package testenv

import (
	"bytes"
	"context"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/asn1"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"math/big"
	"math/bits"
	"net"
	"net/url"
	"os"
	"os/signal"
	"path"
	"path/filepath"
	"runtime"
	"strconv"
	"sync"
	"syscall"
	"testing"
	"time"

	"github.com/pomerium/pomerium/config"
	"github.com/pomerium/pomerium/config/envoyconfig/filemgr"
	"github.com/pomerium/pomerium/internal/log"
	"github.com/pomerium/pomerium/internal/testenv/values"
	"github.com/pomerium/pomerium/pkg/cmd/pomerium"
	"github.com/pomerium/pomerium/pkg/grpc/databroker"
	"github.com/pomerium/pomerium/pkg/health"
	"github.com/pomerium/pomerium/pkg/netutil"
	"github.com/pomerium/pomerium/pkg/slices"
	"github.com/rs/zerolog"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"golang.org/x/sync/errgroup"
	"google.golang.org/grpc/grpclog"
)

// Environment is a lightweight integration test fixture that runs Pomerium
// in-process.
type Environment interface {
	// Context returns the environment's root context. This context holds a
	// top-level logger scoped to this environment. It will be canceled when
	// Stop() is called, or during test cleanup.
	Context() context.Context

	Assert() *assert.Assertions
	Require() *require.Assertions

	// TempDir returns a unique temp directory for this context. Calling this
	// function multiple times returns the same path.
	TempDir() string
	// CACert returns the test environment's root CA certificate and private key.
	CACert() *tls.Certificate
	// ServerCAs returns a new [*x509.CertPool] containing the root CA certificate
	// used to sign the server cert and other test certificates.
	ServerCAs() *x509.CertPool
	// ServerCert returns the Pomerium server's certificate and private key.
	ServerCert() *tls.Certificate
	// NewClientCert generates a new client certificate signed by the root CA
	// certificate. One or more optional templates can be given, which can be
	// used to set or override certain parameters when creating a certificate,
	// including subject, SANs, or extensions. If more than one template is
	// provided, they will be applied in order from left to right.
	//
	// By default (unless overridden in a template), the certificate will have
	// its Common Name set to the file:line string of the call site. Calls to
	// NewClientCert() on different lines will have different subjects. If
	// multiple certs with the same subject are needed, wrap the call to this
	// function in another helper function, or separate calls with commas on the
	// same line.
	NewClientCert(templateOverrides ...*x509.Certificate) *Certificate

	NewServerCert(templateOverrides ...*x509.Certificate) *Certificate

	AuthenticateURL() values.Value[string]
	DatabrokerURL() values.Value[string]
	Ports() Ports
	SharedSecret() []byte
	CookieSecret() []byte

	// Add adds the given [Modifier] to the environment. All modifiers will be
	// invoked upon calling Start() to apply individual modifications to the
	// configuration before starting the Pomerium server.
	Add(m Modifier)
	// AddTask adds the given [Task] to the environment. All tasks will be
	// started in separate goroutines upon calling Start(). If any tasks exit
	// with an error, the environment will be stopped and the test will fail.
	AddTask(r Task)
	// AddUpstream adds the given [Upstream] to the environment. This function is
	// equivalent to calling both Add() and AddTask() with the upstream, but
	// improves readability.
	AddUpstream(u Upstream)

	// Start starts the test environment, and adds a call to Stop() as a cleanup
	// hook to the environment's [testing.T]. All previously added [Modifier]
	// instances are invoked in order to build the configuration, and all
	// previously added [Task] instances are started in the background.
	//
	// Calling Start() more than once, Calling Start() after Stop(), or calling
	// any of the Add* functions after Start() will panic.
	Start()
	// Stop stops the test environment. Calling this function more than once has
	// no effect. It is usually not necessary to call Stop() directly unless you
	// need to stop the test environment before the test is completed.
	Stop()
	// Pause will block and wait until SIGINT is received, then continue. This
	// has the same effect as if the test failed and the PauseOnFailure option was
	// given, but can be called at any time.
	Pause()

	// SubdomainURL returns a string [values.Value] which will contain a complete
	// URL for the given subdomain of the server's domain (given by its serving
	// certificate), including the 'https://' scheme and random http server port.
	// This value will only be resolved some time after Start() is called, and
	// can be used as the 'from' value for routes.
	SubdomainURL(subdomain string) values.Value[string]

