渠道: 模型名称映射(网关生效 + 渠道侧管理)

- 候选渠道携带 upstream_model, prepareUpstream 改写请求体 model 字段为上游名
- 新增渠道视角绑定 CRUD: GET/POST/PATCH/DELETE /admin/channels/:id/models
- 前端渠道页新增"模型映射": 列出绑定、内联改上游名、解除、添加
- rewriteModel 三种协议通用(model 均在顶层)

Co-Authored-By: Claude <noreply@anthropic.com>

server/internal/channel/channel.go

@@ -27,69 +27,74 @@ func NewService(db *gorm.DB, enc *crypto.Encryptor) *Service {
 	return &Service{db: db, enc: enc, sems: map[uint64]chan struct{}{}}
 }
 
+// Candidate 一个候选渠道 + 该模型的映射关系。
+type Candidate struct {
+	Channel       *store.Channel
+	UpstreamModel string // 全局模型在此渠道的映射名（无绑定则为空，用客户端模型名）
+}
+
 // Candidates 返回可用渠道候选：健康 + 启用，按优先级、权重降序、id 升序排列。
-// model 非空时优先取绑定该模型的渠道；无绑定则退回全局。
-func (s *Service) Candidates(model string) []*store.Channel {
+// model 非空时优先取绑定该模型的渠道（携带 upstream_model 映射）；无绑定则退回全局。
+func (s *Service) Candidates(model string) []Candidate {
 	if model != "" {
 		var b []store.ChannelModelBinding
 		var modelIDs []uint64
 		s.db.Model(&store.Model{}).Where("name = ? AND enabled = ?", model, true).Pluck("id", &modelIDs)
 		if len(modelIDs) > 0 {
 			s.db.Where("model_id IN ?", modelIDs).Find(&b)
-			chs := s.loadBound(b)
-			if len(chs) > 0 {
-				return chs
+			if cands := s.loadBound(b); len(cands) > 0 {
+				return cands
 			}
 		}
 	}
 	var chs []store.Channel
 	s.db.Where("enabled = ? AND health_status = ?", true, store.ChannelHealthHealthy).
 		Order("priority ASC, weight DESC, id ASC").Find(&chs)
-	out := make([]*store.Channel, 0, len(chs))
+	out := make([]Candidate, 0, len(chs))
 	for i := range chs {
-		out = append(out, &chs[i])
+		out = append(out, Candidate{Channel: &chs[i]})
 	}
 	return out
 }
 
-// loadBound 按绑定顺序加载渠道，过滤健康/启用。
-func (s *Service) loadBound(bindings []store.ChannelModelBinding) []*store.Channel {
+// loadBound 按绑定顺序加载渠道候选，过滤健康/启用，携带 upstream_model 映射。
+func (s *Service) loadBound(bindings []store.ChannelModelBinding) []Candidate {
 	if len(bindings) == 0 {
 		return nil
 	}
+	// channel_id -> 绑定（取该渠道对该模型的映射）
+	byChannel := map[uint64]store.ChannelModelBinding{}
 	ids := make([]uint64, 0, len(bindings))
-	seen := map[uint64]bool{}
 	for _, b := range bindings {
-		if !seen[b.ChannelID] {
-			seen[b.ChannelID] = true
+		if _, ok := byChannel[b.ChannelID]; !ok {
 			ids = append(ids, b.ChannelID)
 		}
+		byChannel[b.ChannelID] = b
 	}
 	var chs []store.Channel
 	s.db.Where("id IN ? AND enabled = ? AND health_status = ?", ids, true, store.ChannelHealthHealthy).
 		Order("priority ASC, weight DESC, id ASC").Find(&chs)
-	// 保持绑定顺序
 	byID := map[uint64]*store.Channel{}
 	for i := range chs {
 		byID[chs[i].ID] = &chs[i]
 	}
-	out := make([]*store.Channel, 0, len(ids))
+	out := make([]Candidate, 0, len(ids))
 	for _, id := range ids {
 		if ch, ok := byID[id]; ok {
-			out = append(out, ch)
+			out = append(out, Candidate{Channel: ch, UpstreamModel: byChannel[id].UpstreamModel})
 		}
 	}
 	return out
 }
 
-// Pick 按权重加权随机选一个候选（负载均衡）。
-func (s *Service) Pick(cands []*store.Channel) *store.Channel {
+// Pick 按权重加权随机选一个候选渠道（负载均衡）。
+func (s *Service) Pick(cands []Candidate) *store.Channel {
 	if len(cands) == 0 {
 		return nil
 	}
 	total := 0
 	for _, c := range cands {
-		w := c.Weight
+		w := c.Channel.Weight
 		if w <= 0 {
 			w = 1
 		}
@@ -98,16 +103,16 @@ func (s *Service) Pick(cands []*store.Channel) *store.Channel {
 	n, _ := rand.Int(rand.Reader, big.NewInt(int64(total)))
 	acc := 0
 	for _, c := range cands {
-		w := c.Weight
+		w := c.Channel.Weight
 		if w <= 0 {
 			w = 1
 		}
 		acc += w
 		if int(n.Int64()) < acc {
-			return c
+			return c.Channel
 		}
 	}
-	return cands[len(cands)-1]
+	return cands[len(cands)-1].Channel
 }
 
 // TryAcquire 尝试获取渠道并发槽；渠道满载返回 false（调用方可溢出到其他渠道）。

server/internal/channel/channel_test.go

@@ -54,8 +54,8 @@ func TestCandidatesFiltersUnhealthy(t *testing.T) {
 	if len(cands) != 2 {
 		t.Fatalf("candidates = %d, want 2", len(cands))
 	}
-	if cands[0].Name != "a" {
-		t.Fatalf("first by priority should be a, got %s", cands[0].Name)
+	if cands[0].Channel.Name != "a" {
+		t.Fatalf("first by priority should be a, got %s", cands[0].Channel.Name)
 	}
 }