package main

import (
	"bytes"
	"context"
	"crypto/rand"
	"crypto/subtle"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"regexp"
	"strconv"
	"strings"
	"syscall"
	"time"
	"unicode/utf8"

	"github.com/gofiber/fiber/v3"
	"github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
)

const (
	browserUser         = "1000:1000"
	browserEntrypoint   = "/usr/local/bin/docker-entrypoint.sh"
	managedLabel        = "io.creatorhub.managed"
	idLabel             = "io.creatorhub.runtime-id"
	nameLabel           = "io.creatorhub.display-name"
	bindingVersionLabel = "io.creatorhub.binding-version"
	networkExitLabel    = "io.creatorhub.network-exit-id"
	proxyPortLabel      = "io.creatorhub.proxy-port"
	networkIDLabel      = "io.creatorhub.network-id"
	networkRoleLabel    = "io.creatorhub.network-role"
	gatewayMemberLabel  = "io.creatorhub.gateway-member"
	browserNetworkRole  = "browser"
	controlNetworkName  = "creatorhub_control"
	namePrefix          = "creatorhub-browser-"
	reservationPrefix   = "creatorhub-reservation-"
	reservationLabel    = "io.creatorhub.alias-reservation"
	reservationGenLabel = "io.creatorhub.reservation-generation"
	pullTimeout         = 10 * time.Minute
)

var (
	runtimeIDPattern   = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,31}$`)
	networkNamePattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_.-]{0,63}$`)
	imageRefPattern    = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._:/@-]{0,300}$`)
	volumePattern      = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_.-]{0,63}$`)
	exitIDPattern      = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._/-]{0,127}$`)
)

var (
	errInvalidRuntimeID   = errors.New("invalid runtime id")
	errUnmanagedContainer = errors.New("refusing to operate on a container not owned by CreatorHub")
	errGenerationConflict = errors.New("container generation does not match request")
	errUnauthorized       = errors.New("gateway token rejected")
)

type serviceConfig struct {
	listenAddr string
	dockerSock string
	network    string
	token      string
	logLevel   logrus.Level
}

type dockerClient struct {
	baseURL string
	client  *http.Client // 常规 Docker 调用
	slow    *http.Client // 镜像拉取等长操作，不设整体超时
}

type dockerAliasReservations struct {
	docker dockerClient
	self   string
}

type tenantNetworkGeneration struct {
	ID               string
	Name             string
	Created          bool
	ConnectedSelf    bool
	ConnectedRuntime bool
	GatewayMembers   []string
	SelfMember       string
	RuntimeAttached  bool
}

type dockerTenantNetwork struct {
	ID         string            `json:"Id"`
	Name       string            `json:"Name"`
	Driver     string            `json:"Driver"`
	Internal   bool              `json:"Internal"`
	Attachable bool              `json:"Attachable"`
	Ingress    bool              `json:"Ingress"`
	Labels     map[string]string `json:"Labels"`
	Containers map[string]struct {
		Name        string `json:"Name"`
		IPv4Address string `json:"IPv4Address"`
	} `json:"Containers"`
}

type gateway struct {
	docker  dockerClient
	network string
	self    string
	token   string
	browser restrictedBrowser
	proxies *memoryProxyRegistry
	locks   *dockerAliasReservations
}

// createRequest 全量字段由平台下发；网关不做业务决策，只做输入合法性校验。
type createRequest struct {
	Alias          string           `json:"alias"`
	Name           string           `json:"name"`
	Image          string           `json:"image"`
	Cmd            []string         `json:"cmd"`
	Volume         string           `json:"volume"`
	BindingVersion int64            `json:"binding_version"`
	NetworkExitID  string           `json:"network_exit_id"`
	NetworkExit    gatewayProxyExit `json:"network_exit"`
	Stopped        bool             `json:"stopped,omitempty"`
}

type gatewayProxyExit struct {
	Protocol string `json:"protocol"`
	Host     string `json:"host"`
	Port     int    `json:"port"`
	Username string `json:"username"`
	Password string `json:"password"`
}

type generationRequest struct {
	BindingVersion int64  `json:"binding_version"`
	RuntimeID      string `json:"runtime_id"`
	NetworkID      string `json:"network_id"`
}

type proxyRestoreRequest struct {
	BindingVersion int64            `json:"binding_version"`
	RuntimeID      string           `json:"runtime_id"`
	NetworkID      string           `json:"network_id"`
	NetworkExitID  string           `json:"network_exit_id"`
	NetworkExit    gatewayProxyExit `json:"network_exit"`
}

type browser struct {
	ID             string `json:"id"`
	Alias          string `json:"alias"`
	Name           string `json:"name"`
	State          string `json:"state"`
	Status         string `json:"status"`
	Endpoint       string `json:"endpoint"`
	BindingVersion int64  `json:"binding_version"`
	NetworkExitID  string `json:"network_exit_id"`
	NetworkID      string `json:"network_id"`
	ProxyReady     bool   `json:"proxy_ready"`
}

func main() {
	logrus.SetFormatter(&logrus.JSONFormatter{})
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	if err := newCommand().ExecuteContext(ctx); err != nil {
		logrus.WithField("service", "docker-gateway").WithError(err).Error("service stopped")
		os.Exit(1)
	}
}

func newCommand() *cobra.Command {
	command := &cobra.Command{
		Use:           "docker-gateway",
		Short:         "Run the restricted CreatorHub Docker gateway",
		Args:          cobra.NoArgs,
		SilenceErrors: true,
		SilenceUsage:  true,
		RunE: func(command *cobra.Command, _ []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}
			logrus.SetLevel(cfg.logLevel)
			return run(command, cfg)
		},
	}
	return command
}

func loadConfig() (serviceConfig, error) {
	v := viper.New()
	v.SetDefault("listen_addr", ":8081")
	v.SetDefault("docker_socket", "/var/run/docker.sock")
	v.SetDefault("browser_network", "creatorhub_browser")
	v.SetDefault("log_level", "info")
	_ = v.BindEnv("listen_addr", "LISTEN_ADDR")
	_ = v.BindEnv("docker_socket", "DOCKER_SOCKET")
	_ = v.BindEnv("browser_network", "BROWSER_NETWORK")
	_ = v.BindEnv("gateway_token", "GATEWAY_TOKEN")
	_ = v.BindEnv("log_level", "LOG_LEVEL")

	level, err := logrus.ParseLevel(v.GetString("log_level"))
	if err != nil {
		return serviceConfig{}, errors.New("LOG_LEVEL must be panic, fatal, error, warn, info, debug, or trace")
	}
	cfg := serviceConfig{
		listenAddr: strings.TrimSpace(v.GetString("listen_addr")),
		dockerSock: strings.TrimSpace(v.GetString("docker_socket")),
		network:    strings.TrimSpace(v.GetString("browser_network")),
		token:      strings.TrimSpace(v.GetString("gateway_token")),
		logLevel:   level,
	}
	if cfg.listenAddr == "" {
		return serviceConfig{}, errors.New("LISTEN_ADDR must not be empty")
	}
	if err := validateListenAddr(cfg.listenAddr); err != nil {
		return serviceConfig{}, err
	}
	if cfg.dockerSock == "" {
		return serviceConfig{}, errors.New("DOCKER_SOCKET must not be empty")
	}
	if len(cfg.token) < 16 {
		return serviceConfig{}, errors.New("GATEWAY_TOKEN must be at least 16 characters")
	}
	if err := validateBrowserNetwork(cfg.network); err != nil {
		return serviceConfig{}, err
	}
	return cfg, nil
}

