From cdb43e65249e9c6ff53d86fbda0fde43dc441317 Mon Sep 17 00:00:00 2001
From: Iron-E <36409591+Iron-E@users.noreply.github.com>
Date: Fri, 12 May 2023 18:06:37 +0000
Subject: [PATCH] feat: `focus_on_close = 'previous'` (#484)

---
 README.md             |  2 +-
 doc/barbar.txt        | 10 +++++++---
 lua/barbar/bbye.lua   | 13 ++++++++++++-
 lua/barbar/config.lua |  4 ++--
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 5bc59fcd..b2e6a458 100644
--- a/README.md
+++ b/README.md
@@ -282,7 +282,7 @@ require'barbar'.setup {
   exclude_name = {'package.json'},
 
   -- A buffer to this direction will be focused (if it exists) when closing the current buffer.
-  -- Valid options are 'left' (the default) and 'right'
+  -- Valid options are 'left' (the default), 'previous', and 'right'
   focus_on_close = 'left',
 
   -- Hide inactive buffers and file extensions. Other options are `alternate`, `current`, and `visible`.
diff --git a/doc/barbar.txt b/doc/barbar.txt
index d90ca815..5b4a89b8 100644
--- a/doc/barbar.txt
+++ b/doc/barbar.txt
@@ -176,9 +176,13 @@ exclude_name ~
 
                                                  *barbar-setup.focus_on_close*
 focus_on_close ~
-  `'left'|'right'`  (default: `'left'`)
-  A buffer to this direction will be focused (if it exists) when closing the
-  current buffer.
+  `'left'|'previous'|'right'`  (default: `'left'`)
+  The algorithm to use for getting the next buffer after closing the current
+  one:
+
+  - `'left'`: focus the buffer to the left of the current buffer.
+  - `'previous'`: focus the previous buffer.
+  - `'right'`: focus the buffer to the right of the current buffer.
 
                                                            *barbar-setup.hide*
 hide ~
diff --git a/lua/barbar/bbye.lua b/lua/barbar/bbye.lua
index 9f539db1..f9bc1f04 100644
--- a/lua/barbar/bbye.lua
+++ b/lua/barbar/bbye.lua
@@ -74,13 +74,22 @@ local enew = vim.api.nvim_cmd and
   --- @param force boolean
   function(force) command("enew" .. (force and '!' or '')) end
 
+--- Get the bufnr that will be focused when the buffer with `closing_number` closes.
 --- @param closing_number integer
 --- @return nil|integer bufnr of the buffer to focus
 local function get_focus_on_close(closing_number)
   local focus_on_close = config.options.focus_on_close
   local state_bufnrs = state.buffers
 
-  if #state_bufnrs < 1 then -- all of the buffers are excluded or unlisted
+  if focus_on_close == 'previous' then
+    local previous = bufnr('#')
+    if previous > -1 then
+      return previous
+    end
+  end
+
+  -- Edge case: all of the buffers are excluded or unlisted
+  if #state_bufnrs < 1 then
     local open_bufnrs = list_bufs()
 
     local start, end_, step
@@ -104,6 +113,7 @@ local function get_focus_on_close(closing_number)
     state_bufnrs = list.reverse(state.buffers)
   end
 
+  -- Next, try to get the buffer to focus by "looking" left or right of the current buffer
   local index = list.index_of(state_bufnrs, closing_number)
   if index then
     index = index - 1
@@ -114,6 +124,7 @@ local function get_focus_on_close(closing_number)
     end
   end
 
+  -- If all else fails, choose the first available listed buffer
   for _, buffer_number in ipairs(state_bufnrs) do
     if buffer_number ~= closing_number then
       return buffer_number
diff --git a/lua/barbar/config.lua b/lua/barbar/config.lua
index f4eb6db7..243cf735 100644
--- a/lua/barbar/config.lua
+++ b/lua/barbar/config.lua
@@ -155,7 +155,7 @@ local DEPRECATED_OPTIONS = {
 --- @field clickable boolean
 --- @field exclude_ft string[]
 --- @field exclude_name string[]
---- @field focus_on_close side
+--- @field focus_on_close side|'previous'
 --- @field hide barbar.config.options.hide
 --- @field highlight_alternate boolean
 --- @field highlight_inactive_file_icons boolean
@@ -272,7 +272,7 @@ function config.setup(options)
     clickable = true,
     exclude_ft = {},
     exclude_name = {},
-    focus_on_close = 'left',
+    focus_on_close = 'previous',
     hide = {},
     highlight_alternate = false,
     highlight_inactive_file_icons = false,