From 280abe85bb2ecdbac5f427bd44871c2ad716a985 Mon Sep 17 00:00:00 2001
From: JSDurand <mmemmew@gmail.com>
Date: Tue, 17 Aug 2021 11:04:27 +0800
Subject: new function: durand-copy-line-dwim

* basic.el (global-map): Bind to "s-;".

* common.el (durand-copy-line-dwim): This meets my needs to copy or
  duplicate lines.
---
 basic.el  |  4 ++++
 common.el | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/basic.el b/basic.el
index e23688d..cd5fdff 100644
--- a/basic.el
+++ b/basic.el
@@ -209,6 +209,10 @@ This will maintain the frame's width and height as well."
          (display-buffer-in-tab durand-display-in-one-window)
          (tab-name . "man page"))))
 
+;;; copy-duplicate dwim
+
+(define-key global-map (vector ?\s-\;) #'durand-copy-line-dwim)
+
 ;;; Custom kill buffer function
 
 ;;;###autoload
diff --git a/common.el b/common.el
index 0417da5..75fe201 100644
--- a/common.el
+++ b/common.el
@@ -393,6 +393,63 @@ Comparison is done by TEST if that is non-nil, else by `equal'."
        ((setq temp (cdr temp)))))
     temp))
 
+;;;###autoload
+(defun durand-copy-line-dwim (&optional arg)
+  "Copy line or duplicate line, according to ARG.
+If ARG is nil, then duplicate line and put cursor in the line
+below.
+
+If ARG is '(4), just copy line.
+
+If ARG is '(16), copy and duplicate line at the same time.
+
+If ARG is a number strictly greater than 0, then copy and
+duplicate the line ARG times.
+
+In any other case, copy line and use minibuffer to read a number,
+and duplicate the line at the line that is ARG away from the
+current line; negative ARG means to put the line upwards."
+  (interactive "P")
+  (cond
+   ((null arg)
+    (let ((line (buffer-substring (line-beginning-position)
+                                  (line-end-position))))
+      (goto-char (line-end-position))
+      (insert "\n" line)))
+   ((equal arg (list 4))
+    (let ((line (concat (buffer-substring (line-beginning-position)
+                                          (line-end-position))
+                        "\n")))
+      (kill-new line)
+      (message "Copied \"%s\"" (substring-no-properties line))))
+   ((equal arg (list 16))
+    (let ((line (buffer-substring (line-beginning-position)
+                                  (line-end-position))))
+      (kill-new (concat line "\n"))
+      (message "Copied \"%s\n\"" (substring-no-properties line))
+      (goto-char (line-end-position))
+      (insert "\n")
+      (insert line)))
+   ((and (integerp arg)
+         (> arg 0))
+    (let* ((line (buffer-substring (line-beginning-position)
+                                   (line-end-position)))
+           (lines (mapconcat (lambda (_arg) line)
+                             (number-sequence 1 arg)
+                             "\n")))
+      (kill-new (concat line "\n"))
+      (message "Copied \"%s\n\"" (substring-no-properties line))
+      (insert "\n" lines)))
+   (t
+    (let ((line (buffer-substring (line-beginning-position)
+                                  (line-end-position)))
+          (num (read-number "Duplicate to which line? ")))
+      (kill-new (concat line "\n"))
+      (message "Copied \"%s\n\"" (substring-no-properties line))
+      (goto-char (line-end-position (cond ((/= num 0) (1+ num))
+                                          (num))))
+      (insert "\n" line)))))
+
 (provide 'common)
 ;;; common.el ends here.
 
-- 
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