-- Phase 6.7: nvim-ufo for better folding with Treesitter and LSP support
return {
  'kevinhwang91/nvim-ufo',
  dependencies = {
    'kevinhwang91/promise-async',
  },
  event = { 'BufReadPost', 'BufNewFile' },
  keys = {
    { 'zR', function() require('ufo').openAllFolds() end, desc = 'UFO: Open all folds' },
    { 'zM', function() require('ufo').closeAllFolds() end, desc = 'UFO: Close all folds' },
    { 'zr', function() require('ufo').openFoldsExceptKinds() end, desc = 'UFO: Open folds except kinds' },
    { 'zm', function() require('ufo').closeFoldsWith() end, desc = 'UFO: Close folds with' },
    { 'K', function()
      local winid = require('ufo').peekFoldedLinesUnderCursor()
      if not winid then
        -- Fall back to LSP hover if not on a fold
        vim.lsp.buf.hover()
      end
    end, desc = 'UFO: Peek fold or LSP hover' },
  },
  opts = {
    provider_selector = function(bufnr, filetype, buftype)
      -- Use Treesitter for supported languages, LSP for others, indent as fallback
      return { 'treesitter', 'indent' }
    end,
    -- Open folds when searching
    open_fold_hl_timeout = 150,
    close_fold_kinds_for_ft = {
      default = { 'imports', 'comment' },
    },
    preview = {
      win_config = {
        border = { '', '─', '', '', '', '─', '', '' },
        winhighlight = 'Normal:Folded',
        winblend = 0,
      },
      mappings = {
        scrollU = '<C-u>',
        scrollD = '<C-d>',
        jumpTop = '[',
        jumpBot = ']',
      },
    },
    -- Custom fold text showing line count
    fold_virt_text_handler = function(virtText, lnum, endLnum, width, truncate)
      local newVirtText = {}
      local suffix = ('  %d lines '):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)
          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,
  },
  config = function(_, opts)
    -- Set fold settings for nvim-ufo
    vim.o.foldcolumn = '0'      -- Hide fold column (we don't need it)
    vim.o.foldlevel = 99        -- Open all folds by default
    vim.o.foldlevelstart = 99   -- Open all folds when opening a file
    vim.o.foldenable = true     -- Enable folding
    -- Use simple characters for fold indicators (though foldcolumn is hidden)
    vim.o.fillchars = [[eob: ,fold: ,foldopen:▼,foldsep: ,foldclose:▶]]

    require('ufo').setup(opts)
  end,
}