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

backend/internal/service/account_stats_pricing.go

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+package service
+
+import (
+	"context"
+	"strings"
+)
+
+// resolveAccountStatsCost 计算账号统计定价费用。
+// 返回 nil 表示不覆盖，使用默认公式（total_cost × account_rate_multiplier）。
+//
+// 优先级（先命中为准）：
+//  1. 自定义规则（始终尝试，不依赖 ApplyPricingToAccountStats 开关）
+//  2. ApplyPricingToAccountStats 启用时，直接使用本次请求的客户计费（倍率前的 totalCost）
+//  3. 模型定价文件（LiteLLM）中上游模型的默认价格
+//  4. nil → 走默认公式（total_cost × account_rate_multiplier）
+//
+// upstreamModel 是最终发往上游的模型 ID。
+// totalCost 是本次请求的客户计费（倍率前），用于优先级 2。
+// serviceTier 是最终参与用户计费的 OpenAI 服务层级，用于优先级 3。
+func resolveAccountStatsCost(
+	ctx context.Context,
+	channelService *ChannelService,
+	billingService *BillingService,
+	accountID int64,
+	groupID int64,
+	upstreamModel string,
+	tokens UsageTokens,
+	requestCount int,
+	totalCost float64,
+	serviceTier string,
+) *float64 {
+	if channelService == nil || upstreamModel == "" {
+		return nil
+	}
+	channel, err := channelService.GetChannelForGroup(ctx, groupID)
+	if err != nil || channel == nil {
+		return nil
+	}
+
+	platform := channelService.GetGroupPlatform(ctx, groupID)
+
+	// 优先级 1：自定义规则（始终尝试）
+	if cost := tryCustomRules(channel, accountID, groupID, platform, upstreamModel, tokens, requestCount); cost != nil {
+		return cost
+	}
+
+	// 优先级 2：渠道开启"应用模型定价到账号统计"时，直接使用客户计费（倍率前）
+	if channel.ApplyPricingToAccountStats {
+		cost := totalCost
+		if cost <= 0 {
+			return nil
+		}
+		return &cost
+	}
+
+	// 优先级 3：模型定价文件（LiteLLM）默认价格
+	if billingService != nil {
+		return tryModelFilePricing(billingService, upstreamModel, tokens, serviceTier)
+	}
+
+	return nil
+}
+
+// tryModelFilePricing 使用模型定价文件（LiteLLM/fallback）中的价格计算费用。
+func tryModelFilePricing(billingService *BillingService, model string, tokens UsageTokens, serviceTier string) *float64 {
+	pricing, err := billingService.GetModelPricing(model)
+	if err != nil || pricing == nil {
+		return nil
+	}
+	normalizedTier := normalizeBillingServiceTier(serviceTier)
+	if normalizedTier == "priority" || normalizedTier == "fast" || normalizedTier == "flex" ||
+		billingService.shouldApplySessionLongContextPricing(tokens, pricing) {
+		breakdown, err := billingService.CalculateCostWithServiceTier(model, tokens, 1, normalizedTier)
+		if err != nil || breakdown == nil || breakdown.TotalCost <= 0 {
+			return nil
+		}
+		return &breakdown.TotalCost
+	}
+	cost := float64(tokens.InputTokens)*pricing.InputPricePerToken +
+		float64(tokens.OutputTokens)*pricing.OutputPricePerToken +
+		float64(tokens.CacheCreationTokens)*pricing.CacheCreationPricePerToken +
+		float64(tokens.CacheReadTokens)*pricing.CacheReadPricePerToken +
+		float64(tokens.ImageOutputTokens)*pricing.ImageOutputPricePerToken
+	if cost <= 0 {
+		return nil
+	}
+	return &cost
+}
+
+// tryCustomRules 遍历自定义规则，按数组顺序先命中为准。
+func tryCustomRules(
+	channel *Channel, accountID, groupID int64,
+	platform, model string, tokens UsageTokens, requestCount int,
+) *float64 {
+	modelLower := strings.ToLower(model)
+	for _, rule := range channel.AccountStatsPricingRules {
+		if !matchAccountStatsRule(&rule, accountID, groupID) {
+			continue
+		}
+		pricing := findPricingForModel(rule.Pricing, platform, modelLower)
+		if pricing == nil {
+			continue // 规则匹配但模型不在规则定价中，继续下一条
+		}
+		return calculateStatsCost(pricing, tokens, requestCount)
+	}
+	return nil
+}
+
+// matchAccountStatsRule 检查规则是否匹配指定的 accountID 和 groupID。
+// 匹配条件：accountID ∈ rule.AccountIDs 或 groupID ∈ rule.GroupIDs。
+// 如果规则的 AccountIDs 和 GroupIDs 都为空，视为不匹配。
+func matchAccountStatsRule(rule *AccountStatsPricingRule, accountID, groupID int64) bool {
+	if len(rule.AccountIDs) == 0 && len(rule.GroupIDs) == 0 {
+		return false
+	}
+	for _, id := range rule.AccountIDs {
+		if id == accountID {
+			return true
+		}
+	}
+	for _, id := range rule.GroupIDs {
+		if id == groupID {
