sub2api/backend/internal/pkg/lspool/mock_extension_server.go

// Package lspool provides a mock Extension Server that the LS binary connects
// to at startup. The real IDE's extension.js runs a ConnectRPC HTTP/1.1 server
// using connectNodeAdapter. We replicate that protocol here.
//
// Protocol details (from extension.js source):
//   - Transport: HTTP/1.1 on 127.0.0.1 (no TLS)
//   - Auth: x-codeium-csrf-token header on every request
//   - Unary  request  Content-Type: application/proto  (binary protobuf, no envelope)
//     OR application/connect+proto  (with 5-byte envelope)
//   - Unary  response Content-Type: application/proto  (raw binary protobuf, no envelope)
//   - Stream request  Content-Type: application/connect+proto (with 5-byte envelope)
//   - Stream response Content-Type: application/connect+proto (envelope-framed messages)
//
// The LS sends requests with content-type "application/connect+proto" for BOTH
// unary and streaming RPCs.  ConnectRPC's content-type regex:
//
//	/^application\/(connect\+)?(?:(json)(?:; ?charset=utf-?8)?|(proto))$/i
//
// If "connect+" prefix is present → stream mode; otherwise → unary mode.
// However the LS Go client uses the Connect protocol client which always sends
// "application/proto" for unary and "application/connect+proto" for streaming.
//
// We detect the RPC kind from the URL path and respond accordingly.
package lspool

import (
	"encoding/base64"
	"encoding/binary"
	"fmt"
	"io"
	"log/slog"
	"net"
	"net/http"
	"strings"
	"sync"
	"time"

	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
)

// ============================================================
// Proto helpers — hand-encode minimal proto messages so we don't
// need to import the full generated proto package.
// ============================================================

// encodeProtoString writes a proto string field (wire type 2) to a byte slice.
func encodeProtoString(fieldNum int, val string) []byte {
	tag := encodeVarint(uint64(fieldNum<<3 | 2))
	length := encodeVarint(uint64(len(val)))
	out := make([]byte, 0, len(tag)+len(length)+len(val))
	out = append(out, tag...)
	out = append(out, length...)
	out = append(out, []byte(val)...)
	return out
}

// encodeProtoBytes writes a proto bytes/message field (wire type 2).
func encodeProtoBytes(fieldNum int, val []byte) []byte {
	tag := encodeVarint(uint64(fieldNum<<3 | 2))
	length := encodeVarint(uint64(len(val)))
	out := make([]byte, 0, len(tag)+len(length)+len(val))
	out = append(out, tag...)
	out = append(out, length...)
	out = append(out, val...)
	return out
}

// encodeProtoVarint writes a proto varint field (wire type 0).
func encodeProtoVarint(fieldNum int, val uint64) []byte {
	tag := encodeVarint(uint64(fieldNum<<3 | 0))
	v := encodeVarint(val)
	out := make([]byte, 0, len(tag)+len(v))
	out = append(out, tag...)
	out = append(out, v...)
	return out
}

// encodeProtoBool writes a proto bool field.
func encodeProtoBool(fieldNum int, val bool) []byte {
	v := uint64(0)
	if val {
		v = 1
	}
	return encodeProtoVarint(fieldNum, v)
}

func encodeVarint(v uint64) []byte {
	buf := make([]byte, binary.MaxVarintLen64)
	n := binary.PutUvarint(buf, v)
	return buf[:n]
}

// decodeProtoString extracts a string field from raw proto bytes.
func decodeProtoString(data []byte, targetField int) string {
	i := 0
	for i < len(data) {
		if i >= len(data) {
			break
		}
		tag, n := binary.Uvarint(data[i:])
		if n <= 0 {
			break
		}
		i += n
		fieldNum := int(tag >> 3)
		wireType := tag & 0x7

		switch wireType {
		case 0: // varint
			_, n = binary.Uvarint(data[i:])
			if n <= 0 {
				return ""
			}
			i += n
		case 2: // length-delimited
			length, n := binary.Uvarint(data[i:])
			if n <= 0 {
				return ""
			}
			i += n
			if fieldNum == targetField {
				end := i + int(length)
				if end > len(data) {
					return ""
				}
				return string(data[i:end])
			}
			i += int(length)
		case 1: // 64-bit
			i += 8
		case 5: // 32-bit
			i += 4
		default:
			return ""
		}
	}
	return ""
}

