package server

import (
	"context"
	"encoding/binary"
	"io"
	"log/slog"
	"net"
	"sync"
	"testing"
	"time"

	"git.wntrmute.dev/kyle/mc-proxy/internal/config"
	"git.wntrmute.dev/kyle/mc-proxy/internal/firewall"
)

// echoServer accepts one connection, copies everything back, then closes.
func echoServer(t *testing.T, ln net.Listener) {
	t.Helper()
	conn, err := ln.Accept()
	if err != nil {
		return
	}
	defer conn.Close()
	io.Copy(conn, conn)
}

// newTestServer creates a Server with the given listener data and no firewall rules.
func newTestServer(t *testing.T, listeners []ListenerData) *Server {
	t.Helper()
	fw, err := firewall.New("", nil, nil, nil)
	if err != nil {
		t.Fatalf("creating firewall: %v", err)
	}
	cfg := &config.Config{
		Proxy: config.Proxy{
			ConnectTimeout:  config.Duration{Duration: 5 * time.Second},
			IdleTimeout:     config.Duration{Duration: 30 * time.Second},
			ShutdownTimeout: config.Duration{Duration: 5 * time.Second},
		},
	}
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	return New(cfg, fw, listeners, logger, "test")
}

// startAndStop starts the server in a goroutine and returns a cancel function
// that shuts it down and waits for it to exit.
func startAndStop(t *testing.T, srv *Server) context.CancelFunc {
	t.Helper()
	ctx, cancel := context.WithCancel(context.Background())
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		if err := srv.Run(ctx); err != nil {
			t.Errorf("server.Run: %v", err)
		}
	}()
	// Give the listeners a moment to bind.
	time.Sleep(50 * time.Millisecond)
	return func() {
		cancel()
		wg.Wait()
	}
}

func TestProxyRoundTrip(t *testing.T) {
	// Start an echo backend.
	backendLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend listen: %v", err)
	}
	defer backendLn.Close()
	go echoServer(t, backendLn)

	// Pick a free port for the proxy listener.
	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"echo.test": backendLn.Addr().String(),
			},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	// Connect through the proxy with a fake ClientHello.
	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("echo.test")
	if _, err := conn.Write(hello); err != nil {
		t.Fatalf("write ClientHello: %v", err)
	}

	// The backend will echo our ClientHello back. Read it.
	echoed := make([]byte, len(hello))
	conn.SetReadDeadline(time.Now().Add(5 * time.Second))
	if _, err := io.ReadFull(conn, echoed); err != nil {
		t.Fatalf("read echoed data: %v", err)
	}

	// Send some additional data.
	payload := []byte("hello from client")
	if _, err := conn.Write(payload); err != nil {
		t.Fatalf("write payload: %v", err)
	}

	buf := make([]byte, len(payload))
	if _, err := io.ReadFull(conn, buf); err != nil {
		t.Fatalf("read echoed payload: %v", err)
	}
	if string(buf) != string(payload) {
		t.Fatalf("got %q, want %q", buf, payload)
	}
}

func TestNoRouteResets(t *testing.T) {
	// Proxy listener with no routes for the requested hostname.
	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"other.test": "127.0.0.1:1", // exists but won't match
			},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("unknown.test")
	if _, err := conn.Write(hello); err != nil {
		t.Fatalf("write ClientHello: %v", err)
	}

	// The proxy should close the connection (no route match).
	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	_, err = conn.Read(make([]byte, 1))
	if err == nil {
		t.Fatal("expected connection to be closed, but read succeeded")
	}
}

func TestFirewallBlocks(t *testing.T) {
	// Start a backend that should never be reached.
	backendLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend listen: %v", err)
	}
	defer backendLn.Close()

	reached := make(chan struct{}, 1)
	go func() {
		conn, err := backendLn.Accept()
		if err != nil {
			return
		}
		conn.Close()
		reached <- struct{}{}
	}()

