Make action-functions interactive commands

Makes core action-functions interactive by adding a new
`bibtex-completion--read` function, with configurable completion
systems. The default uses `completing-read`.

bibtex-completion.el

@@ -56,9 +56,24 @@
 (declare-function org-element-property "org-element")
 
 (defgroup bibtex-completion nil
-  "Helm plugin for searching entries in a BibTeX bibliography."
+  "Provides searching of entries in a BibTeX bibliography, and running actions on them."
   :group 'completion)
 
+(defvar bibtex-completion-map
+  "Keymap for bibtex-completion commands"
+  (let ((map (make-sparse-keymap)))
+    (define-key map (kbd "p") 'bibtex-completion-open-pdf)
+    (define-key map (kbd "u") 'bibtex-completion-open-url-or-doi)
+    (define-key map (kbd "c") 'bibtex-completion-insert-citation)
+    (define-key map (kbd "r") 'bibtex-completion-insert-reference)
+    (define-key map (kbd "k") 'bibtex-completion-insert-key)
+    (define-key map (kbd "b") 'bibtex-completion-insert-bibtex)
+    (define-key map (kbd "a") 'bibtex-completion-add-PDF-attachment)
+    (define-key map (kbd "e") 'bibtex-completion-edit-notes)
+    (define-key map (kbd "s") 'bibtex-completion-show-entry)
+    (define-key map (kbd "l") 'bibtex-completion-add-pdf-to-library)
+    map))
+
 (defcustom bibtex-completion-bibliography nil
   "The BibTeX file or list of BibTeX files.
 Org-bibtex users can also specify org mode bibliography files, in
@@ -478,6 +493,26 @@ for string replacement."
 (defvar bibtex-completion-cached-notes-keys nil
   "A cache storing notes keys obtained when the bibliography was last parsed.")
 
+(defun bibtex-completion--read ()
+  "Select BibTeX entries in completion system."
+  ;; define a completion function that defaults to completing-read, but can be overridden
+  (list (cdr (assoc (completing-read-bibtex--read) (bibtex-completion--get-candidates)))))
+
+(defun bibtex-completion--completing-read ()
+  "Read bibtex-completion entries for completion using completing-read."
+  (bibtex-completion-init)
+  (completing-read
+   "BibTeX entries: "
+   (bibtex-completion--get-candidates)))
+
+(defun bibtex-completion--get-candidates ()
+  "Return all keys from bibtex-completion-candidates."
+  (mapcar
+   (lambda (cand)
+     (cons (bibtex-completion-format-entry cand (1- (frame-width)))
+           (cdr (assoc "=key=" cand))))
+   (bibtex-completion-candidates)))
+
 (defun bibtex-completion-candidates ()
   "Read the BibTeX files and return a list of conses, one for each entry.
 The first element of these conses is a string containing authors,
@@ -1087,6 +1122,7 @@ The format depends on
   (let ((format-function
          (cdr (or (assoc major-mode bibtex-completion-format-citation-functions)
                   (assoc 'default   bibtex-completion-format-citation-functions)))))
+    (interactive (list (bibtex-completion--read)))
     (insert
      (funcall format-function keys))))
 
@@ -1096,6 +1132,7 @@ The format depends on
                 (s-word-wrap fill-column
                              (concat "\n- " (bibtex-completion-apa-format-reference it)))
                 keys)))
+    (interactive (list (bibtex-completion--read)))
     (insert "\n" (s-join "\n" refs) "\n")))
 
 (defun bibtex-completion-apa-format-reference (key)
@@ -1293,11 +1330,13 @@ Surrounding curly braces are stripped."
 
 (defun bibtex-completion-insert-key (keys)
   "Insert BibTeX KEYS at point."
+  (interactive (list (bibtex-completion--read)))
   (insert
    (funcall 'bibtex-completion-format-citation-default keys)))
 
 (defun bibtex-completion-insert-bibtex (keys)
   "Insert BibTeX entries for entries in KEYS at point."
+  (interactive (list (bibtex-completion--read)))
   (insert (s-join "\n" (--map (bibtex-completion-make-bibtex it) keys))))
 
 (defun bibtex-completion-make-bibtex (key)