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+;;; cider-eldoc.el --- eldoc support for Clojure
+
+;; Copyright © 2012-2013 Tim King, Phil Hagelberg
+;; Copyright © 2013 Bozhidar Batsov, Hugo Duncan, Steve Purcell
+;;
+;; Author: Tim King <kingtim@gmail.com>
+;;         Phil Hagelberg <technomancy@gmail.com>
+;;         Bozhidar Batsov <bozhidar@batsov.com>
+;;         Hugo Duncan <hugo@hugoduncan.org>
+;;         Steve Purcell <steve@sanityinc.com>
+
+;; This program 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.
+
+;; This program 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/>.
+
+;; This file is not part of GNU Emacs.
+
+;;; Commentary:
+
+;; eldoc support for Clojure.
+
+;;; Code:
+
+(require 'nrepl-client)
+
+(require 'eldoc)
+(require 'dash)
+
+(defvar cider-extra-eldoc-commands '("cider-complete" "yas/expand")
+  "Extra commands to be added to eldoc's safe commands list.")
+
+(defun cider-eldoc-format-thing (thing)
+  "Format the eldoc THING."
+  (propertize thing 'face 'font-lock-function-name-face))
+
+(defun cider-highlight-args (arglist pos)
+  "Format the the function ARGLIST for eldoc.
+POS is the index of the currently highlighted argument."
+  (let* ((rest-pos (cider--find-rest-args-position arglist))
+         (i 0))
+    (mapconcat
+     (lambda (arg)
+       (let ((argstr (format "%s" arg)))
+         (if (eq arg '&)
+             argstr
+           (prog1
+               (if (or (= (1+ i) pos)
+                       (and rest-pos (> (+ 1 i) rest-pos)
+                            (> pos rest-pos)))
+                   (propertize argstr 'face
+                               'eldoc-highlight-function-argument)
+                 argstr)
+             (setq i (1+ i)))))) arglist " ")))
+
+(defun cider--find-rest-args-position (arglist)
+  "Find the position of & in the ARGLIST vector."
+  (-elem-index '& (append arglist ())))
+
+(defun cider-highlight-arglist (arglist pos)
+  "Format the ARGLIST for eldoc.
+POS is the index of the argument to highlight."
+  (concat "[" (cider-highlight-args arglist pos) "]"))
+
+(defun cider-eldoc-format-arglist (arglist pos)
+  "Format all the ARGLIST for eldoc.
+POS is the index of current argument."
+  (concat "("
+          (mapconcat (lambda (args) (cider-highlight-arglist args pos))
+                     (read arglist) " ") ")"))
+
+(defun cider-eldoc-info-in-current-sexp ()
+  "Return a list of the current sexp and the current argument index."
+  (save-excursion
+    (let ((argument-index (1- (eldoc-beginning-of-sexp))))
+      ;; If we are at the beginning of function name, this will be -1.
+      (when (< argument-index 0)
+        (setq argument-index 0))
+      ;; Don't do anything if current word is inside a string.
+      (if (= (or (char-after (1- (point))) 0) ?\")
+          nil
+        (list (cider-symbol-at-point) argument-index)))))
+
+(defun cider-eldoc ()
+  "Backend function for eldoc to show argument list in the echo area."
+  (when (nrepl-current-connection-buffer)
+    (let* ((info (cider-eldoc-info-in-current-sexp))
+           (thing (car info))
+           (pos (cadr info))
+           (form (format "(try
+                           (:arglists
+                            (clojure.core/meta
+                             (clojure.core/resolve
+                              (clojure.core/read-string \"%s\"))))
+                           (catch Throwable t nil))" thing))
+           (result (when thing
+                     (nrepl-send-string-sync form
+                                             nrepl-buffer-ns
+                                             (nrepl-current-tooling-session))))
+           (value (plist-get result :value)))
+      (unless (string= value "nil")
+        (format "%s: %s"
+                (cider-eldoc-format-thing thing)
+                (cider-eldoc-format-arglist value pos))))))
+
+(defun cider-turn-on-eldoc-mode ()
+  "Turn on eldoc mode in the current buffer."
+  (setq-local eldoc-documentation-function 'cider-eldoc)
+  (apply 'eldoc-add-command cider-extra-eldoc-commands)
+  (turn-on-eldoc-mode))
+
+(provide 'cider-eldoc)
+;;; cider-eldoc ends here