feat: bootstrap goaichat CLI and config system

internal/openai/client.go

@@ -0,0 +1,110 @@
+package openai
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+const defaultTimeout = 30 * time.Second
+
+// Client wraps HTTP access to the OpenAI-compatible Chat Completions API.
+type Client struct {
+	apiKey     string
+	baseURL    string
+	httpClient *http.Client
+}
+
+// ClientOption customizes client construction.
+type ClientOption func(*Client)
+
+// WithHTTPClient overrides the default HTTP client.
+func WithHTTPClient(hc *http.Client) ClientOption {
+	return func(c *Client) {
+		c.httpClient = hc
+	}
+}
+
+// WithBaseURL overrides the default base URL.
+func WithBaseURL(url string) ClientOption {
+	return func(c *Client) {
+		c.baseURL = url
+	}
+}
+
+// NewClient creates a Client with the provided API key and options.
+func NewClient(apiKey string, opts ...ClientOption) (*Client, error) {
+	apiKey = strings.TrimSpace(apiKey)
+	if apiKey == "" {
+		return nil, errors.New("api key cannot be empty")
+	}
+
+	client := &Client{
+		apiKey:  apiKey,
+		baseURL: "https://api.openai.com/v1",
+		httpClient: &http.Client{
+			Timeout: defaultTimeout,
+		},
+	}
+
+	for _, opt := range opts {
+		opt(client)
+	}
+
+	return client, nil
+}
+
+// CreateChatCompletion issues a chat completion request.
+func (c *Client) CreateChatCompletion(ctx context.Context, req ChatCompletionRequest) (*ChatCompletionResponse, error) {
+	if c == nil {
+		return nil, errors.New("client is nil")
+	}
+
+	payload, err := json.Marshal(req)
+	if err != nil {
+		return nil, fmt.Errorf("encode request: %w", err)
+	}
+
+	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/chat/completions", bytes.NewReader(payload))
+	if err != nil {
+		return nil, fmt.Errorf("create request: %w", err)
+	}
+
+	httpReq.Header.Set("Content-Type", "application/json")
+	httpReq.Header.Set("Authorization", "Bearer "+c.apiKey)
+
+	resp, err := c.httpClient.Do(httpReq)
+	if err != nil {
+		return nil, fmt.Errorf("execute request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+		return decodeSuccess(resp.Body)
+	}
+
+	return nil, decodeError(resp.Body, resp.StatusCode)
+}
+
+func decodeSuccess(r io.Reader) (*ChatCompletionResponse, error) {
+	var response ChatCompletionResponse
+	if err := json.NewDecoder(r).Decode(&response); err != nil {
+		return nil, fmt.Errorf("decode response: %w", err)
+	}
+	return &response, nil
+}
+
+func decodeError(r io.Reader, status int) error {
+	var apiErr ErrorResponse
+	if err := json.NewDecoder(r).Decode(&apiErr); err != nil {
+		return fmt.Errorf("api error (status %d): failed to decode body: %w", status, err)
+	}
+
+	return fmt.Errorf("api error (status %d): %s", status, apiErr.Error.Message)
+}