// ============================================================
// ConnectRPC envelope helpers
// ============================================================

// connectEnvelope wraps a proto payload in a ConnectRPC streaming envelope:
// 1 byte flags + 4 byte big-endian length + payload
func connectEnvelope(flags byte, payload []byte) []byte {
	frame := make([]byte, 5+len(payload))
	frame[0] = flags
	binary.BigEndian.PutUint32(frame[1:5], uint32(len(payload)))
	copy(frame[5:], payload)
	return frame
}

// connectEndOfStream returns the end-of-stream trailer frame for ConnectRPC.
// flags=0x02 signals end of stream. The payload is a JSON object with empty metadata.
func connectEndOfStream() []byte {
	trailer := []byte("{}")
	return connectEnvelope(0x02, trailer)
}

// unwrapConnectEnvelope strips the 5-byte envelope header from a ConnectRPC message.
// Returns the raw proto payload. If the input is shorter than 5 bytes, returns as-is.
func unwrapConnectEnvelope(body []byte) []byte {
	if len(body) < 5 {
		return body
	}
	// Check if it looks like an envelope: first byte should be 0x00 or 0x01
	if body[0] > 0x02 {
		return body // Not envelope-framed, return raw
	}
	plen := binary.BigEndian.Uint32(body[1:5])
	if int(plen)+5 > len(body) {
		return body // Length mismatch, return raw
	}
	return body[5 : 5+plen]
}

// ============================================================
// OAuthTokenInfo proto builder
// ============================================================

// buildOAuthTokenInfoBinary creates binary-encoded OAuthTokenInfo proto.
//
//	message OAuthTokenInfo {
//	  string access_token = 1;
//	  string token_type = 2;
//	  string refresh_token = 3;
//	  google.protobuf.Timestamp expiry = 4;
//	  bool is_gcp_tos = 6;
//	}
func buildOAuthTokenInfoBinary(accessToken, refreshToken string, expiresAt time.Time) []byte {
	var buf []byte
	buf = append(buf, encodeProtoString(1, accessToken)...)
	buf = append(buf, encodeProtoString(2, "Bearer")...)
	if refreshToken != "" {
		buf = append(buf, encodeProtoString(3, refreshToken)...)
	}
	// Use real expiry if provided, otherwise default to 1 hour from now
	expiry := expiresAt
	if expiry.IsZero() {
		expiry = time.Now().Add(1 * time.Hour)
	}
	ts := &timestamppb.Timestamp{
		Seconds: expiry.Unix(),
	}
	tsBytes, _ := proto.Marshal(ts)
	buf = append(buf, encodeProtoBytes(4, tsBytes)...)
	buf = append(buf, encodeProtoBool(6, true)...)
	return buf
}

// buildUSSTopicWithOAuth creates a USS Topic proto with the OAuth token.
//
//	message Topic { map<string, Row> data = 1; }
//	message Row { string value = 1; int64 e_tag = 2; }
//
// The key in the map is "oauthTokenInfoSentinelKey" and the Row.value is
// base64(toBinary(OAuthTokenInfo)).
func buildUSSTopicWithOAuth(accessToken, refreshToken string, expiresAt time.Time) []byte {
	tokenBin := buildOAuthTokenInfoBinary(accessToken, refreshToken, expiresAt)
	tokenB64 := base64.StdEncoding.EncodeToString(tokenBin)

	// Row: value=tokenB64 (field 1), e_tag=1 (field 2)
	var row []byte
	row = append(row, encodeProtoString(1, tokenB64)...)
	row = append(row, encodeProtoVarint(2, 1)...)