func validateListenAddr(addr string) error {
	_, port, err := net.SplitHostPort(addr)
	if err != nil {
		return errors.New("LISTEN_ADDR must be a host:port address")
	}
	number, err := strconv.Atoi(port)
	if err != nil || number < 1 || number > 65535 {
		return errors.New("LISTEN_ADDR port must be 1..65535")
	}
	return nil
}

func run(command *cobra.Command, cfg serviceConfig) error {
	transport := &http.Transport{
		DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
			return (&net.Dialer{}).DialContext(ctx, "unix", cfg.dockerSock)
		},
	}
	defer transport.CloseIdleConnections()
	docker := dockerClient{
		baseURL: "http://docker/v1.43",
		client:  &http.Client{Transport: transport, Timeout: 30 * time.Second},
		slow:    &http.Client{Transport: transport},
	}
	logrus.WithFields(logrus.Fields{
		"service":     "docker-gateway",
		"listen_addr": cfg.listenAddr,
		"network":     cfg.network,
	}).Info("service starting")
	return newGateway(docker, cfg.network, cfg.token).Listen(cfg.listenAddr, fiber.ListenConfig{
		GracefulContext:       command.Context(),
		DisableStartupMessage: true,
	})
}

func newGateway(client dockerClient, network, token string) *fiber.App {
	self, _ := os.Hostname()
	return newGatewayWithSelf(client, network, token, self)
}

func newGatewayWithSelf(client dockerClient, network, token, self string) *fiber.App {
	return newGatewayWithBrowser(client, network, token, self, cdpBrowser{})
}

func newGatewayWithBrowser(client dockerClient, network, token, self string, browser restrictedBrowser) *fiber.App {
	api := gateway{docker: client, network: network, self: self, token: token, proxies: newMemoryProxyRegistry(),
		locks: &dockerAliasReservations{docker: client, self: self}, browser: browser}
	app := fiber.New(fiber.Config{
		AppName:     "CreatorHub Docker gateway",
		BodyLimit:   1 << 20,
		ReadTimeout: 5 * time.Second,
		IdleTimeout: 60 * time.Second,
		ErrorHandler: func(c fiber.Ctx, err error) error {
			status := http.StatusInternalServerError
			var fiberError *fiber.Error
			if errors.As(err, &fiberError) && fiberError != nil {
				status = fiberError.Code
			}
			return writeError(c, status, err)
		},
	})
	app.Get("/healthz", func(c fiber.Ctx) error {
		c.Status(fiber.StatusNoContent)
		return nil
	})
	app.Use("/v1", api.authorize)
	app.Get("/v1/browsers", api.list)
	app.Post("/v1/browsers", api.create)
	app.Post("/v1/browsers/:id/proxy", api.restoreProxy)
	app.Post("/v1/browsers/:id/douyin/cookies", api.setDouyinCookies)
	app.Post("/v1/browsers/:id/douyin/get", api.getDouyin)
	app.Post("/v1/browsers/:id/:action", api.changeState)
	app.Delete("/v1/browsers/:id", api.remove)
	return app
}

func (api gateway) authorize(c fiber.Ctx) error {
	expected := "Bearer " + api.token
	if subtle.ConstantTimeCompare([]byte(c.Get(fiber.HeaderAuthorization)), []byte(expected)) != 1 {
		return writeError(c, http.StatusUnauthorized, errUnauthorized)
	}
	return c.Next()
}

func (api gateway) list(c fiber.Ctx) error {
	filters, _ := json.Marshal(map[string][]string{"label": {managedLabel + "=true"}})
	result, err := api.docker.request(http.MethodGet, "/containers/json?all=1&filters="+url.QueryEscape(string(filters)), nil)
	if err != nil {
		return writeError(c, http.StatusBadGateway, err)
	}
	defer result.Body.Close()
	if result.StatusCode != http.StatusOK {
		return forwardDockerError(c, result)
	}

	var containers []struct {
		ID     string            `json:"Id"`
		State  string            `json:"State"`
		Status string            `json:"Status"`
		Labels map[string]string `json:"Labels"`
	}
	if err := json.NewDecoder(result.Body).Decode(&containers); err != nil {
		return writeError(c, http.StatusBadGateway, fmt.Errorf("decode Docker response: %w", err))
	}

	browsers := make([]browser, 0, len(containers))
	for _, container := range containers {
		alias := container.Labels[idLabel]
		if !runtimeIDPattern.MatchString(alias) {
			continue
		}
		name := container.Labels[nameLabel]
		if name == "" {
			name = alias
		}
		bindingVersion, _ := strconv.ParseInt(container.Labels[bindingVersionLabel], 10, 64)
		proxyPort, _ := strconv.Atoi(container.Labels[proxyPortLabel])
		direct := container.Labels[networkExitLabel] == ""
		browsers = append(browsers, browser{
			ID:             container.ID,
			Alias:          alias,
			Name:           name,
			State:          container.State,
			Status:         container.Status,
			Endpoint:       "http://" + namePrefix + alias + ":9222",
			BindingVersion: bindingVersion,
			NetworkExitID:  container.Labels[networkExitLabel],
			NetworkID:      container.Labels[networkIDLabel],
			ProxyReady:     direct || api.proxies.ready(alias, proxyPort, container.ID, container.Labels[networkIDLabel]),
		})
	}
	return writeJSON(c, http.StatusOK, browsers)
}

func (api gateway) create(c fiber.Ctx) error {
	var input createRequest
	decoder := json.NewDecoder(bytes.NewReader(c.Body()))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil {
		return writeError(c, http.StatusBadRequest, errors.New("body must contain only alias, name, image, cmd, volume, binding_version, network_exit_id, network_exit and stopped"))
	}
	if err := validateCreate(input); err != nil {
		return writeError(c, http.StatusBadRequest, err)
	}
	if err := api.docker.pullIfMissing(c.Context(), input.Image); err != nil {
		return writeError(c, http.StatusBadGateway, err)
	}
	if _, _, err := api.managedContainer(input.Alias); err == nil {
		return writeError(c, http.StatusConflict, errors.New("browser alias is already in use"))
	} else if !errors.Is(err, os.ErrNotExist) {
		return writeError(c, statusFor(err), err)
	}
	_, release, err := api.locks.acquire(input.Alias)
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	defer release()
	if _, _, err := api.managedContainer(input.Alias); err == nil {
		return writeError(c, http.StatusConflict, errors.New("browser alias is already in use"))
	} else if !errors.Is(err, os.ErrNotExist) {
		return writeError(c, statusFor(err), err)
	}
	direct := input.NetworkExitID == ""
	network, proxyServer, undoProxy := "none", "", func() {}
	var networkGeneration tenantNetworkGeneration
	keepNetwork := input.Stopped
	if !input.Stopped {
		var err error
		var bindHost string
		networkGeneration, bindHost, err = api.docker.ensureTenantNetwork(api.network, input.Alias, api.self, input.BindingVersion, "", "", false)
		if networkGeneration.ID != "" {
			defer func() {
				if keepNetwork {
					return
				}
				var cleanupErr error
				if networkGeneration.Created {
					cleanupErr = api.removeTenantNetwork(input.Alias, input.BindingVersion, "", networkGeneration, nil, "", false)
				} else if networkGeneration.ConnectedSelf {
					_, cleanupErr = api.disconnectTenantNetworkMember(input.Alias, input.BindingVersion, "", networkGeneration,
						networkGeneration.SelfMember, nil, "", false)
				}
				if cleanupErr != nil {
					logrus.WithError(cleanupErr).WithField("alias", input.Alias).Error("rollback isolated browser network")
				}
			}()
		}
		if err != nil {
			return writeNetworkError(c, http.StatusBadGateway, errors.New("configure isolated browser network"), networkGeneration.ID)
		}
		network = networkGeneration.ID
		if !direct {
			proxyServer, undoProxy, err = api.proxies.configure(input.Alias, input.BindingVersion, bindHost, 0, input.NetworkExit, networkGeneration.ID)
			if err != nil {
				return writeNetworkError(c, statusFor(err), errors.Join(errors.New("configure in-memory proxy"), err), networkGeneration.ID)
			}
		}
	}
	keepProxy := false
	defer func() {
		if !keepProxy {
			undoProxy()
		}
	}()

