dotfiles/config/nvim/lua/plugins/ufo.lua

local handler = function(virtText, lnum, endLnum, width, truncate)
  local newVirtText = {}
  local suffix = (' 󰁂 %d '):format(endLnum - lnum)
  local sufWidth = vim.fn.strdisplaywidth(suffix)
  local targetWidth = width - sufWidth
  local curWidth = 0
  for _, chunk in ipairs(virtText) do
    local chunkText = chunk[1]
    local chunkWidth = vim.fn.strdisplaywidth(chunkText)
    if targetWidth > curWidth + chunkWidth then
      table.insert(newVirtText, chunk)
    else
      chunkText = truncate(chunkText, targetWidth - curWidth)
      local hlGroup = chunk[2]
      table.insert(newVirtText, { chunkText, hlGroup })
      chunkWidth = vim.fn.strdisplaywidth(chunkText)
      -- str width returned from truncate() may less than 2nd argument, need padding
      if curWidth + chunkWidth < targetWidth then
        suffix = suffix .. (' '):rep(targetWidth - curWidth - chunkWidth)
      end
      break
    end
    curWidth = curWidth + chunkWidth
  end
  table.insert(newVirtText, { suffix, 'MoreMsg' })
  return newVirtText
end

return {
  -- Not UFO in the sky, but an ultra fold in Neovim.
  -- https://github.com/kevinhwang91/nvim-ufo/
  {
    'kevinhwang91/nvim-ufo',
    lazy = false,
    enabled = true,
    version = '*',
    dependencies = {
      'kevinhwang91/promise-async',
      { 'nvim-treesitter/nvim-treesitter', run = ':TSUpdate' },
      {
        'luukvbaal/statuscol.nvim',
        config = function()
          local builtin = require 'statuscol.builtin'
          require('statuscol').setup {
            relculright = true,
            segments = {
              { text = { builtin.foldfunc }, click = 'v:lua.ScFa' },
              { text = { '%s' }, click = 'v:lua.ScSa' },
              { text = { builtin.lnumfunc, ' ' }, click = 'v:lua.ScLa' },
            },
          }
        end,
      },
    },
    init = function()
      vim.o.fillchars = [[eob: ,fold: ,foldopen:,foldsep: ,foldclose:]]
      vim.o.foldcolumn = '1' -- '0' is not bad
      vim.o.foldlevel = 99 -- Using ufo provider need a large value, feel free to decrease the value
      vim.o.foldlevelstart = 99
      vim.o.foldenable = true
    end,
    opts = {
      open_fold_hl_timeout = 150,
      close_fold_kinds_for_ft = { 'imports', 'comment' },
      preview = {
        win_config = {
          border = { '', '─', '', '', '', '─', '', '' },
          winhighlight = 'Normal:Folded',
          winblend = 0,
        },
        mappings = {
          scrollU = '<C-u>',
          scrollD = '<C-d>',
          jumpTop = '[',
          jumpBot = ']',
        },
      },
      provider_selector = function(_, _, _) -- bufnr, filetype, buftype
        return { 'treesitter', 'indent' }
      end,
      fold_virt_text_handler = handler,
    },
  },
}