feat(infra/llm): Gemini client with stream + count_tokens via google.golang.org/genai

go.mod

@@ -15,6 +15,9 @@ require (
 )
 
 require (
+	cloud.google.com/go v0.121.6 // indirect
+	cloud.google.com/go/auth v0.16.4 // indirect
+	cloud.google.com/go/compute/metadata v0.8.0 // indirect
 	dario.cat/mergo v1.0.2 // indirect
 	github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c // indirect
 	github.com/Microsoft/go-winio v0.6.2 // indirect
@@ -40,6 +43,11 @@ require (
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-ole/go-ole v1.2.6 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
+	github.com/google/go-cmp v0.7.0 // indirect
+	github.com/google/s2a-go v0.1.9 // indirect
+	github.com/googleapis/enterprise-certificate-proxy v0.3.6 // indirect
+	github.com/googleapis/gax-go/v2 v2.15.0 // indirect
+	github.com/gorilla/websocket v1.5.3 // indirect
 	github.com/invopop/jsonschema v0.13.0 // indirect
 	github.com/jackc/pgerrcode v0.0.0-20250907135507-afb5586c32a6 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
@@ -90,8 +98,13 @@ require (
 	go.opentelemetry.io/otel/trace v1.41.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/crypto v0.48.0 // indirect
+	golang.org/x/net v0.49.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
 	golang.org/x/text v0.34.0 // indirect
+	google.golang.org/genai v1.55.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250818200422-3122310a409c // indirect
+	google.golang.org/grpc v1.74.2 // indirect
+	google.golang.org/protobuf v1.36.7 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,3 +1,9 @@
+cloud.google.com/go v0.121.6 h1:waZiuajrI28iAf40cWgycWNgaXPO06dupuS+sgibK6c=
+cloud.google.com/go v0.121.6/go.mod h1:coChdst4Ea5vUpiALcYKXEpR1S9ZgXbhEzzMcMR66vI=
+cloud.google.com/go/auth v0.16.4 h1:fXOAIQmkApVvcIn7Pc2+5J8QTMVbUGLscnSVNl11su8=
+cloud.google.com/go/auth v0.16.4/go.mod h1:j10ncYwjX/g3cdX7GpEzsdM+d+ZNsXAbb6qXA7p1Y5M=
+cloud.google.com/go/compute/metadata v0.8.0 h1:HxMRIbao8w17ZX6wBnjhcDkW6lTFpgcaobyVfZWqRLA=
+cloud.google.com/go/compute/metadata v0.8.0/go.mod h1:sYOGTp851OV9bOFJ9CH7elVvyzopvWQFNNghtDQ/Biw=
 dario.cat/mergo v1.0.2 h1:85+piFYR1tMbRrLcDwR18y4UKJ3aH1Tbzi24VRW1TK8=
 dario.cat/mergo v1.0.2/go.mod h1:E/hbnu0NxMFBjpMIE34DRGLWqDy0g5FuKDhCb31ngxA=
 github.com/AdaLogics/go-fuzz-headers v0.0.0-20240806141605-e8a1dd7889d6 h1:He8afgbRMd7mFxO99hRNu+6tazq8nFF9lIwo9JFroBk=
@@ -71,8 +77,16 @@ github.com/golang-migrate/migrate/v4 v4.19.1/go.mod h1:CTcgfjxhaUtsLipnLoQRWCrjY
 github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/s2a-go v0.1.9 h1:LGD7gtMgezd8a/Xak7mEWL0PjoTQFvpRudN895yqKW0=
+github.com/google/s2a-go v0.1.9/go.mod h1:YA0Ei2ZQL3acow2O62kdp9UlnvMmU7kA6Eutn0dXayM=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/googleapis/enterprise-certificate-proxy v0.3.6 h1:GW/XbdyBFQ8Qe+YAmFU9uHLo7OnF5tL52HFAgMmyrf4=
+github.com/googleapis/enterprise-certificate-proxy v0.3.6/go.mod h1:MkHOF77EYAE7qfSuSS9PU6g4Nt4e11cnsDUowfwewLA=
+github.com/googleapis/gax-go/v2 v2.15.0 h1:SyjDc1mGgZU5LncH8gimWo9lW1DtIfPibOG81vgd/bo=
+github.com/googleapis/gax-go/v2 v2.15.0/go.mod h1:zVVkkxAQHa1RQpg9z2AUCMnKhi0Qld9rcmyfL1OZhoc=
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/invopop/jsonschema v0.13.0 h1:KvpoAJWEjR3uD9Kbm2HWJmqsEaHt8lBUpd0qHcIi21E=
 github.com/invopop/jsonschema v0.13.0/go.mod h1:ffZ5Km5SWWRAIN6wbDXItl95euhFz2uON45H2qjYt+0=
 github.com/jackc/pgerrcode v0.0.0-20250907135507-afb5586c32a6 h1:D/V0gu4zQ3cL2WKeVNVM4r2gLxGGf6McLwgXzRTo2RQ=
@@ -220,6 +234,8 @@ golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
 golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
+golang.org/x/net v0.49.0 h1:eeHFmOGUTtaaPSGNmjBKpbng9MulQsJURQUAfUwY++o=
+golang.org/x/net v0.49.0/go.mod h1:/ysNB2EvaqvesRkuLAyjI1ycPZlQHM3q01F02UY/MV8=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -259,6 +275,15 @@ golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/genai v1.55.0 h1:iLHGk4Bj/IZ/GNNZb7hYqwSJMRBvqLeu2Hb6YQ+rYGw=
+google.golang.org/genai v1.55.0/go.mod h1:A3kkl0nyBjyFlNjgxIwKq70julKbIxpSxqKO5gw/gmk=
+google.golang.org/genproto v0.0.0-20250603155806-513f23925822 h1:rHWScKit0gvAPuOnu87KpaYtjK5zBMLcULh7gxkCXu4=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250818200422-3122310a409c h1:qXWI/sQtv5UKboZ/zUk7h+mrf/lXORyI+n9DKDAusdg=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250818200422-3122310a409c/go.mod h1:gw1tLEfykwDz2ET4a12jcXt4couGAm7IwsVaTy0Sflo=
+google.golang.org/grpc v1.74.2 h1:WoosgB65DlWVC9FqI82dGsZhWFNBSLjQ84bjROOpMu4=
+google.golang.org/grpc v1.74.2/go.mod h1:CtQ+BGjaAIXHs/5YS3i473GqwBBa1zGQNevxdeBEXrM=
+google.golang.org/protobuf v1.36.7 h1:IgrO7UwFQGJdRNXH/sQux4R1Dj1WAKcLElzeeRaXV2A=
+google.golang.org/protobuf v1.36.7/go.mod h1:jduwjTPXsFjZGTmRluh+L6NjiWu7pchiJ2/5YcXBHnY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

