;;; verilog-align-ports.el --- Align SystemVerilog port declarations -*- lexical-binding: t; -*-

;;; Commentary:
;; Align SystemVerilog ANSI-style port declarations in a contiguous block.

;;; Code:

(require 'cl-lib)
(require 'subr-x)

(defun verilog-align-ports--line-port-p (pos)
  (save-excursion
    (goto-char pos)
    (let ((line (buffer-substring-no-properties
                 (line-beginning-position)
                 (line-end-position))))
      (string-match-p "^\\s-*\\(input\\|output\\|inout\\)\\b" line))))

(defun verilog-align-ports--split-comment (line)
  (let ((pos (string-match "//" line)))
    (if pos
        (cons (substring line 0 pos) (substring line pos))
      (cons line nil))))

(defun verilog-align-ports--parse-line (line)
  (let* ((split (verilog-align-ports--split-comment line))
         (code (string-trim-right (car split)))
         (comment (cdr split)))
    (when (string-match
           "^\\(\\s-*\\)\\(input\\|output\\|inout\\)\\b\\s-*\\(.*\\)$"
           code)
      (let* ((indent (match-string 1 code))
             (dir (match-string 2 code))
             (rest (string-trim (match-string 3 code)))
             (name nil)
             (comma nil)
             (type "")
             (range "")
             (before ""))
        (if (string-match
            "\\(\\\\[^[:space:]]+\\|[A-Za-z_][A-Za-z0-9_$]*\\)\\(\\s-*,\\)?\\s-*$"
             rest)
            (progn
              (setq name (match-string 1 rest))
              (setq comma (when (match-string 2 rest) ","))
              (setq before
                    (string-trim-right (substring rest 0 (match-beginning 1)))))
          (setq name rest)
          (setq comma nil)
          (setq before ""))
        (setq before (string-trim-right before))
        (if (and (not (string-empty-p before))
                 (string-match "\\(\\[[^][]+\\]\\)\\s-*$" before))
            (progn
              (setq range (match-string 1 before))
              (setq type
                    (string-trim-right (substring before 0 (match-beginning 1)))))
          (setq type (string-trim before))
          (setq range ""))
        (list :indent indent
              :dir dir
              :type type
              :range range
              :name name
              :comma comma
              :comment comment)))))

(defun verilog-align-ports--bounds ()
  (save-excursion
    (and (verilog-align-ports--line-port-p (line-beginning-position))
         (let ((start (line-beginning-position))
               (end nil))
           (while (and (not (bobp))
                       (save-excursion
                         (forward-line -1)
                         (verilog-align-ports--line-port-p
                          (line-beginning-position))))
             (forward-line -1)
             (setq start (line-beginning-position)))
           (goto-char start)
           (while (and (not (eobp))
                       (verilog-align-ports--line-port-p
                        (line-beginning-position)))
             (forward-line 1))
           (setq end (line-beginning-position))
           (cons start end)))))

(defun verilog-align-ports--collect (start end)
  (let (entries)
    (save-excursion
      (goto-char start)
      (while (< (point) end)
        (let* ((line (buffer-substring-no-properties
                      (line-beginning-position)
                      (line-end-position)))
               (entry (verilog-align-ports--parse-line line)))
          (when entry
            (push entry entries)))
        (forward-line 1)))
    (nreverse entries)))

(defun verilog-align-ports--max-lengths (entries)
  (let ((max-dir 0)
        (max-type 0)
        (max-range 0)
        (max-name 0)
        (has-comment nil))
    (dolist (entry entries)
      (setq max-dir (max max-dir (length (plist-get entry :dir))))
      (setq max-type (max max-type (length (plist-get entry :type))))
      (setq max-range (max max-range (length (plist-get entry :range))))
      (let ((name (concat (plist-get entry :name)
                          (or (plist-get entry :comma) ""))))
        (setq max-name (max max-name (length name))))
      (when (plist-get entry :comment)
        (setq has-comment t)))
    (list max-dir max-type max-range max-name has-comment)))

(defun verilog-align-ports--pad (max-len len)
  (make-string (+ 1 (- max-len len)) ?\s))

(defun verilog-align-ports--format-lines (entries)
  (let* ((base-indent (plist-get (car entries) :indent))
         (maxes (verilog-align-ports--max-lengths entries))
         (max-dir (nth 0 maxes))
         (max-type (nth 1 maxes))
         (max-range (nth 2 maxes))
         (max-name (nth 3 maxes))
         (has-comment (nth 4 maxes))
         (has-type (> max-type 0))
         (has-range (> max-range 0)))
    (mapcar
     (lambda (entry)
       (let* ((dir (plist-get entry :dir))
              (type (plist-get entry :type))
              (range (plist-get entry :range))
              (name (concat (plist-get entry :name)
                            (or (plist-get entry :comma) "")))
              (comment (plist-get entry :comment))
              (dir-pad (verilog-align-ports--pad max-dir (length dir)))
              (type-pad (when has-type
                          (verilog-align-ports--pad max-type (length type))))
              (range-pad (when has-range
                           (verilog-align-ports--pad max-range (length range))))
              (name-pad (when (and has-comment comment)
                          (verilog-align-ports--pad max-name (length name)))))
         (concat base-indent
                 dir
                 dir-pad
                 (when has-type type)
                 (when has-type type-pad)
                 (when has-range range)
                 (when has-range range-pad)
                 name
                 (when (and has-comment comment) name-pad)
                 (or comment ""))))
     entries)))

(defun verilog-align-ports--apply (start lines)
  (save-excursion
    (goto-char start)
    (dolist (line lines)
      (delete-region (line-beginning-position) (line-end-position))
      (insert line)
      (forward-line 1))))

;;;###autoload
(defun verilog-align-ports ()
  "Align SystemVerilog port declarations around point."
  (interactive)
  (let ((bounds (verilog-align-ports--bounds)))
    (and bounds
         (let* ((start (car bounds))
                (end (cdr bounds))
                (entries (verilog-align-ports--collect start end)))
           (and entries
                (let ((lines (verilog-align-ports--format-lines entries)))
                  (verilog-align-ports--apply start lines)
                  t))))))

(provide 'verilog-align-ports)

;;; verilog-align-ports.el ends here