M = {}

local builtin = function(picker, opts)
  return function(title)
    return function()
      local args = vim.tbl_extend('keep', { prompt_title = title }, opts or {})
      return require('telescope.builtin')[picker](args)
    end
  end
end

---Preserve register contents over function call.
---@param reg string: register to save, must be a valid register name.
---@param func function: function that may freely clobber the register.
---@return any: return value of calling `func`.
local with_saved_register = function(reg, func)
  local saved = vim.fn.getreg(reg)
  local result = func()
  vim.fn.setreg(reg, saved)
  return result
end

---Get selected text.
---@return string: selected text, or work under cursor if not in visual mode.
local get_selected_text = function()
  if vim.fn.mode() ~= 'v' then return vim.fn.expand '<cword>' end

  return with_saved_register('v', function()
    vim.cmd [[noautocmd sil norm "vy]]
    return vim.fn.getreg 'v'
  end)
end

M.pickers = setmetatable({
  all_files = builtin('find_files', {
    hidden = true,
    no_ignore = true,
    no_ignore_parent = true,
  }),
  colorscheme = builtin('colorscheme', {
    enable_preview = true,
  }),
  diagnostics = builtin('diagnostics', {
    bufnr = 0
  }),
  dotfiles = builtin('find_files', {
    cwd = '~/.dotfiles',
    hidden = true,
  }),
  selection = function(title)
    return function()
      local text = get_selected_text()
      return require('telescope.builtin').grep_string {
        prompt_title = string.format(title .. ': %s  ', text),
        search = text,
      }
    end
  end,
  here = builtin('current_buffer_fuzzy_find'),
}, {
  -- Fall back to telescope's built-in pickers if a custom one is not defined
  -- above, but make sure to keep the title we defined.
  __index = function(_, picker)
    return builtin(picker)
  end
})

return M