From ae5c474d5f3be945be41f5883143aff8f50ab3c8 Mon Sep 17 00:00:00 2001
From: Pierre Neidhardt <ambrevar@gmail.com>
Date: Wed, 1 Nov 2017 16:06:15 +0100
Subject: [PATCH] Eshell: Add support for auto-suggestions

---
 .emacs.d/lisp/init-eshell.el                | 10 ++++-
 .emacs.d/lisp/package-eshell-autosuggest.el | 42 +++++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 .emacs.d/lisp/package-eshell-autosuggest.el

diff --git a/.emacs.d/lisp/init-eshell.el b/.emacs.d/lisp/init-eshell.el
index 67e163bf..a3e0121c 100644
--- a/.emacs.d/lisp/init-eshell.el
+++ b/.emacs.d/lisp/init-eshell.el
@@ -189,6 +189,7 @@ See `eshell' for the numeric prefix ARG."
           (switch-to-buffer (car last))
         (eshell (or arg t))))))
 
+;;; Completion
 (when (require 'bash-completion nil t)
   (defun eshell-bash-completion ()
     (while (pcomplete-here
@@ -199,6 +200,13 @@ See `eshell' for the numeric prefix ARG."
 
 (when (and (executable-find "fish")
            (require 'fish-completion nil t))
-  (fish-completion-eshell-global-toggle))
+  (fish-completion-eshell-toggle-globally))
+
+;;; Auto-suggestion
+(when (require 'package-eshell-autosuggest)
+  (add-hook 'eshell-mode-hook 'company-mode)
+  (when (require 'helm-config nil t)
+    (define-key company-active-map (kbd "M-p") 'helm-eshell-history))
+  (add-hook 'eshell-mode-hook 'eshell-setup-autosuggest))
 
 (provide 'init-eshell)
diff --git a/.emacs.d/lisp/package-eshell-autosuggest.el b/.emacs.d/lisp/package-eshell-autosuggest.el
new file mode 100644
index 00000000..dfa89d87
--- /dev/null
+++ b/.emacs.d/lisp/package-eshell-autosuggest.el
@@ -0,0 +1,42 @@
+(require 'company)
+
+(defun company-eshell-autosuggest-candidates (prefix)
+  (let* ((history
+          (cl-remove-duplicates
+           (mapcar (lambda (str)
+                     (string-trim (substring-no-properties str)))
+                   (ring-elements eshell-history-ring))
+           :from-end t
+           :test #'string=))
+         (most-similar (cl-find-if
+                        (lambda (str)
+                          (string-prefix-p prefix str))
+                        history)))
+    (when most-similar
+      `(,most-similar))))
+
+(defun company-eshell-autosuggest--prefix ()
+  (let ((prefix
+         (string-trim-left
+          (buffer-substring-no-properties
+           (save-excursion
+             (eshell-bol))
+           (save-excursion (end-of-line) (point))))))
+    (if (not (string-empty-p prefix))
+        prefix
+      'stop)))
+
+(defun company-eshell-autosuggest (command &optional arg &rest ignored)
+  (interactive (list 'interactive))
+  (cl-case command
+    (interactive (company-begin-backend 'company-eshell))
+    (prefix (and (eq major-mode 'eshell-mode)
+                 (company-eshell-autosuggest--prefix)))
+    (candidates (company-eshell-autosuggest-candidates arg))))
+
+(defun eshell-setup-autosuggest ()
+  (setq-local company-idle-delay 0.5)
+  (setq-local company-backends '(company-eshell-autosuggest))
+  (setq-local company-frontends '(company-preview-frontend)))
+
+(provide 'package-eshell-autosuggest)