	// Map entry: key="oauthTokenInfoSentinelKey" (field 1), value=row (field 2)
	var entry []byte
	entry = append(entry, encodeProtoString(1, "oauthTokenInfoSentinelKey")...)
	entry = append(entry, encodeProtoBytes(2, row)...)

	// Topic: data map entries use field 1
	var topic []byte
	topic = append(topic, encodeProtoBytes(1, entry)...)

	return topic
}

func buildPrimitiveBoolBinary(val bool) []byte {
	// Primitive.bool_value is field 13 in the proto definition
	return encodeProtoBool(13, val)
}

func buildPrimitiveInt32Binary(val int32) []byte {
	// Primitive.int32_value is field 3 in the proto definition
	return encodeProtoVarint(3, uint64(uint32(val)))
}

func encodeUSSBinaryValue(value []byte) string {
	return base64.StdEncoding.EncodeToString(value)
}

func encodeUSSPrimitiveBoolValue(val bool) string {
	return encodeUSSBinaryValue(buildPrimitiveBoolBinary(val))
}

func encodeUSSPrimitiveInt32Value(val int32) string {
	return encodeUSSBinaryValue(buildPrimitiveInt32Binary(val))
}

func buildUSSTopicRow(key string, value string) []byte {
	row := buildUSSRowBinary(value)

	var entry []byte
	entry = append(entry, encodeProtoString(1, key)...)
	entry = append(entry, encodeProtoBytes(2, row)...)
	return entry
}

func buildUSSRowBinary(value string) []byte {
	var row []byte
	row = append(row, encodeProtoString(1, value)...)
	row = append(row, encodeProtoVarint(2, 1)...)
	return row
}

func buildUSSTopicWithModelCredits(info *ModelCreditsInfo) []byte {
	if info == nil {
		info = &ModelCreditsInfo{}
	}

	minimum := defaultMinimumCreditAmountForUsage
	if info.MinimumCreditAmountForUsage != nil {
		minimum = *info.MinimumCreditAmountForUsage
	}

	entries := make([][]byte, 0, 3)
	entries = append(entries, buildUSSTopicRow(
		useAICreditsSentinelKey,
		encodeUSSPrimitiveBoolValue(info.UseAICredits),
	))
	// JS protocol: useAICreditsSentinelKey carries the toggle state.
	// availableCreditsSentinelKey is only present when credits are enabled.
	if info.UseAICredits {
		credits := int32(9999)
		if info.AvailableCredits != nil {
			credits = *info.AvailableCredits
		}
		entries = append(entries, buildUSSTopicRow(availableCreditsSentinelKey, encodeUSSPrimitiveInt32Value(credits)))
	}
	entries = append(entries, buildUSSTopicRow(minimumCreditAmountForUsageKey, encodeUSSPrimitiveInt32Value(minimum)))

	var topic []byte
	for _, entry := range entries {
		topic = append(topic, encodeProtoBytes(1, entry)...)
	}
	return topic
}

// buildEmptyTopic returns an empty USS Topic proto (for non-oauth topics).
func buildEmptyTopic() []byte {
	return []byte{} // Empty message = no map entries
}

// ============================================================
// UnifiedStateSyncUpdate builder
// ============================================================

// buildInitialStateUpdate creates a UnifiedStateSyncUpdate with initial_state set.
//
//	message UnifiedStateSyncUpdate {
//	  oneof update_type {
//	    Topic initial_state = 1;
//	    AppliedUpdate applied_update = 2;
//	  }
//	}
func buildInitialStateUpdate(topicData []byte) []byte {
	return encodeProtoBytes(1, topicData)
}

func buildAppliedUpdate(key string, row []byte) []byte {
	var applied []byte
	applied = append(applied, encodeProtoString(1, key)...)
	if len(row) > 0 {
		applied = append(applied, encodeProtoBytes(2, row)...)
	}
	return encodeProtoBytes(2, applied)
}

// ============================================================
// MockExtensionServer
// ============================================================

