rustic-interaction.el

;;; rustic-interaction.el --- Common interactive functions -*-lexical-binding: t-*-

;;; Code:

(defun rustic-rewind-to-beginning-of-current-level-expr ()
  (let ((current-level (rustic-paren-level)))
    (back-to-indentation)
    (when (looking-at "->")
      (rustic-rewind-irrelevant)
      (back-to-indentation))
    (while (> (rustic-paren-level) current-level)
      (backward-up-list)
      (back-to-indentation))
    ;; When we're in the where clause, skip over it.  First find out the start
    ;; of the function and its paren level.
    (let ((function-start nil) (function-level nil))
      (save-excursion
        (rustic-beginning-of-defun)
        (back-to-indentation)
        ;; Avoid using multiple-value-bind
        (setq function-start (point)
              function-level (rustic-paren-level)))
      ;; On a where clause
      (when (or (rustic-looking-at-where)
                ;; or in one of the following lines, e.g.
                ;; where A: Eq
                ;;       B: Hash <- on this line
                (and (save-excursion
                       (rustic-rewind-to-where function-start))
                     (= current-level function-level)))
        (goto-char function-start)))))

(defun rustic-align-to-expr-after-brace ()
  (save-excursion
    (forward-char)
    ;; We don't want to indent out to the open bracket if the
    ;; open bracket ends the line
    (when (not (looking-at "[[:blank:]]*\\(?://.*\\)?$"))
      (when (looking-at "[[:space:]]")
        (forward-word 1)
        (backward-word 1))
      (current-column))))

(defun rustic-align-to-method-chain ()
  (save-excursion
    ;; for method-chain alignment to apply, we must be looking at
    ;; another method call or field access or something like
    ;; that. This avoids rather "eager" jumps in situations like:
    ;;
    ;; {
    ;;     something.foo()
    ;; <indent>
    ;;
    ;; Without this check, we would wind up with the cursor under the
    ;; `.`. In an older version, I had the inverse of the current
    ;; check, where we checked for situations that should NOT indent,
    ;; vs checking for the one situation where we SHOULD. It should be
    ;; clear that this is more robust, but also I find it mildly less
    ;; annoying to have to press tab again to align to a method chain
    ;; than to have an over-eager indent in all other cases which must
    ;; be undone via tab.

    (when (looking-at (concat "\s*\." rustic-re-ident))
      (forward-line -1)
      (end-of-line)
      ;; Keep going up (looking for a line that could contain a method chain)
      ;; while we're in a comment or on a blank line. Stop when the paren
      ;; level changes.
      (let ((level (rustic-paren-level)))
        (while (and (or (rustic-in-str-or-cmnt)
                        ;; Only whitespace (or nothing) from the beginning to
                        ;; the end of the line.
                        (looking-back "^\s*" (point-at-bol)))
                    (= (rustic-paren-level) level))
          (forward-line -1)
          (end-of-line)))

      (let
          ;; skip-dot-identifier is used to position the point at the
          ;; `.` when looking at something like
          ;;
          ;;      foo.bar
          ;;         ^   ^
          ;;         |   |
          ;;         |  position of point
          ;;       returned offset
          ;;
          ((skip-dot-identifier
            (lambda ()
              (when (and (rustic-looking-back-ident) (save-excursion (forward-thing 'symbol -1) (= ?. (char-before))))
                (forward-thing 'symbol -1)
                (backward-char)
                (- (current-column) rustic-indent-offset)))))
        (cond
         ;; foo.bar(...)
         ((rustic-looking-back-str ")")
          (backward-list 1)
          (funcall skip-dot-identifier))

         ;; foo.bar
         (t (funcall skip-dot-identifier)))))))


;;;;;;;;;;;;;;;;
;; Interactive

(defun rustic-indent-line ()
  (interactive)
  (let ((indent
         (save-excursion
           (back-to-indentation)
           ;; Point is now at beginning of current line
           (let* ((level (rustic-paren-level))
                  (baseline
                   ;; Our "baseline" is one level out from the indentation of the expression
                   ;; containing the innermost enclosing opening bracket.  That
                   ;; way if we are within a block that has a different
                   ;; indentation than this mode would give it, we still indent
                   ;; the inside of it correctly relative to the outside.
                   (if (= 0 level)
                       0
                     (or
                      (when rustic-indent-method-chain
                        (rustic-align-to-method-chain))
                      (save-excursion
                        (rustic-rewind-irrelevant)
                        (backward-up-list)
                        (rustic-rewind-to-beginning-of-current-level-expr)
                        (+ (current-column) rustic-indent-offset))))))
             (cond
              ;; Indent inside a non-raw string only if the the previous line
              ;; ends with a backslash that is inside the same string
              ((nth 3 (syntax-ppss))
               (let*
                   ((string-begin-pos (nth 8 (syntax-ppss)))
                    (end-of-prev-line-pos (when (> (line-number-at-pos) 1)
                                            (save-excursion
                                              (forward-line -1)
                                              (end-of-line)
                                              (point)))))
                 (when
                     (and
                      ;; If the string begins with an "r" it's a raw string and
                      ;; we should not change the indentation
                      (/= ?r (char-after string-begin-pos))