	// NewLogRecorder returns a new [*LogRecorder] and starts capturing logs for
	// the Pomerium server and Envoy.
	NewLogRecorder(opts ...LogRecorderOption) *LogRecorder

	// OnStateChanged registers a callback to be invoked when the environment's
	// state changes to the given state. The callback is invoked in a separate
	// goroutine.
	OnStateChanged(state EnvironmentState, callback func())
}

type Certificate tls.Certificate

func (c *Certificate) Fingerprint() string {
	sum := sha256.Sum256(c.Leaf.Raw)
	return hex.EncodeToString(sum[:])
}

func (c *Certificate) SPKIHash() string {
	sum := sha256.Sum256(c.Leaf.RawSubjectPublicKeyInfo)
	return base64.StdEncoding.EncodeToString(sum[:])
}

type EnvironmentState uint32

const NotRunning EnvironmentState = 0

const (
	Starting EnvironmentState = 1 << iota
	Running
	Stopping
	Stopped
)

func (e EnvironmentState) String() string {
	switch e {
	case NotRunning:
		return "NotRunning"
	case Starting:
		return "Starting"
	case Running:
		return "Running"
	case Stopping:
		return "Stopping"
	case Stopped:
		return "Stopped"
	default:
		return fmt.Sprintf("EnvironmentState(%d)", e)
	}
}

type environment struct {
	EnvironmentOptions
	t               testing.TB
	assert          *assert.Assertions
	require         *require.Assertions
	tempDir         string
	domain          string
	ports           Ports
	sharedSecret    [32]byte
	cookieSecret    [32]byte
	workspaceFolder string
	silent          bool

	ctx         context.Context
	cancel      context.CancelCauseFunc
	cleanupOnce sync.Once
	logWriter   *log.MultiWriter

	mods         []WithCaller[Modifier]
	tasks        []WithCaller[Task]
	taskErrGroup *errgroup.Group

	stateMu              sync.Mutex
	state                EnvironmentState
	stateChangeListeners map[EnvironmentState][]func()

	src *configSource
}

type EnvironmentOptions struct {
	debug          bool
	pauseOnFailure bool
	forceSilent    bool
}

type EnvironmentOption func(*EnvironmentOptions)

func (o *EnvironmentOptions) apply(opts ...EnvironmentOption) {
	for _, op := range opts {
		op(o)
	}
}

func Debug(enable ...bool) EnvironmentOption {
	if len(enable) == 0 {
		enable = append(enable, true)
	}
	return func(o *EnvironmentOptions) {
		o.debug = enable[0]
	}
}

func PauseOnFailure(enable ...bool) EnvironmentOption {
	if len(enable) == 0 {
		enable = append(enable, true)
	}
	return func(o *EnvironmentOptions) {
		o.pauseOnFailure = enable[0]
	}
}

func Silent(silent ...bool) EnvironmentOption {
	if len(silent) == 0 {
		silent = append(silent, true)
	}
	return func(o *EnvironmentOptions) {
		o.forceSilent = silent[0]
	}
}

var setGrpcLoggerOnce sync.Once

func New(t testing.TB, opts ...EnvironmentOption) Environment {
	if runtime.GOOS != "linux" {
		t.Skip("test environment only supported on linux")
	}
	options := EnvironmentOptions{}
	options.apply(opts...)
	if testing.Short() {
		t.Helper()
		t.Skip("test environment disabled in short mode")
	}
	databroker.DebugUseFasterBackoff.Store(true)
	workspaceFolder, err := os.Getwd()
	require.NoError(t, err)
	for {
		if _, err := os.Stat(filepath.Join(workspaceFolder, ".git")); err == nil {
			break
		}
		workspaceFolder = filepath.Dir(workspaceFolder)
		if workspaceFolder == "/" {
			panic("could not find workspace root")
		}
	}
	workspaceFolder, err = filepath.Abs(workspaceFolder)
	require.NoError(t, err)