	pidsLimit := int64(512)
	cmd := append([]string{}, input.Cmd...)
	if !input.Stopped && !direct {
		cmd = append(cmd[:len(cmd)-1], "--proxy-server="+proxyServer, "--disable-non-proxied-udp", cmd[len(cmd)-1])
	}
	payload := map[string]any{
		"Image":      input.Image,
		"User":       browserUser,
		"Entrypoint": []string{browserEntrypoint},
		"Cmd":        cmd,
		"Env":        []string{"REMOTE_DEBUGGING_PORT=9222"},
		"Labels": map[string]string{
			managedLabel:        "true",
			idLabel:             input.Alias,
			nameLabel:           input.Name,
			bindingVersionLabel: strconv.FormatInt(input.BindingVersion, 10),
			networkExitLabel:    input.NetworkExitID,
			networkIDLabel:      networkGeneration.ID,
			proxyPortLabel:      strconv.Itoa(proxyPort(proxyServer)),
		},
		"ExposedPorts": map[string]any{"9222/tcp": map[string]any{}},
		"HostConfig": map[string]any{
			"NetworkMode":    network,
			"ReadonlyRootfs": true,
			"CapDrop":        []string{"ALL"},
			"SecurityOpt":    []string{"no-new-privileges"},
			"PidsLimit":      &pidsLimit,
			"Memory":         int64(1 << 30),
			"NanoCpus":       int64(2_000_000_000),
			"Tmpfs": map[string]string{
				"/tmp":           "rw,nosuid,nodev,noexec,mode=1777,size=256m",
				"/tmp/.X11-unix": "rw,nosuid,nodev,noexec,mode=1777,size=1m",
				"/dev/shm":       "rw,nosuid,nodev,noexec,size=256m",
				"/home/ubuntu":   "rw,nosuid,nodev,noexec,uid=1000,gid=1000,mode=700,size=64m",
			},
			"Mounts": []map[string]any{{
				"Type":   "volume",
				"Source": input.Volume,
				"Target": "/data",
			}},
		},
	}
	result, err := api.docker.request(http.MethodPost, "/containers/create?name="+url.QueryEscape(namePrefix+input.Alias), payload)
	var created struct {
		ID string `json:"Id"`
	}
	status, createErr := http.StatusBadGateway, err
	if result != nil {
		if result.StatusCode == http.StatusConflict {
			status = http.StatusConflict
		}
		if result.StatusCode == http.StatusCreated {
			createErr = json.NewDecoder(result.Body).Decode(&created)
		} else {
			createErr = errors.New("Docker container creation failed")
		}
		result.Body.Close()
	}
	if createErr != nil || created.ID == "" {
		containerID, labels, inspectErr := api.managedContainer(input.Alias)
		if inspectErr == nil && labels[bindingVersionLabel] == strconv.FormatInt(input.BindingVersion, 10) &&
			labels[networkIDLabel] == networkGeneration.ID {
			created.ID = containerID
		} else {
			if createErr == nil {
				createErr = errors.New("Docker returned an invalid container id")
			}
			return writeNetworkError(c, status, createErr, networkGeneration.ID)
		}
	}
	if !input.Stopped {
		if !direct {
			if !api.proxies.bind(input.Alias, input.BindingVersion, proxyServer, created.ID, networkGeneration.ID) {
				cleanupErr := api.docker.expect(http.MethodDelete, "/containers/"+url.PathEscape(created.ID)+"?force=1&v=0", nil, http.StatusNoContent)
				if cleanupErr != nil {
					return writeNetworkError(c, http.StatusBadGateway, fmt.Errorf("proxy generation changed and container cleanup failed: %w", cleanupErr), networkGeneration.ID)
				}
				return writeNetworkError(c, http.StatusConflict, errGenerationConflict, networkGeneration.ID)
			}
			undoProxy = func() { api.proxies.remove(input.Alias, input.BindingVersion, created.ID) }
		}
		if err := api.docker.expect(http.MethodPost, "/containers/"+url.PathEscape(created.ID)+"/start", nil, http.StatusNoContent, http.StatusNotModified); err != nil {
			cleanupErr := api.docker.expect(http.MethodDelete, "/containers/"+url.PathEscape(created.ID)+"?force=1&v=0", nil, http.StatusNoContent)
			if cleanupErr != nil {
				return writeNetworkError(c, http.StatusBadGateway, fmt.Errorf("container did not start and cleanup failed: %w; cleanup: %v", err, cleanupErr), networkGeneration.ID)
			}
			return writeNetworkError(c, http.StatusBadGateway, fmt.Errorf("container did not start and was removed while preserving its Profile volume: %w", err), networkGeneration.ID)
		}
	}
	keepProxy, keepNetwork = !input.Stopped && !direct, true
	return writeJSON(c, http.StatusCreated, map[string]string{"id": created.ID, "alias": input.Alias, "network_id": networkGeneration.ID})
}

func validateCreate(input createRequest) error {
	if !runtimeIDPattern.MatchString(input.Alias) {
		return errors.New("alias must match [a-z0-9][a-z0-9-]{0,31}")
	}
	if input.Name == "" || utf8.RuneCountInString(input.Name) > 64 || hasControlRunes(input.Name) {
		return errors.New("name must be 1..64 visible characters")
	}
	if !imageRefPattern.MatchString(input.Image) {
		return errors.New("image must be a valid image reference")
	}
	if !volumePattern.MatchString(input.Volume) {
		return errors.New("volume must be a valid volume name")
	}
	direct := input.NetworkExitID == "" && input.NetworkExit == (gatewayProxyExit{})
	if input.BindingVersion < 1 || (input.Stopped && !direct) ||
		(!input.Stopped && !direct && !exitIDPattern.MatchString(input.NetworkExitID)) ||
		(input.NetworkExitID == "") != (input.NetworkExit == (gatewayProxyExit{})) {
		return errors.New("binding_version and network_exit_id must identify the current binding")
	}
	if len(input.Cmd) == 0 || len(input.Cmd) > 64 || input.Cmd[len(input.Cmd)-1] != "about:blank" {
		return errors.New("cmd must contain 1..64 arguments")
	}
	total := 0
	for _, arg := range input.Cmd {
		if arg == "" || hasControlRunes(arg) {
			return errors.New("cmd arguments must be non-empty visible strings")
		}
		if strings.HasPrefix(arg, "--proxy-server") || arg == "--disable-non-proxied-udp" {
			return errors.New("proxy arguments are platform-controlled")
		}
		total += len(arg)
	}
	if total > 4096 {
		return errors.New("cmd arguments exceed 4096 characters")
	}
	if input.Stopped || direct {
		return nil
	}
	proxy := input.NetworkExit
	if (proxy.Protocol != "http" && proxy.Protocol != "https" && proxy.Protocol != "socks4" && proxy.Protocol != "socks5") ||
		proxy.Host == "" || len(proxy.Host) > 253 || strings.ContainsAny(proxy.Host, "@/[]?# \t\r\n") ||
		proxy.Port < 1 || proxy.Port > 65535 || (proxy.Username == "" && proxy.Password != "") ||
		len(proxy.Username) > 255 || len(proxy.Password) > 255 ||
		hasControlRunes(proxy.Username) || hasControlRunes(proxy.Password) {
		return errors.New("network_exit must contain a valid proxy endpoint and optional credentials")
	}
	return nil
}

