jdhao-nvim-config/lua/config/statusline.lua

local fn = vim.fn

local function spell()
  if vim.o.spell then
    return string.format("[SPELL]")
  end

  return ""
end

local function ime_state()
  if vim.g.is_mac then
    -- ref: https://github.com/vim-airline/vim-airline/blob/master/autoload/airline/extensions/xkblayout.vim#L11
    local layout = fn.libcall(vim.g.XkbSwitchLib, 'Xkb_Switch_getXkbLayout', '')
    if layout == '0' then
      return '[CN]'
    end
  end

  return ""
end

local function trailing_space()
  local line_num = nil

  for i=1, fn.line('$') do
    local linetext = fn.getline(i)
    -- To prevent invalid escape error, we wrap the regex string with `[[]]`.
    local idx = fn.match(linetext, [[\v\s+$]])

    if idx ~= -1 then
      line_num = i
      break
    end
  end

  local msg = ""
  if line_num ~= nil then
    msg = string.format("[%d]trailing", line_num)
  end

  return msg
end

local function mixed_indent()
  local space_pat = [[\v^ +]]
  local tab_pat = [[\v^\t+]]
  local space_indent = fn.search(space_pat, 'nwc')
  local tab_indent = fn.search(tab_pat, 'nwc')
  local mixed = (space_indent > 0 and tab_indent > 0)
  local mixed_same_line
  if not mixed then
    mixed_same_line = fn.search([[\v^(\t+ | +\t)]], 'nwc')
    mixed = mixed_same_line > 0
  end
  if not mixed then return '' end
  if mixed_same_line ~= nil and mixed_same_line > 0 then
     return 'MI:'..mixed_same_line
  end
  local space_indent_cnt = fn.searchcount({pattern=space_pat, max_count=1e3}).total
  local tab_indent_cnt =  fn.searchcount({pattern=tab_pat, max_count=1e3}).total
  if space_indent_cnt > tab_indent_cnt then
    return 'MI:'..tab_indent
  else
    return 'MI:'..space_indent
  end
end

require("lualine").setup({
  options = {
    icons_enabled = true,
    theme = "auto",
    -- component_separators = { left = "", right = "" },
    -- section_separators = { left = "", right = "" },
    section_separators = "",
    component_separators = "",
    disabled_filetypes = {},
    always_divide_middle = true,
  },
  sections = {
    lualine_a = { "mode" },
    lualine_b = { "branch", "diff" },
    lualine_c = {
      "filename",
      {
        ime_state,
        color = {fg = 'black', bg = '#f46868'}
      },
      {
        spell,
        color = {fg = 'black', bg = '#a7c080'}
      },
    },
    lualine_x = {
      "encoding",
      {
        "fileformat",
        symbols = {
          unix = "unix",
          dos = "win",
          mac = "mac",
        },
      },
      "filetype",
    },
    lualine_y = { "progress" },
    lualine_z = {
      "location",
      {
        "diagnostics",
        sources = { "nvim_diagnostic" }
      },
      {
        trailing_space,
        color = "WarningMsg"
      },
      {
        mixed_indent,
        color = "WarningMsg"
      },
    },
  },
  inactive_sections = {
    lualine_a = {},
    lualine_b = {},
    lualine_c = { "filename" },
    lualine_x = { "location" },
    lualine_y = {},
    lualine_z = {},
  },
  tabline = {},
  extensions = {'quickfix', 'fugitive', 'nvim-tree'},
})