	writer := log.NewMultiWriter()
	silent := options.forceSilent || isSilent(t)
	if silent {
		// this sets the global zap level to fatal, then resets the global zerolog
		// level to debug
		log.SetLevel(zerolog.FatalLevel)
		zerolog.SetGlobalLevel(zerolog.DebugLevel)
	} else {
		log.SetLevel(zerolog.InfoLevel)
		writer.Add(os.Stdout)
	}
	log.DebugDisableGlobalWarnings.Store(silent)
	log.DebugDisableGlobalMessages.Store(silent)
	log.DebugDisableZapLogger.Store(silent)
	setGrpcLoggerOnce.Do(func() {
		grpclog.SetLoggerV2(grpclog.NewLoggerV2WithVerbosity(io.Discard, io.Discard, io.Discard, 0))
	})
	logger := zerolog.New(writer).With().Timestamp().Logger().Level(zerolog.DebugLevel)

	ctx, cancel := context.WithCancelCause(logger.WithContext(context.Background()))
	taskErrGroup, ctx := errgroup.WithContext(ctx)

	e := &environment{
		EnvironmentOptions: options,
		t:                  t,
		assert:             assert.New(t),
		require:            require.New(t),
		tempDir:            t.TempDir(),
		ports: Ports{
			ProxyHTTP:    values.Deferred[int](),
			ProxyGRPC:    values.Deferred[int](),
			ProxyMetrics: values.Deferred[int](),
			GRPC:         values.Deferred[int](),
			HTTP:         values.Deferred[int](),
			Outbound:     values.Deferred[int](),
			Metrics:      values.Deferred[int](),
			Debug:        values.Deferred[int](),
			ALPN:         values.Deferred[int](),
		},
		workspaceFolder: workspaceFolder,
		silent:          silent,
		ctx:             ctx,
		cancel:          cancel,
		logWriter:       writer,
		taskErrGroup:    taskErrGroup,
	}
	_, err = rand.Read(e.sharedSecret[:])
	require.NoError(t, err)
	_, err = rand.Read(e.cookieSecret[:])
	require.NoError(t, err)

	health.SetProvider(e)

	require.NoError(t, os.Mkdir(filepath.Join(e.tempDir, "certs"), 0o777))
	copyFile := func(src, dstRel string) {
		data, err := os.ReadFile(src)
		require.NoError(t, err)
		require.NoError(t, os.WriteFile(filepath.Join(e.tempDir, dstRel), data, 0o600))
	}

	certsToCopy := []string{
		"trusted.pem",
		"trusted-key.pem",
		"ca.pem",
		"ca-key.pem",
	}
	for _, crt := range certsToCopy {
		copyFile(filepath.Join(workspaceFolder, "integration/tpl/files", crt), filepath.Join("certs/", filepath.Base(crt)))
	}
	e.domain = wildcardDomain(e.ServerCert().Leaf.DNSNames)

	return e
}

func (e *environment) debugf(format string, args ...any) {
	if !e.debug {
		return
	}

	e.t.Logf("\x1b[34m[debug] "+format+"\x1b[0m", args...)
}

type WithCaller[T any] struct {
	Caller string
	Value  T
}

type Ports struct {
	ProxyHTTP    values.MutableValue[int]
	ProxyGRPC    values.MutableValue[int]
	ProxyMetrics values.MutableValue[int]
	GRPC         values.MutableValue[int]
	HTTP         values.MutableValue[int]
	Outbound     values.MutableValue[int]
	Metrics      values.MutableValue[int]
	Debug        values.MutableValue[int]
	ALPN         values.MutableValue[int]
}

func (e *environment) TempDir() string {
	return e.tempDir
}

func (e *environment) Context() context.Context {
	return ContextWithEnv(e.ctx, e)
}

func (e *environment) Assert() *assert.Assertions {
	return e.assert
}

func (e *environment) Require() *require.Assertions {
	return e.require
}

func (e *environment) SubdomainURL(subdomain string) values.Value[string] {
	return values.Bind(e.ports.ProxyHTTP, func(port int) string {
		return fmt.Sprintf("https://%s.%s:%d", subdomain, e.domain, port)
	})
}

func (e *environment) AuthenticateURL() values.Value[string] {
	return e.SubdomainURL("authenticate")
}

func (e *environment) DatabrokerURL() values.Value[string] {
	return values.Bind(e.ports.Outbound, func(port int) string {
		return fmt.Sprintf("127.0.0.1:%d", port)
	})
}

