package starssh

import (
	"context"
	"io"
	"net"
	"sync/atomic"
	"testing"
	"time"

	"golang.org/x/crypto/ssh"
)

func TestStartLocalForwardUsesExistingConnectionByDefault(t *testing.T) {
	oldDialSSHClient := dialSSHClient
	oldNewDetachedForwardClient := newDetachedForwardClient
	oldCloseSSHClient := closeSSHClient
	t.Cleanup(func() {
		dialSSHClient = oldDialSSHClient
		newDetachedForwardClient = oldNewDetachedForwardClient
		closeSSHClient = oldCloseSSHClient
	})

	baseClient := &ssh.Client{}
	star := &StarSSH{}
	star.setTransport(baseClient, nil)

	var detachedCalls atomic.Int32
	newDetachedForwardClient = func(ctx context.Context, input LoginInput) (*StarSSH, error) {
		detachedCalls.Add(1)
		return nil, nil
	}

	dialSSHClient = func(ctx context.Context, client *ssh.Client, network, address string) (net.Conn, error) {
		if client != baseClient {
			t.Errorf("expected existing ssh client, got %p want %p", client, baseClient)
		}
		serverConn, clientConn := net.Pipe()
		go echoForwardPipe(serverConn)
		return clientConn, nil
	}

	closeSSHClient = func(client sshClientRequester) error {
		t.Fatal("default local forward should not close the main ssh client")
		return nil
	}

	forwarder, err := star.StartLocalForward(ForwardRequest{
		ListenAddr: "127.0.0.1:0",
		TargetAddr: "example.internal:22",
	})
	if err != nil {
		t.Fatalf("start local forward: %v", err)
	}
	defer forwarder.Close()

	reply := exerciseForwarder(t, forwarder.Addr().String(), []byte("ping"))
	if string(reply) != "ping" {
		t.Fatalf("unexpected forwarded reply: %q", string(reply))
	}
	if detachedCalls.Load() != 0 {
		t.Fatalf("default local forward should not create detached ssh client, calls=%d", detachedCalls.Load())
	}
}

func TestStartLocalForwardDetachedUsesSeparateConnection(t *testing.T) {
	oldDialSSHClient := dialSSHClient
	oldNewDetachedForwardClient := newDetachedForwardClient
	oldCloseSSHClient := closeSSHClient
	t.Cleanup(func() {
		dialSSHClient = oldDialSSHClient
		newDetachedForwardClient = oldNewDetachedForwardClient
		closeSSHClient = oldCloseSSHClient
	})

	baseClient := &ssh.Client{}
	detachedClient := &ssh.Client{}
	star := &StarSSH{LoginInfo: LoginInput{User: "tester", Addr: "127.0.0.1"}}
	star.setTransport(baseClient, nil)

	forwardClient := &StarSSH{}
	forwardClient.setTransport(detachedClient, nil)

	var detachedCalls atomic.Int32
	newDetachedForwardClient = func(ctx context.Context, input LoginInput) (*StarSSH, error) {
		detachedCalls.Add(1)
		return forwardClient, nil
	}

	dialSSHClient = func(ctx context.Context, client *ssh.Client, network, address string) (net.Conn, error) {
		if client != detachedClient {
			t.Errorf("expected detached ssh client, got %p want %p", client, detachedClient)
		}
		serverConn, clientConn := net.Pipe()
		go echoForwardPipe(serverConn)
		return clientConn, nil
	}

	var closeCalls atomic.Int32
	closeSSHClient = func(client sshClientRequester) error {
		closeCalls.Add(1)
		return nil
	}

	forwarder, err := star.StartLocalForwardDetached(ForwardRequest{
		ListenAddr: "127.0.0.1:0",
		TargetAddr: "example.internal:22",
	})
	if err != nil {
		t.Fatalf("start detached local forward: %v", err)
	}

	reply := exerciseForwarder(t, forwarder.Addr().String(), []byte("pong"))
	if string(reply) != "pong" {
		t.Fatalf("unexpected detached forwarded reply: %q", string(reply))
	}

	if err := forwarder.Close(); err != nil {
		t.Fatalf("close detached local forward: %v", err)
	}
	if detachedCalls.Load() != 1 {
		t.Fatalf("expected one detached ssh login, got %d", detachedCalls.Load())
	}
	if closeCalls.Load() != 1 {
		t.Fatalf("expected detached ssh client cleanup once, got %d", closeCalls.Load())
	}
	if got := star.snapshotSSHClient(); got != baseClient {
		t.Fatal("detached local forward should not detach the main ssh client")
	}
	if got := forwardClient.snapshotSSHClient(); got != nil {
		t.Fatal("detached local forward should close its detached ssh client")
	}
}

func echoForwardPipe(conn net.Conn) {
	defer conn.Close()
	buf := make([]byte, 4096)
	n, err := conn.Read(buf)
	if err != nil {
		return
	}
	_, _ = conn.Write(buf[:n])
}

func exerciseForwarder(t *testing.T, addr string, payload []byte) []byte {
	t.Helper()

	conn, err := net.DialTimeout("tcp", addr, time.Second)
	if err != nil {
		t.Fatalf("dial forward listener: %v", err)
	}
	defer conn.Close()
	_ = conn.SetDeadline(time.Now().Add(2 * time.Second))

	if _, err := conn.Write(payload); err != nil {
		t.Fatalf("write forwarded payload: %v", err)
	}

	reply := make([]byte, len(payload))
	if _, err := io.ReadFull(conn, reply); err != nil {
		t.Fatalf("read forwarded reply: %v", err)
	}
	return reply
}