Add generic LLM worker

internal/llm/client.go

@@ -0,0 +1,159 @@
+package llm
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type Client struct {
+	baseURL string
+	apiKey  string
+	model   string
+	http    *http.Client
+}
+
+type Message struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+type ChatInput struct {
+	System         string          `json:"system,omitempty"`
+	User           string          `json:"user,omitempty"`
+	Messages       []Message       `json:"messages,omitempty"`
+	Temperature    *float64        `json:"temperature,omitempty"`
+	MaxTokens      int             `json:"max_tokens,omitempty"`
+	ResponseFormat json.RawMessage `json:"response_format,omitempty"`
+}
+
+type Usage struct {
+	PromptTokens     int `json:"prompt_tokens"`
+	CompletionTokens int `json:"completion_tokens"`
+	TotalTokens      int `json:"total_tokens"`
+}
+
+type ChatResult struct {
+	Content    string `json:"content"`
+	Model      string `json:"model"`
+	Usage      *Usage `json:"usage,omitempty"`
+	DurationMS int64  `json:"duration_ms"`
+}
+
+type chatRequest struct {
+	Model          string           `json:"model"`
+	Messages       []Message        `json:"messages"`
+	Temperature    float64          `json:"temperature"`
+	MaxTokens      int              `json:"max_tokens,omitempty"`
+	ResponseFormat *json.RawMessage `json:"response_format,omitempty"`
+}
+
+type chatResponse struct {
+	Model   string `json:"model,omitempty"`
+	Choices []struct {
+		Message Message `json:"message"`
+	} `json:"choices"`
+	Usage *Usage `json:"usage,omitempty"`
+	Error *struct {
+		Message string `json:"message"`
+	} `json:"error,omitempty"`
+}
+
+func New(baseURL, apiKey, model string, timeout time.Duration) *Client {
+	return &Client{
+		baseURL: strings.TrimRight(strings.TrimSpace(baseURL), "/"),
+		apiKey:  apiKey,
+		model:   model,
+		http:    &http.Client{Timeout: timeout},
+	}
+}
+
+func (c *Client) Chat(ctx context.Context, in ChatInput) (*ChatResult, error) {
+	if c == nil || c.baseURL == "" {
+		return nil, fmt.Errorf("llm not configured")
+	}
+	messages := normalizeMessages(in)
+	if len(messages) == 0 {
+		return nil, fmt.Errorf("messages are required")
+	}
+	temp := 0.1
+	if in.Temperature != nil {
+		temp = *in.Temperature
+	}
+	reqBody := chatRequest{
+		Model:       c.model,
+		Messages:    messages,
+		Temperature: temp,
+		MaxTokens:   in.MaxTokens,
+	}
+	if len(in.ResponseFormat) > 0 {
+		reqBody.ResponseFormat = &in.ResponseFormat
+	}
+	body, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/v1/chat/completions", bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if c.apiKey != "" {
+		req.Header.Set("Authorization", "Bearer "+c.apiKey)
+	}
+
+	start := time.Now()
+	resp, err := c.http.Do(req)
+	duration := time.Since(start)
+	if err != nil {
+		return nil, fmt.Errorf("llm do: %w", err)
+	}
+	defer resp.Body.Close()
+
+	raw, err := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+	if err != nil {
+		return nil, fmt.Errorf("llm read: %w", err)
+	}
+	if resp.StatusCode >= 300 {
+		return nil, fmt.Errorf("llm HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(raw)))
+	}
+	var out chatResponse
+	if err := json.Unmarshal(raw, &out); err != nil {
+		return nil, fmt.Errorf("llm decode: %w", err)
+	}
+	if out.Error != nil {
+		return nil, fmt.Errorf("llm error: %s", out.Error.Message)
+	}
+	if len(out.Choices) == 0 {
+		return nil, fmt.Errorf("llm: empty choices")
+	}
+	modelName := out.Model
+	if modelName == "" {
+		modelName = c.model
+	}
+	return &ChatResult{
+		Content:    out.Choices[0].Message.Content,
+		Model:      modelName,
+		Usage:      out.Usage,
+		DurationMS: duration.Milliseconds(),
+	}, nil
+}
+
+func normalizeMessages(in ChatInput) []Message {
+	if len(in.Messages) > 0 {
+		return in.Messages
+	}
+	var out []Message
+	if strings.TrimSpace(in.System) != "" {
+		out = append(out, Message{Role: "system", Content: in.System})
+	}
+	if strings.TrimSpace(in.User) != "" {
+		out = append(out, Message{Role: "user", Content: in.User})
+	}
+	return out
+}