func (e *environment) Ports() Ports {
	return e.ports
}

func (e *environment) CACert() *tls.Certificate {
	caCert, err := tls.LoadX509KeyPair(
		filepath.Join(e.tempDir, "certs", "ca.pem"),
		filepath.Join(e.tempDir, "certs", "ca-key.pem"),
	)
	require.NoError(e.t, err)
	return &caCert
}

func (e *environment) ServerCAs() *x509.CertPool {
	pool := x509.NewCertPool()
	caCert, err := os.ReadFile(filepath.Join(e.tempDir, "certs", "ca.pem"))
	require.NoError(e.t, err)
	pool.AppendCertsFromPEM(caCert)
	return pool
}

func (e *environment) ServerCert() *tls.Certificate {
	serverCert, err := tls.LoadX509KeyPair(
		filepath.Join(e.tempDir, "certs", "trusted.pem"),
		filepath.Join(e.tempDir, "certs", "trusted-key.pem"),
	)
	require.NoError(e.t, err)
	return &serverCert
}

// Used as the context's cancel cause during normal cleanup
var ErrCauseTestCleanup = errors.New("test cleanup")

// Used as the context's cancel cause when Stop() is called
var ErrCauseManualStop = errors.New("Stop() called")

func (e *environment) Start() {
	e.debugf("Start()")
	e.advanceState(Starting)
	e.t.Cleanup(e.cleanup)
	e.t.Setenv("TMPDIR", e.TempDir())
	e.debugf("temp dir: %s", e.TempDir())

	cfg := &config.Config{
		Options: config.NewDefaultOptions(),
	}
	ports, err := netutil.AllocatePorts(9)
	require.NoError(e.t, err)
	atoi := func(str string) int {
		p, err := strconv.Atoi(str)
		if err != nil {
			panic(err)
		}
		return p
	}
	e.ports.ProxyHTTP.Resolve(atoi(ports[0]))
	e.ports.ProxyGRPC.Resolve(atoi(ports[1]))
	e.ports.ProxyMetrics.Resolve(atoi(ports[2]))
	e.ports.GRPC.Resolve(atoi(ports[3]))
	e.ports.HTTP.Resolve(atoi(ports[4]))
	e.ports.Outbound.Resolve(atoi(ports[5]))
	e.ports.Metrics.Resolve(atoi(ports[6]))
	e.ports.Debug.Resolve(atoi(ports[7]))
	e.ports.ALPN.Resolve(atoi(ports[8]))
	cfg.AllocatePorts(*(*[6]string)(ports[3:]))

	cfg.Options.AutocertOptions = config.AutocertOptions{Enable: false}
	cfg.Options.Services = "all"
	cfg.Options.LogLevel = config.LogLevelDebug
	cfg.Options.ProxyLogLevel = config.LogLevelInfo
	cfg.Options.Addr = fmt.Sprintf("127.0.0.1:%d", e.ports.ProxyHTTP.Value())
	cfg.Options.GRPCAddr = fmt.Sprintf("127.0.0.1:%d", e.ports.ProxyGRPC.Value())
	cfg.Options.MetricsAddr = fmt.Sprintf("127.0.0.1:%d", e.ports.ProxyMetrics.Value())
	cfg.Options.CAFile = filepath.Join(e.tempDir, "certs", "ca.pem")
	cfg.Options.CertFile = filepath.Join(e.tempDir, "certs", "trusted.pem")
	cfg.Options.KeyFile = filepath.Join(e.tempDir, "certs", "trusted-key.pem")
	cfg.Options.AuthenticateURLString = e.AuthenticateURL().Value()
	cfg.Options.DataBrokerStorageType = "memory"
	cfg.Options.SharedKey = base64.StdEncoding.EncodeToString(e.sharedSecret[:])
	cfg.Options.CookieSecret = base64.StdEncoding.EncodeToString(e.cookieSecret[:])
	cfg.Options.AccessLogFields = []log.AccessLogField{
		log.AccessLogFieldAuthority,
		log.AccessLogFieldDuration,
		log.AccessLogFieldForwardedFor,
		log.AccessLogFieldIP,
		log.AccessLogFieldMethod,
		log.AccessLogFieldPath,
		log.AccessLogFieldQuery,
		log.AccessLogFieldReferer,
		log.AccessLogFieldRequestID,
		log.AccessLogFieldResponseCode,
		log.AccessLogFieldResponseCodeDetails,
		log.AccessLogFieldSize,
		log.AccessLogFieldUpstreamCluster,
		log.AccessLogFieldUserAgent,
		log.AccessLogFieldClientCertificate,
	}