func proxyPort(proxyServer string) int {
	parsed, _ := url.Parse(proxyServer)
	port, _ := strconv.Atoi(parsed.Port())
	return port
}

func hasControlRunes(value string) bool {
	for _, r := range value {
		if r < 0x20 || r == 0x7f {
			return true
		}
	}
	return false
}

func (api gateway) changeState(c fiber.Ctx) error {
	id := c.Params("id")
	action := c.Params("action")
	var input generationRequest
	switch action {
	case "start":
		var err error
		input, err = decodeGeneration(c)
		if err != nil {
			return writeError(c, http.StatusBadRequest, err)
		}
		if input.NetworkID == "" {
			return writeError(c, http.StatusBadRequest, errors.New("network_id must identify the expected network generation"))
		}
		_, exists, err := api.requireGeneration(id, input)
		if err != nil {
			return writeError(c, statusFor(err), err)
		}
		if !exists {
			return writeError(c, http.StatusNotFound, os.ErrNotExist)
		}
	case "stop":
		var err error
		input, err = decodeGeneration(c)
		if err != nil {
			return writeError(c, http.StatusBadRequest, err)
		}
		_, exists, err := api.requireGeneration(id, input)
		if err != nil {
			return writeError(c, statusFor(err), err)
		}
		if !exists {
			return writeError(c, http.StatusNotFound, os.ErrNotExist)
		}
	default:
		return writeError(c, http.StatusNotFound, errors.New("unknown action"))
	}
	_, release, err := api.locks.acquire(id)
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	defer release()
	var path string
	if action == "start" {
		containerID, exists, err := api.requireGeneration(id, input)
		if err != nil {
			return writeError(c, statusFor(err), err)
		}
		if !exists {
			return writeError(c, http.StatusNotFound, os.ErrNotExist)
		}
		path = "/containers/" + url.PathEscape(containerID) + "/start"
	} else {
		containerID, exists, err := api.requireGeneration(id, input)
		if err != nil {
			return writeError(c, statusFor(err), err)
		}
		if !exists {
			return writeError(c, http.StatusNotFound, os.ErrNotExist)
		}
		path = "/containers/" + url.PathEscape(containerID) + "/stop?t=10"
	}
	if err := api.docker.expect(http.MethodPost, path, nil, http.StatusNoContent, http.StatusNotModified); err != nil {
		return writeError(c, http.StatusBadGateway, err)
	}
	c.Status(http.StatusNoContent)
	return nil
}

func (api gateway) remove(c fiber.Ctx) error {
	id := c.Params("id")
	input, err := decodeGeneration(c)
	if err != nil {
		return writeError(c, http.StatusBadRequest, err)
	}
	containerID, exists, err := api.requireGeneration(id, input)
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	_, release, err := api.locks.acquire(id)
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	defer release()
	currentID, currentExists, err := api.requireGeneration(id, input)
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	if currentExists != exists || currentID != containerID {
		return writeError(c, http.StatusConflict, errGenerationConflict)
	}
	expectedNetworkID := input.NetworkID
	if currentExists {
		_, labels, inspectErr := api.managedContainer(id)
		if inspectErr != nil {
			return writeError(c, statusFor(inspectErr), inspectErr)
		}
		containerNetworkID := labels[networkIDLabel]
		if containerNetworkID != input.NetworkID {
			return writeError(c, http.StatusConflict, errGenerationConflict)
		}
	} else if expectedNetworkID == "" {
		return writeError(c, http.StatusConflict, errGenerationConflict)
	}
	var networkGeneration tenantNetworkGeneration
	networkExists := false
	if expectedNetworkID != "" {
		networkGeneration, _, networkExists, err = api.docker.inspectTenantNetwork(api.network, id, input.BindingVersion,
			input.RuntimeID, api.self, expectedNetworkID, false)
		if err != nil {
			return writeError(c, statusFor(err), err)
		}
	}
	if networkExists {
		err = api.removeTenantNetwork(id, input.BindingVersion, input.RuntimeID, networkGeneration, &input, containerID, exists)
	} else if expectedNetworkID != "" {
		return writeError(c, http.StatusConflict, errGenerationConflict)
	}
	if err != nil {
		if errors.Is(err, errGenerationConflict) {
			return writeError(c, http.StatusConflict, err)
		}
		return c.Status(http.StatusAccepted).JSON(map[string]string{
			"status": "runtime_cleanup_pending",
		})
	}
	if !api.proxies.remove(id, input.BindingVersion, input.RuntimeID, input.NetworkID) {
		return writeError(c, http.StatusConflict, errGenerationConflict)
	}
	if exists {
		path := "/containers/" + url.PathEscape(containerID) + "?force=1&v=0"
		if err := api.requireRuntimeState(id, input, containerID, true); err != nil {
			return writeError(c, http.StatusConflict, err)
		}
		if err := api.docker.expect(http.MethodDelete, path, nil, http.StatusNoContent); err != nil {
			currentID, currentExists, generationErr := api.requireGeneration(id, input)
			if errors.Is(err, os.ErrNotExist) && generationErr == nil && !currentExists {
				return c.SendStatus(http.StatusNoContent)
			}
			if generationErr != nil || currentID != containerID {
				err = errGenerationConflict
			}
			if errors.Is(err, errGenerationConflict) {
				return writeError(c, http.StatusConflict, err)
			}
			return writeError(c, http.StatusBadGateway, err)
		}
	}
	c.Status(http.StatusNoContent)
	return nil
}

