Sub2API v1.0 - AI API 网关（二开初始版本，基于上游 Wei-Shaw/sub2api）

backend/internal/handler/openai_chat_completions.go

@@ -0,0 +1,422 @@
+package handler
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ip"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/openai_compat"
+	middleware2 "github.com/Wei-Shaw/sub2api/internal/server/middleware"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+	"go.uber.org/zap"
+)
+
+// ChatCompletions handles OpenAI Chat Completions API requests.
+// POST /v1/chat/completions
+func (h *OpenAIGatewayHandler) ChatCompletions(c *gin.Context) {
+	streamStarted := false
+	defer h.recoverResponsesPanic(c, &streamStarted)
+
+	requestStart := time.Now()
+
+	apiKey, ok := middleware2.GetAPIKeyFromContext(c)
+	if !ok {
+		h.errorResponse(c, http.StatusUnauthorized, "authentication_error", "Invalid API key")
+		return
+	}
+
+	subject, ok := middleware2.GetAuthSubjectFromContext(c)
+	if !ok {
+		h.errorResponse(c, http.StatusInternalServerError, "api_error", "User context not found")
+		return
+	}
+	reqLog := requestLogger(
+		c,
+		"handler.openai_gateway.chat_completions",
+		zap.Int64("user_id", subject.UserID),
+		zap.Int64("api_key_id", apiKey.ID),
+		zap.Any("group_id", apiKey.GroupID),
+	)
+
+	if !h.ensureResponsesDependencies(c, reqLog) {
+		return
+	}
+
+	body, err := readLenientJSONRequestBodyWithPrealloc(c.Request, h.cfg)
+	if err != nil {
+		if maxErr, ok := extractMaxBytesError(err); ok {
+			h.errorResponse(c, http.StatusRequestEntityTooLarge, "invalid_request_error", buildBodyTooLargeMessage(maxErr.Limit))
+			return
+		}
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to read request body")
+		return
+	}
+	if len(body) == 0 {
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Request body is empty")
+		return
+	}
+
+	if !gjson.ValidBytes(body) {
+		logRequestBodyParseFailure(reqLog, body, nil)
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
+		return
+	}
+
+	modelResult := gjson.GetBytes(body, "model")
+	if !modelResult.Exists() || modelResult.Type != gjson.String || modelResult.String() == "" {
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "model is required")
+		return
+	}
+	reqModel := modelResult.String()
+	ensureCompositeTargetPlatform(c, apiKey, reqModel)
+	if !openAICompatibleTextTargetAllowed(c, apiKey, reqModel) {
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Model is not supported by this OpenAI-compatible endpoint for composite groups")
+		return
+	}
+	if cappedBody, changed := applyOpenAIReasoningEffortPolicyForRequest(c, apiKey, body); changed {
+		body = cappedBody
+	}
+	reqStream, ok := parseOpenAICompatibleStream(body)
+	if !ok {
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", invalidStreamFieldTypeMessage)
+		return
+	}
+	if service.IsGPTImageGenerationModel(reqModel) {
+		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "This model is not supported on the Chat Completions endpoint")
+		return
+	}
+
+	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
+
+	setOpsRequestContext(c, reqModel, reqStream)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
+
+	if decision := h.checkSecurityAudit(c, reqLog, apiKey, subject, service.ContentModerationProtocolOpenAIChat, reqModel, body); decision != nil && !decision.AllowNextStage {
+		h.openAISecurityAuditError(c, decision)
+		return
+	}
+	if h.rejectIfCyberSessionBlocked(c, apiKey, body, reqModel, cyberBlockFormatChat) {
+		return
+	}
+
+	// 解析渠道级模型映射
+	channelMapping, _ := h.gatewayService.ResolveChannelMappingAndRestrict(c.Request.Context(), apiKey.GroupID, reqModel)
+
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
+
+	subscription, _ := middleware2.GetSubscriptionFromContext(c)
+	requestPlatform := openAICompatibleRequestPlatform(c.Request.Context(), apiKey)
+
+	service.SetOpsLatencyMs(c, service.OpsAuthLatencyMsKey, time.Since(requestStart).Milliseconds())
+	routingStart := time.Now()
+
+	userReleaseFunc, acquired := h.acquireResponsesUserSlot(c, subject.UserID, subject.Concurrency, reqStream, &streamStarted, reqLog)
+	if !acquired {
+		return
+	}
