fix wrong action preview window position

lua/lspsaga/codeaction/preview.lua

@@ -109,23 +109,42 @@ local function create_preview_win(content, main_winid)
   else
     opt.width = content_width < win_conf.width and win_conf.width or content_width
   end
-
   local winheight = api.nvim_win_get_height(win_conf.win)
-  local win_margin = config.ui.border == 'none' and 0 or 2
-  if win_conf.anchor:find('^S') then
-    opt.row = util.is_ten and win_conf.row - 3 or win_conf.row[false] - win_conf.height - win_margin
-    max_height = util.is_ten and win_conf.row or win_conf.row[false] - win_conf.height
-  elseif win_conf.anchor:find('^N') then
-    opt.row = util.is_ten and win_conf.row + 3 or win_conf.row[false] + win_conf.height + win_margin
-    max_height = winheight - opt.row
+  local margin = config.ui.border == 'none' and 0 or 2
+  local north = win_conf.anchor:sub(1, 1) == 'N'
+  local row = util.is_ten and win_conf.row or win_conf.row[false]
+  local valid_top_height = north and row or row - win_conf.height - margin
+  local valid_bot_height = north and winheight - row - win_conf.height - margin
+    or winheight - row - margin
+  local new_win_height = #content + margin
+  -- action is NW under cursor and top is enough to show preview
+  if north then
+    if valid_top_height > new_win_height then
+      opt.anchor = 'SW'
+      opt.row = row
+      opt.height = math.min(valid_top_height, #content)
+    elseif valid_bot_height > new_win_height then
+      opt.anchor = 'NW'
+      opt.row = row + win_conf.height + margin
+      opt.height = math.min(valid_bot_height, #content)
+    end
+  else
+    if valid_bot_height > new_win_height then
+      opt.anchor = 'NW'
+      opt.row = row
+      opt.height = math.min(valid_bot_height, #content)
+    else
+      opt.anchor = 'SW'
+      opt.row = row - win_conf.height - margin
+      opt.height = math.min(valid_top_height, #content)
+    end
   end
 
-  opt.height = math.min(max_height, #content)
-
   if config.ui.title then
     opt.title = { { 'Action Preview', 'ActionPreviewTitle' } }
     opt.title_pos = 'center'
   end
+  print(vim.inspect(opt))
 
   preview_buf, preview_winid = win
     :new_float(opt, false, true)