1 files changed, 85 insertions, 0 deletions
diff --git a/internal/pushrules/validate.go b/internal/pushrules/validate.go
new file mode 100644
index 00000000..5d260f0b
--- /dev/null
+++ b/internal/pushrules/validate.go
@@ -0,0 +1,85 @@
+package pushrules
+
+import (
+	"fmt"
+	"regexp"
+)
+
+// ValidateRule checks the rule for errors. These follow from Sytests
+// and the specification.
+func ValidateRule(kind Kind, rule *Rule) []error {
+	var errs []error
+
+	if !validRuleIDRE.MatchString(rule.RuleID) {
+		errs = append(errs, fmt.Errorf("invalid rule ID: %s", rule.RuleID))
+	}
+
+	if len(rule.Actions) == 0 {
+		errs = append(errs, fmt.Errorf("missing actions"))
+	}
+	for _, action := range rule.Actions {
+		errs = append(errs, validateAction(action)...)
+	}
+
+	for _, cond := range rule.Conditions {
+		errs = append(errs, validateCondition(cond)...)
+	}
+
+	switch kind {
+	case OverrideKind, UnderrideKind:
+		// The empty list is allowed, but for JSON-encoding reasons,
+		// it must not be nil.
+		if rule.Conditions == nil {
+			errs = append(errs, fmt.Errorf("missing rule conditions"))
+		}
+
+	case ContentKind:
+		if rule.Pattern == "" {
+			errs = append(errs, fmt.Errorf("missing content rule pattern"))
+		}
+
+	case RoomKind, SenderKind:
+		// Do nothing.
+
+	default:
+		errs = append(errs, fmt.Errorf("invalid rule kind: %s", kind))
+	}
+
+	return errs
+}
+
+// validRuleIDRE is a regexp for valid IDs.
+//
+// TODO: the specification doesn't seem to say what the rule ID syntax
+// is. A Sytest fails if it contains a backslash.
+var validRuleIDRE = regexp.MustCompile(`^([^\\]+)$`)
+
+// validateAction returns issues with an Action.
+func validateAction(action *Action) []error {
+	var errs []error
+
+	switch action.Kind {
+	case NotifyAction, DontNotifyAction, CoalesceAction, SetTweakAction:
+		// Do nothing.
+
+	default:
+		errs = append(errs, fmt.Errorf("invalid rule action kind: %s", action.Kind))
+	}
+
+	return errs
+}
+
+// validateCondition returns issues with a Condition.
+func validateCondition(cond *Condition) []error {
+	var errs []error
+
+	switch cond.Kind {
+	case EventMatchCondition, ContainsDisplayNameCondition, RoomMemberCountCondition, SenderNotificationPermissionCondition:
+		// Do nothing.
+
+	default:
+		errs = append(errs, fmt.Errorf("invalid rule condition kind: %s", cond.Kind))
+	}
+
+	return errs
+}