refactor: make Preview a singleton

Author: cseickel

lua/neo-tree/sources/common/commands.lua

@@ -346,64 +346,15 @@ M.delete_visual = function(state, selected_nodes, callback)
 end
 
 M.preview = function(state)
-  local node = state.tree:get_node()
-  if node.type == "directory" then
-    return
-  end
-
-  if not state.preview then
-    state.preview = Preview:new(state)
-  else
-    state.preview.active = true
-    state.preview:findWindow(state)
-  end
-
-  local extra = node.extra or {}
-  local position = extra.position
-  local end_position = extra.end_position
-  local path = node.path or node:get_id()
-  local bufnr = extra.bufnr or vim.fn.bufadd(path)
-
-  if bufnr and bufnr > 0 and state.preview then
-    if renderer.is_window_valid(state.preview.winid) then
-      state.preview:preview(bufnr, position, end_position)
-    else
-      log.warn("Preview window is not valid")
-      Preview.dispose(state)
-    end
-  end
+  Preview.show(state)
 end
 
-M.revert_preview = function(state)
-  Preview.dispose(state)
+M.revert_preview = function()
+  Preview.hide()
 end
 
 M.toggle_preview = function(state)
-  if state.preview then
-    M.revert_preview(state)
-  else
-    state.commands.preview(state)
-    if not state.preview then
-      return
-    end
-    local preview_event = {
-      event = events.VIM_CURSOR_MOVED,
-      handler = function()
-        if not state.preview then
-          return
-        end
-        if vim.api.nvim_get_current_win() == state.winid then
-          if state.preview.active then
-            state.commands.preview(state)
-          end
-        else
-          Preview.dispose(state)
-        end
-      end,
-      id = "preview-event",
-    }
-    state.preview:subscribe(state.name, preview_event)
-  end
+  Preview.toggle(state)
 end
 
 ---Open file or directory
@@ -423,7 +374,7 @@ local open_with_cmd = function(state, open_cmd, toggle_directory, open_file)
   end
 
   local function open()
-    M.revert_preview(state)
+    M.revert_preview()
     local path = node.path or node:get_id()
     if type(open_file) == "function" then
       open_file(state, path, open_cmd)

lua/neo-tree/sources/common/preview.lua

@@ -78,7 +78,9 @@ local function create_floating_preview_window(state)
   win:mount()
   return win
 end
-Preview = {}
+
+local Preview = {}
+local instance = nil
 
 ---Creates a new preview.
 ---@param state table The state of the source.
@@ -107,6 +109,7 @@ end
 ---@param start_pos table? The (0-indexed) starting position of the previewed text. May be absent.
 ---@param end_pos table? The (0-indexed) ending position of the previewed text. May be absent
 function Preview:preview(bufnr, start_pos, end_pos)
+  log.warn("Creating preview window")
   if self.is_neo_tree_window then
     log.error("Could not find appropriate window for preview")
     return
@@ -136,15 +139,6 @@ function Preview:preview(bufnr, start_pos, end_pos)
   self:highlight()
 end
 
-function Preview.dispose(state)
-  if state.preview and state.preview.active then
-    if state.preview.active then
-      state.preview:revert()
-    end
-  end
-  state.preview = nil
-end
-
 ---Reverts the preview and inactivates it, restoring the preview window to its previous state.
 function Preview:revert()
   self.active = false
@@ -343,4 +337,63 @@ function Preview:clearHighlight()
   end
 end
 
+Preview.hide = function()
+  if instance then
+    instance:revert()
+  end
+  instance = nil
+end
+
+Preview.show = function(state)
+  local node = state.tree:get_node()
+  if node.type == "directory" then
+    return
+  end
+
+  if instance then
+    instance:findWindow(state)
+    if not renderer.is_window_valid(instance.winid) then
+      log.warn("Preview window is not valid")
+      Preview.hide()
+      instance = Preview:new(state)
+    end
+  else
+    instance = Preview:new(state)
+  end
+
+  local extra = node.extra or {}
+  local position = extra.position
+  local end_position = extra.end_position
+  local path = node.path or node:get_id()
+  local bufnr = extra.bufnr or vim.fn.bufadd(path)
+
+  if bufnr and bufnr > 0 and instance then
+    instance:preview(bufnr, position, end_position)
+  end
+end
+
+Preview.toggle = function(state)
+  if instance then
+    Preview.hide()
+  else
+    Preview.show(state)
+    local preview_event = {
+      event = events.VIM_CURSOR_MOVED,
+      handler = function()
+        if not instance.active then
+          return
+        end
+        if vim.api.nvim_get_current_win() == state.winid then
+          Preview.show(state)
+        else
+          log.debug("Neo-tree window lost focus, disposing preview")
+          Preview.hide()
+        end
+      end,
+      id = "preview-event",
+    }
+    instance:subscribe(state.name, preview_event)
+  end
+end
+
 return Preview