local M = {}

-- Flip function arguments.
--
--    flip(f)(a, b) == f(b, a)
--
M.flip = function(f)
  return function(a, b)
    return f(b, a)
  end
end

-- Extend lists.
--
--    extend({'a', 'b'}, {'c', 'd'}) == {'a', 'b', 'c', 'd'}
--    extend({1, 2}, {3, 4}, {5, 6}) == {1, 2, 3, 4, 5, 6}
--
M.extend = function(...)
  local result = {}
  for _, tbl in ipairs {...} do
    for _, v in pairs(tbl) do
      result[#result+1] = v
    end
  end
  return result
end

-- Partial function application:
--
--    partial(f, x)(...)    == f(x, ...)
--    partial(f, x, y)(...) == f(x, y, ...)
--
M.partial = function(f, ...)
  local argv = {...}
  return function(...)
    return f(unpack(M.extend(argv, {...})))
  end
end

-- Perform `func` (which can freely use register `reg`) and make sure `reg`
-- is restored afterwards.
M.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, or word under cursor if not in visual mode.
M.get_selected_text = function()
  if vim.fn.mode() ~= 'v' then return vim.fn.expand '<cword>' end

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

M.use_local = function()
end

return M