[PATCH 13/18] lei query: Add next/previous line variants that update message buffer

[Kyle Meyer <kyle@kyleam.com>]

Using next-line and previous-line directly is inconvenient for viewing
results because the associated message buffer needs to be manually
displayed even if a piem-lei-show-mode buffer is visible.

Add commands that 1) automatically call piem-lei-query-show and 2)
skip over ghost messages, because in that case there's nothing to
display or otherwise act on.

If the command is executed quickly, unconditionally showing the buffer
is wasteful and won't perform well, so something like
magit-update-other-window-delay should probably be added.
---
 piem-lei.el | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/piem-lei.el b/piem-lei.el
index 3760176c..37502d07 100644
--- a/piem-lei.el
+++ b/piem-lei.el
@@ -26,6 +26,7 @@ (require 'iso8601)
 (require 'json)
 (require 'message)
 (require 'piem)
+(require 'seq)
 
 (defgroup piem-lei nil
   "lei integration for piem."
@@ -243,6 +244,47 @@ (defun piem-lei-query-show ()
      (inhibit-same-window . t)
      (window-height . 0.8))))
 
+(defun piem-lei-query--get-visible-message-window ()
+  (seq-some
+   (lambda (w)
+     (with-current-buffer (window-buffer w)
+       (and (derived-mode-p 'piem-lei-show-mode)
+            w)))
+   (window-list (selected-frame))))
+
+(defun piem-lei-query-next-line (n)
+  "Move to the Nth next query result.
+If a `piem-lei-show-mode' buffer is visible in the frame, update
+it to display the message."
+  (interactive "p")
+  (unless (= n 0)
+    (pcase-let ((ntimes (abs n))
+                (`(,move-fn ,pos-fn)
+                 (if (> n 0)
+                     (list #'next-single-property-change
+                           #'line-end-position)
+                   (list #'previous-single-property-change
+                         #'line-beginning-position)))
+                (target nil))
+      (while (and (> ntimes 0)
+                  (setq target (funcall move-fn
+                                        (funcall pos-fn)
+                                        'piem-lei-query-result)))
+        (cl-decf ntimes))
+      (if (not target)
+          (ding)
+        (goto-char target)
+        (goto-char (line-beginning-position))
+        (when (piem-lei-query--get-visible-message-window)
+          (piem-lei-query-show))))))
+
+(defun piem-lei-query-previous-line (n)
+  "Move to the Nth previous query result.
+If a `piem-lei-show-mode' buffer is visible in the frame, update
+it to display the message."
+  (interactive "p")
+  (piem-lei-query-next-line (- n)))
+
 (define-derived-mode piem-lei-query-mode special-mode "lei-query"
   "Major mode for displaying overview of `lei q' results."
   :group 'piem-lei
-- 
2.31.1