internal/infra/llm/gemini.go

@@ -0,0 +1,144 @@
+package llm
+
+import (
+	"context"
+	"fmt"
+
+	"google.golang.org/genai"
+)
+
+// GeminiClient 通过 google.golang.org/genai SDK 调用 Generative AI API。
+// baseURL 可改写以走 Vertex AI 或内部网关。
+type GeminiClient struct {
+	sdk *genai.Client
+}
+
+// Compile-time assertion: GeminiClient must satisfy LLMClient.
+var _ LLMClient = (*GeminiClient)(nil)
+
+// NewGemini 构造 GeminiClient。apiKey 不可空；baseURL 可空（用 SDK 默认端点）。
+func NewGemini(apiKey, baseURL string) (*GeminiClient, error) {
+	cfg := &genai.ClientConfig{
+		APIKey:  apiKey,
+		Backend: genai.BackendGeminiAPI,
+	}
+	if baseURL != "" {
+		// SDK v1.55: HTTPOptions.BaseURL 改写 API 端点，用于 httptest 或自定义网关。
+		cfg.HTTPOptions = genai.HTTPOptions{BaseURL: baseURL}
+	}
+	c, err := genai.NewClient(context.Background(), cfg)
+	if err != nil {
+		return nil, fmt.Errorf("gemini client: %w", err)
+	}
+	return &GeminiClient{sdk: c}, nil
+}
+
+func (c *GeminiClient) Provider() string { return "gemini" }
+
+// toGeminiContents 把中立 Message 切片转换为 SDK *Content 切片。
+// image/document 的 Data 字段为原始字节，Gemini SDK 直接接受（InlineData 不需要 base64 编码）。
+func toGeminiContents(req Request) []*genai.Content {
+	out := make([]*genai.Content, 0, len(req.Messages))
+	for _, m := range req.Messages {
+		role := "user"
+		if m.Role == RoleAssistant {
+			role = "model"
+		}
+		parts := make([]*genai.Part, 0, len(m.Blocks))
+		for _, b := range m.Blocks {
+			switch b.Type {
+			case "text":
+				parts = append(parts, genai.NewPartFromText(b.Text))
+			case "image", "document":
+				// SDK v1.55: Blob.MIMEType 大写，Data 为原始字节（SDK 内部处理编码）。
+				parts = append(parts, &genai.Part{InlineData: &genai.Blob{
+					MIMEType: b.MimeType,
+					Data:     b.Data,
+				}})
+			}
+		}
+		out = append(out, &genai.Content{Role: role, Parts: parts})
+	}
+	return out
+}
+
+func (c *GeminiClient) Stream(ctx context.Context, modelID string, req Request) (<-chan StreamEvent, error) {
+	cfg := &genai.GenerateContentConfig{
+		MaxOutputTokens: int32(req.MaxOutputTokens),
+	}
+	if req.SystemPrompt != "" {
+		cfg.SystemInstruction = &genai.Content{
+			Parts: []*genai.Part{genai.NewPartFromText(req.SystemPrompt)},
+		}
+	}
+	if req.Reasoning {
+		// SDK v1.55: ThinkingConfig.IncludeThoughts 是 bool，不是 *bool；无需 genai.Ptr()。
+		cfg.ThinkingConfig = &genai.ThinkingConfig{IncludeThoughts: true}
+	}
+
+	// SDK v1.55: GenerateContentStream 返回 iter.Seq2[*GenerateContentResponse, error]，
+	// 可用 Go 1.23+ range-over-func 语法直接遍历。
+	iter := c.sdk.Models.GenerateContentStream(ctx, modelID, toGeminiContents(req), cfg)
+	out := make(chan StreamEvent, 16)
+
+	// send 在 ctx 取消时立即放弃发送，防止下游 reader 已退出导致 goroutine 永久阻塞。
+	send := func(ev StreamEvent) bool {
+		select {
+		case <-ctx.Done():
+			return false
+		case out <- ev:
+			return true
+		}
+	}
+
+	go func() {
+		defer close(out)
+		var lastReason string
+		for resp, err := range iter {