+			return true
+		}
+	}
+	return false
+}
+
+// findPricingForModel 在定价列表中查找匹配的模型定价。
+// 先精确匹配，再通配符匹配（按配置顺序，先匹配先使用）。
+func findPricingForModel(pricingList []ChannelModelPricing, platform, modelLower string) *ChannelModelPricing {
+	// 精确匹配优先
+	for i := range pricingList {
+		p := &pricingList[i]
+		if !isPlatformMatch(platform, p.Platform) {
+			continue
+		}
+		for _, m := range p.Models {
+			if strings.ToLower(m) == modelLower {
+				return p
+			}
+		}
+	}
+	// 通配符匹配：按配置顺序，先匹配先使用
+	for i := range pricingList {
+		p := &pricingList[i]
+		if !isPlatformMatch(platform, p.Platform) {
+			continue
+		}
+		for _, m := range p.Models {
+			ml := strings.ToLower(m)
+			if !strings.HasSuffix(ml, "*") {
+				continue
+			}
+			prefix := strings.TrimSuffix(ml, "*")
+			if strings.HasPrefix(modelLower, prefix) {
+				return p
+			}
+		}
+	}
+	return nil
+}
+
+// isPlatformMatch 判断平台是否匹配（空平台视为不限平台）。
+func isPlatformMatch(queryPlatform, pricingPlatform string) bool {
+	if queryPlatform == "" || pricingPlatform == "" {
+		return true
+	}
+	return queryPlatform == pricingPlatform
+}
+
+// calculateStatsCost 使用给定的定价计算费用（不含任何倍率，原始费用）。
+func calculateStatsCost(pricing *ChannelModelPricing, tokens UsageTokens, requestCount int) *float64 {
+	if pricing == nil {
+		return nil
+	}
+	switch pricing.BillingMode {
+	case BillingModePerRequest, BillingModeImage:
+		return calculatePerRequestStatsCost(pricing, requestCount)
+	default:
+		return calculateTokenStatsCost(pricing, tokens)
+	}
+}
+
+// calculatePerRequestStatsCost 按次/图片计费。
+func calculatePerRequestStatsCost(pricing *ChannelModelPricing, requestCount int) *float64 {
+	if pricing.PerRequestPrice == nil || *pricing.PerRequestPrice <= 0 {
+		return nil
+	}
+	cost := *pricing.PerRequestPrice * float64(requestCount)
+	return &cost
+}
+
+// calculateTokenStatsCost Token 计费。
+// If the pricing has intervals, find the matching interval by total token count
+// and use its prices instead of the flat pricing fields.
+func calculateTokenStatsCost(pricing *ChannelModelPricing, tokens UsageTokens) *float64 {
+	p := pricing
+	if len(pricing.Intervals) > 0 {
+		totalTokens := tokens.InputTokens + tokens.OutputTokens + tokens.CacheCreationTokens + tokens.CacheReadTokens
+		if iv := FindMatchingInterval(pricing.Intervals, totalTokens); iv != nil {
+			p = &ChannelModelPricing{
+				InputPrice:      iv.InputPrice,
+				OutputPrice:     iv.OutputPrice,
+				CacheWritePrice: iv.CacheWritePrice,
+				CacheReadPrice:  iv.CacheReadPrice,
+				PerRequestPrice: iv.PerRequestPrice,
+			}
+		}
+	}
+	deref := func(ptr *float64) float64 {
+		if ptr == nil {
+			return 0
+		}
+		return *ptr
+	}
+	cost := float64(tokens.InputTokens)*deref(p.InputPrice) +
+		float64(tokens.OutputTokens)*deref(p.OutputPrice) +
+		float64(tokens.CacheCreationTokens)*deref(p.CacheWritePrice) +
+		float64(tokens.CacheReadTokens)*deref(p.CacheReadPrice) +
+		float64(tokens.ImageOutputTokens)*deref(p.ImageOutputPrice)
+	if cost <= 0 {
+		return nil
+	}
+	return &cost
+}
+
+// applyAccountStatsCost resolves the account stats cost for a usage log entry.
+// It resolves the upstream model (falling back to the requested model) and calls
+// the 4-level priority chain via resolveAccountStatsCost.
+func applyAccountStatsCost(
+	ctx context.Context,
+	usageLog *UsageLog,
+	cs *ChannelService, bs *BillingService,
+	accountID int64, groupID int64,
+	upstreamModel, requestedModel string,
+	tokens UsageTokens,
+	totalCost float64,
+) {
+	model := upstreamModel
+	if model == "" {
+		model = requestedModel
+	}
+	requestCount := 1
+	if usageLog != nil && usageLog.ImageCount > 0 {
+		requestCount = usageLog.ImageCount
+	}
+	serviceTier := ""
+	if usageLog != nil && usageLog.ServiceTier != nil {
+		serviceTier = *usageLog.ServiceTier
+	}
+	usageLog.AccountStatsCost = resolveAccountStatsCost(
+		ctx, cs, bs, accountID, groupID, model, tokens, requestCount, totalCost, serviceTier,
+	)
+}