feat: Check and apply Windows updates through the Windows Update COM API

internal/updates/winparse.go

@@ -0,0 +1,48 @@
+package updates
+
+import (
+	"encoding/json"
+	"strings"
+)
+
+// winUpdate is one row of the Windows Update searcher's output, in the shape
+// searchScript emits it.
+type winUpdate struct {
+	Title string `json:"title"`
+	KB    string `json:"kb"`
+}
+
+// parseUpdateSearch reads the searcher's JSON.
+//
+// It carries no build tag on purpose: this is the half of the Windows update
+// path that can be tested on a development machine, and the agent module has no
+// Windows CI.
+func parseUpdateSearch(jsonText string) ([]PackageUpdate, error) {
+	s := strings.TrimSpace(jsonText)
+	if s == "" || s == "null" {
+		return nil, nil
+	}
+
+	var rows []winUpdate
+	if err := json.Unmarshal([]byte(s), &rows); err != nil {
+		// ConvertTo-Json renders a one-element array as a bare object.
+		var one winUpdate
+		if err2 := json.Unmarshal([]byte(s), &one); err2 != nil {
+			return nil, err
+		}
+		rows = []winUpdate{one}
+	}
+
+	out := make([]PackageUpdate, 0, len(rows))
+	for _, r := range rows {
+		u := PackageUpdate{Name: r.Title}
+		if kb := strings.TrimSpace(r.KB); kb != "" {
+			if !strings.HasPrefix(strings.ToUpper(kb), "KB") {
+				kb = "KB" + kb
+			}
+			u.NewVersion = kb
+		}
+		out = append(out, u)
+	}
+	return out, nil
+}