func (api gateway) restoreProxy(c fiber.Ctx) error {
	input := proxyRestoreRequest{}
	decoder := json.NewDecoder(bytes.NewReader(c.Body()))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil || input.BindingVersion < 1 || !exitIDPattern.MatchString(input.RuntimeID) ||
		!exitIDPattern.MatchString(input.NetworkID) ||
		!exitIDPattern.MatchString(input.NetworkExitID) ||
		validateCreate(createRequest{Alias: c.Params("id"), Name: "x", Image: "x", Cmd: []string{"about:blank"}, Volume: "x",
			BindingVersion: input.BindingVersion, NetworkExitID: input.NetworkExitID, NetworkExit: input.NetworkExit}) != nil {
		return writeError(c, http.StatusBadRequest, errors.New("invalid proxy recovery request"))
	}
	removeStaleProxy := func() { api.proxies.remove(c.Params("id"), input.BindingVersion, input.RuntimeID, input.NetworkID) }
	runtimeID, labels, err := api.requireProxyGeneration(c.Params("id"), input)
	if err != nil {
		removeStaleProxy()
		return writeError(c, statusFor(err), err)
	}
	port, _ := strconv.Atoi(labels[proxyPortLabel])
	if port < 1 {
		removeStaleProxy()
		return writeError(c, http.StatusConflict, errors.New("container binding does not match recovery request"))
	}
	_, release, err := api.locks.acquire(c.Params("id"))
	if err != nil {
		return writeError(c, statusFor(err), err)
	}
	defer release()
	if runtimeID, labels, err = api.requireProxyGeneration(c.Params("id"), input); err != nil {
		removeStaleProxy()
		return writeError(c, statusFor(err), err)
	}
	port, _ = strconv.Atoi(labels[proxyPortLabel])
	if port < 1 {
		removeStaleProxy()
		return writeError(c, http.StatusConflict, errors.New("container binding does not match recovery request"))
	}
	networkGeneration, bindHost, err := api.docker.ensureTenantNetwork(api.network, c.Params("id"), api.self, input.BindingVersion,
		input.RuntimeID, labels[networkIDLabel], true)
	keepNetwork := false
	if networkGeneration.ID != "" {
		defer func() {
			if keepNetwork {
				return
			}
			var cleanupErr error
			if networkGeneration.Created {
				cleanupErr = api.removeTenantNetwork(c.Params("id"), input.BindingVersion, input.RuntimeID, networkGeneration, nil, "", false)
			} else {
				if networkGeneration.ConnectedRuntime {
					_, cleanupErr = api.disconnectTenantNetworkMember(c.Params("id"), input.BindingVersion, input.RuntimeID,
						networkGeneration, input.RuntimeID, nil, "", false)
				}
				if cleanupErr == nil && networkGeneration.ConnectedSelf {
					_, cleanupErr = api.disconnectTenantNetworkMember(c.Params("id"), input.BindingVersion, input.RuntimeID,
						networkGeneration, networkGeneration.SelfMember, nil, "", false)
				}
			}
			if cleanupErr != nil {
				logrus.WithError(cleanupErr).WithField("alias", c.Params("id")).Error("rollback restored browser network")
			}
		}()
	}
	if err != nil {
		removeStaleProxy()
		return writeError(c, http.StatusBadGateway, errors.New("restore isolated browser network"))
	}
	if err = api.requireProxyNetworkGeneration(c.Params("id"), input, networkGeneration, bindHost); err != nil {
		removeStaleProxy()
		return writeError(c, statusFor(err), err)
	}
	proxyServer, undoProxy, err := api.proxies.configure(c.Params("id"), input.BindingVersion, bindHost, port, input.NetworkExit, input.NetworkID)
	if err != nil {
		removeStaleProxy()
		return writeError(c, statusFor(err), errors.Join(errors.New("restore in-memory proxy"), err))
	}
	if err = api.requireProxyNetworkGeneration(c.Params("id"), input, networkGeneration, bindHost); err != nil {
		undoProxy()
		return writeError(c, statusFor(err), err)
	}
	if !api.proxies.bind(c.Params("id"), input.BindingVersion, proxyServer, runtimeID, input.NetworkID) {
		undoProxy()
		return writeError(c, http.StatusConflict, errGenerationConflict)
	}
	if err = api.requireProxyNetworkGeneration(c.Params("id"), input, networkGeneration, bindHost); err != nil {
		undoProxy()
		return writeError(c, statusFor(err), err)
	}
	keepNetwork = true
	return c.SendStatus(http.StatusNoContent)
}

func (api gateway) requireProxyNetworkGeneration(alias string, input proxyRestoreRequest, expected tenantNetworkGeneration, bindHost string) error {
	_, labels, err := api.requireProxyGeneration(alias, input)
	if err != nil {
		return err
	}
	if networkID := labels[networkIDLabel]; networkID != "" && networkID != expected.ID {
		return errGenerationConflict
	}
	current, addresses, exists, err := api.docker.inspectTenantNetwork(api.network, alias, input.BindingVersion,
		input.RuntimeID, api.self, expected.ID, false)
	host, _, _ := net.ParseCIDR(addresses[current.SelfMember])
	if err != nil || !exists || !sameTenantNetworkMembers(current, expected) || host == nil || host.String() != bindHost {
		return errGenerationConflict
	}
	return nil
}

func sameTenantNetworkMembers(current, expected tenantNetworkGeneration) bool {
	if current.ID != expected.ID || current.Name != expected.Name || current.RuntimeAttached != expected.RuntimeAttached ||
		current.SelfMember != expected.SelfMember || len(current.GatewayMembers) != len(expected.GatewayMembers) {
		return false
	}
	members := make(map[string]struct{}, len(current.GatewayMembers))
	for _, member := range current.GatewayMembers {
		members[member] = struct{}{}
	}
	for _, member := range expected.GatewayMembers {
		if _, ok := members[member]; !ok {
			return false
		}
	}
	return true
}

func (api gateway) requireProxyGeneration(alias string, input proxyRestoreRequest) (string, map[string]string, error) {
	runtimeID, labels, err := api.managedContainer(alias)
	if err != nil {
		return "", nil, err
	}
	version, _ := strconv.ParseInt(labels[bindingVersionLabel], 10, 64)
	if runtimeID != input.RuntimeID || version != input.BindingVersion || labels[networkExitLabel] != input.NetworkExitID ||
		labels[networkIDLabel] != input.NetworkID {
		return "", nil, errGenerationConflict
	}
	return runtimeID, labels, nil
}

func decodeGeneration(c fiber.Ctx) (generationRequest, error) {
	var input generationRequest
	decoder := json.NewDecoder(bytes.NewReader(c.Body()))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil || input.BindingVersion < 1 ||
		(input.RuntimeID != "" && !exitIDPattern.MatchString(input.RuntimeID)) ||
		(input.NetworkID != "" && !exitIDPattern.MatchString(input.NetworkID)) {
		return generationRequest{}, errors.New("binding_version, runtime_id and network_id must identify the expected generation")
	}
	return input, nil
}

func (api gateway) requireGeneration(id string, input generationRequest) (string, bool, error) {
	runtimeID, labels, err := api.managedContainer(id)
	if errors.Is(err, os.ErrNotExist) {
		return "", false, nil
	}
	if err != nil {
		return "", false, err
	}
	version, _ := strconv.ParseInt(labels[bindingVersionLabel], 10, 64)
	if input.RuntimeID == "" || runtimeID != input.RuntimeID || version != input.BindingVersion || labels[networkIDLabel] != input.NetworkID {
		return "", false, errGenerationConflict
	}
	return runtimeID, true, nil
}

func (api gateway) managedContainer(id string) (string, map[string]string, error) {
	runtimeID, labels, _, err := api.managedContainerState(id)
	return runtimeID, labels, err
}

func (api gateway) managedContainerState(id string) (string, map[string]string, map[string]string, error) {
	if !runtimeIDPattern.MatchString(id) {
		return "", nil, nil, errInvalidRuntimeID
	}
	result, err := api.docker.request(http.MethodGet, "/containers/"+url.PathEscape(namePrefix+id)+"/json", nil)
	if err != nil {
		return "", nil, nil, err
	}
	defer result.Body.Close()
	if result.StatusCode == http.StatusNotFound {
		return "", nil, nil, os.ErrNotExist
	}
	if result.StatusCode != http.StatusOK {
		return "", nil, nil, fmt.Errorf("Docker inspect returned %s", result.Status)
	}
	var inspected struct {
		ID     string `json:"Id"`
		Config struct {
			Labels map[string]string `json:"Labels"`
		} `json:"Config"`
		NetworkSettings struct {
			Networks map[string]struct {
				NetworkID string `json:"NetworkID"`
			} `json:"Networks"`
		} `json:"NetworkSettings"`
	}
	if err := json.NewDecoder(result.Body).Decode(&inspected); err != nil {
		return "", nil, nil, fmt.Errorf("decode Docker inspect: %w", err)
	}
	if inspected.Config.Labels[managedLabel] != "true" || inspected.Config.Labels[idLabel] != id {
		return "", nil, nil, errUnmanagedContainer
	}
	networks := make(map[string]string, len(inspected.NetworkSettings.Networks))
	for name, network := range inspected.NetworkSettings.Networks {
		networks[name] = network.NetworkID
	}
	return inspected.ID, inspected.Config.Labels, networks, nil
}

