feat: establish Orbit models, migrations and development baseline

sdk/go/client.go

@@ -0,0 +1,80 @@
+package orbit
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// Options currently configures bootstrap health calls. Task, Worker and workflow
+// clients will be added alongside their corresponding server endpoints.
+type Options struct{ HTTPClient *http.Client }
+type Client struct {
+	baseURL string
+	http    *http.Client
+}
+type Health struct {
+	Status string `json:"status"`
+	Scope  string `json:"scope,omitempty"`
+}
+
+// HTTPError exposes the status code without including sensitive response bodies.
+type HTTPError struct{ StatusCode int }
+
+func (e *HTTPError) Error() string { return fmt.Sprintf("orbit returned HTTP %d", e.StatusCode) }
+
+func NewClient(baseURL string, opts Options) (*Client, error) {
+	u, err := url.Parse(baseURL)
+	if err != nil || u == nil || u.Host == "" || (u.Scheme != "http" && u.Scheme != "https") || u.User != nil || u.RawQuery != "" || u.Fragment != "" {
+		return nil, errors.New("Orbit base URL must be absolute HTTP(S), without credentials, query or fragment")
+	}
+	client := opts.HTTPClient
+	if client == nil {
+		client = &http.Client{Timeout: 10 * time.Second}
+	}
+	clone := *client
+	// Do not silently forward requests to another origin through redirects.
+	clone.CheckRedirect = func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }
+	return &Client{baseURL: strings.TrimRight(u.String(), "/"), http: &clone}, nil
+}
+func (c *Client) Liveness(ctx context.Context) (Health, error) { return c.health(ctx, "/health/live") }
+func (c *Client) Readiness(ctx context.Context) (Health, error) {
+	return c.health(ctx, "/health/ready")
+}
+func (c *Client) health(ctx context.Context, path string) (Health, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+path, nil)
+	if err != nil {
+		return Health{}, err
+	}
+	req.Header.Set("Accept", "application/json")
+	response, err := c.http.Do(req)
+	if err != nil {
+		return Health{}, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		return Health{}, &HTTPError{StatusCode: response.StatusCode}
+	}
+	const maxBody = 16 << 10
+	body, err := io.ReadAll(io.LimitReader(response.Body, maxBody+1))
+	if err != nil {
+		return Health{}, err
+	}
+	if len(body) > maxBody {
+		return Health{}, errors.New("Orbit health response exceeds limit")
+	}
+	var health Health
+	if err := json.Unmarshal(body, &health); err != nil {
+		return Health{}, fmt.Errorf("decode Orbit health response: %w", err)
+	}
+	if health.Status == "" {
+		return Health{}, errors.New("Orbit health response is missing status")
+	}
+	return health, nil
+}