	e.src = &configSource{cfg: cfg}
	e.AddTask(TaskFunc(func(ctx context.Context) error {
		fileMgr := filemgr.NewManager(filemgr.WithCacheDir(filepath.Join(e.TempDir(), "cache")))
		for _, mod := range e.mods {
			mod.Value.Modify(cfg)
			require.NoError(e.t, cfg.Options.Validate(), "invoking modifier resulted in an invalid configuration:\nadded by: "+mod.Caller)
		}
		return pomerium.Run(ctx, e.src, pomerium.WithOverrideFileManager(fileMgr))
	}))

	for i, task := range e.tasks {
		log.Ctx(e.ctx).Debug().Str("caller", task.Caller).Msgf("starting task %d", i)
		e.taskErrGroup.Go(func() error {
			defer log.Ctx(e.ctx).Debug().Str("caller", task.Caller).Msgf("task %d exited", i)
			return task.Value.Run(e.ctx)
		})
	}

	runtime.Gosched()

	e.advanceState(Running)
}

func (e *environment) NewClientCert(templateOverrides ...*x509.Certificate) *Certificate {
	caCert := e.CACert()

	priv, err := rsa.GenerateKey(rand.Reader, 2048)
	require.NoError(e.t, err)

	sn, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	require.NoError(e.t, err)
	now := time.Now()
	tmpl := &x509.Certificate{
		SerialNumber: sn,
		Subject: pkix.Name{
			CommonName: getCaller(),
		},
		NotBefore: now,
		NotAfter:  now.Add(12 * time.Hour),
		KeyUsage:  x509.KeyUsageDigitalSignature,
		ExtKeyUsage: []x509.ExtKeyUsage{
			x509.ExtKeyUsageClientAuth,
		},
		BasicConstraintsValid: true,
	}
	for _, override := range templateOverrides {
		tmpl.CRLDistributionPoints = slices.Unique(append(tmpl.CRLDistributionPoints, override.CRLDistributionPoints...))
		tmpl.DNSNames = slices.Unique(append(tmpl.DNSNames, override.DNSNames...))
		tmpl.EmailAddresses = slices.Unique(append(tmpl.EmailAddresses, override.EmailAddresses...))
		tmpl.ExtraExtensions = append(tmpl.ExtraExtensions, override.ExtraExtensions...)
		tmpl.IPAddresses = slices.UniqueBy(append(tmpl.IPAddresses, override.IPAddresses...), net.IP.String)
		tmpl.URIs = slices.UniqueBy(append(tmpl.URIs, override.URIs...), (*url.URL).String)
		tmpl.UnknownExtKeyUsage = slices.UniqueBy(append(tmpl.UnknownExtKeyUsage, override.UnknownExtKeyUsage...), asn1.ObjectIdentifier.String)
		seq := override.Subject.ToRDNSequence()
		tmpl.Subject.FillFromRDNSequence(&seq)
		tmpl.KeyUsage |= override.KeyUsage
		tmpl.ExtKeyUsage = slices.Unique(append(tmpl.ExtKeyUsage, override.ExtKeyUsage...))
	}

	clientCertDER, err := x509.CreateCertificate(rand.Reader, tmpl, caCert.Leaf, priv.Public(), caCert.PrivateKey)
	require.NoError(e.t, err)

	cert, err := x509.ParseCertificate(clientCertDER)
	require.NoError(e.t, err)
	e.debugf("provisioned client certificate for %s", cert.Subject.String())

	clientCert := &tls.Certificate{
		Certificate: [][]byte{cert.Raw, caCert.Leaf.Raw},
		PrivateKey:  priv,
		Leaf:        cert,
	}

