Initial commit: GovAI 政务AI平台

server/pkg/llm/manager.go

@@ -0,0 +1,197 @@
+package llm
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Manager manages multiple LLM providers and routes requests.
+type Manager struct {
+	providers map[string]Provider
+	fallback  string
+}
+
+func NewManager() *Manager {
+	return &Manager{
+		providers: make(map[string]Provider),
+	}
+}
+
+func (m *Manager) Register(name string, provider Provider) {
+	m.providers[name] = provider
+	if m.fallback == "" {
+		m.fallback = name
+	}
+}
+
+func (m *Manager) SetFallback(name string) {
+	m.fallback = name
+}
+
+func (m *Manager) GetProvider(name string) (Provider, error) {
+	if p, ok := m.providers[name]; ok {
+		return p, nil
+	}
+	if p, ok := m.providers[m.fallback]; ok {
+		return p, nil
+	}
+	return nil, fmt.Errorf("no provider found: %s", name)
+}
+
+// Chat performs a blocking chat completion using the specified provider.
+func (m *Manager) Chat(ctx context.Context, providerName string, req *ChatRequest) (*ChatResponse, error) {
+	provider, err := m.GetProvider(providerName)
+	if err != nil {
+		return nil, err
+	}
+	return provider.ChatCompletion(ctx, req)
+}
+
+// ChatStream performs a streaming chat and returns the raw SSE body.
+func (m *Manager) ChatStream(ctx context.Context, providerName string, req *ChatRequest) (io.ReadCloser, error) {
+	provider, err := m.GetProvider(providerName)
+	if err != nil {
+		return nil, err
+	}
+	req.Stream = true
+	return provider.ChatStream(ctx, req)
+}
+
+// StreamEvent represents a normalized SSE event for the frontend.
+type StreamEvent struct {
+	Event     string `json:"event"`
+	Answer    string `json:"answer,omitempty"`
+	MessageID string `json:"message_id,omitempty"`
+	Usage     *Usage `json:"usage,omitempty"`
+}
+
+type Usage struct {
+	PromptTokens     int `json:"prompt_tokens"`
+	CompletionTokens int `json:"completion_tokens"`
+	TotalTokens      int `json:"total_tokens"`
+	Model            string `json:"model"`
+}
+
+// TransformOpenAIStream reads an OpenAI SSE stream and writes normalized events to the writer.
+func TransformOpenAIStream(reader io.Reader, write func(event StreamEvent)) error {
+	scanner := bufio.NewScanner(reader)
+	scanner.Buffer(make([]byte, 64*1024), 256*1024)
+
+	var totalContent string
+	var model string
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "data: ") {
+			continue
+		}
+		data := strings.TrimPrefix(line, "data: ")
+		if data == "[DONE]" {
+			write(StreamEvent{
+				Event: "message_end",
+				Usage: &Usage{
+					TotalTokens: estimateTokens(totalContent),
+					Model:       model,
+				},
+			})
+			break
+		}
+
+		var chunk struct {
+			ID      string `json:"id"`
+			Model   string `json:"model"`
+			Choices []struct {
+				Delta struct {
+					Content string `json:"content"`
+				} `json:"delta"`
+				FinishReason *string `json:"finish_reason"`
+			} `json:"choices"`
+		}
+		if err := json.Unmarshal([]byte(data), &chunk); err != nil {
+			continue
+		}
+
+		model = chunk.Model
+		if len(chunk.Choices) > 0 && chunk.Choices[0].Delta.Content != "" {
+			content := chunk.Choices[0].Delta.Content
+			totalContent += content
+			write(StreamEvent{
+				Event:     "message",
+				Answer:    content,
+				MessageID: chunk.ID,
+			})
+		}
+	}
+	return scanner.Err()
+}
+
+// TransformAnthropicStream reads an Anthropic SSE stream and writes normalized events.
+func TransformAnthropicStream(reader io.Reader, write func(event StreamEvent)) error {
+	scanner := bufio.NewScanner(reader)
+	scanner.Buffer(make([]byte, 64*1024), 256*1024)
+
+	var model string
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "data: ") {
+			if strings.HasPrefix(line, "event: ") {
+				continue
+			}
+			continue
+		}
+		data := strings.TrimPrefix(line, "data: ")
+
+		var event map[string]any
+		if err := json.Unmarshal([]byte(data), &event); err != nil {
+			continue
+		}
+
+		eventType, _ := event["type"].(string)
+		switch eventType {
+		case "message_start":
+			if msg, ok := event["message"].(map[string]any); ok {
+				if m, ok := msg["model"].(string); ok {
+					model = m
+				}
+			}
+		case "content_block_delta":
+			if delta, ok := event["delta"].(map[string]any); ok {
+				if text, ok := delta["text"].(string); ok {
+					write(StreamEvent{
+						Event:  "message",
+						Answer: text,
+					})
+				}
+			}
+		case "message_delta":
+			if usage, ok := event["usage"].(map[string]any); ok {
+				outputTokens := int(getFloat(usage, "output_tokens"))
+				write(StreamEvent{
+					Event: "message_end",
+					Usage: &Usage{
+						CompletionTokens: outputTokens,
+						TotalTokens:      outputTokens,
+						Model:            model,
+					},
+				})
+			}
+		}
+	}
+	return scanner.Err()
+}
+
+func getFloat(m map[string]any, key string) float64 {
+	if v, ok := m[key].(float64); ok {
+		return v
+	}
+	return 0
+}
+
+func estimateTokens(text string) int {
+	return len(text) / 4
+}