import os
import os.notify

// make a pipe and return the (read, write) file descriptors
fn make_pipe() ?(int, int) {
	$if linux {
		pipefd := [2]int{}
		if C.pipe(&pipefd[0]) != 0 {
			return error('error $C.errno: ' + os.posix_get_error_msg(C.errno))
		}
		return pipefd[0], pipefd[1]
	}
	return -1, -1
}

fn test_level_trigger() ? {
	// currently only linux is supported
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			os.fd_close(writer)
			notifier.close() or {}
		}
		notifier.add(reader, .read) ?

		os.fd_write(writer, 'foobar')
		check_read_event(notifier, reader, 'foo')
		check_read_event(notifier, reader, 'bar')

		assert notifier.wait(0).len == 0
	}
}

fn test_edge_trigger() ? {
	// currently only linux is supported
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			os.fd_close(writer)
			notifier.close() or {}
		}
		notifier.add(reader, .read, .edge_trigger) ?

		os.fd_write(writer, 'foobar')
		check_read_event(notifier, reader, 'foo')

		assert notifier.wait(0).len == 0

		os.fd_write(writer, 'baz')
		// we do not get an event because there is still data
		// to be read
		assert notifier.wait(0).len == 0
	}
}

fn test_one_shot() ? {
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			os.fd_close(writer)
			notifier.close() or {}
		}
		notifier.add(reader, .read, .one_shot) ?

		os.fd_write(writer, 'foobar')
		check_read_event(notifier, reader, 'foo')
		os.fd_write(writer, 'baz')

		assert notifier.wait(0).len == 0

		// rearm
		notifier.modify(reader, .read) ?
		check_read_event(notifier, reader, 'barbaz')
	}
}

fn test_hangup() ? {
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			notifier.close() or {}
		}
		notifier.add(reader, .hangup) ?

		assert notifier.wait(0).len == 0

		// closing on the writer end of the pipe will
		// cause a hangup on the reader end
		os.fd_close(writer)
		events := notifier.wait(0)
		assert events.len == 1
		assert events[0].fd == reader
		assert events[0].kind.has(.hangup)
	}
}

fn test_write() ? {
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			os.fd_close(writer)
			notifier.close() or {}
		}

		notifier.add(reader, .write) ?
		assert notifier.wait(0).len == 0

		notifier.add(writer, .write) ?
		events := notifier.wait(0)
		assert events.len == 1
		assert events[0].fd == writer
		assert events[0].kind.has(.write)
	}
}

fn test_remove() ? {
	$if linux {
		mut notifier := notify.new() ?
		reader, writer := make_pipe() ?
		defer {
			os.fd_close(reader)
			os.fd_close(writer)
			notifier.close() or {}
		}

		// level triggered - will keep getting events while
		// there is data to read
		notifier.add(reader, .read) ?
		os.fd_write(writer, 'foobar')
		assert notifier.wait(0).len == 1
		assert notifier.wait(0).len == 1

		notifier.remove(reader) ?
		assert notifier.wait(0).len == 0
	}
}

fn check_read_event(notifier notify.FdNotifier, reader_fd int, expected string) {
	events := notifier.wait(0)
	assert events.len == 1
	assert events[0].fd == reader_fd
	assert events[0].kind.has(.read)
	s, _ := os.fd_read(events[0].fd, expected.len)
	assert s == expected
}