+	if userReleaseFunc != nil {
+		defer userReleaseFunc()
+	}
+
+	if err := h.billingCacheService.CheckBillingEligibility(c.Request.Context(), apiKey.User, apiKey, apiKey.Group, subscription, service.QuotaPlatform(c.Request.Context(), apiKey)); err != nil {
+		reqLog.Info("openai_chat_completions.billing_eligibility_check_failed", zap.Error(err))
+		status, code, message, retryAfter := billingErrorDetails(err)
+		if retryAfter > 0 {
+			c.Header("Retry-After", strconv.Itoa(retryAfter))
+		}
+		h.handleStreamingAwareError(c, status, code, message, streamStarted)
+		return
+	}
+
+	sessionHash := h.gatewayService.GenerateSessionHash(c, body)
+	promptCacheKey := h.gatewayService.ExtractSessionID(c, body)
+
+	maxAccountSwitches := h.maxAccountSwitches
+	switchCount := 0
+	profitVetoCount := 0
+	failedAccountIDs := make(map[int64]struct{})
+	sameAccountRetryCount := make(map[int64]int)
+	var lastFailoverErr *service.UpstreamFailoverError
+	var oauth429FailoverState service.OpenAIOAuth429FailoverState
+
+	// 分组利润控制：chat completions 文本入口请求级装门并固定 pricingAt。
+	ccPricingCtx, pricingAt := h.gatewayService.WithOpenAIRequestPricingContext(c.Request.Context(), apiKey.GroupID)
+	c.Request = c.Request.WithContext(ccPricingCtx)
+
+	for {
+		if failoverClientGone(c) {
+			return
+		}
+		reqLog.Debug("openai_chat_completions.account_selecting", zap.Int("excluded_account_count", len(failedAccountIDs)))
+		selection, scheduleDecision, err := h.gatewayService.SelectAccountWithSchedulerForCapability(
+			c.Request.Context(),
+			apiKey.GroupID,
+			"",
+			sessionHash,
+			reqModel,
+			failedAccountIDs,
+			service.OpenAIUpstreamTransportAny,
+			service.OpenAIEndpointCapabilityChatCompletions,
+			false,
+			false,
+			true,
+			requestPlatform,
+		)
+		if err != nil {
+			if failoverClientGone(c) {
+				reqLog.Info("openai_chat_completions.account_select_aborted_client_disconnected", zap.Error(err))
+				return
+			}
+			reqLog.Warn("openai_chat_completions.account_select_failed",
+				zap.Error(openAICompatibleSelectionErrorForLog(err, requestPlatform)),
+				zap.Int("excluded_account_count", len(failedAccountIDs)),
+			)
+			if len(failedAccountIDs) == 0 {
+				cls := classifyOpenAICompatibleNoAccountErrorFromGin(c, h.gatewayService, apiKey, reqModel, reqModel)
+				if !cls.ModelNotFound {
+					markOpsRoutingCapacityLimitedIfNoAvailable(c, err)
+				}
+				h.handleStreamingAwareError(c, cls.Status, cls.ErrType, cls.Message, streamStarted)
+				return
+			} else {
+				if lastFailoverErr != nil {
+					h.handleFailoverExhausted(c, lastFailoverErr, streamStarted)
+				} else {
+					h.handleStreamingAwareError(c, http.StatusBadGateway, "api_error", "Upstream request failed", streamStarted)
+				}
+				return
+			}
+		}
+		if selection == nil || selection.Account == nil {
+			cls := classifyOpenAICompatibleNoAccountErrorFromGin(c, h.gatewayService, apiKey, reqModel, reqModel)
+			if !cls.ModelNotFound {
+				markOpsRoutingCapacityLimited(c)
+			}
+			h.handleStreamingAwareError(c, cls.Status, cls.ErrType, cls.Message, streamStarted)
+			return
+		}
+		account := selection.Account
+		sessionHash = ensureOpenAIPoolModeSessionHash(sessionHash, account)
+		reqLog.Debug("openai_chat_completions.account_selected", zap.Int64("account_id", account.ID), zap.String("account_name", account.Name))
+		_ = scheduleDecision
+		setOpsSelectedAccount(c, account.ID, account.Platform)
+
+		accountReleaseFunc, slotResult := h.acquireResponsesAccountSlot(c, apiKey.GroupID, sessionHash, selection, reqStream, &streamStarted, reqLog)
+		if slotResult == openAISlotAcquireProfitVetoed {
+			// 利润终检否决：排除该账号重新选号；否决次数达上限则按无可用账号终止。
+			if !recordOpenAIProfitVeto(failedAccountIDs, account.ID, &profitVetoCount) {
+				h.handleOpenAIProfitVetoExhausted(c, streamStarted, reqLog, profitVetoCount)
+				return
+			}
+			continue
+		}
+		if slotResult != openAISlotAcquireOK {
+			return
+		}
+
+		service.SetOpsLatencyMs(c, service.OpsRoutingLatencyMsKey, time.Since(routingStart).Milliseconds())
+		forwardStart := time.Now()
+
+		forwardBody := body
+		if channelMapping.Mapped {