// MockExtensionServer provides a ConnectRPC-compatible HTTP server that the
// Language Server binary connects to. It implements just enough of the
// ExtensionServerService to keep the LS operational.
type MockExtensionServer struct {
	listener      net.Listener
	server        *http.Server
	port          int
	csrf          string
	mu            sync.RWMutex
	tokens        map[string]*TokenInfo        // account_id -> token info
	credits       map[string]*ModelCreditsInfo // account_id -> model credits info
	subscribers   map[string]map[int]*stateSubscriber
	nextSubID     int
	lastAccountID string
	logger        *slog.Logger

	// Trajectory callback — when LS pushes trajectory updates, we forward them
	onTrajectoryUpdate func(topic, key string, data []byte)
}

// TokenInfo holds OAuth token details for an account.
type TokenInfo struct {
	AccessToken  string
	RefreshToken string
	ExpiresAt    time.Time // zero value means unknown; defaults to now+1h
}

// ModelCreditsInfo mirrors the JS uss-modelCredits topic state.
type ModelCreditsInfo struct {
	UseAICredits                bool
	AvailableCredits            *int32
	MinimumCreditAmountForUsage *int32
}

type stateSubscriber struct {
	id        int
	accountID string
	topic     string
	updates   chan []byte
}

const (
	useAICreditsSentinelKey            = "useAICreditsSentinelKey"
	availableCreditsSentinelKey        = "availableCreditsSentinelKey"
	minimumCreditAmountForUsageKey     = "minimumCreditAmountForUsageKey"
	defaultMinimumCreditAmountForUsage = int32(50)
)

// NewMockExtensionServer creates a mock extension server with proper ConnectRPC handling.
func NewMockExtensionServer(csrf string) (*MockExtensionServer, error) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return nil, fmt.Errorf("listen: %w", err)
	}

	m := &MockExtensionServer{
		listener:    listener,
		port:        listener.Addr().(*net.TCPAddr).Port,
		csrf:        csrf,
		tokens:      make(map[string]*TokenInfo),
		credits:     make(map[string]*ModelCreditsInfo),
		subscribers: make(map[string]map[int]*stateSubscriber),
		logger:      slog.Default().With("component", "mock-ext-server"),
	}

	mux := http.NewServeMux()
	extService := "/exa.extension_server_pb.ExtensionServerService/"

	// Register all RPCs the LS calls on the Extension Server.
	// Unary RPCs — return application/proto
	mux.HandleFunc(extService+"LanguageServerStarted", m.handleUnary(m.onLanguageServerStarted))
	mux.HandleFunc(extService+"Heartbeat", m.handleUnary(m.onHeartbeat))
	mux.HandleFunc(extService+"GetSecretValue", m.handleUnary(m.onGetSecretValue))
	mux.HandleFunc(extService+"StoreSecretValue", m.handleUnary(m.onStoreSecretValue))
	mux.HandleFunc(extService+"IsAgentManagerEnabled", m.handleUnary(m.onIsAgentManagerEnabled))
	mux.HandleFunc(extService+"PushUnifiedStateSyncUpdate", m.handleUnary(m.onPushUnifiedStateSyncUpdate))
	mux.HandleFunc(extService+"RecordError", m.handleUnary(m.onRecordError))
	mux.HandleFunc(extService+"LogEvent", m.handleUnary(m.onLogEvent))
	mux.HandleFunc(extService+"UpdateCascadeTrajectorySummaries", m.handleUnary(m.onUpdateTrajectorySummaries))
	mux.HandleFunc(extService+"BroadcastConversationDeletion", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"WriteCascadeEdit", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"OpenDiffZones", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"HandleAsyncPostMessage", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"OpenFilePointer", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"OpenVirtualFile", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"SaveDocument", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"RestartUserStatusUpdater", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"FocusIDEWindow", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"SmartFocusConversation", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"RunExtensionCode", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"UpdateDetailedViewWithCascadeInput", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"FindAllReferences", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"GetDefinition", m.handleUnary(m.onDefault))
	mux.HandleFunc(extService+"GetLintErrors", m.handleUnary(m.onDefault))