	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	// Create a firewall that blocks 127.0.0.1 (the test client).
	fw, err := firewall.New("", []string{"127.0.0.1"}, nil, nil)
	if err != nil {
		t.Fatalf("creating firewall: %v", err)
	}

	cfg := &config.Config{
		Proxy: config.Proxy{
			ConnectTimeout:  config.Duration{Duration: 5 * time.Second},
			IdleTimeout:     config.Duration{Duration: 30 * time.Second},
			ShutdownTimeout: config.Duration{Duration: 5 * time.Second},
		},
	}
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	srv := New(cfg, fw, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"echo.test": backendLn.Addr().String(),
			},
		},
	}, logger, "test")

	ctx, cancel := context.WithCancel(context.Background())
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		srv.Run(ctx)
	}()
	time.Sleep(50 * time.Millisecond)

	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("echo.test")
	conn.Write(hello)

	// Connection should be closed (blocked by firewall).
	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	_, err = conn.Read(make([]byte, 1))
	if err == nil {
		t.Fatal("expected connection to be closed by firewall")
	}

	// Backend should not have been reached.
	select {
	case <-reached:
		t.Fatal("backend was reached despite firewall block")
	case <-time.After(200 * time.Millisecond):
		// Expected.
	}

	cancel()
	wg.Wait()
}

func TestNotTLSResets(t *testing.T) {
	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:     1,
			Addr:   proxyAddr,
			Routes: map[string]string{"x.test": "127.0.0.1:1"},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	// Send HTTP, not TLS.
	conn.Write([]byte("GET / HTTP/1.1\r\nHost: x.test\r\n\r\n"))

	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	_, err = conn.Read(make([]byte, 1))
	if err == nil {
		t.Fatal("expected connection to be closed for non-TLS data")
	}
}

func TestConnectionTracking(t *testing.T) {
	// Backend that holds connections open until we close it.
	backendLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend listen: %v", err)
	}
	defer backendLn.Close()

	var backendConns []net.Conn
	var mu sync.Mutex
	go func() {
		for {
			conn, err := backendLn.Accept()
			if err != nil {
				return
			}
			mu.Lock()
			backendConns = append(backendConns, conn)
			mu.Unlock()
			// Hold connection open, drain input.
			go io.Copy(io.Discard, conn)
		}
	}()

	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"conn.test": backendLn.Addr().String(),
			},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	if got := srv.TotalConnections(); got != 0 {
		t.Fatalf("expected 0 connections before any clients, got %d", got)
	}

	// Open two connections through the proxy.
	var clientConns []net.Conn
	for i := range 2 {
		conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
		if err != nil {
			t.Fatalf("dial proxy %d: %v", i, err)
		}
		hello := buildClientHello("conn.test")
		if _, err := conn.Write(hello); err != nil {
			t.Fatalf("write ClientHello %d: %v", i, err)
		}
		clientConns = append(clientConns, conn)
	}

	// Give connections time to be established.
	time.Sleep(100 * time.Millisecond)

	if got := srv.TotalConnections(); got != 2 {
		t.Fatalf("expected 2 active connections, got %d", got)
	}

	// Close one client and its corresponding backend connection.
	clientConns[0].Close()
	mu.Lock()
	if len(backendConns) > 0 {
		backendConns[0].Close()
	}
	mu.Unlock()

	// Wait for the relay goroutines to detect the close.
	deadline := time.Now().Add(5 * time.Second)
	for time.Now().Before(deadline) {
		if srv.TotalConnections() == 1 {
			break
		}
		time.Sleep(50 * time.Millisecond)
	}
	if got := srv.TotalConnections(); got != 1 {
		t.Fatalf("expected 1 active connection after closing one, got %d", got)
	}

	// Clean up.
	clientConns[1].Close()
	mu.Lock()
	for _, c := range backendConns {
		c.Close()
	}
	mu.Unlock()
}

func TestMultipleListeners(t *testing.T) {
	// Two backends.
	backendA, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend A listen: %v", err)
	}
	defer backendA.Close()

	backendB, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend B listen: %v", err)
	}
	defer backendB.Close()

	// Each backend writes its identity and closes.
	serve := func(ln net.Listener, id string) {
		conn, err := ln.Accept()
		if err != nil {
			return
		}
		defer conn.Close()
		// Drain the incoming data, then write identity.
		go io.Copy(io.Discard, conn)
		conn.Write([]byte(id))
	}
	go serve(backendA, "A")
	go serve(backendB, "B")

