Initial push to gitea

internal/summarize/anthropic.go

@@ -0,0 +1,123 @@
+package summarize
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"time"
+)
+
+// Anthropic talks to the Claude Messages API directly via net/http to avoid an
+// SDK dependency. Requires ANTHROPIC_API_KEY (or APIKey set explicitly).
+type Anthropic struct {
+	APIKey    string
+	Model     string
+	MaxTokens int
+	BaseURL   string // optional override; defaults to https://api.anthropic.com
+	Client    *http.Client
+}
+
+func (a *Anthropic) Name() string { return "anthropic-api" }
+
+type anthroMessage struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+type anthroRequest struct {
+	Model     string          `json:"model"`
+	MaxTokens int             `json:"max_tokens"`
+	System    string          `json:"system,omitempty"`
+	Messages  []anthroMessage `json:"messages"`
+}
+
+type anthroContentBlock struct {
+	Type string `json:"type"`
+	Text string `json:"text"`
+}
+
+type anthroResponse struct {
+	Content []anthroContentBlock `json:"content"`
+	Error   *struct {
+		Type    string `json:"type"`
+		Message string `json:"message"`
+	} `json:"error,omitempty"`
+}
+
+func (a *Anthropic) Summarize(ctx context.Context, systemPrompt, userContent string) (string, error) {
+	key := a.APIKey
+	if key == "" {
+		key = os.Getenv("ANTHROPIC_API_KEY")
+	}
+	if key == "" {
+		return "", fmt.Errorf("ANTHROPIC_API_KEY is not set")
+	}
+	model := a.Model
+	if model == "" {
+		model = "claude-sonnet-4-6"
+	}
+	maxTokens := a.MaxTokens
+	if maxTokens == 0 {
+		maxTokens = 4096
+	}
+	baseURL := a.BaseURL
+	if baseURL == "" {
+		baseURL = "https://api.anthropic.com"
+	}
+	client := a.Client
+	if client == nil {
+		client = &http.Client{Timeout: 5 * time.Minute}
+	}
+
+	body := anthroRequest{
+		Model:     model,
+		MaxTokens: maxTokens,
+		System:    systemPrompt,
+		Messages: []anthroMessage{
+			{Role: "user", Content: userContent},
+		},
+	}
+	buf, err := json.Marshal(body)
+	if err != nil {
+		return "", err
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", baseURL+"/v1/messages", bytes.NewReader(buf))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("x-api-key", key)
+	req.Header.Set("anthropic-version", "2023-06-01")
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	respBody, _ := io.ReadAll(resp.Body)
+
+	if resp.StatusCode/100 != 2 {
+		return "", fmt.Errorf("anthropic API %d: %s", resp.StatusCode, string(respBody))
+	}
+
+	var out anthroResponse
+	if err := json.Unmarshal(respBody, &out); err != nil {
+		return "", fmt.Errorf("decoding anthropic response: %w", err)
+	}
+	if out.Error != nil {
+		return "", fmt.Errorf("anthropic error: %s: %s", out.Error.Type, out.Error.Message)
+	}
+
+	var text bytes.Buffer
+	for _, c := range out.Content {
+		if c.Type == "text" {
+			text.WriteString(c.Text)
+		}
+	}
+	return text.String(), nil
+}