                      ;; If we're on the first line this will be nil and the
                      ;; rest does not apply
                      end-of-prev-line-pos

                      ;; The end of the previous line needs to be inside the
                      ;; current string...
                      (> end-of-prev-line-pos string-begin-pos)

                      ;; ...and end with a backslash
                      (= ?\\ (char-before end-of-prev-line-pos)))

                   ;; Indent to the same level as the previous line, or the
                   ;; start of the string if the previous line starts the string
                   (if (= (line-number-at-pos end-of-prev-line-pos) (line-number-at-pos string-begin-pos))
                       ;; The previous line is the start of the string.
                       ;; If the backslash is the only character after the
                       ;; string beginning, indent to the next indent
                       ;; level.  Otherwise align with the start of the string.
                       (if (> (- end-of-prev-line-pos string-begin-pos) 2)
                           (save-excursion
                             (goto-char (+ 1 string-begin-pos))
                             (current-column))
                         baseline)

                     ;; The previous line is not the start of the string, so
                     ;; match its indentation.
                     (save-excursion
                       (goto-char end-of-prev-line-pos)
                       (back-to-indentation)
                       (current-column))))))

              ;; A function return type is indented to the corresponding
	          ;; function arguments, if -to-arguments is selected.
              ((and rust-indent-return-type-to-arguments
		            (looking-at "->"))
               (save-excursion
                 (backward-list)
                 (or (rustic-align-to-expr-after-brace)
                     (+ baseline rustic-indent-offset))))

              ;; A closing brace is 1 level unindented
              ((looking-at "[]})]") (- baseline rustic-indent-offset))

              ;; Doc comments in /** style with leading * indent to line up the *s
              ((and (nth 4 (syntax-ppss)) (looking-at "*"))
               (+ 1 baseline))

              ;; When the user chose not to indent the start of the where
              ;; clause, put it on the baseline.
              ((and (not rustic-indent-where-clause)
                    (rustic-looking-at-where))
               baseline)

              ;; If we're in any other token-tree / sexp, then:
              (t
               (or
                ;; If we are inside a pair of braces, with something after the
                ;; open brace on the same line and ending with a comma, treat
                ;; it as fields and align them.
                (when (> level 0)
                  (save-excursion
                    (rustic-rewind-irrelevant)
                    (backward-up-list)
                    ;; Point is now at the beginning of the containing set of braces
                    (rustic-align-to-expr-after-brace)))

                ;; When where-clauses are spread over multiple lines, clauses
                ;; should be aligned on the type parameters.  In this case we
                ;; take care of the second and following clauses (the ones
                ;; that don't start with "where ")
                (save-excursion
                  ;; Find the start of the function, we'll use this to limit
                  ;; our search for "where ".
                  (let ((function-start nil) (function-level nil))
                    (save-excursion
                      ;; If we're already at the start of a function,
                      ;; don't go back any farther.  We can easily do
                      ;; this by moving to the end of the line first.
                      (end-of-line)
                      (rustic-beginning-of-defun)
                      (back-to-indentation)
                      ;; Avoid using multiple-value-bind
                      (setq function-start (point)
                            function-level (rustic-paren-level)))
                    ;; When we're not on a line starting with "where ", but
                    ;; still on a where-clause line, go to "where "
                    (when (and
                           (not (rustic-looking-at-where))
                           ;; We're looking at something like "F: ..."
                           (looking-at (concat rustic-re-ident ":"))
                           ;; There is a "where " somewhere after the
                           ;; start of the function.
                           (rustic-rewind-to-where function-start)
                           ;; Make sure we're not inside the function
                           ;; already (e.g. initializing a struct) by
                           ;; checking we are the same level.
                           (= function-level level))
                      ;; skip over "where"
                      (forward-char 5)
                      ;; Unless "where" is at the end of the line
                      (if (eolp)
                          ;; in this case the type parameters bounds are just
                          ;; indented once
                          (+ baseline rustic-indent-offset)
                        ;; otherwise, skip over whitespace,
                        (skip-chars-forward "[:space:]")
                        ;; get the column of the type parameter and use that
                        ;; as indentation offset
                        (current-column)))))

