`tab_switcher`: Sort entries by last focused and add "hold" mode (#308)

* `tab_switcher`: Sort entries by last focused

The last entry in `tab-switcher:tab-list{,-current-split}` is the 
previously focused tab, so that pressing enter is enough to switch to 
it.

Also added `tab-switcher:switch-to-last-tab{,-in-current-split}` 
commands.

* `tab_switcher`: Implement "hold" mode

2 files changed, 116 insertions, 17 deletions

diff --git a/manifest.json b/manifest.json
index 053e8bf..2f7163c 100644
--- a/manifest.json
+++ b/manifest.json
@@ -1589,7 +1589,7 @@
     },
     {
       "description": "Switch between open tabs by searching by name",
-      "version": "0.1",
+      "version": "0.2",
       "path": "plugins/tab_switcher.lua",
       "id": "tab_switcher",
       "mod_version": "3"
diff --git a/plugins/tab_switcher.lua b/plugins/tab_switcher.lua
index 3d55eed..41fdf84 100644
--- a/plugins/tab_switcher.lua
+++ b/plugins/tab_switcher.lua
@@ -5,7 +5,62 @@ local keymap = require "core.keymap"
 local common = require "core.common"
 local DocView = require "core.docview"
 
+local nodes_visit_order = setmetatable({}, {__mode = "k"})
+
+---When true, releasing all the modifier keys will accept the selection
+local hold_mode = false
+---Whether or not the CommandView relative to this plugin is active
+local in_switcher = false
+
+---@param t table<any, boolean?>
+---@return boolean
+local function any_true(t)
+  for _, v in pairs(t) do
+    if v then return true end
+  end
+  return false
+end
+
+-- We need to override keymap.on_key_released to detect that all the modifier
+-- keys were released while in "hold" mode, to accept the current selection.
+local old_keymap_on_key_released = keymap.on_key_released
+function keymap.on_key_released(k)
+  -- Check if hold_mode has been triggered erroneously
+  if hold_mode and not in_switcher then
+    hold_mode = false
+    core.warning("Something went wrong with the tab_switcher plugin. " ..
+                 "Please open an issue about it in the plugins repository on Github.")
+  end
+
+  local was_pressed = any_true(keymap.modkeys)
+  old_keymap_on_key_released(k)
+  local still_pressed = any_true(keymap.modkeys)
+
+  if hold_mode and was_pressed and not still_pressed then
+    hold_mode = false
+    command.perform("command:submit")
+  end
+end
+
+
+local order_counter = 0
+
+local core_set_active_view = core.set_active_view
+function core.set_active_view(view)
+  nodes_visit_order[view] = order_counter
+  order_counter = order_counter + 1
+  return core_set_active_view(view)
+end
+
 local tab_switcher = {}
+
+---@class tab_switcher.tab_item
+---@field text string The tab name
+---@field view core.view
+
+---Returns the list of DocView tabs under a specific node tree.
+---@param base_node core.node Where to start the search from
+---@return tab_switcher.tab_item[]
 function tab_switcher.get_tab_list(base_node)
   local raw_list = base_node:get_children()
   local list = {}
@@ -21,40 +76,84 @@ function tab_switcher.get_tab_list(base_node)
       }, mt))
     end
   end
+  table.sort(list, function(a, b)
+    return (nodes_visit_order[a.view] or -1) > (nodes_visit_order[b.view] or -1)
+  end)
   return list
 end
 
+local function set_active_view(view)
+  local n = core.root_view.root_node:get_node_for_view(view)
+  if n then n:set_active_view(view) end
+end
+
+---@param label string
+---@param items tab_switcher.tab_item[]
 local function ask_selection(label, items)
-  if #items == 0 then
-    core.warn("No tabs available")
-    return
-  end
+  in_switcher = true
   core.command_view:enter(label, {
     submit = function(_, item)
-      local n = core.root_view.root_node:get_node_for_view(item.view)
-      if n then n:set_active_view(item.view) end
+      in_switcher = false
+      set_active_view(item.view)
     end,
     suggest = function(text)
-      return common.fuzzy_match(items, text, true)
+      if #text > 1 then
+        return common.fuzzy_match(items, text, true)
+      else
+        return items
+      end
     end,
     validate = function(_, item)
       return item
-    end
+    end,
+    cancel = function()
+      in_switcher = false
+    end,
   })
 end
 
-command.add(nil,{
-  ["tab-switcher:tab-list"] = function()
-    ask_selection("Switch to tab", tab_switcher.get_tab_list(core.root_view.root_node))
+command.add(function(items)
+    items = items or tab_switcher.get_tab_list(core.root_view.root_node)
+    return #items > 0, items
+  end, {
+  ["tab-switcher:tab-list"] = function(items)
+    ask_selection("Switch to tab", items)
+  end,
+  ["tab-switcher:switch-to-last-tab"] = function(items)
+    command.perform("tab-switcher:tab-list", items)
+    command.perform("tab-switcher:previous-tab")
+  end,
+})
+
+command.add(function(items)
+    items = items or tab_switcher.get_tab_list(core.root_view:get_active_node())
+    return #items > 0, items
+  end, {
+  ["tab-switcher:tab-list-current-split"] = function(items)
+    ask_selection("Switch to tab in current split", items)
+  end,
+  ["tab-switcher:switch-to-last-tab-in-current-split"] = function(items)
+    command.perform("tab-switcher:tab-list-current-split", items)
+    command.perform("tab-switcher:previous-tab")
+  end,
+})
+
+command.add(function() return in_switcher end, {
+  ["tab-switcher:next-tab"] = function()
+    hold_mode = true
+    command.perform("command:select-next")
+  end,
+  ["tab-switcher:previous-tab"] = function()
+    hold_mode = true
+    command.perform("command:select-previous")
   end,
-  ["tab-switcher:tab-list-current-split"] = function()
-    ask_selection("Switch to tab in current split", tab_switcher.get_tab_list(core.root_view:get_active_node()))
-  end
 })
 
 keymap.add({
-  ["alt+p"]       = "tab-switcher:tab-list",
-  ["alt+shift+p"] = "tab-switcher:tab-list-current-split"
+  ["alt+p"]             = { "tab-switcher:previous-tab", "tab-switcher:tab-list" },
+  ["ctrl+alt+p"]        = { "tab-switcher:previous-tab", "tab-switcher:switch-to-last-tab" },
+  ["alt+shift+p"]       = { "tab-switcher:next-tab", "tab-switcher:tab-list-current-split" },
+  ["ctrl+alt+shift+p"]  = { "tab-switcher:next-tab", "tab-switcher:switch-to-last-tab-in-current-split" },
 })
 
 return tab_switcher