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

-- Not UFO in the sky, but an ultra fold in Neovim.
-- https://github.com/kevinhwang91/nvim-ufo/
return {
  'kevinhwang91/nvim-ufo',
  version = '*',
  dependencies = {
    { 'neovim/nvim-lspconfig' },
    { 'kevinhwang91/promise-async' },
    { 'nvim-treesitter/nvim-treesitter' },
    {
      -- Status column plugin that provides a configurable
      -- 'statuscolumn' and click handlers.
      -- https://github.com/luukvbaal/statuscol.nvim
      'luukvbaal/statuscol.nvim',
      config = function()
        local builtin = require 'statuscol.builtin'
        require('statuscol').setup {
          relculright = true,
          segments = {
            {
              text = { builtin.foldfunc },
              click = 'v:lua.ScFa',
            },
            {
              sign = {
                namespace = { 'diagnostic/signs' },
                maxwidth = 2,
                -- auto = true,
              },
              click = 'v:lua.ScSa',
            },
            {
              text = { builtin.lnumfunc, ' ' },
              click = 'v:lua.ScLa',
            },
          },
        }
      end,
    },
  },
  config = function()
    local capabilities = vim.lsp.protocol.make_client_capabilities()
    capabilities.textDocument.foldingRange = {
      dynamicRegistration = true,
      lineFoldingOnly = true,
    }
    local language_servers = require('lspconfig').util.available_servers() -- or list servers manually like {'gopls', 'clangd'}
    for _, ls in ipairs(language_servers) do
      require('lspconfig')[ls].setup {
        capabilities = capabilities,
        -- you can add other fields for setting up lsp server in this table
      }
    end

    require('ufo').setup {
      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
      --
      -- This handler is called when the fold text is too long to fit in the window.
      -- It is expected to truncate the text and return a new list of virtual text.
      --
      ---@param virtText table The current virtual text list.
      ---@param lnum number The line number of the first line in the fold.
      ---@param endLnum number The line number of the last line in the fold.
      ---@param width number The width of the window.
      ---@param truncate function Truncate function
      ---@return table
      fold_virt_text_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,
    }
  end,
}