/*
 * ============================================================================
 * Projekt.....: rs2322tcp
 * Datei.......: control_test.go
 * Copyright (C) 2026 Dieter Lang
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * Beschreibung:
 * Tests für den TCP-Control-Server einschließlich Session-Verwaltung,
 * dynamischer Data-Ports und der bidirektionalen Verbindung zur
 * seriellen Schnittstelle.
 * ============================================================================
 */
package server_test

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"testing"
	"time"

	"git.lang-dieter.de/rs2322tcp/internal/config"
	"git.lang-dieter.de/rs2322tcp/internal/server"
	"git.lang-dieter.de/rs2322tcp/internal/transport"
)

///////////////////////////////////////////////////////////////////////////////
// Test configuration
///////////////////////////////////////////////////////////////////////////////

func testServerConfig() *config.ServerConfig {
	return &config.ServerConfig{
		Listen: config.ListenConfig{
			Address: "127.0.0.1",
			Port:    5000,
		},
		Devices: []config.DeviceConfig{
			{
				ID:         "radio",
				Name:       "Funkgerät",
				SerialPort: "/dev/ttyUSB0",
				BaudRate:   9600,
				DataBits:   8,
				Parity:     "none",
				StopBits:   1,
			},
			{
				ID:         "rotor",
				Name:       "Antennenrotor",
				SerialPort: "/dev/ttyUSB1",
				BaudRate:   4800,
				DataBits:   8,
				Parity:     "none",
				StopBits:   1,
			},
		},
	}
}

///////////////////////////////////////////////////////////////////////////////
// Basic server tests
///////////////////////////////////////////////////////////////////////////////

func TestNewControlServer(t *testing.T) {
	cfg := testServerConfig()

	srv, err := server.NewControlServer(cfg)
	if err != nil {
		t.Fatalf("NewControlServer() failed: %v", err)
	}

	if srv == nil {
		t.Fatal("NewControlServer() returned nil server")
	}
}

func TestControlServerHello(t *testing.T) {
	cfg := testServerConfig()

	srv, err := server.NewControlServer(cfg)
	if err != nil {
		t.Fatalf("NewControlServer() failed: %v", err)
	}

	serverConn, clientConn := net.Pipe()
	defer serverConn.Close()
	defer clientConn.Close()

	done := make(chan struct{})

	var session *server.Session

	go func() {
		session = srv.HandleConnectionForTest(serverConn)
		close(done)
	}()

	if err := transport.WriteMessage(
		clientConn,
		transport.NewHello(),
	); err != nil {
		t.Fatalf("WriteMessage() failed: %v", err)
	}

	reader := bufio.NewReader(clientConn)

	var response transport.HelloResponseMessage

	if err := transport.ReadMessage(reader, &response); err != nil {
		t.Fatalf("ReadMessage() failed: %v", err)
	}

	if response.Type != transport.MessageHelloResponse {
		t.Errorf(
			"Type = %q, want %q",
			response.Type,
			transport.MessageHelloResponse,
		)
	}

	clientConn.Close()

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("server connection handler did not terminate")
	}

	if session == nil {
		t.Fatal("server returned nil session")
	}

	if session.ID() != 1 {
		t.Errorf("Session ID = %d, want 1", session.ID())
	}

	if !session.IsClosed() {
		t.Fatal("session is not closed")
	}
}

func TestControlServerGetDevices(t *testing.T) {
	cfg := testServerConfig()

	srv, err := server.NewControlServer(cfg)
	if err != nil {
		t.Fatalf("NewControlServer() failed: %v", err)
	}

	serverConn, clientConn := net.Pipe()
	defer serverConn.Close()
	defer clientConn.Close()

	done := make(chan struct{})

	go func() {
		srv.HandleConnectionForTest(serverConn)
		close(done)
	}()

	if err := transport.WriteMessage(
		clientConn,
		transport.NewGetDevices(),
	); err != nil {
		t.Fatalf("WriteMessage() failed: %v", err)
	}

	reader := bufio.NewReader(clientConn)

	var response transport.DeviceListMessage

	if err := transport.ReadMessage(reader, &response); err != nil {
		t.Fatalf("ReadMessage() failed: %v", err)
	}

	if response.Type != transport.MessageDeviceList {
		t.Errorf(
			"Type = %q, want %q",
			response.Type,
			transport.MessageDeviceList,
		)
	}

	if len(response.Devices) != 2 {
		t.Fatalf(
			"len(Devices) = %d, want 2",
			len(response.Devices),
		)
	}

	if response.Devices[0].ID != "radio" {
		t.Errorf(
			"Devices[0].ID = %q, want %q",
			response.Devices[0].ID,
			"radio",
		)
	}

	if response.Devices[1].ID != "rotor" {
		t.Errorf(
			"Devices[1].ID = %q, want %q",
			response.Devices[1].ID,
			"rotor",
		)
	}

	if response.Devices[0].DataPort == 0 {
		t.Fatal("radio data port is zero")
	}

	if response.Devices[1].DataPort == 0 {
		t.Fatal("rotor data port is zero")
	}

	clientConn.Close()

