Initial commit

checker/rules_common.go

@@ -0,0 +1,88 @@
+package checker
+
+import (
+	"context"
+	"fmt"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// Default values for shared and per-rule options. Kept here so documentation
+// (Definition / rule Options()) and runtime reads stay in sync.
+const (
+	defaultMaxChainLength          = 8
+	defaultMinTargetTTL            = 60
+	defaultRequireResolvableTarget = true
+	defaultAllowApexCNAME          = false
+	defaultRecognizeApexFlattening = true
+
+	// hintKey is the CheckState.Meta key that carries a short remediation
+	// suggestion. The HTML report surfaces it as the "How to fix" block.
+	hintKey = "hint"
+)
+
+// loadAlias reads the primary AliasData observation. When the observation is
+// missing or malformed, it returns a single StatusError state ready to be
+// returned by the rule.
+func loadAlias(ctx context.Context, obs sdk.ObservationGetter) (*AliasData, []sdk.CheckState) {
+	var data AliasData
+	if err := obs.Get(ctx, ObservationKeyAlias, &data); err != nil {
+		return nil, []sdk.CheckState{{
+			Status:  sdk.StatusError,
+			Message: fmt.Sprintf("failed to read alias observation: %v", err),
+		}}
+	}
+	return &data, nil
+}
+
+// skipped wraps a single StatusInfo state describing why a rule did not fire.
+// Rules must always return at least one state; "skipped" is how we encode
+// "this rule has nothing to judge right now" without masking the check.
+func skipped(reason string) []sdk.CheckState {
+	return []sdk.CheckState{{
+		Status:  sdk.StatusInfo,
+		Message: "skipped: " + reason,
+	}}
+}
+
+// okState builds a single StatusOK result for rules whose condition is clean.
+func okState(subject, message string) []sdk.CheckState {
+	return []sdk.CheckState{{
+		Status:  sdk.StatusOK,
+		Subject: subject,
+		Message: message,
+	}}
+}
+
+// withHint attaches a remediation hint to a state's Meta. No-op when hint is
+// empty so callers can hand through the option unconditionally.
+func withHint(s sdk.CheckState, hint string) sdk.CheckState {
+	if hint == "" {
+		return s
+	}
+	if s.Meta == nil {
+		s.Meta = map[string]any{}
+	}
+	s.Meta[hintKey] = hint
+	return s
+}
+
+// apexKnown is the gate most chain-oriented rules apply: when apex lookup
+// failed there is nothing to evaluate. Rules that gate on this return
+// skipped("apex lookup failed") uniformly so the UI shows a consistent line.
+func apexKnown(data *AliasData) bool {
+	return data.ApexLookupError == "" && data.Apex != ""
+}
+
+// allowApexCNAME reads the shared option governing whether a CNAME at apex is
+// downgraded to a warning.
+func allowApexCNAME(opts sdk.CheckerOptions) bool {
+	return sdk.GetBoolOption(opts, "allowApexCNAME", defaultAllowApexCNAME)
+}
+
+// recognizeApexFlattening reads the shared option governing whether
+// provider-side ALIAS/ANAME flattening is recognised (and A/AAAA alongside a
+// CNAME at apex is excused from coexistence).
+func recognizeApexFlattening(opts sdk.CheckerOptions) bool {
+	return sdk.GetBoolOption(opts, "recognizeApexFlattening", defaultRecognizeApexFlattening)
+}