	// Two proxy listeners, same hostname, different backends.
	ln1, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port 1: %v", err)
	}
	addr1 := ln1.Addr().String()
	ln1.Close()

	ln2, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port 2: %v", err)
	}
	addr2 := ln2.Addr().String()
	ln2.Close()

	srv := newTestServer(t, []ListenerData{
		{ID: 1, Addr: addr1, Routes: map[string]string{"svc.test": backendA.Addr().String()}},
		{ID: 2, Addr: addr2, Routes: map[string]string{"svc.test": backendB.Addr().String()}},
	})

	stop := startAndStop(t, srv)
	defer stop()

	readID := func(proxyAddr string) string {
		t.Helper()
		conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
		if err != nil {
			t.Fatalf("dial %s: %v", proxyAddr, err)
		}
		defer conn.Close()

		hello := buildClientHello("svc.test")
		conn.Write(hello)

		conn.SetReadDeadline(time.Now().Add(5 * time.Second))
		buf := make([]byte, 128)
		// Read what the backend sends back: echoed ClientHello + ID.
		// The backend drains input and writes the ID, so we read until we
		// find the ID byte at the end.
		var all []byte
		for {
			n, err := conn.Read(buf)
			all = append(all, buf[:n]...)
			if err != nil {
				break
			}
		}
		if len(all) == 0 {
			t.Fatalf("no data from %s", proxyAddr)
		}
		// The ID is the last byte.
		return string(all[len(all)-1:])
	}

	idA := readID(addr1)
	idB := readID(addr2)

	if idA != "A" {
		t.Fatalf("listener 1: got backend %q, want A", idA)
	}
	if idB != "B" {
		t.Fatalf("listener 2: got backend %q, want B", idB)
	}
}

func TestCaseInsensitiveRouting(t *testing.T) {
	backendLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend listen: %v", err)
	}
	defer backendLn.Close()
	go echoServer(t, backendLn)

	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"echo.test": backendLn.Addr().String(),
			},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	// SNI extraction lowercases the hostname, so "ECHO.TEST" should match
	// the route for "echo.test".
	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("ECHO.TEST")
	if _, err := conn.Write(hello); err != nil {
		t.Fatalf("write ClientHello: %v", err)
	}

	echoed := make([]byte, len(hello))
	conn.SetReadDeadline(time.Now().Add(5 * time.Second))
	if _, err := io.ReadFull(conn, echoed); err != nil {
		t.Fatalf("read echoed data: %v", err)
	}
}

func TestBackendUnreachable(t *testing.T) {
	// Find a port that nothing is listening on.
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	deadAddr := ln.Addr().String()
	ln.Close()

	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	srv := newTestServer(t, []ListenerData{
		{
			ID:   1,
			Addr: proxyAddr,
			Routes: map[string]string{
				"dead.test": deadAddr,
			},
		},
	})

	stop := startAndStop(t, srv)
	defer stop()

	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("dead.test")
	conn.Write(hello)

	// Proxy should close the connection after failing to dial backend.
	conn.SetReadDeadline(time.Now().Add(5 * time.Second))
	_, err = conn.Read(make([]byte, 1))
	if err == nil {
		t.Fatal("expected connection to be closed when backend is unreachable")
	}
}

func TestGracefulShutdown(t *testing.T) {
	// Backend that holds the connection open.
	backendLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("backend listen: %v", err)
	}
	defer backendLn.Close()

	go func() {
		conn, err := backendLn.Accept()
		if err != nil {
			return
		}
		defer conn.Close()
		io.Copy(io.Discard, conn)
	}()

	proxyLn, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("finding free port: %v", err)
	}
	proxyAddr := proxyLn.Addr().String()
	proxyLn.Close()

	fw, err := firewall.New("", nil, nil, nil)
	if err != nil {
		t.Fatalf("creating firewall: %v", err)
	}
	cfg := &config.Config{
		Proxy: config.Proxy{
			ConnectTimeout:  config.Duration{Duration: 5 * time.Second},
			IdleTimeout:     config.Duration{Duration: 30 * time.Second},
			ShutdownTimeout: config.Duration{Duration: 2 * time.Second},
		},
	}
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	srv := New(cfg, fw, []ListenerData{
		{ID: 1, Addr: proxyAddr, Routes: map[string]string{"hold.test": backendLn.Addr().String()}},
	}, logger, "test")