	// Server-streaming RPCs — return application/connect+proto
	mux.HandleFunc(extService+"SubscribeToUnifiedStateSyncTopic", m.handleStream(m.onSubscribeStateSyncTopic))
	mux.HandleFunc(extService+"ExecuteCommand", m.handleStream(m.onExecuteCommand))

	// Catch-all for any unregistered RPCs
	mux.HandleFunc("/", m.handleCatchAll)

	m.server = &http.Server{Handler: mux}

	go func() {
		if err := m.server.Serve(listener); err != http.ErrServerClosed {
			m.logger.Error("extension server error", "err", err)
		}
	}()

	m.logger.Info("mock extension server started", "port", m.port, "csrf_len", len(csrf))
	return m, nil
}

// Port returns the listening port.
func (m *MockExtensionServer) Port() int {
	return m.port
}

// SetToken sets the OAuth token for an account.
func (m *MockExtensionServer) SetToken(accountID string, info *TokenInfo) {
	m.mu.Lock()
	m.tokens[accountID] = info
	m.lastAccountID = accountID
	subscribers := m.snapshotSubscribersLocked("uss-oauth", accountID)
	m.mu.Unlock()

	if info == nil {
		return
	}
	tokenBin := buildOAuthTokenInfoBinary(info.AccessToken, info.RefreshToken, info.ExpiresAt)
	tokenB64 := base64.StdEncoding.EncodeToString(tokenBin)
	m.publishTopicUpdate(subscribers, buildAppliedUpdate("oauthTokenInfoSentinelKey", buildUSSRowBinary(tokenB64)))
}

// SetModelCredits sets the uss-modelCredits state for an account.
func (m *MockExtensionServer) SetModelCredits(accountID string, info *ModelCreditsInfo) {
	if info == nil {
		info = &ModelCreditsInfo{}
	}
	copyInfo := *info
	m.mu.Lock()
	m.credits[accountID] = &copyInfo
	m.lastAccountID = accountID
	subscribers := m.snapshotSubscribersLocked("uss-modelCredits", accountID)
	m.mu.Unlock()

	m.publishTopicUpdate(subscribers, buildModelCreditsAppliedUpdates(&copyInfo)...)
}

// SetTrajectoryCallback registers a callback for when the LS pushes trajectory data.
func (m *MockExtensionServer) SetTrajectoryCallback(fn func(topic, key string, data []byte)) {
	m.onTrajectoryUpdate = fn
}

func (m *MockExtensionServer) currentTokenLocked() *TokenInfo {
	if m.lastAccountID != "" {
		if info := m.tokens[m.lastAccountID]; info != nil {
			return info
		}
	}
	for _, info := range m.tokens {
		return info
	}
	return nil
}

func (m *MockExtensionServer) currentModelCreditsLocked() *ModelCreditsInfo {
	if m.lastAccountID != "" {
		if info := m.credits[m.lastAccountID]; info != nil {
			return info
		}
	}
	for _, info := range m.credits {
		return info
	}
	return nil
}

func (m *MockExtensionServer) tokenForAccountLocked(accountID string) *TokenInfo {
	if accountID != "" {
		if info := m.tokens[accountID]; info != nil {
			return info
		}
	}
	return m.currentTokenLocked()
}

func (m *MockExtensionServer) creditsForAccountLocked(accountID string) *ModelCreditsInfo {
	if accountID != "" {
		if info := m.credits[accountID]; info != nil {
			return info
		}
	}
	return m.currentModelCreditsLocked()
}

func (m *MockExtensionServer) snapshotSubscribersLocked(topic, accountID string) []*stateSubscriber {
	topicSubs := m.subscribers[topic]
	if len(topicSubs) == 0 {
		return nil
	}
	out := make([]*stateSubscriber, 0, len(topicSubs))
	for _, sub := range topicSubs {
		if sub == nil {
			continue
		}
		if accountID != "" && sub.accountID != "" && sub.accountID != accountID {
			continue
		}
		out = append(out, sub)
	}
	return out
}

