From 3c8fe70d8e525f67be9f19e88c33adc965e260d6 Mon Sep 17 00:00:00 2001
From: Jim Myhrberg <contact@jimeh.me>
Date: Sun, 24 May 2020 00:18:30 +0100
Subject: [PATCH] feat(persp-mode): Enable switching to most recent persp

Keep a list of most recently visited persps whenever you switch, and
enable switching back and forth between the current and most recently
visited persp.

Also when killing current persp, switch to the most recently visited
persp, instead of back to the default/nil persp.

Minor bug remaining is that the when killing current persp, the echo
area shows all persps like usual when switching, but it includes the
persp that was just killed, despite it already being killed.
---
 modules/workspaces/siren-persp-mode.el | 63 ++++++++++++++++++++++----
 1 file changed, 54 insertions(+), 9 deletions(-)

diff --git a/modules/workspaces/siren-persp-mode.el b/modules/workspaces/siren-persp-mode.el
index 8d02b8c..427ef18 100644
--- a/modules/workspaces/siren-persp-mode.el
+++ b/modules/workspaces/siren-persp-mode.el
@@ -41,6 +41,7 @@
         ("C-z K" . persp-kill-buffer)
         ("C-z w" . persp-save-state-to-file)
         ("C-z W" . persp-save-to-file-by-names)
+        ("C-z C-l" . siren-persp-mode-switch-to-most-recent)
         ("C-z l" . persp-load-state-from-file)
         ("C-z L" . persp-load-from-file-by-names)
         ("C-z ;" . siren-persp-mode-show-current-perspective-name)
@@ -73,28 +74,72 @@
     (interactive)
     (refine 'persp-names-cache))
 
+  (defun siren-persp-before-switch-hook (name frame)
+    "Store the persp we're switching away from as the most recently active."
+    (when (framep frame)
+      (let ((recent-list (frame-parameter frame 'persp-recent-persps))
+            (current-persp (safe-persp-name (get-current-persp))))
+        (set-frame-parameter frame 'persp-recent-persps
+                             (append (list current-persp)
+                                     (delete current-persp recent-list))))))
+
+  (defun siren-persp-before-kill-hook (persp)
+    "Remove the killed perspective's name from persp-recent-persps."
+    (let* ((frame (selected-frame))
+          (recent-list (frame-parameter frame 'persp-recent-persps))
+          (persp-name (safe-persp-name persp))
+          (current-persp (safe-persp-name (get-current-persp))))
+      (set-frame-parameter frame 'persp-recent-persps
+                           (delete persp-name recent-list))
+      (if (equal persp-name current-persp)
+          (siren-persp-mode-switch-to-most-recent))))
+
+  (defun siren-persp-activated-hook (type)
+    "Remove any persp names from recent list that no longer exist."
+    (let* ((frame (selected-frame))
+           (recent-list (frame-parameter frame 'persp-recent-persps))
+           (perspectives (persp-names-current-frame-fast-ordered))
+           (current-persp (safe-persp-name (get-current-persp))))
+      (setq recent-list (delete current-persp recent-list))
+      (dolist (persp-name recent-list)
+        (if (not (member persp-name perspectives))
+            (setq recent-list (delete persp-name recent-list))))
+      (set-frame-parameter frame 'persp-recent-persps recent-list)))
+
+  (defun siren-persp-mode-switch-to-most-recent ()
+    "Switch to the most recently active persp."
+    (interactive)
+    (let* ((frame (selected-frame))
+           (persp-name (car (frame-parameter frame 'persp-recent-persps))))
+      (if (member persp-name (persp-names-current-frame-fast-ordered))
+          (persp-frame-switch persp-name frame)
+        (message "perspective %s is no longer available" persp-name))))
+
   (defun siren-persp-mode-show-current-perspective-name (&rest _)
     "Show current perspectives, highlighting the active one."
     (interactive)
     (let ((perspectives (persp-names-current-frame-fast-ordered))
-          (active-persp-name (safe-persp-name (get-current-persp)))
+          (current-persp-name (safe-persp-name (get-current-persp)))
           (output ""))
-      (dolist (current-name perspectives)
-        (message "%s" current-name)
+      (dolist (persp-name perspectives)
         (setq output
-              (concat output (if (string= active-persp-name current-name)
-                                 (propertize current-name
+              (concat output (if (string= current-persp-name persp-name)
+                                 (propertize persp-name
                                              'face 'persp-face-lighter-default)
-                               current-name)
+                               persp-name)
                       " ")))
       (message "perspectives: %s" output)))
 
   :config
-  (add-to-list 'persp-common-buffer-filter-functions
-               'siren-persp-mode-filter-magit-buffers)
+  (add-hook 'persp-common-buffer-filter-functions
+            'siren-persp-mode-filter-magit-buffers)
+
+  (add-hook 'persp-before-switch-functions 'siren-persp-before-switch-hook)
+  (add-hook 'persp-before-kill-functions 'siren-persp-before-kill-hook)
+  (add-hook 'persp-activated-functions 'siren-persp-activated-hook)
 
   (add-hook 'persp-activated-functions
-            #'siren-persp-mode-show-current-perspective-name))
+            'siren-persp-mode-show-current-perspective-name))
 
 (provide 'siren-persp-mode)
 ;;; siren-persp-mode.el ends here