// pullIfMissing 在镜像不在本地时从远端仓库拉取；镜像缺失属于可恢复错误，调用方可直接重试。
func (docker dockerClient) pullIfMissing(ctx context.Context, ref string) error {
	inspect, err := docker.request(http.MethodGet, "/images/"+url.PathEscape(ref)+"/json", nil)
	if err != nil {
		return fmt.Errorf("inspect image %s: %w", ref, err)
	}
	_, _ = io.Copy(io.Discard, inspect.Body)
	_ = inspect.Body.Close()
	switch inspect.StatusCode {
	case http.StatusOK:
		return nil
	case http.StatusNotFound:
		// 本地无此镜像，继续拉取
	default:
		return fmt.Errorf("inspect image %s returned %s", ref, inspect.Status)
	}

	pullCtx, cancel := context.WithTimeout(ctx, pullTimeout)
	defer cancel()
	query := url.Values{"fromImage": {ref}}
	if !strings.Contains(ref, "@") {
		if repository, tag := splitImageRef(ref); tag != "" {
			query = url.Values{"fromImage": {repository}, "tag": {tag}}
		}
	}
	request, err := http.NewRequestWithContext(pullCtx, http.MethodPost, docker.baseURL+"/images/create?"+query.Encode(), nil)
	if err != nil {
		return fmt.Errorf("build image pull request: %w", err)
	}
	response, err := docker.slow.Do(request)
	if err != nil {
		return fmt.Errorf("pull image %s: %w", ref, err)
	}
	defer response.Body.Close()
	if response.StatusCode != http.StatusOK {
		message, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
		return fmt.Errorf("pull image %s returned %s: %s", ref, response.Status, strings.TrimSpace(string(message)))
	}
	_, _ = io.Copy(io.Discard, response.Body)
	return nil
}

func splitImageRef(ref string) (repository, tag string) {
	if at := strings.Index(ref, "@"); at >= 0 {
		return ref[:at], ref[at+1:]
	}
	if colon := strings.LastIndex(ref, ":"); colon > strings.LastIndex(ref, "/") {
		return ref[:colon], ref[colon+1:]
	}
	return ref, ""
}

func (docker dockerClient) request(method, path string, payload any) (*http.Response, error) {
	var body io.Reader
	if payload != nil {
		encoded, err := json.Marshal(payload)
		if err != nil {
			return nil, err
		}
		body = bytes.NewReader(encoded)
	}
	request, err := http.NewRequest(method, docker.baseURL+path, body)
	if err != nil {
		return nil, err
	}
	if payload != nil {
		request.Header.Set("Content-Type", "application/json")
	}
	return docker.client.Do(request)
}

func (docker dockerClient) expect(method, path string, payload any, allowed ...int) error {
	response, err := docker.request(method, path, payload)
	if err != nil {
		return err
	}
	defer response.Body.Close()
	for _, status := range allowed {
		if response.StatusCode == status {
			return nil
		}
	}
	if response.StatusCode == http.StatusNotFound {
		return os.ErrNotExist
	}
	message, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
	return fmt.Errorf("Docker returned %s: %s", response.Status, strings.TrimSpace(string(message)))
}

func (locks *dockerAliasReservations) acquire(alias string) (string, func(), error) {
	inspected, err := locks.docker.request(http.MethodGet, "/containers/"+url.PathEscape(locks.self)+"/json", nil)
	if err != nil {
		return "", nil, err
	}
	var gatewayContainer struct {
		Image  string `json:"Image"`
		Config struct {
			Labels map[string]string `json:"Labels"`
		} `json:"Config"`
	}
	if inspected.StatusCode != http.StatusOK || json.NewDecoder(inspected.Body).Decode(&gatewayContainer) != nil || gatewayContainer.Image == "" ||
		gatewayContainer.Config.Labels[gatewayMemberLabel] != "true" {
		inspected.Body.Close()
		return "", nil, errors.New("inspect trusted gateway for alias reservation")
	}
	inspected.Body.Close()
	generationBytes := make([]byte, 16)
	if _, err := rand.Read(generationBytes); err != nil {
		return "", nil, errors.New("create alias reservation generation")
	}
	generation := hex.EncodeToString(generationBytes)

	response, err := locks.docker.request(http.MethodPost, "/containers/create?name="+url.QueryEscape(reservationPrefix+alias), map[string]any{
		"Image":      gatewayContainer.Image,
		"Labels":     map[string]string{reservationLabel: "true", idLabel: alias, reservationGenLabel: generation},
		"HostConfig": map[string]any{"NetworkMode": "none"},
	})
	if err != nil {
		return "", nil, locks.reconcile(alias, generation, "", fmt.Errorf("create alias reservation result unknown: %w", err))
	}
	defer response.Body.Close()
	if response.StatusCode == http.StatusConflict {
		return "", nil, errGenerationConflict
	}
	if response.StatusCode != http.StatusCreated {
		return "", nil, locks.reconcile(alias, generation, "", fmt.Errorf("create alias reservation returned %s", response.Status))
	}
	var created struct {
		ID string `json:"Id"`
	}
	if json.NewDecoder(response.Body).Decode(&created) != nil || created.ID == "" {
		return "", nil, locks.reconcile(alias, generation, "", errors.New("Docker returned an invalid alias reservation id"))
	}
	actualID, inspectErr := locks.inspect(alias, generation)
	if inspectErr != nil {
		return "", nil, fmt.Errorf("Docker returned an unverified alias reservation id; generation %s requires manual reconcile: %w", generation, inspectErr)
	}
	if actualID != created.ID {
		return "", nil, fmt.Errorf("Docker returned an alias reservation id that conflicts with generation %s; manual reconcile required", generation)
	}
	return created.ID, func() {
		if err := locks.remove(alias, generation, created.ID); err != nil {
			logrus.WithError(err).WithFields(logrus.Fields{"alias": alias, "reservation_id": created.ID,
				"reservation_generation": generation}).Error("alias reservation cleanup pending; manual reconcile required")
		}
	}, nil
}

func (locks *dockerAliasReservations) reconcile(alias, generation, expectedID string, cause error) error {
	actualID, inspectErr := locks.inspect(alias, generation)
	if inspectErr != nil {
		return fmt.Errorf("%w; reservation generation %s requires manual reconcile: %v", cause, generation, inspectErr)
	}
	if expectedID != "" && actualID != expectedID {
		return fmt.Errorf("%w; reservation generation %s conflicts with immutable id", cause, generation)
	}
	if cleanupErr := locks.remove(alias, generation, actualID); cleanupErr != nil {
		return fmt.Errorf("%w; reservation %s generation %s cleanup pending: %v", cause, actualID, generation, cleanupErr)
	}
	return fmt.Errorf("%w; reservation %s was removed", cause, actualID)
}

func (locks *dockerAliasReservations) remove(alias, generation, expectedID string) error {
	var deleteErr error
	for attempt := 0; attempt < 2; attempt++ {
		actualID, inspectErr := locks.inspect(alias, generation)
		if errors.Is(inspectErr, os.ErrNotExist) {
			return nil
		}
		if inspectErr != nil {
			return inspectErr
		}
		if actualID != expectedID {
			return errors.New("reservation generation conflicts with immutable id")
		}
		deleteErr = locks.docker.expect(http.MethodDelete, "/containers/"+url.PathEscape(expectedID)+"?force=1&v=0", nil,
			http.StatusNoContent)
		if deleteErr == nil {
			return nil
		}
		if errors.Is(deleteErr, os.ErrNotExist) {
			_, confirmErr := locks.inspect(alias, generation)
			if errors.Is(confirmErr, os.ErrNotExist) {
				return nil
			}
			return errors.Join(deleteErr, confirmErr)
		}
	}
	return deleteErr
}