func (m *MockExtensionServer) publishTopicUpdate(subscribers []*stateSubscriber, updates ...[]byte) {
	for _, sub := range subscribers {
		if sub == nil {
			continue
		}
		for _, update := range updates {
			if len(update) == 0 {
				continue
			}
			payload := append([]byte(nil), update...)
			select {
			case sub.updates <- payload:
			default:
				m.logger.Warn("dropping USS update", "topic", sub.topic, "account", sub.accountID)
			}
		}
	}
}

func buildModelCreditsAppliedUpdates(info *ModelCreditsInfo) [][]byte {
	if info == nil {
		info = &ModelCreditsInfo{}
	}
	minimum := defaultMinimumCreditAmountForUsage
	if info.MinimumCreditAmountForUsage != nil {
		minimum = *info.MinimumCreditAmountForUsage
	}

	updates := make([][]byte, 0, 3)
	updates = append(updates, buildAppliedUpdate(
		useAICreditsSentinelKey,
		buildUSSRowBinary(encodeUSSPrimitiveBoolValue(info.UseAICredits)),
	))

	if info.UseAICredits {
		credits := int32(9999)
		if info.AvailableCredits != nil {
			credits = *info.AvailableCredits
		}
		updates = append(updates, buildAppliedUpdate(
			availableCreditsSentinelKey,
			buildUSSRowBinary(encodeUSSPrimitiveInt32Value(credits)),
		))
	} else {
		updates = append(updates, buildAppliedUpdate(availableCreditsSentinelKey, nil))
	}
	updates = append(updates, buildAppliedUpdate(
		minimumCreditAmountForUsageKey,
		buildUSSRowBinary(encodeUSSPrimitiveInt32Value(minimum)),
	))

	return updates
}

// Close shuts down the server.
func (m *MockExtensionServer) Close() error {
	return m.server.Close()
}

// ============================================================
// Middleware
// ============================================================

type unaryHandler func(body []byte) []byte
type streamHandler func(body []byte, w http.ResponseWriter, r *http.Request)

// handleUnary wraps a unary RPC handler with CSRF check and proper content-type.
func (m *MockExtensionServer) handleUnary(handler unaryHandler) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// CSRF check
		if !m.checkCSRF(w, r) {
			return
		}

		body, err := io.ReadAll(r.Body)
		if err != nil {
			m.logger.Error("read body", "err", err, "path", r.URL.Path)
			w.Header().Set("Content-Type", "application/proto")
			w.WriteHeader(200)
			return
		}

		// The LS might send with envelope framing (application/connect+proto)
		// or without (application/proto). Detect and unwrap.
		ct := r.Header.Get("Content-Type")
		protoBody := body
		if strings.Contains(ct, "connect+proto") && len(body) >= 5 {
			protoBody = unwrapConnectEnvelope(body)
		}

		m.logger.Debug("unary RPC", "path", r.URL.Path, "body_len", len(protoBody), "content_type", ct)

		responseProto := handler(protoBody)

		// Respond with proper unary ConnectRPC content-type.
		// If the request used "connect+proto", the response should be "application/proto"
		// for unary RPCs (ConnectRPC spec: unary uses application/proto, not connect+proto).
		w.Header().Set("Content-Type", "application/proto")
		w.WriteHeader(200)
		if len(responseProto) > 0 {
			w.Write(responseProto)
		}
	}
}

// handleStream wraps a server-streaming RPC handler with CSRF and content-type.
func (m *MockExtensionServer) handleStream(handler streamHandler) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !m.checkCSRF(w, r) {
			return
		}

		body, err := io.ReadAll(r.Body)
		if err != nil {
			m.logger.Error("read body", "err", err, "path", r.URL.Path)
			return
		}