+			if err != nil {
+				send(StreamEvent{Type: EventError, Err: fmt.Errorf("gemini stream: %w", err)})
+				return
+			}
+			if len(resp.Candidates) == 0 {
+				continue
+			}
+			cand := resp.Candidates[0]
+			if cand.Content != nil {
+				for _, p := range cand.Content.Parts {
+					if p.Thought {
+						if !send(StreamEvent{Type: EventThinkingDelta, Text: p.Text}) {
+							return
+						}
+					} else if p.Text != "" {
+						if !send(StreamEvent{Type: EventTextDelta, Text: p.Text}) {
+							return
+						}
+					}
+				}
+			}
+			if resp.UsageMetadata != nil {
+				if !send(StreamEvent{Type: EventUsage, Usage: &Usage{
+					PromptTokens:     int(resp.UsageMetadata.PromptTokenCount),
+					CompletionTokens: int(resp.UsageMetadata.CandidatesTokenCount),
+					ThinkingTokens:   int(resp.UsageMetadata.ThoughtsTokenCount),
+				}}) {
+					return
+				}
+			}
+			if cand.FinishReason != "" {
+				lastReason = string(cand.FinishReason)
+			}
+		}
+		send(StreamEvent{Type: EventDone, Reason: lastReason})
+	}()
+	return out, nil
+}
+
+// CountTokens 调用 Gemini 远程 CountTokens 端点计算 token 数。
+func (c *GeminiClient) CountTokens(ctx context.Context, modelID string, req Request) (int, error) {
+	res, err := c.sdk.Models.CountTokens(ctx, modelID, toGeminiContents(req), nil)
+	if err != nil {
+		return 0, fmt.Errorf("gemini count_tokens: %w", err)
+	}
+	return int(res.TotalTokens), nil
+}

internal/infra/llm/gemini_test.go

@@ -0,0 +1,55 @@
+package llm
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Gemini SSE 行格式：每行 "data: {json}\n"，body 内含完整 candidates。
+const geminiStreamFixture = `data: {"candidates":[{"content":{"parts":[{"text":"Hello"}],"role":"model"},"finishReason":null}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":1}}
+
+data: {"candidates":[{"content":{"parts":[{"text":" world"}],"role":"model"},"finishReason":"STOP"}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":2}}
+
+`
+
+func TestGemini_Stream_TextDelta(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(geminiStreamFixture))
+	}))
+	defer srv.Close()
+
+	c, _ := NewGemini("k", srv.URL)
+	ch, err := c.Stream(context.Background(), "gemini-2.0-flash", Request{
+		Messages:        []Message{{Role: RoleUser, Blocks: []ContentBlock{{Type: "text", Text: "hi"}}}},
+		MaxOutputTokens: 100,
+	})
+	require.NoError(t, err)
+
+	var deltas []string
+	var sawUsage, sawDone bool
+	for ev := range ch {
+		switch ev.Type {
+		case EventTextDelta:
+			deltas = append(deltas, ev.Text)
+		case EventUsage:
+			sawUsage = true
+			require.Equal(t, 10, ev.Usage.PromptTokens)
+		case EventDone:
+			sawDone = true
+		}
+	}
+	require.Equal(t, "Hello world", strings.Join(deltas, ""))
+	require.True(t, sawUsage)
+	require.True(t, sawDone)
+}
+
+func TestGemini_Provider(t *testing.T) {
+	c, _ := NewGemini("k", "http://localhost")
+	require.Equal(t, "gemini", c.Provider())
+}