func (locks *dockerAliasReservations) inspect(alias, generation string) (string, error) {
	response, err := locks.docker.request(http.MethodGet, "/containers/"+url.PathEscape(reservationPrefix+alias)+"/json", nil)
	if err != nil {
		return "", err
	}
	defer response.Body.Close()
	if response.StatusCode == http.StatusNotFound {
		return "", os.ErrNotExist
	}
	var reservation struct {
		ID     string `json:"Id"`
		Config struct {
			Labels map[string]string `json:"Labels"`
		} `json:"Config"`
	}
	if response.StatusCode != http.StatusOK || json.NewDecoder(response.Body).Decode(&reservation) != nil || reservation.ID == "" ||
		reservation.Config.Labels[reservationLabel] != "true" || reservation.Config.Labels[idLabel] != alias ||
		reservation.Config.Labels[reservationGenLabel] != generation {
		return "", errors.New("reservation name does not identify the expected alias generation")
	}
	return reservation.ID, nil
}

func tenantNetworkName(base, alias string) (string, error) {
	name := base + "-" + alias
	if !networkNamePattern.MatchString(name) {
		return "", errors.New("isolated browser network name is invalid")
	}
	return name, nil
}

func sameContainerReference(id, name, reference string) bool {
	if reference == "" {
		return false
	}
	return id == reference || name == reference || strings.HasPrefix(id, reference) || strings.HasPrefix(reference, id)
}

func (docker dockerClient) trustedGatewayMember(id string) bool {
	response, err := docker.request(http.MethodGet, "/containers/"+url.PathEscape(id)+"/json", nil)
	if err != nil {
		return false
	}
	defer response.Body.Close()
	var container struct {
		ID     string `json:"Id"`
		Config struct {
			Labels map[string]string `json:"Labels"`
		} `json:"Config"`
	}
	return response.StatusCode == http.StatusOK && json.NewDecoder(response.Body).Decode(&container) == nil &&
		container.ID != "" && container.Config.Labels[gatewayMemberLabel] == "true"
}

func (docker dockerClient) inspectTenantNetwork(base, alias string, bindingVersion int64, runtimeID, self, expectedID string,
	allowUnversioned bool) (tenantNetworkGeneration, map[string]string, bool, error) {
	name, err := tenantNetworkName(base, alias)
	if err != nil {
		return tenantNetworkGeneration{}, nil, false, err
	}
	generation := tenantNetworkGeneration{ID: expectedID, Name: name}
	reference := name
	if expectedID != "" {
		reference = expectedID
	}
	response, err := docker.request(http.MethodGet, "/networks/"+url.PathEscape(reference), nil)
	if err != nil {
		return generation, nil, false, err
	}
	defer response.Body.Close()
	if response.StatusCode == http.StatusNotFound {
		return generation, nil, false, nil
	}
	var network dockerTenantNetwork
	if response.StatusCode != http.StatusOK || json.NewDecoder(response.Body).Decode(&network) != nil || network.ID == "" ||
		network.Name != name || network.Driver != "bridge" || network.Internal || network.Attachable || network.Ingress ||
		network.Labels[managedLabel] != "true" || network.Labels[networkRoleLabel] != browserNetworkRole || network.Labels[idLabel] != alias {
		return generation, nil, false, errors.New("refusing to operate on an unowned browser network")
	}
	if expectedID != "" && network.ID != expectedID {
		return generation, nil, false, errGenerationConflict
	}
	networkVersion := network.Labels[bindingVersionLabel]
	if networkVersion != strconv.FormatInt(bindingVersion, 10) && !(allowUnversioned && networkVersion == "") {
		return generation, nil, false, errGenerationConflict
	}
	generation.ID = network.ID
	addresses := make(map[string]string, len(network.Containers))
	for id, member := range network.Containers {
		addresses[id] = member.IPv4Address
		if id == runtimeID {
			generation.RuntimeAttached = true
			continue
		}
		if !docker.trustedGatewayMember(id) {
			return generation, nil, false, errGenerationConflict
		}
		generation.GatewayMembers = append(generation.GatewayMembers, id)
		if sameContainerReference(id, member.Name, self) {
			generation.SelfMember = id
		}
	}
	return generation, addresses, true, nil
}

func (docker dockerClient) ensureTenantNetwork(base, alias, self string, bindingVersion int64, runtimeID, expectedID string,
	allowUnversioned bool) (tenantNetworkGeneration, string, error) {
	if self == "" {
		return tenantNetworkGeneration{}, "", errors.New("isolated browser network identity is invalid")
	}
	generation, addresses, exists, err := docker.inspectTenantNetwork(base, alias, bindingVersion, runtimeID, self, expectedID, allowUnversioned)
	if err != nil {
		return generation, "", err
	}
	if !exists {
		if expectedID != "" {
			return generation, "", errGenerationConflict
		}
		response, createErr := docker.request(http.MethodPost, "/networks/create", map[string]any{
			"Name": generation.Name, "CheckDuplicate": true, "Driver": "bridge",
			"Labels": map[string]string{managedLabel: "true", networkRoleLabel: browserNetworkRole, idLabel: alias,
				bindingVersionLabel: strconv.FormatInt(bindingVersion, 10)},
		})
		if createErr != nil {
			return generation, "", fmt.Errorf("create isolated browser network result unknown; immutable generation requires manual reconcile: %w", createErr)
		}
		var created struct {
			ID string `json:"Id"`
		}
		if response.StatusCode != http.StatusCreated || json.NewDecoder(response.Body).Decode(&created) != nil || created.ID == "" {
			response.Body.Close()
			return generation, "", errors.New("create isolated browser network result has no immutable id; manual reconcile required")
		}
		response.Body.Close()
		generation.ID, generation.Created = created.ID, true
		observed, currentAddresses, observedExists, inspectErr := docker.inspectTenantNetwork(base, alias, bindingVersion, runtimeID, self, generation.ID, false)
		generation = preserveTenantNetworkGeneration(generation, observed)
		addresses, err = currentAddresses, inspectErr
		if err != nil || !observedExists {
			if err == nil {
				err = errGenerationConflict
			}
			return generation, "", err
		}
	}
	if runtimeID != "" && !generation.RuntimeAttached {
		generation.ConnectedRuntime = true
		if err := docker.expect(http.MethodPost, "/networks/"+url.PathEscape(generation.ID)+"/connect", map[string]any{
			"Container": runtimeID,
		}, http.StatusOK); err != nil {
			observed, _, _, _ := docker.inspectTenantNetwork(base, alias, bindingVersion, runtimeID, self, generation.ID, allowUnversioned)
			generation = preserveTenantNetworkGeneration(generation, observed)
			return generation, "", err
		}
		generation.RuntimeAttached = true
	}
	if generation.SelfMember == "" {
		generation.ConnectedSelf = true
		if err := docker.expect(http.MethodPost, "/networks/"+url.PathEscape(generation.ID)+"/connect", map[string]any{
			"Container": self, "EndpointConfig": map[string]any{"Aliases": []string{browserProxyHost}},
		}, http.StatusOK); err != nil {
			observed, _, _, _ := docker.inspectTenantNetwork(base, alias, bindingVersion, runtimeID, self, generation.ID, allowUnversioned)
			generation = preserveTenantNetworkGeneration(generation, observed)
			return generation, "", err
		}
	}
	observed, currentAddresses, observedExists, inspectErr := docker.inspectTenantNetwork(base, alias, bindingVersion, runtimeID, self, generation.ID, allowUnversioned)
	generation = preserveTenantNetworkGeneration(generation, observed)
	addresses, err = currentAddresses, inspectErr
	if err != nil || !observedExists || generation.SelfMember == "" {
		if err == nil && !observedExists {
			err = errGenerationConflict
		}
		return generation, "", errors.Join(err, errors.New("Docker did not connect the gateway to the isolated network"))
	}
	host, _, _ := net.ParseCIDR(addresses[generation.SelfMember])
	if host == nil {
		return generation, "", errors.New("Docker did not assign the gateway an isolated network address")
	}
	return generation, host.String(), nil
}

