func NewPolicyRuleEvaluator(policy *audit.Policy) auditinternal.PolicyRuleEvaluator {
	for i, rule := range policy.Rules {
		policy.Rules[i].OmitStages = unionStages(policy.OmitStages, rule.OmitStages)
	}
	return &policyRuleEvaluator{*policy}
}

func unionStages(stageLists ...[]audit.Stage) []audit.Stage {
	m := make(map[audit.Stage]bool)
	for _, sl := range stageLists {
		for _, s := range sl {
			m[s] = true
		}
	}

		},
		{
			nil,
			[]audit.Stage{audit.StageRequestReceived},
			[]audit.Stage{audit.StageRequestReceived},
		},
	}

	for _, tc := range testCases {
		result := unionStages(tc.s1, tc.s2)
		assert.Len(t, result, len(tc.exp))
		for _, expStage := range tc.exp {
			ok := false
			for _, resultStage := range result {
				if resultStage == expStage {
					ok = true
					break