		// Unwrap envelope from request
		ct := r.Header.Get("Content-Type")
		if strings.Contains(ct, "connect+proto") || strings.Contains(ct, "connect+json") {
			body = unwrapConnectEnvelope(body)
		}

		m.logger.Debug("stream RPC", "path", r.URL.Path, "body_len", len(body))

		// Set streaming response content-type
		w.Header().Set("Content-Type", "application/connect+proto")
		w.WriteHeader(200)

		handler(body, w, r)
	}
}

func (m *MockExtensionServer) checkCSRF(w http.ResponseWriter, r *http.Request) bool {
	token := r.Header.Get("x-codeium-csrf-token")
	if m.csrf != "" && token != m.csrf {
		m.logger.Warn("CSRF mismatch", "path", r.URL.Path, "got", token[:min(8, len(token))])
		w.Header().Set("Content-Type", "text/plain")
		w.WriteHeader(403)
		w.Write([]byte("Invalid CSRF token"))
		return false
	}
	return true
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

// ============================================================
// Unary RPC Handlers — each receives raw proto request body,
// returns raw proto response body.
// ============================================================

func (m *MockExtensionServer) onLanguageServerStarted(body []byte) []byte {
	// LanguageServerStartedRequest has: https_port(1), http_port(2), lsp_port(3), csrf_token(4)
	// We just log the ports — they're informational.
	m.logger.Info("LanguageServerStarted",
		"body_len", len(body))
	// Return empty LanguageServerStartedResponse
	return nil
}

func (m *MockExtensionServer) onHeartbeat(body []byte) []byte {
	// Return empty HeartbeatResponse
	return nil
}

func (m *MockExtensionServer) onGetSecretValue(body []byte) []byte {
	// GetSecretValueRequest: key = field 1
	key := decodeProtoString(body, 1)
	m.logger.Debug("GetSecretValue", "key", key)

	m.mu.RLock()
	var token string
	if info := m.currentTokenLocked(); info != nil {
		token = info.AccessToken
	}
	m.mu.RUnlock()

	// GetSecretValueResponse: value = field 1
	if token != "" {
		return encodeProtoString(1, token)
	}
	return nil
}

func (m *MockExtensionServer) onStoreSecretValue(body []byte) []byte {
	key := decodeProtoString(body, 1)
	m.logger.Debug("StoreSecretValue", "key", key)
	return nil
}

func (m *MockExtensionServer) onIsAgentManagerEnabled(body []byte) []byte {
	// IsAgentManagerEnabledResponse: enabled = field 1 (bool)
	return encodeProtoBool(1, false)
}

func (m *MockExtensionServer) onPushUnifiedStateSyncUpdate(body []byte) []byte {
	// PushUnifiedStateSyncUpdateRequest: update = field 1 (UpdateRequest message)
	// UpdateRequest: topic_name = field 1, applied_update = field 5, key = field 2
	m.logger.Debug("PushUnifiedStateSyncUpdate", "body_len", len(body))

	// Extract topic name from the embedded UpdateRequest
	// The body is PushUnifiedStateSyncUpdateRequest, field 1 is the UpdateRequest
	// We need to dig into the nested message to get topic_name
	if m.onTrajectoryUpdate != nil {
		// For now, just notify that an update was pushed
		m.onTrajectoryUpdate("", "", body)
	}

	// Return empty PushUnifiedStateSyncUpdateResponse
	return nil
}

func (m *MockExtensionServer) onRecordError(body []byte) []byte {
	m.logger.Debug("RecordError", "body_len", len(body))
	return nil
}

func (m *MockExtensionServer) onLogEvent(body []byte) []byte {
	return nil
}

func (m *MockExtensionServer) onUpdateTrajectorySummaries(body []byte) []byte {
	m.logger.Debug("UpdateCascadeTrajectorySummaries", "body_len", len(body))
	return nil
}

func (m *MockExtensionServer) onDefault(body []byte) []byte {
	return nil
}

// ============================================================
// Streaming RPC Handlers
// ============================================================

