Initial implementation: AI code review bot for Gitea

- CLI binary with flag/env var configuration
- Gitea API client (PR metadata, diff, CI status, post review)
- OpenAI-compatible LLM client
- Structured review prompt with conventions support
- JSON response parser with validation
- Markdown review formatter for Gitea
- CI failure auto-detection (REQUEST_CHANGES)
- Dry-run mode for testing

llm/client.go

@@ -0,0 +1,99 @@
+package llm
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// Client calls an OpenAI-compatible chat completion API.
+type Client struct {
+	BaseURL string
+	APIKey  string
+	Model   string
+	HTTP    *http.Client
+}
+
+// NewClient creates a new LLM client.
+func NewClient(baseURL, apiKey, model string) *Client {
+	return &Client{
+		BaseURL: strings.TrimRight(baseURL, "/"),
+		APIKey:  apiKey,
+		Model:   model,
+		HTTP:    &http.Client{},
+	}
+}
+
+// Message represents a chat message.
+type Message struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+// ChatRequest is the request payload.
+type ChatRequest struct {
+	Model       string    `json:"model"`
+	Messages    []Message `json:"messages"`
+	Temperature float64   `json:"temperature"`
+}
+
+// ChatResponse is the response from the API.
+type ChatResponse struct {
+	Choices []struct {
+		Message struct {
+			Content string `json:"content"`
+		} `json:"message"`
+	} `json:"choices"`
+}
+
+// Complete sends a chat completion request and returns the assistant's response content.
+func (c *Client) Complete(messages []Message) (string, error) {
+	reqBody := ChatRequest{
+		Model:       c.Model,
+		Messages:    messages,
+		Temperature: 0.1,
+	}
+
+	data, err := json.Marshal(reqBody)
+	if err != nil {
+		return "", fmt.Errorf("marshal request: %w", err)
+	}
+
+	url := c.BaseURL + "/chat/completions"
+	req, err := http.NewRequest("POST", url, bytes.NewReader(data))
+	if err != nil {
+		return "", fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.APIKey)
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.HTTP.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("LLM request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		body, _ := io.ReadAll(resp.Body)
+		return "", fmt.Errorf("LLM API error (status %d): %s", resp.StatusCode, string(body))
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("read response: %w", err)
+	}
+
+	var chatResp ChatResponse
+	if err := json.Unmarshal(body, &chatResp); err != nil {
+		return "", fmt.Errorf("parse response: %w", err)
+	}
+
+	if len(chatResp.Choices) == 0 {
+		return "", fmt.Errorf("no choices in LLM response")
+	}
+
+	return chatResp.Choices[0].Message.Content, nil
+}