	_, err = clientCert.Leaf.Verify(x509.VerifyOptions{
		KeyUsages: []x509.ExtKeyUsage{
			x509.ExtKeyUsageClientAuth,
		},
		Roots: e.ServerCAs(),
	})
	require.NoError(e.t, err, "bug: generated client cert is not valid")
	return (*Certificate)(clientCert)
}

func (e *environment) NewServerCert(templateOverrides ...*x509.Certificate) *Certificate {
	caCert := e.CACert()

	priv, err := rsa.GenerateKey(rand.Reader, 2048)
	require.NoError(e.t, err)

	sn, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	require.NoError(e.t, err)
	now := time.Now()
	tmpl := &x509.Certificate{
		SerialNumber: sn,
		NotBefore:    now,
		NotAfter:     now.Add(12 * time.Hour),
		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
		ExtKeyUsage: []x509.ExtKeyUsage{
			x509.ExtKeyUsageServerAuth,
		},
		BasicConstraintsValid: true,
	}
	for _, override := range templateOverrides {
		tmpl.DNSNames = slices.Unique(append(tmpl.DNSNames, override.DNSNames...))
		tmpl.IPAddresses = slices.UniqueBy(append(tmpl.IPAddresses, override.IPAddresses...), net.IP.String)
	}
	certDER, err := x509.CreateCertificate(rand.Reader, tmpl, caCert.Leaf, priv.Public(), caCert.PrivateKey)
	require.NoError(e.t, err)

	cert, err := x509.ParseCertificate(certDER)
	require.NoError(e.t, err)
	e.debugf("provisioned server certificate for %v", cert.DNSNames)

	tlsCert := &tls.Certificate{
		Certificate: [][]byte{cert.Raw, caCert.Leaf.Raw},
		PrivateKey:  priv,
		Leaf:        cert,
	}

	_, err = tlsCert.Leaf.Verify(x509.VerifyOptions{Roots: e.ServerCAs()})
	require.NoError(e.t, err, "bug: generated client cert is not valid")
	return (*Certificate)(tlsCert)
}

func (e *environment) SharedSecret() []byte {
	return bytes.Clone(e.sharedSecret[:])
}

func (e *environment) CookieSecret() []byte {
	return bytes.Clone(e.cookieSecret[:])
}

func (e *environment) Stop() {
	if b, ok := e.t.(*testing.B); ok {
		// when calling Stop() manually, ensure we aren't timing this
		b.StopTimer()
		defer b.StartTimer()
	}
	e.cleanupOnce.Do(func() {
		e.debugf("stop: Stop() called manually")
		e.advanceState(Stopping)
		e.cancel(ErrCauseManualStop)
		err := e.taskErrGroup.Wait()
		e.advanceState(Stopped)
		e.debugf("stop: done waiting")
		assert.ErrorIs(e.t, err, ErrCauseManualStop)
	})
}

func (e *environment) Pause() {
	e.t.Log("\x1b[31m*** test manually paused; continue with ctrl+c ***\x1b[0m")
	c := make(chan os.Signal, 1)
	signal.Notify(c, syscall.SIGINT)
	<-c
	e.t.Log("\x1b[31mctrl+c received, continuing\x1b[0m")
}

func (e *environment) cleanup() {
	e.cleanupOnce.Do(func() {
		e.debugf("stop: test cleanup")
		if e.t.Failed() {
			if e.pauseOnFailure {
				e.t.Log("\x1b[31m*** pausing on test failure; continue with ctrl+c ***\x1b[0m")
				c := make(chan os.Signal, 1)
				signal.Notify(c, syscall.SIGINT)
				<-c
				e.t.Log("\x1b[31mctrl+c received, continuing\x1b[0m")
				signal.Stop(c)
			}
		}
		e.advanceState(Stopping)
		e.cancel(ErrCauseTestCleanup)
		err := e.taskErrGroup.Wait()
		e.advanceState(Stopped)
		e.debugf("stop: done waiting")
		assert.ErrorIs(e.t, err, ErrCauseTestCleanup)
	})
}

func (e *environment) Add(m Modifier) {
	e.t.Helper()
	caller := getCaller()
	e.debugf("Add: %T from %s", m, caller)
	switch e.getState() {
	case NotRunning:
		for _, mod := range e.mods {
			if mod.Value == m {
				e.t.Fatalf("test bug: duplicate modifier added\nfirst added by: %s", mod.Caller)
			}
		}
		e.mods = append(e.mods, WithCaller[Modifier]{
			Caller: caller,
			Value:  m,
		})
		e.debugf("Add: state=NotRunning; calling Attach")
		m.Attach(e.Context())
	case Starting:
		panic("test bug: cannot call Add() before Start() has returned")
	case Running:
		e.debugf("Add: state=Running; calling ModifyConfig")
		e.src.ModifyConfig(e.ctx, m)
	case Stopped, Stopping:
		panic("test bug: cannot call Add() after Stop()")
	default:
		panic(fmt.Sprintf("unexpected environment state: %s", e.getState()))
	}
}

