Add update command

* undone/main.scm (args->alist): Place argument parsing for add/update
  in separate function for reuse.
  (delete-item): Renamed from `delete', which is in conflict with
  guile's own `delete'.
  (update): New function.

undone/main.scm

@@ -2,6 +2,7 @@
   #:use-module (ice-9 format)
   #:use-module (ice-9 rdelim)
   #:use-module (oop goops)
+  #:use-module (srfi srfi-1)
   #:use-module (undone view)
   #:export (main))
 
@@ -133,6 +134,16 @@
                           todo-list)))
       1))
 
+(define (args->alist args)
+  (map (lambda (arg)
+         (let* ((pair (string-split arg #\=))
+                (var (string->symbol (car pair)))
+                (val (cadr pair)))
+           (when (char=? (string-ref val 0) #\,)
+             (set! val (string-split (substring val 1) #\,)))
+           (cons var  val)))
+       args))
+
 (define (add args)
   "Add item to the list."
   (set! todo-list
@@ -141,18 +152,9 @@
                  (append
                   `((id . ,(next-id))
                     (content . ,(string-trim-right (read-delimited ""))))
-                  (map (lambda (arg)
+                  (args->alist args))))))
-                         (let* ((pair (string-split arg #\=))
-                                (var (string->symbol (car pair)))
-                                (val (cadr pair)))
-                           (if (char=? (string-ref val 0) #\,)
-                               (set! val (string-split
-                                          (substring val 1) #\,)))
 
-                           (cons var val)))
+(define (delete-item args)
-                       args))))))
-
-(define (delete args)
   "Delete the specified element."
   (set! todo-list
         (filter (lambda (elm)
@@ -180,6 +182,20 @@
      (set-current-module (resolve-module '(undone main)))
      (load rc-file))))
 
+(define (update args)
+  (let ((item
+         (find (lambda (elm)
+                 (let ((id (assq 'id elm)))
+                   (and id (eq? (cdr id) (string->number (car args))))))
+               todo-list))
+        (alist (args->alist (cdr args))))
+    (set! todo-list (delete item todo-list))
+    (for-each
+     (lambda (elm)
+       (set! item (assq-set! item (car elm) (cdr elm))))
+     alist)
+    (set! todo-list (append (list item) todo-list))))
+
 (define (main args)
   (when (and rc-file (file-exists? rc-file))
     (load-rc-file))
@@ -190,10 +206,13 @@
          (add (list-tail args 2))
          (save))
         ((delete)
-         (delete (list-tail args 2))
+         (delete-item (list-tail args 2))
          (save))
         ((view)
          (view (list-tail args 2)))
+        ((update)
+         (update (list-tail args 2))
+         (save))
         ((views)
          (display "Defined views:")
          (newline)