Make product API versions independently installable

backend/product/app/runtime/mounts.go

@@ -0,0 +1,58 @@
+package runtime
+
+import (
+	"path"
+	"strings"
+
+	"git.sendico.io/tech/sxchnge/product/app/api"
+	"git.sendico.io/tech/sxchnge/shared/errors"
+)
+
+func validMount(value string) bool {
+	if value == "" || value == "/" || !strings.HasPrefix(value, "/") || path.Clean(value) != value {
+		return false
+	}
+	for _, c := range value {
+		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || strings.ContainsRune("/-._~", c) {
+			continue
+		}
+		return false
+	}
+	return true
+}
+func overlaps(a, b string) bool {
+	return a == b || strings.HasPrefix(a, b+"/") || strings.HasPrefix(b, a+"/")
+}
+
+func resolveMounts(configured []api.Mount, endpoint string, supported map[string]api.Installer) ([]api.Mount, error) {
+	if !validMount(endpoint) {
+		return nil, merrors.InvalidArgument("a canonical absolute API endpoint is required", "api_endpoint")
+	}
+	if configured == nil {
+		configured = []api.Mount{{Version: "v1", Path: endpoint}}
+	}
+	seen := map[string]bool{}
+	for i, mount := range configured {
+		if supported[mount.Version] == nil {
+			return nil, merrors.InvalidArgument("unknown or unavailable API version: "+mount.Version, "api.versions")
+		}
+		if seen[mount.Version] {
+			return nil, merrors.InvalidArgument("duplicate API version: "+mount.Version, "api.versions")
+		}
+		seen[mount.Version] = true
+		if !validMount(mount.Path) {
+			return nil, merrors.InvalidArgument("invalid API mount: "+mount.Path, "api.versions")
+		}
+		for _, reserved := range []string{"/metrics", endpoint + "/metrics", endpoint + "/health"} {
+			if mount.Path == reserved || strings.HasPrefix(mount.Path, reserved+"/") {
+				return nil, merrors.InvalidArgument("API mount conflicts with operational endpoint", "api.versions")
+			}
+		}
+		for _, previous := range configured[:i] {
+			if overlaps(mount.Path, previous.Path) {
+				return nil, merrors.InvalidArgument("overlapping API mounts", "api.versions")
+			}
+		}
+	}
+	return configured, nil
+}