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("server connection handler did not terminate")
	}
}

func TestControlServerReconnectCreatesNewSession(t *testing.T) {
	cfg := testServerConfig()

	srv, err := server.NewControlServer(cfg)
	if err != nil {
		t.Fatalf("NewControlServer() failed: %v", err)
	}

	// First connection.
	serverConn1, clientConn1 := net.Pipe()

	done1 := make(chan *server.Session)

	go func() {
		done1 <- srv.HandleConnectionForTest(serverConn1)
	}()

	if err := transport.WriteMessage(
		clientConn1,
		transport.NewHello(),
	); err != nil {
		t.Fatalf("first WriteMessage() failed: %v", err)
	}

	reader1 := bufio.NewReader(clientConn1)

	var response1 transport.HelloResponseMessage

	if err := transport.ReadMessage(reader1, &response1); err != nil {
		t.Fatalf("first ReadMessage() failed: %v", err)
	}

	if response1.Type != transport.MessageHelloResponse {
		t.Errorf(
			"first response Type = %q, want %q",
			response1.Type,
			transport.MessageHelloResponse,
		)
	}

	if err := clientConn1.Close(); err != nil {
		t.Fatalf("close first client connection: %v", err)
	}

	session1 := <-done1

	if session1 == nil {
		t.Fatal("first session is nil")
	}

	if session1.ID() != 1 {
		t.Errorf(
			"first session ID = %d, want 1",
			session1.ID(),
		)
	}

	if !session1.IsClosed() {
		t.Fatal("first session is not closed")
	}

	// Second connection - simulates reconnect.
	serverConn2, clientConn2 := net.Pipe()

	done2 := make(chan *server.Session)

	go func() {
		done2 <- srv.HandleConnectionForTest(serverConn2)
	}()

	if err := transport.WriteMessage(
		clientConn2,
		transport.NewHello(),
	); err != nil {
		t.Fatalf("second WriteMessage() failed: %v", err)
	}

	reader2 := bufio.NewReader(clientConn2)

	var response2 transport.HelloResponseMessage

	if err := transport.ReadMessage(reader2, &response2); err != nil {
		t.Fatalf("second ReadMessage() failed: %v", err)
	}

	if response2.Type != transport.MessageHelloResponse {
		t.Errorf(
			"second response Type = %q, want %q",
			response2.Type,
			transport.MessageHelloResponse,
		)
	}

	if err := clientConn2.Close(); err != nil {
		t.Fatalf("close second client connection: %v", err)
	}

	session2 := <-done2

	if session2 == nil {
		t.Fatal("second session is nil")
	}

	if session2.ID() != 2 {
		t.Errorf(
			"second session ID = %d, want 2",
			session2.ID(),
		)
	}

	if session2.ID() == session1.ID() {
		t.Fatal("reconnect reused the old session ID")
	}

	if !session2.IsClosed() {
		t.Fatal("second session is not closed")
	}
}

///////////////////////////////////////////////////////////////////////////////
// Virtual serial pair
///////////////////////////////////////////////////////////////////////////////

func startVirtualSerialPair(t *testing.T) (string, string, func()) {
	t.Helper()

	if _, err := exec.LookPath("socat"); err != nil {
		t.Skip("socat not installed")
	}

	dir := t.TempDir()

	portA := filepath.Join(dir, "ttyA")
	portB := filepath.Join(dir, "ttyB")

	cmd := exec.Command(
		"socat",
		"-d",
		"-d",
		fmt.Sprintf(
			"pty,raw,echo=0,link=%s",
			portA,
		),
		fmt.Sprintf(
			"pty,raw,echo=0,link=%s",
			portB,
		),
	)

	if err := cmd.Start(); err != nil {
		t.Fatalf("failed to start socat: %v", err)
	}

	cleanup := func() {
		if cmd.Process != nil {
			_ = cmd.Process.Kill()
			_ = cmd.Wait()
		}
	}

	deadline := time.Now().Add(2 * time.Second)

	for {
		_, errA := os.Stat(portA)
		_, errB := os.Stat(portB)

		if errA == nil && errB == nil {
			break
		}

		if time.Now().After(deadline) {
			cleanup()
			t.Fatal("timeout waiting for virtual serial ports")
		}

		time.Sleep(10 * time.Millisecond)
	}

	return portA, portB, cleanup
}

///////////////////////////////////////////////////////////////////////////////
// Read helper
///////////////////////////////////////////////////////////////////////////////

func readExactWithTimeout(
	t *testing.T,
	reader io.Reader,
	buffer []byte,
	timeout time.Duration,
) {
	t.Helper()

	done := make(chan error, 1)

	go func() {
		_, err := io.ReadFull(reader, buffer)
		done <- err
	}()