+			forwardBody = h.gatewayService.ReplaceModelInBody(body, channelMapping.MappedModel)
+		}
+		writerSizeBeforeForward := c.Writer.Size()
+		result, err := func() (*service.OpenAIForwardResult, error) {
+			defer func() {
+				if accountReleaseFunc != nil {
+					accountReleaseFunc()
+				}
+			}()
+			return h.gatewayService.ForwardAsChatCompletions(c.Request.Context(), c, account, forwardBody, promptCacheKey, "")
+		}()
+		cyberBlockKeyChat := ""
+		if service.GetOpsCyberPolicy(c) != nil {
+			cyberBlockKeyChat = service.CyberSessionBlockKey(apiKey.ID, c, body)
+		}
+		h.recordCyberPolicyIfMarked(c, apiKey, account, subscription, reqModel, err != nil, cyberBlockKeyChat, clientRequestedUsageFields(c, channelMapping, reqModel, ""), service.HashUsageRequestPayload(body))
+
+		forwardDurationMs := time.Since(forwardStart).Milliseconds()
+		upstreamLatencyMs, _ := getContextInt64(c, service.OpsUpstreamLatencyMsKey)
+		responseLatencyMs := forwardDurationMs
+		if upstreamLatencyMs > 0 && forwardDurationMs > upstreamLatencyMs {
+			responseLatencyMs = forwardDurationMs - upstreamLatencyMs
+		}
+		service.SetOpsLatencyMs(c, service.OpsResponseLatencyMsKey, responseLatencyMs)
+		if err == nil && result != nil && result.FirstTokenMs != nil {
+			service.SetOpsLatencyMs(c, service.OpsTimeToFirstTokenMsKey, int64(*result.FirstTokenMs))
+		}
+		// #5148 对齐：错误返回携带的部分 result（流中断前上游已计量的 usage）照常
+		// 入账；failover 错误恒定 result=nil，不会重复计费。
+		submitChatUsage := func(res *service.OpenAIForwardResult) {
+			if res == nil {
+				return
+			}
+			userAgent := c.GetHeader("User-Agent")
+			clientIP := ip.GetClientIP(c)
+			inboundEndpoint := GetInboundEndpoint(c)
+			upstreamEndpoint := resolveOpenAIUpstreamEndpoint(c, account, res)
+			quotaPlatform := service.QuotaPlatform(c.Request.Context(), apiKey)
+			sessionID := service.ExtractClientSessionID(c)
+			cyberBlocked := service.GetOpsCyberPolicy(c) != nil
+			h.submitOpenAIUsageRecordTask(c.Request.Context(), res, func(ctx context.Context) {
+				if err := h.gatewayService.RecordUsage(ctx, &service.OpenAIRecordUsageInput{
+					Result:             res,
+					APIKey:             apiKey,
+					User:               apiKey.User,
+					Account:            account,
+					Subscription:       subscription,
+					InboundEndpoint:    inboundEndpoint,
+					UpstreamEndpoint:   upstreamEndpoint,
+					UserAgent:          userAgent,
+					IPAddress:          clientIP,
+					APIKeyService:      h.apiKeyService,
+					QuotaPlatform:      quotaPlatform,
+					SessionID:          sessionID,
+					ChannelUsageFields: clientRequestedUsageFields(c, channelMapping, reqModel, res.UpstreamModel),
+					PricingAt:          pricingAt,
+					CyberBlocked:       cyberBlocked,
+				}); err != nil {
+					logger.L().With(
+						zap.String("component", "handler.openai_gateway.chat_completions"),
+						zap.Int64("user_id", subject.UserID),
+						zap.Int64("api_key_id", apiKey.ID),
+						zap.Any("group_id", apiKey.GroupID),
+						zap.String("model", reqModel),
+						zap.Int64("account_id", account.ID),
+					).Error("openai_chat_completions.record_usage_failed", zap.Error(err))
+				}
+			})
+		}
+		if err != nil {
+			if result != nil && result.ImageCount > 0 {
+				reqLog.Warn("openai_chat_completions.forward_partial_error_with_image_result",
+					zap.Int64("account_id", account.ID),
+					zap.Int("image_count", result.ImageCount),
+					zap.Error(err),
+				)
+			} else {
+				var failoverErr *service.UpstreamFailoverError
+				if errors.As(err, &failoverErr) {
+					if failoverClientGone(c) {
+						reqLog.Info("openai_chat_completions.failover_aborted_client_disconnected",
+							zap.Int64("account_id", account.ID),
+							zap.Int("upstream_status", failoverErr.StatusCode),
+						)
+						return
+					}
+					if c.Writer.Size() != writerSizeBeforeForward {
+						h.handleFailoverExhausted(c, failoverErr, true)
+						return
+					}
+					if failoverErr.ShouldReportAccountScheduleFailure() {
+						h.gatewayService.ReportOpenAIAccountScheduleResult(account.ID, account.GetMappedModel(reqModel), false, nil)
