;;; smartparens-rust.el --- Additional configuration for Rust based modes.  -*- lexical-binding: t; -*-

;; Copyright (C) 2015 Wilfred Hughes

;; Created: 3 November 2015
;; Keywords: abbrev convenience editing
;; URL: https://github.com/Fuco1/smartparens

;; This file is not part of GNU Emacs.

;;; License:

;; This file is part of Smartparens.

;; Smartparens 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.

;; Smartparens 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 Smartparens.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This file provides some additional configuration for Rust.  To use
;; it, simply add:
;;
;; (require 'smartparens-config)
;;
;; alternatively, you can explicitly load these preferences:
;;
;; (require 'smartparens-rust)
;;
;; in your configuration.

;; For more info, see github readme at
;; https://github.com/Fuco1/smartparens

;;; Code:
(require 'smartparens)

(declare-function rust-mode "rust-mode")

(defun sp-in-rust-lifetime-context (&rest _args)
  "Return t if point is in a Rust context where ' represents a lifetime.
If we return nil, ' should be used for character literals.
ARGS."
  (or
   (condition-case nil
       ;; If point is just after a &', it's probably a &'foo.
       (save-excursion
         (backward-char 2)
         (looking-at "&"))
     ;; If we're at the beginning of the buffer, just carry on.
     (beginning-of-buffer))
   ;; If point is inside < > it's probably a parameterised function.
   (let ((paren-pos (nth 1 (syntax-ppss))))
     (and paren-pos
          (save-excursion
            (goto-char paren-pos)
            (looking-at "<"))))))

(defun sp-rust-skip-match-angle-bracket (_ms _mb me)
  "Non-nil if we should ignore the bracket as valid delimiter."
  (save-excursion
    (goto-char me)
    (let ((on-fn-return-type
           (sp--looking-back-p (rx "->") nil))
          (on-match-branch
           (sp--looking-back-p (rx "=>") nil))
          (on-comparison
           (sp--looking-back-p (rx (or
                                    (seq space "<")
                                    (seq space ">")
                                    (seq space "<<")
                                    (seq space ">>")))
                               nil)))
      (or on-comparison on-fn-return-type on-match-branch))))

(defun sp-rust-filter-angle-brackets (_id action context)
  "Non-nil if we should allow ID's ACTION in CONTEXT for angle brackets."
  ;; See the docstring for `sp-pair' for the possible values of ID,
  ;; ACTION and CONTEXT.
  (cond
   ;; Inside strings, don't do anything with < or >.
   ((eq context 'string)
    nil)
   ;; Don't do any smart pairing inside comments either.
   ((eq context 'comment)
    nil)
   ;; Otherwise, we're in code.
   ((eq context 'code)
    (let ((on-fn-return-type
           (looking-back (rx "->") nil))
          (on-match-branch
           (looking-back (rx "=>") nil))
          (on-comparison
           (looking-back (rx (or
                              (seq space "<")
                              (seq space ">")
                              (seq space "<<")
                              (seq space ">>")))
                         nil)))
      (cond
       ;; Only insert a matching > if we're not looking at a
       ;; comparison.
       ((eq action 'insert)
        (and (not on-comparison) (not on-fn-return-type) (not on-match-branch)))
       ;; Always allow wrapping in a pair if the region is active.
       ((eq action 'wrap)
        (not on-match-branch))
       ;; When pressing >, autoskip if we're not looking at a
       ;; comparison.
       ((eq action 'autoskip)
        (and (not on-comparison) (not on-fn-return-type) (not on-match-branch)))
       ;; Allow navigation, highlighting and strictness checks if it's
       ;; not a comparison.
       ((eq action 'navigate)
        (and (not on-comparison) (not on-fn-return-type) (not on-match-branch))))))))

(sp-with-modes '(rust-mode)
  (sp-local-pair "'" "'"
                 :unless '(sp-in-comment-p sp-in-string-quotes-p sp-in-rust-lifetime-context)
                 :post-handlers'(:rem sp-escape-quotes-after-insert))
  (sp-local-pair "<" ">"
                 :when '(sp-rust-filter-angle-brackets)
                 :skip-match 'sp-rust-skip-match-angle-bracket))

;; Rust has no sexp suffices.  This fixes slurping
;; (|foo).bar -> (foo.bar)
(add-to-list 'sp-sexp-suffix (list #'rust-mode 'regexp ""))

(provide 'smartparens-rust)

;;; smartparens-rust.el ends here