	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("read failed: %v", err)
		}

	case <-time.After(timeout):
		t.Fatalf("read timeout after %s", timeout)
	}
}

///////////////////////////////////////////////////////////////////////////////
// Data connection integration test
///////////////////////////////////////////////////////////////////////////////

func TestControlServerDataConnection(t *testing.T) {
	portA, portB, cleanup := startVirtualSerialPair(t)
	defer cleanup()

	cfg := &config.ServerConfig{
		Listen: config.ListenConfig{
			Address: "127.0.0.1",
			Port:    5000,
		},
		Devices: []config.DeviceConfig{
			{
				ID:         "radio",
				Name:       "Funkgerät",
				SerialPort: portA,
				BaudRate:   9600,
				DataBits:   8,
				Parity:     "none",
				StopBits:   1,
			},
		},
	}

	srv, err := server.NewControlServer(cfg)
	if err != nil {
		t.Fatalf("NewControlServer() failed: %v", err)
	}

	////////////////////////////////////////////////////////////////////////////
	// Control connection
	////////////////////////////////////////////////////////////////////////////

	serverConn, clientConn := net.Pipe()
	defer serverConn.Close()
	defer clientConn.Close()

	done := make(chan *server.Session)

	go func() {
		done <- srv.HandleConnectionForTest(serverConn)
	}()

	if err := transport.WriteMessage(
		clientConn,
		transport.NewGetDevices(),
	); err != nil {
		t.Fatalf("WriteMessage() failed: %v", err)
	}

	controlReader := bufio.NewReader(clientConn)

	var deviceList transport.DeviceListMessage

	if err := transport.ReadMessage(
		controlReader,
		&deviceList,
	); err != nil {
		t.Fatalf("ReadMessage() failed: %v", err)
	}

	if len(deviceList.Devices) != 1 {
		t.Fatalf(
			"len(Devices) = %d, want 1",
			len(deviceList.Devices),
		)
	}

	if deviceList.Devices[0].ID != "radio" {
		t.Fatalf(
			"device ID = %q, want %q",
			deviceList.Devices[0].ID,
			"radio",
		)
	}

	dataPort := deviceList.Devices[0].DataPort
	if dataPort == 0 {
		t.Fatal("data port is zero")
	}

	////////////////////////////////////////////////////////////////////////////
	// Data connection
	////////////////////////////////////////////////////////////////////////////

	dataConn, err := net.DialTimeout(
		"tcp",
		net.JoinHostPort("127.0.0.1", fmt.Sprintf("%d", dataPort)),
		time.Second,
	)
	if err != nil {
		t.Fatalf("connect data port failed: %v", err)
	}
	defer dataConn.Close()

	////////////////////////////////////////////////////////////////////////////
	// Serial peer
	////////////////////////////////////////////////////////////////////////////

	serialPeer, err := os.OpenFile(
		portB,
		os.O_RDWR,
		0,
	)
	if err != nil {
		t.Fatalf("open serial peer failed: %v", err)
	}
	defer serialPeer.Close()

	////////////////////////////////////////////////////////////////////////////
	// TCP -> Serial
	////////////////////////////////////////////////////////////////////////////

	tcpToSerial := []byte("hello from tcp")

	if _, err := dataConn.Write(tcpToSerial); err != nil {
		t.Fatalf("TCP Write() failed: %v", err)
	}

	serialReceived := make([]byte, len(tcpToSerial))

	readExactWithTimeout(
		t,
		serialPeer,
		serialReceived,
		2*time.Second,
	)

	if string(serialReceived) != string(tcpToSerial) {
		t.Fatalf(
			"serial received %q, want %q",
			string(serialReceived),
			string(tcpToSerial),
		)
	}

	////////////////////////////////////////////////////////////////////////////
	// Serial -> TCP
	////////////////////////////////////////////////////////////////////////////

	serialToTCP := []byte("hello from serial")

	if _, err := serialPeer.Write(serialToTCP); err != nil {
		t.Fatalf("serial Write() failed: %v", err)
	}

	tcpReceived := make([]byte, len(serialToTCP))

	readExactWithTimeout(
		t,
		dataConn,
		tcpReceived,
		2*time.Second,
	)

	if string(tcpReceived) != string(serialToTCP) {
		t.Fatalf(
			"TCP received %q, want %q",
			string(tcpReceived),
			string(serialToTCP),
		)
	}

	////////////////////////////////////////////////////////////////////////////
	// Close data connection
	////////////////////////////////////////////////////////////////////////////

	if err := dataConn.Close(); err != nil {
		t.Fatalf("close data connection failed: %v", err)
	}

	////////////////////////////////////////////////////////////////////////////
	// Close control connection
	////////////////////////////////////////////////////////////////////////////

	if err := clientConn.Close(); err != nil {
		t.Fatalf("close control connection failed: %v", err)
	}

	select {
	case session := <-done:
		if session == nil {
			t.Fatal("server returned nil session")
		}

		if !session.IsClosed() {
			t.Fatal("session is not closed")
		}

	case <-time.After(2 * time.Second):
		t.Fatal("server connection handler did not terminate")
	}
}