+					}
+					if !failoverErr.ShouldRetryNextAccount() {
+						h.handleFailoverExhausted(c, failoverErr, streamStarted)
+						return
+					}
+					// Pool mode: retry on the same account
+					if failoverErr.RetryableOnSameAccount {
+						retryLimit := account.GetPoolModeRetryCount()
+						if sameAccountRetryCount[account.ID] < retryLimit {
+							sameAccountRetryCount[account.ID]++
+							retryDelay := sameAccountRetryDelayFor(failoverErr, sameAccountRetryCount[account.ID])
+							reqLog.Warn("openai_chat_completions.pool_mode_same_account_retry",
+								zap.Int64("account_id", account.ID),
+								zap.Int("upstream_status", failoverErr.StatusCode),
+								zap.Int("retry_limit", retryLimit),
+								zap.Int("retry_count", sameAccountRetryCount[account.ID]),
+								zap.Duration("retry_delay", retryDelay),
+							)
+							select {
+							case <-c.Request.Context().Done():
+								return
+							case <-time.After(retryDelay):
+							}
+							continue
+						}
+					}
+					h.gatewayService.RecordOpenAIAccountSwitch()
+					failedAccountIDs[account.ID] = struct{}{}
+					lastFailoverErr = failoverErr
+					if switchCount >= maxAccountSwitches {
+						h.handleFailoverExhausted(c, failoverErr, streamStarted)
+						return
+					}
+					switchCount++
+					if h.gatewayService.ShouldStopOpenAIOAuth429Failover(account, failoverErr.StatusCode, switchCount, &oauth429FailoverState) {
+						h.handleFailoverExhausted(c, failoverErr, streamStarted)
+						return
+					}
+					reqLog.Warn("openai_chat_completions.upstream_failover_switching",
+						zap.Int64("account_id", account.ID),
+						zap.Int("upstream_status", failoverErr.StatusCode),
+						zap.Int("switch_count", switchCount),
+						zap.Int("max_switches", maxAccountSwitches),
+					)
+					continue
+				}
+				h.gatewayService.ReportOpenAIAccountScheduleResult(account.ID, account.GetMappedModel(reqModel), false, nil)
+				upstreamErrorAlreadyCommunicated := openAIForwardErrorAlreadyCommunicated(c, writerSizeBeforeForward, err)
+				wroteFallback := false
+				if !upstreamErrorAlreadyCommunicated {
+					wroteFallback = h.ensureOpenAIStreamReadErrorResponse(c, err, streamStarted)
+					if !wroteFallback {
+						wroteFallback = h.ensureForwardErrorResponse(c, streamStarted)
+					}
+				}
+				reqLog.Warn("openai_chat_completions.forward_failed",
+					zap.Int64("account_id", account.ID),
+					zap.Bool("fallback_error_response_written", wroteFallback),
+					zap.Bool("upstream_error_response_already_written", upstreamErrorAlreadyCommunicated),
+					zap.Error(err),
+				)
+				submitChatUsage(result)
+				return
+			}
+		}
+		if result != nil {
+			h.gatewayService.ReportOpenAIAccountScheduleResult(account.ID, account.GetMappedModel(reqModel), true, result.FirstTokenMs)
+		} else {
+			h.gatewayService.ReportOpenAIAccountScheduleResult(account.ID, account.GetMappedModel(reqModel), true, nil)
+		}
+
+		submitChatUsage(result)
+		reqLog.Debug("openai_chat_completions.request_completed",
+			zap.Int64("account_id", account.ID),
+			zap.Int("switch_count", switchCount),
+		)
+		return
+	}
+}
+
+// resolveOpenAIUpstreamEndpoint returns the actual upstream endpoint for an
+// OpenAI-compatible account. A forwarding result is authoritative because a
+// single inbound route may choose raw Chat or a Responses bridge at runtime.
+// The account-based derivation remains as a fallback for existing callers and
+// forwarding paths that do not report their endpoint yet.
+func resolveOpenAIUpstreamEndpoint(c *gin.Context, account *service.Account, result *service.OpenAIForwardResult) string {
+	if result != nil {
+		if endpoint := strings.TrimSpace(result.UpstreamEndpoint); endpoint != "" {
+			return endpoint
+		}
+	}
+	if endpoint := service.GetActualOpenAIUpstreamEndpoint(c); endpoint != "" {
+		return endpoint
+	}
+	if account != nil && account.Type == service.AccountTypeAPIKey &&
+		!openai_compat.ShouldUseResponsesAPI(account.Extra) {
+		return EndpointChatCompletions
+	}
+	return GetUpstreamEndpoint(c, account.Platform)
+}