feat: add updater package for in-place self-update

internal/updater/updater.go

@@ -0,0 +1,55 @@
+package updater
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/mathismqn/godeez/internal/buildinfo"
+)
+
+const (
+	apiTimeout = 30 * time.Second
+	tmpPattern = ".godeez-update-*"
+)
+
+type Updater struct {
+	client *http.Client
+	Out    io.Writer
+}
+
+func New() *Updater {
+	return &Updater{
+		client: &http.Client{},
+		Out:    io.Discard,
+	}
+}
+
+func (u *Updater) step(format string, args ...any) {
+	fmt.Fprintf(u.Out, format+"...\n", args...)
+}
+
+func (u *Updater) get(ctx context.Context, url string, headers map[string]string) (io.ReadCloser, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("User-Agent", buildinfo.UserAgent())
+	for name, value := range headers {
+		req.Header.Set(name, value)
+	}
+
+	resp, err := u.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		resp.Body.Close()
+
+		return nil, fmt.Errorf("unexpected status code %d from %s", resp.StatusCode, url)
+	}
+
+	return resp.Body, nil
+}