# `Stream` that can read from a File
class FileReader
	super FileStream
	super PollableReader
	# Misc

	# Open the same file again.
	# The original path is reused, therefore the reopened file can be a different file.
	#
	#     var f = new FileReader.open("/etc/issue")
	#     var l = f.read_line
	#     f.reopen
	#     assert l == f.read_line
	fun reopen
	do
		var fl = _file
		if fl != null and not fl.address_is_null then close
		last_error = null
		_file = new NativeFile.io_open_read(path.as(not null).to_cstring)
		if _file.as(not null).address_is_null then
			last_error = new IOError("Cannot open `{path.as(not null)}`: {sys.errno.strerror}")
			return
		end
	end

	redef fun raw_read_byte
	do
		var nb = _file.as(not null).io_read(write_buffer, 1)
		if last_error == null and _file.as(not null).ferror then
			last_error = new IOError("Cannot read `{path.as(not null)}`: {sys.errno.strerror}")
		end
		if nb == 0 then return -1
		return write_buffer[0].to_i
	end

	redef fun raw_read_bytes(cstr, max)
	do
		var nb = _file.as(not null).io_read(cstr, max)
		if last_error == null and _file.as(not null).ferror then
			last_error = new IOError("Cannot read `{path.as(not null)}`: {sys.errno.strerror}")
		end
		return nb
	end

	redef fun eof do
		var fl = _file
		if fl == null then return true
		if fl.address_is_null then return true
		if last_error != null then return true
		if super then
			if last_error != null then return true
			return fl.feof
		end
		return false
	end

	# Open the file at `path` for reading.
	#
	#     var f = new FileReader.open("/etc/issue")
	#     assert not f.eof
	#     f.close
	#
	# In case of error, `last_error` is set
	#
	#     f = new FileReader.open("/fail/does not/exist")
	#     assert f.eof
	#     assert f.last_error != null
	init open(path: String)
	do
		self.path = path
		_file = new NativeFile.io_open_read(path.to_cstring)
		if _file.as(not null).address_is_null then
			last_error = new IOError("Cannot open `{path}`: {sys.errno.strerror}")
		end
	end

	# Creates a new File stream from a file descriptor
	#
	# This is a low-level method.
	init from_fd(fd: Int) do
		self.path = ""
		_file = fd.fd_to_stream(read_only)
		if _file.as(not null).address_is_null then
			last_error = new IOError("Error: Converting fd {fd} to stream failed with '{sys.errno.strerror}'")
		end
	end

	redef fun poll_in
	do
		var res = native_poll_in(fd)
		if res == -1 then
			last_error = new IOError(errno.to_s)
			return false
		else return res > 0
	end

	private fun native_poll_in(fd: Int): Int `{
#ifndef _WIN32
		struct pollfd fds = {(int)fd, POLLIN, 0};
		return poll(&fds, 1, 0);
#else
		return 0;
#endif
	`}
end