func preserveTenantNetworkGeneration(known, observed tenantNetworkGeneration) tenantNetworkGeneration {
	if observed.ID == "" {
		observed.ID = known.ID
	}
	if observed.Name == "" {
		observed.Name = known.Name
	}
	observed.Created = observed.Created || known.Created
	observed.RuntimeAttached = observed.RuntimeAttached || known.RuntimeAttached
	observed.ConnectedRuntime = observed.ConnectedRuntime || known.ConnectedRuntime
	observed.ConnectedSelf = observed.ConnectedSelf || known.ConnectedSelf
	if observed.SelfMember == "" {
		observed.SelfMember = known.SelfMember
	}
	for _, member := range known.GatewayMembers {
		if !memberPresent(observed, member, "") {
			observed.GatewayMembers = append(observed.GatewayMembers, member)
		}
	}
	return observed
}

func (api gateway) requireRuntimeState(alias string, input generationRequest, expectedID string, expectedExists bool) error {
	runtimeID, exists, err := api.requireGeneration(alias, input)
	if err != nil || exists != expectedExists || runtimeID != expectedID {
		return errGenerationConflict
	}
	return nil
}

func memberPresent(generation tenantNetworkGeneration, id, runtimeID string) bool {
	if generation.RuntimeAttached && runtimeID != "" && sameContainerReference(id, "", runtimeID) {
		return true
	}
	for _, member := range generation.GatewayMembers {
		if sameContainerReference(member, "", id) {
			return true
		}
	}
	return false
}

func generationWithoutMember(generation tenantNetworkGeneration, member, runtimeID string) tenantNetworkGeneration {
	if generation.RuntimeAttached && runtimeID != "" && sameContainerReference(member, "", runtimeID) {
		generation.RuntimeAttached = false
	}
	if sameContainerReference(member, "", generation.SelfMember) {
		generation.SelfMember = ""
	}
	members := generation.GatewayMembers[:0:0]
	for _, current := range generation.GatewayMembers {
		if !sameContainerReference(current, "", member) {
			members = append(members, current)
		}
	}
	generation.GatewayMembers = members
	return generation
}

func (api gateway) disconnectTenantNetworkMember(alias string, bindingVersion int64, runtimeID string,
	generation tenantNetworkGeneration, member string, input *generationRequest, expectedRuntime string, expectedExists bool) (tenantNetworkGeneration, error) {
	if input != nil {
		if err := api.requireRuntimeState(alias, *input, expectedRuntime, expectedExists); err != nil {
			return generation, err
		}
	}
	current, _, exists, err := api.docker.inspectTenantNetwork(api.network, alias, bindingVersion, runtimeID, api.self, generation.ID, false)
	if err != nil || !exists {
		return current, err
	}
	if !sameTenantNetworkMembers(current, generation) {
		return current, errGenerationConflict
	}
	if !memberPresent(current, member, runtimeID) {
		return current, nil
	}
	err = api.docker.expect(http.MethodPost, "/networks/"+url.PathEscape(generation.ID)+"/disconnect", map[string]any{
		"Container": member, "Force": true,
	}, http.StatusOK)
	current, _, exists, fenceErr := api.docker.inspectTenantNetwork(api.network, alias, bindingVersion, runtimeID, api.self, generation.ID, false)
	if fenceErr != nil || !exists {
		return current, errGenerationConflict
	}
	if sameTenantNetworkMembers(current, generationWithoutMember(generation, member, runtimeID)) {
		return current, nil
	}
	if err != nil {
		if sameTenantNetworkMembers(current, generation) {
			return current, err
		}
		return current, errGenerationConflict
	}
	if !sameTenantNetworkMembers(current, generation) {
		return current, errGenerationConflict
	}
	return current, errors.New("Docker retained an isolated network member after disconnect")
}

func (api gateway) deleteTenantNetwork(alias string, bindingVersion int64, runtimeID string,
	generation tenantNetworkGeneration, input *generationRequest, expectedRuntime string, expectedExists bool) error {
	if input != nil {
		if err := api.requireRuntimeState(alias, *input, expectedRuntime, expectedExists); err != nil {
			return err
		}
	}
	current, _, exists, err := api.docker.inspectTenantNetwork(api.network, alias, bindingVersion, runtimeID, api.self, generation.ID, false)
	if err != nil {
		return err
	}
	if !exists {
		return nil
	}
	if current.RuntimeAttached || len(current.GatewayMembers) != 0 {
		return errGenerationConflict
	}
	err = api.docker.expect(http.MethodDelete, "/networks/"+url.PathEscape(generation.ID), nil, http.StatusNoContent)
	_, _, exists, fenceErr := api.docker.inspectTenantNetwork(api.network, alias, bindingVersion, runtimeID, api.self, generation.ID, false)
	if fenceErr != nil {
		return errGenerationConflict
	}
	if !exists {
		return nil
	}
	if err != nil {
		return err
	}
	return errors.New("Docker retained the isolated browser network after delete")
}

func (api gateway) removeTenantNetwork(alias string, bindingVersion int64, runtimeID string,
	generation tenantNetworkGeneration, input *generationRequest, expectedRuntime string, expectedExists bool) error {
	if generation.RuntimeAttached || generation.ConnectedRuntime {
		var err error
		generation, err = api.disconnectTenantNetworkMember(alias, bindingVersion, runtimeID, generation, runtimeID,
			input, expectedRuntime, expectedExists)
		if err != nil {
			return fmt.Errorf("disconnect browser from isolated network: %w", err)
		}
	}
	for len(generation.GatewayMembers) > 0 {
		gatewayID := generation.GatewayMembers[0]
		var err error
		generation, err = api.disconnectTenantNetworkMember(alias, bindingVersion, runtimeID, generation, gatewayID,
			input, expectedRuntime, expectedExists)
		if err != nil {
			return fmt.Errorf("disconnect trusted gateway from isolated network: %w", err)
		}
	}
	if err := api.deleteTenantNetwork(alias, bindingVersion, runtimeID, generation, input, expectedRuntime, expectedExists); err != nil {
		return fmt.Errorf("remove isolated browser network: %w", err)
	}
	return nil
}

func validateBrowserNetwork(name string) error {
	if !networkNamePattern.MatchString(name) || len(name) > 31 {
		return errors.New("BROWSER_NETWORK must be a valid network prefix of at most 31 characters")
	}
	if name == controlNetworkName {
		return errors.New("BROWSER_NETWORK must not reuse the control network")
	}
	return nil
}

func statusFor(err error) int {
	switch {
	case errors.Is(err, errInvalidRuntimeID):
		return http.StatusBadRequest
	case errors.Is(err, os.ErrNotExist):
		return http.StatusNotFound
	case errors.Is(err, errUnmanagedContainer):
		return http.StatusForbidden
	case errors.Is(err, errGenerationConflict):
		return http.StatusConflict
	default:
		return http.StatusBadGateway
	}
}

func forwardDockerError(c fiber.Ctx, result *http.Response) error {
	message, _ := io.ReadAll(io.LimitReader(result.Body, 4096))
	status := http.StatusBadGateway
	if result.StatusCode == http.StatusConflict {
		status = http.StatusConflict
	}
	return writeError(c, status, fmt.Errorf("Docker returned %s: %s", result.Status, strings.TrimSpace(string(message))))
}

func writeError(c fiber.Ctx, status int, err error) error {
	return writeJSON(c, status, map[string]string{"error": err.Error()})
}

func writeNetworkError(c fiber.Ctx, status int, err error, networkID string) error {
	return writeJSON(c, status, map[string]string{"error": err.Error(), "network_id": networkID})
}

func writeJSON(c fiber.Ctx, status int, value any) error {
	return c.Status(status).JSON(value)
}