func (e *environment) AddTask(t Task) {
	e.t.Helper()
	caller := getCaller()
	e.debugf("AddTask: %T from %s", t, caller)
	for _, task := range e.tasks {
		if task.Value == t {
			e.t.Fatalf("test bug: duplicate task added\nfirst added by: %s", task.Caller)
		}
	}
	e.tasks = append(e.tasks, WithCaller[Task]{
		Caller: getCaller(),
		Value:  t,
	})
}

func (e *environment) AddUpstream(up Upstream) {
	e.t.Helper()
	caller := getCaller()
	e.debugf("AddUpstream: %T from %s", up, caller)
	e.Add(up)
	e.AddTask(up)
}

// ReportError implements health.Provider.
func (e *environment) ReportError(check health.Check, err error, attributes ...health.Attr) {
	// note: don't use e.t.Fatal here, it will deadlock
	panic(fmt.Sprintf("%s: %v %v", check, err, attributes))
}

// ReportOK implements health.Provider.
func (e *environment) ReportOK(_ health.Check, _ ...health.Attr) {}

func (e *environment) advanceState(newState EnvironmentState) {
	e.stateMu.Lock()
	defer e.stateMu.Unlock()
	if newState <= e.state {
		panic(fmt.Sprintf("internal test environment bug: changed state to <= current: newState=%s, current=%s", newState, e.state))
	}
	e.debugf("state %s -> %s", e.state.String(), newState.String())
	e.state = newState
	e.debugf("notifying %d listeners of state change", len(e.stateChangeListeners[newState]))
	for _, listener := range e.stateChangeListeners[newState] {
		go listener()
	}
}

func (e *environment) getState() EnvironmentState {
	e.stateMu.Lock()
	defer e.stateMu.Unlock()
	return e.state
}

func (e *environment) OnStateChanged(state EnvironmentState, callback func()) {
	e.stateMu.Lock()
	defer e.stateMu.Unlock()

	if e.state&state != 0 {
		go callback()
		return
	}

	// add change listeners for all states, if there are multiple bits set
	for state > 0 {
		stateBit := EnvironmentState(bits.TrailingZeros32(uint32(state)))
		state &= (state - 1)
		e.stateChangeListeners[stateBit] = append(e.stateChangeListeners[stateBit], callback)
	}
}

func getCaller(skip ...int) string {
	if len(skip) == 0 {
		skip = append(skip, 3)
	}
	callers := make([]uintptr, 8)
	runtime.Callers(skip[0], callers)
	frames := runtime.CallersFrames(callers)
	var caller string
	for {
		next, ok := frames.Next()
		if !ok {
			break
		}
		if path.Base(next.Function) == "testenv.(*environment).AddUpstream" {
			continue
		}
		caller = fmt.Sprintf("%s:%d", next.File, next.Line)
		break
	}
	return caller
}

func wildcardDomain(names []string) string {
	for _, name := range names {
		if name[0] == '*' {
			return name[2:]
		}
	}
	panic("test bug: no wildcard domain in certificate")
}

func isSilent(t testing.TB) bool {
	switch t.(type) {
	case *testing.B:
		return !slices.Contains(os.Args, "-test.v=true")
	default:
		return false
	}
}

type configSource struct {
	mu  sync.Mutex
	cfg *config.Config
	lis []config.ChangeListener
}

var _ config.Source = (*configSource)(nil)

// GetConfig implements config.Source.
func (src *configSource) GetConfig() *config.Config {
	src.mu.Lock()
	defer src.mu.Unlock()

	return src.cfg
}

// OnConfigChange implements config.Source.
func (src *configSource) OnConfigChange(_ context.Context, li config.ChangeListener) {
	src.mu.Lock()
	defer src.mu.Unlock()

	src.lis = append(src.lis, li)
}

// ModifyConfig updates the current configuration by applying a [Modifier].
func (src *configSource) ModifyConfig(ctx context.Context, m Modifier) {
	src.mu.Lock()
	defer src.mu.Unlock()

	m.Modify(src.cfg)
	for _, li := range src.lis {
		li(ctx, src.cfg)
	}
}