local path = {}

-- TODO: Can we use vim.loop for this?
path.separator = package.config:sub(1, 1)
path.home = vim.fn.expand("~")

path.make_relative = function(filepath, cwd)
  if not cwd or not filepath then return filepath end

  if filepath:sub(1, #cwd) == cwd  then
    local offset =  0
    -- if  cwd does ends in the os separator, we need to take it off
    if cwd:sub(#cwd, #cwd) ~= path.separator then
      offset = 1
    end

    filepath = filepath:sub(#cwd + 1 + offset, #filepath)
  end

  return filepath
end

path.shorten = (function()
  if jit then
    local ffi = require('ffi')
    ffi.cdef [[
    typedef unsigned char char_u;
    char_u *shorten_dir(char_u *str);
    ]]

    return function(filepath)
      if not filepath then
        return filepath
      end

      local c_str = ffi.new("char[?]", #filepath + 1)
      ffi.copy(c_str, filepath)
      return ffi.string(ffi.C.shorten_dir(c_str))
    end
  else
    return function(filepath)
      return filepath
    end
  end
end)()

path.normalize = function(filepath, cwd)
  filepath = path.make_relative(filepath, cwd)

  -- Substitute home directory w/ "~"
  filepath = filepath:gsub("^" .. path.home, '~', 1)

  -- Remove double path separators, it's annoying
  filepath = filepath:gsub(path.separator .. path.separator, path.separator)

  return filepath
end

path.read_last_line = function(filepath)
  local fd = vim.loop.fs_open(filepath, "r", 438)
  if fd == nil then return '' end
  local stat = assert(vim.loop.fs_fstat(fd))
  local data = ''
  local index = stat.size - 2
  while true do
    local char = assert(vim.loop.fs_read(fd, 1, index))
    if char == '\n' then break end
    data = char .. data
    index = index - 1
  end
  assert(vim.loop.fs_close(fd))
  return data
end

path.read_file = function(filepath)
  local fd = vim.loop.fs_open(filepath, "r", 438)
  if fd == nil then return '' end
  local stat = assert(vim.loop.fs_fstat(fd))
  local data = assert(vim.loop.fs_read(fd, stat.size, 0))
  assert(vim.loop.fs_close(fd))
  return data
end

path.read_file_async = function(filepath, callback)
  vim.loop.fs_open(filepath, "r", 438, function(err_open, fd)
    assert(not err_open, err_open)
    vim.loop.fs_fstat(fd, function(err_fstat, stat)
      assert(not err_fstat, err_fstat)
      vim.loop.fs_read(fd, stat.size, 0, function(err_read, data)
        assert(not err_read, err_read)
        vim.loop.fs_close(fd, function(err_close)
          assert(not err_close, err_close)
          return callback(data)
        end)
      end)
    end)
  end)
end

return path