eshell: Add completion support for the gv command

* eshell-conf.el (pcomplete/gv): This function will be called by
  pcomplete to provide completions for the gv command, in Eshell.

(gv-complete-switches): This function provides completions for the
switches of the gv command.

(gv-complete-files): This function provides completions for source
files that are valid for the gv command.

1 files changed, 65 insertions, 0 deletions

diff --git a/eshell-conf.el b/eshell-conf.el
index 0884d49..f77f5d3 100644
--- a/eshell-conf.el
+++ b/eshell-conf.el
@@ -723,6 +723,8 @@ For example, \"...\" expands into \"../..\"."
 ;; It is convenient to be able to compile multiple GraphViz files or
 ;; delete multiple image files simultaneously.
 
+;;;; A convenient Command
+
 (require 'vc)
 
 (defun eshell/gv (&rest args)
@@ -849,5 +851,68 @@ The file names should not include any extension."
        args))))
   nil)
 
+;;;; Completion
+
+(defun gv-complete-switches ()
+  "Return a completion table for the switches of the gv command."
+  (pcomplete-from-help
+   (list
+    "emacs" "-Q" "-l" "~/.emacs.d/eshell-conf.el" "--batch" "--eval" "(eshell/gv)")
+   :narrow-end "mapbacktrace"
+   :narrow-start "extension."))
+
+(defun gv-complete-files (dir)
+  "Return a completion table for the file arguments of the gv \
+command."
+  (lambda (string pred action)
+    (let ((default-directory (expand-file-name "output" dir))
+          (pred (lambda (name) (string-suffix-p ".gv" name)))
+          (filter (lambda (result)
+                    (cond
+                     ((string-suffix-p ".gv" result)
+                      (substring result 0 -3))
+                     (result)))))
+      (cond
+       ((eq action t)
+        (let ((results
+               (completion-table-with-predicate
+                #'completion-file-name-table
+                pred 'strict string pred action)))
+          (mapcar filter results)))
+       ((null action)
+        (funcall filter (completion-table-with-predicate
+                         #'completion-file-name-table
+                         pred 'strict string pred action)))
+       ((completion-table-with-predicate
+         #'completion-file-name-table
+         pred 'strict string pred action))))))
+
+(defun pcomplete/gv ()
+  "Completion for `eshell/gv'."
+  (let (finding-dir continue-loop)
+    (while (or (string-prefix-p "-" (pcomplete-arg)) continue-loop)
+      (let ((arg (pcomplete-arg)))
+        (pcomplete-here (cond
+                         ((eq finding-dir t) (pcomplete-dirs))
+                         (continue-loop
+                          (list "png" "jpeg" "jpg" "svg"))
+                         ((gv-complete-switches))))
+        (cond
+         ((eq finding-dir t)
+          (setq finding-dir arg)
+          (setq continue-loop nil))
+         (continue-loop (setq continue-loop nil))
+         ((string-prefix-p "-d" arg)
+          (setq finding-dir
+                (cond
+                 ((string= arg "-d") (setq continue-loop t))
+                 ((substring-no-properties arg 2)))))
+         ((string= "--format" arg)
+          (setq continue-loop t))
+         ((string= "--root" arg)
+          (setq finding-dir (setq continue-loop t)))
+         ((setq continue-loop nil)))))
+    (while (pcomplete-here (gv-complete-files finding-dir)))))
+
 (provide 'eshell-conf)
 ;;; eshell-conf.el ends here