                (progn
                  (back-to-indentation)
                  ;; Point is now at the beginning of the current line
                  (if (or
                       ;; If this line begins with "else" or "{", stay on the
                       ;; baseline as well (we are continuing an expression,
                       ;; but the "else" or "{" should align with the beginning
                       ;; of the expression it's in.)
                       ;; Or, if this line starts a comment, stay on the
                       ;; baseline as well.
                       (looking-at "\\<else\\>\\|{\\|/[/*]")

                       ;; If this is the start of a top-level item,
                       ;; stay on the baseline.
                       (looking-at rustic-top-item-beg-re)

                       (save-excursion
                         (rustic-rewind-irrelevant)
                         ;; Point is now at the end of the previous line
                         (or
                          ;; If we are at the start of the buffer, no
                          ;; indentation is needed, so stay at baseline...
                          (= (point) 1)
                          ;; ..or if the previous line ends with any of these:
                          ;;     { ? : ( , ; [ }
                          ;; then we are at the beginning of an expression, so stay on the baseline...
                          (looking-back "[(,:;?[{}]\\|[^|]|" (- (point) 2))
                          ;; or if the previous line is the end of an attribute, stay at the baseline...
                          (progn (rustic-rewind-to-beginning-of-current-level-expr) (looking-at "#")))))
                      baseline

                    ;; Otherwise, we are continuing the same expression from the previous line,
                    ;; so add one additional indent level
                    (+ baseline rustic-indent-offset))))))))))

    (when indent
      ;; If we're at the beginning of the line (before or at the current
      ;; indentation), jump with the indentation change.  Otherwise, save the
      ;; excursion so that adding the indentations will leave us at the
      ;; equivalent position within the line to where we were before.
      (if (<= (current-column) (current-indentation))
          (indent-line-to indent)
        (save-excursion (indent-line-to indent))))))

(defun rustic-promote-module-into-dir ()
  "Promote the module file visited by the current buffer into its own directory.

For example, if the current buffer is visiting the file `foo.rs',
then this function creates the directory `foo' and renames the
file to `foo/mod.rs'.  The current buffer will be updated to
visit the new file."
  (interactive)
  (let ((filename (buffer-file-name)))
    (if (not filename)
        (message "Buffer is not visiting a file.")
      (if (string-equal (file-name-nondirectory filename) "mod.rs")
          (message "Won't promote a module file already named mod.rs.")
        (let* ((basename (file-name-sans-extension
                          (file-name-nondirectory filename)))
               (mod-dir (file-name-as-directory
                         (concat (file-name-directory filename) basename)))
               (new-name (concat mod-dir "mod.rs")))
          (mkdir mod-dir t)
          (rename-file filename new-name 1)
          (set-visited-file-name new-name))))))

;;; Defun Motions

(defun rustic-beginning-of-defun (&optional arg)
  "Move backward to the beginning of the current defun.

With ARG, move backward multiple defuns.  Negative ARG means
move forward.

This is written mainly to be used as `beginning-of-defun-function' for Rust.
Don't move to the beginning of the line. `beginning-of-defun',
which calls this, does that afterwards."
  (interactive "p")
  (let* ((arg (or arg 1))
	     (magnitude (abs arg))
	     (sign (if (< arg 0) -1 1)))
    ;; If moving forward, don't find the defun we might currently be
    ;; on.
    (when (< sign 0)
      (end-of-line))
    (catch 'done
      (dotimes (_ magnitude)
	    ;; Search until we find a match that is not in a string or comment.
	    (while (if (re-search-backward (concat "^\\(" rustic-top-item-beg-re "\\)")
				                       nil 'move sign)
		           (rustic-in-str-or-cmnt)
		         ;; Did not find it.
		         (throw 'done nil)))))
    t))

(defun rustic-end-of-defun ()
  "Move forward to the next end of defun.

With argument, do it that many times.
Negative argument -N means move back to Nth preceding end of defun.

Assume that this is called after beginning-of-defun. So point is
at the beginning of the defun body.

This is written mainly to be used as `end-of-defun-function' for Rust."
  (interactive)
  ;; Find the opening brace
  (if (re-search-forward "[{]" nil t)
      (progn
        (goto-char (match-beginning 0))
        ;; Go to the closing brace
        (condition-case nil
            (forward-sexp)
          (scan-error
           ;; The parentheses are unbalanced; instead of being unable to fontify, just jump to the end of the buffer
           (goto-char (point-max)))))
    ;; There is no opening brace, so consider the whole buffer to be one "defun"
    (goto-char (point-max))))


(provide 'rustic-interaction)
;;; rustic-interaction.el ends here