//go:build linux

package client

import (
	"bytes"
	"testing"

	"golang.org/x/sys/unix"
)

func TestVirtualSerialPTYByteStream(t *testing.T) {
	serial, err := newVirtualSerial()
	if err != nil {
		t.Fatalf("newVirtualSerial() failed: %v", err)
	}
	defer serial.Close()

	path := serial.Path()

	if path == "" {
		t.Fatal("virtual serial returned an empty path")
	}

	t.Logf("virtual serial path: %s", path)

	// Die externe Software wird durch diesen direkten Zugriff
	// auf den PTY-Slave simuliert.
	slaveFD, err := unix.Open(
		path,
		unix.O_RDWR|unix.O_NOCTTY,
		0,
	)
	if err != nil {
		t.Fatalf("open PTY slave %s: %v", path, err)
	}
	defer unix.Close(slaveFD)

	expected := make([]byte, 256)

	for i := range expected {
		expected[i] = byte(i)
	}

	// ------------------------------------------------------------
	// Slave -> Client
	// ------------------------------------------------------------

	n, err := unix.Write(slaveFD, expected)
	if err != nil {
		t.Fatalf("write to PTY slave failed: %v", err)
	}

	if n != len(expected) {
		t.Fatalf(
			"write to PTY slave incomplete: got %d, want %d",
			n,
			len(expected),
		)
	}

	received := make([]byte, len(expected))
	offset := 0

	for offset < len(received) {
		n, err := serial.Read(received[offset:])
		if err != nil {
			t.Fatalf("read from virtual serial failed: %v", err)
		}

		offset += n
	}

	if !bytes.Equal(received, expected) {
		t.Fatalf("Slave -> Client data mismatch")
	}

	// ------------------------------------------------------------
	// Client -> Slave
	// ------------------------------------------------------------

	n, err = serial.Write(expected)
	if err != nil {
		t.Fatalf("write to virtual serial failed: %v", err)
	}

	if n != len(expected) {
		t.Fatalf(
			"write from virtual serial incomplete: got %d, want %d",
			n,
			len(expected),
		)
	}

	received = make([]byte, len(expected))
	offset = 0

	for offset < len(received) {
		n, err := unix.Read(slaveFD, received[offset:])
		if err != nil {
			t.Fatalf("read from PTY slave failed: %v", err)
		}

		offset += n
	}

	if !bytes.Equal(received, expected) {
		t.Fatalf("Client -> Slave data mismatch")
	}

	t.Log("256-byte bidirectional PTY test successful")
}