done\nFinished updating symlinks.\n\n")))))
(define (update-symlinks-gexp _)
#~(primitive-load #$(update-symlinks-script)))
(define home-symlink-manager-service-type
(service-type (name 'home-symlink-manager)
(extensions
(list
(service-extension
home-activation-service-type
update-symlinks-gexp)))
(default-value #f)
(description "Provide an @code{update-symlinks}
script, which creates symlinks to configuration files and directories
on every activation. If an existing file would be overwritten by a
symlink, backs up that file first.")))
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