func (m *MockExtensionServer) onSubscribeStateSyncTopic(body []byte, w http.ResponseWriter, r *http.Request) {
	// SubscribeToUnifiedStateSyncTopicRequest: topic = field 1
	topic := decodeProtoString(body, 1)
	m.logger.Info("SubscribeToUnifiedStateSyncTopic", "topic", topic)

	flusher, ok := w.(http.Flusher)
	if !ok {
		m.logger.Error("ResponseWriter does not support Flush")
		return
	}

	m.mu.Lock()
	accountID := m.lastAccountID
	subID := m.nextSubID
	m.nextSubID++
	sub := &stateSubscriber{
		id:        subID,
		accountID: accountID,
		topic:     topic,
		updates:   make(chan []byte, 16),
	}
	if m.subscribers[topic] == nil {
		m.subscribers[topic] = make(map[int]*stateSubscriber)
	}
	m.subscribers[topic][subID] = sub

	// Build initial state based on topic
	var topicData []byte
	switch topic {
	case "uss-oauth":
		tokenInfo := m.tokenForAccountLocked(accountID)
		if tokenInfo != nil {
			topicData = buildUSSTopicWithOAuth(tokenInfo.AccessToken, tokenInfo.RefreshToken, tokenInfo.ExpiresAt)
		} else {
			topicData = buildEmptyTopic()
		}
	case "uss-modelCredits":
		creditsInfo := m.creditsForAccountLocked(accountID)
		if creditsInfo != nil {
			topicData = buildUSSTopicWithModelCredits(creditsInfo)
		} else {
			topicData = buildEmptyTopic()
		}
	default:
		// For all other topics (browserPreferences, enterprisePreferences, etc.),
		// return empty topic data.
		topicData = buildEmptyTopic()
	}
	m.mu.Unlock()
	defer func() {
		m.mu.Lock()
		if topicSubs := m.subscribers[topic]; topicSubs != nil {
			delete(topicSubs, subID)
			if len(topicSubs) == 0 {
				delete(m.subscribers, topic)
			}
		}
		m.mu.Unlock()
	}()

	// Send initial state as envelope-framed message
	initialUpdate := buildInitialStateUpdate(topicData)
	frame := connectEnvelope(0x00, initialUpdate)
	w.Write(frame)
	flusher.Flush()

	for {
		select {
		case <-r.Context().Done():
			m.logger.Debug("SubscribeToUnifiedStateSyncTopic stream closed", "topic", topic)
			return
		case update := <-sub.updates:
			if len(update) == 0 {
				continue
			}
			if _, err := w.Write(connectEnvelope(0x00, update)); err != nil {
				m.logger.Debug("SubscribeToUnifiedStateSyncTopic write failed", "topic", topic, "err", err)
				return
			}
			flusher.Flush()
		}
	}
}

func (m *MockExtensionServer) onExecuteCommand(body []byte, w http.ResponseWriter, r *http.Request) {
	m.logger.Debug("ExecuteCommand (mock)", "body_len", len(body))
	// Send end-of-stream immediately — we don't execute commands
	flusher, ok := w.(http.Flusher)
	if !ok {
		return
	}
	w.Write(connectEndOfStream())
	flusher.Flush()
}

// ============================================================
// Catch-all handler
// ============================================================

func (m *MockExtensionServer) handleCatchAll(w http.ResponseWriter, r *http.Request) {
	if !m.checkCSRF(w, r) {
		return
	}
	m.logger.Debug("unhandled RPC (returning empty proto)", "path", r.URL.Path, "method", r.Method)

	// Drain request body
	io.ReadAll(r.Body)

	// Determine if this is likely a unary or streaming request based on content-type.
	ct := r.Header.Get("Content-Type")
	if strings.Contains(ct, "connect+") {
		// Could be streaming — respond with unary proto to be safe
		// (unary Connect requests can also use connect+ prefix in some client impls)
		w.Header().Set("Content-Type", "application/proto")
	} else {
		w.Header().Set("Content-Type", "application/proto")
	}
	w.WriteHeader(200)
}