enhanced version of tabline to show calendar in neovim by using floating window.

float_tabline.lua

-- original source: https://www.reddit.com/r/neovim/comments/1egdcql/show_upcoming_notion_calendar_event_in_neovim/
-- plugin/tabline.lua

---@return string|osdate
local function current_time()
  return os.date("%H:%M")
end

---@return string|osdate
local function current_day()
  return os.date("%A")
end

---@return string|osdate
local function current_file()
  local filename = vim.fn.expand("%:t")
  return filename == "" and current_day() or filename
end

---@class EventCache
---@field value string
---@field timestamp number
---@field refresh_interval number
---@type EventCache
local event_cache = {
  value = "",
  timestamp = 0,
  refresh_interval = 30,
}

---@return string
local function current_cal_event()
  local now = os.time()
  -- Check if the cache is still valid
  if
    event_cache.value
    and (now - event_cache.timestamp < event_cache.refresh_interval)
  then
    return event_cache.value
  end
  -- AppleScript code as a single string
  local script = [[
        set processExists to false
        tell application "System Events"
            set processList to name of every process
            if processList contains "Notion Calendar" then
                set processExists to true
            end if
        end tell

        if processExists then
          tell application "System Events"
            tell process "Notion Calendar"
              -- Get the second menu bar
              set theSecondMenuBar to menu bar 2

              -- Get all menu bar items in the second menu bar
              set menuBarItems to menu bar items of theSecondMenuBar

              -- Collect the titles or values of each menu bar item
              set menuBarItemTitles to {}
              repeat with itemIndex from 1 to count of menuBarItems
                set menuBarItemTitle to value of attribute "AXTitle" of item itemIndex of menuBarItems
                set end of menuBarItemTitles to menuBarItemTitle
              end repeat
            end tell
          end tell
          return menuBarItemTitles as string
        else
          return "Open Notion Calendar to see upcoming events"
        end if
    ]]

  -- NOTE: might using vim.system here

  -- Execute the AppleScript using osascript
  ---@type file*?
  local handle = io.popen("osascript -e '" .. script .. "'")

  if handle == nil then
    event_cache.value = "Nothing's up"
    event_cache.timestamp = now
    return event_cache.value
  end
  ---@type string?
  local result = handle:read("*a")
  handle:close()
  -- Update the cache
  if result == nil or result == "" then
    event_cache.value = "No event information available"
  else
    event_cache.value = result:gsub("^%s*(.-)%s*$", "%1")
  end
  event_cache.timestamp = now

  return event_cache.value
end

---create a floting buffer for the calendar event
---@return integer
local function create_buffer()
  local buf = vim.api.nvim_create_buf(false, true)
  local event_text = current_cal_event() or "No event information available"
  local lines = vim.split(event_text, "\n", { plain = true })

  if #lines > 0 then
    -- Add the 🌱 icon to the first line
    lines[1] = "🌱 " .. lines[1]
  else
    -- If there are no lines, add a default line with the icon
    lines = { "🌱 No event" }
  end

  vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
  return buf
end

---@return integer
local function create_window()
  local height, width, buf, win, padding
  height = 1
  width = 25
  padding = 0
  buf = create_buffer()
  win = vim.api.nvim_open_win(buf, false, {
    relative = "editor",
    anchor = "NE",
    width = width,
    height = height,
    focusable = false,
    row = padding,
    col = vim.o.columns - padding,
    style = "minimal",
    border = "none",
  })

  local buf_options = {
    buftype = "nofile",
    modifiable = false,
  }
  local win_options = {
    winblend = 0,
    winhighlight = "Normal:TabLineFile",
  }
  for option, value in pairs(buf_options) do
    vim.api.nvim_set_option_value(option, value, { buf = buf })
  end
  for option, value in pairs(win_options) do
    vim.api.nvim_set_option_value(option, value, { win = win })
  end
  return win
end

---@type integer?
local current_window = nil

---@return nil
local function close_window()
  if current_window and vim.api.nvim_win_is_valid(current_window) then
    vim.api.nvim_win_close(current_window, true)
    current_window = nil
  end
end

---@return nil
local function toggle_window()
  if current_window and vim.api.nvim_win_is_valid(current_window) then
    close_window()
  else
    current_window = create_window()
  end
end

vim.keymap.set("n", "gC", toggle_window, { noremap = true, silent = true })

-- vim.opt.showtabline = 2
-- vim.cmd("highlight! link TabLineFile @field")
-- vim.cmd("highlight! link TabLineTime @diff.minus")
-- vim.cmd("highlight! link TabLineEvent @diff.plus")
-- vim.cmd("highlight! TabLineEventBg guifg=#333c48")
-- vim.cmd("highlight! TabLineTimeBg guifg=#43293a")
-- -- vim.o.tabline = " 🌱 %#TabLineFile# %{v:lua.current_file()} %h%m%r %= %#TabLineTime# %{v:lua.current_time()} " -- " ♥ "
-- vim.o.tabline =
--   " 🌱 %#TabLineFile# %{v:lua.current_file()} %h%m%r %= %#TabLineEventBg#%#TabLineEvent#%{v:lua.current_cal_event()}%#TabLineEventBg#%#Normal# %#TabLineTimeBg#%#TabLineTime#%{v:lua.current_time()}%#TabLineTimeBg#" -- " ♥ "
--
_G.current_time = current_time
_G.current_file = current_file
_G.current_cal_event = current_cal_event