	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- srv.Run(ctx)
	}()
	time.Sleep(50 * time.Millisecond)

	// Establish a connection that will be in-flight during shutdown.
	conn, err := net.DialTimeout("tcp", proxyAddr, 2*time.Second)
	if err != nil {
		t.Fatalf("dial proxy: %v", err)
	}
	defer conn.Close()

	hello := buildClientHello("hold.test")
	conn.Write(hello)
	time.Sleep(50 * time.Millisecond)

	// Trigger shutdown.
	cancel()

	// Server should exit within the shutdown timeout.
	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("server.Run returned error: %v", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("server did not shut down within 5 seconds")
	}
}

func TestListenerStateRoutes(t *testing.T) {
	ls := &ListenerState{
		ID:   1,
		Addr: ":443",
		routes: map[string]string{
			"a.test": "127.0.0.1:1",
		},
	}

	// AddRoute
	if err := ls.AddRoute("b.test", "127.0.0.1:2"); err != nil {
		t.Fatalf("AddRoute: %v", err)
	}

	// AddRoute duplicate
	if err := ls.AddRoute("b.test", "127.0.0.1:3"); err == nil {
		t.Fatal("expected error for duplicate route")
	}

	// Routes snapshot
	routes := ls.Routes()
	if len(routes) != 2 {
		t.Fatalf("expected 2 routes, got %d", len(routes))
	}

	// RemoveRoute
	if err := ls.RemoveRoute("a.test"); err != nil {
		t.Fatalf("RemoveRoute: %v", err)
	}

	// RemoveRoute not found
	if err := ls.RemoveRoute("nonexistent.test"); err == nil {
		t.Fatal("expected error for removing nonexistent route")
	}

	routes = ls.Routes()
	if len(routes) != 1 {
		t.Fatalf("expected 1 route, got %d", len(routes))
	}
	if routes["b.test"] != "127.0.0.1:2" {
		t.Fatalf("expected b.test → 127.0.0.1:2, got %q", routes["b.test"])
	}
}

// --- ClientHello builder helpers (mirrors internal/sni test helpers) ---

func buildClientHello(serverName string) []byte {
	return buildClientHelloWithExtensions(sniExtension(serverName))
}

func buildClientHelloWithExtensions(extensions []byte) []byte {
	var hello []byte

	hello = append(hello, 0x03, 0x03)          // TLS 1.2
	hello = append(hello, make([]byte, 32)...)  // random
	hello = append(hello, 0x00)                 // session ID: empty
	hello = append(hello, 0x00, 0x02, 0x00, 0x9C) // cipher suites
	hello = append(hello, 0x01, 0x00)           // compression methods

	if len(extensions) > 0 {
		hello = binary.BigEndian.AppendUint16(hello, uint16(len(extensions)))
		hello = append(hello, extensions...)
	}

	handshake := []byte{0x01, 0x00, 0x00, 0x00}
	handshake[1] = byte(len(hello) >> 16)
	handshake[2] = byte(len(hello) >> 8)
	handshake[3] = byte(len(hello))
	handshake = append(handshake, hello...)

	record := []byte{0x16, 0x03, 0x01}
	record = binary.BigEndian.AppendUint16(record, uint16(len(handshake)))
	record = append(record, handshake...)

	return record
}

func sniExtension(serverName string) []byte {
	name := []byte(serverName)

	var entry []byte
	entry = append(entry, 0x00)
	entry = binary.BigEndian.AppendUint16(entry, uint16(len(name)))
	entry = append(entry, name...)

	var list []byte
	list = binary.BigEndian.AppendUint16(list, uint16(len(entry)))
	list = append(list, entry...)

	var ext []byte
	ext = binary.BigEndian.AppendUint16(ext, 0x0000)
	ext = binary.BigEndian.AppendUint16(ext, uint16(len(list)))
	ext = append(ext, list...)

	return ext
}