feat(rules): add Rule interface, Pipeline, and WhitelistRule

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/rules/pipeline_test.go

@@ -0,0 +1,106 @@
+package rules
+
+import (
+	"testing"
+)
+
+func TestPipeline_NoRules_Accepts(t *testing.T) {
+	p := NewPipeline(nil)
+	result := p.Evaluate(EmailContext{Sender: "anyone@test.com"})
+	if !result.Accepted {
+		t.Fatal("expected accept with no rules")
+	}
+}
+
+func TestPipeline_AllRulesAccept_Accepts(t *testing.T) {
+	allowAll := &stubRule{name: "allow-all", result: Accept()}
+	p := NewPipeline([]Rule{allowAll})
+	result := p.Evaluate(EmailContext{Sender: "a@b.com"})
+	if !result.Accepted {
+		t.Fatal("expected accept")
+	}
+}
+
+func TestPipeline_OneRuleRejects_Rejects(t *testing.T) {
+	rejector := &stubRule{name: "rejector", result: Reject("nope")}
+	p := NewPipeline([]Rule{rejector})
+	result := p.Evaluate(EmailContext{Sender: "a@b.com"})
+	if result.Accepted {
+		t.Fatal("expected reject")
+	}
+	if result.Reason != "nope" {
+		t.Fatalf("expected reason 'nope', got %s", result.Reason)
+	}
+}
+
+func TestPipeline_MergesMetadata(t *testing.T) {
+	r1 := &stubRule{name: "r1", result: Accept().WithMetadata("a", "1")}
+	r2 := &stubRule{name: "r2", result: Accept().WithMetadata("b", "2")}
+	p := NewPipeline([]Rule{r1, r2})
+	result := p.Evaluate(EmailContext{})
+	if result.Metadata["a"] != "1" {
+		t.Fatal("missing metadata a")
+	}
+	if result.Metadata["b"] != "2" {
+		t.Fatal("missing metadata b")
+	}
+}
+
+func TestPipeline_StopsOnFirstReject(t *testing.T) {
+	rejector := &stubRule{name: "rejector", result: Reject("stop")}
+	neverCalled := &trackingRule{}
+	p := NewPipeline([]Rule{rejector, neverCalled})
+	p.Evaluate(EmailContext{})
+	if neverCalled.called {
+		t.Fatal("expected second rule not to be called after rejection")
+	}
+}
+
+func TestWhitelistRule_EmptyList_Accepts(t *testing.T) {
+	r := NewWhitelistRule(nil)
+	result := r.Evaluate(EmailContext{Sender: "anyone@test.com"})
+	if !result.Accepted {
+		t.Fatal("empty whitelist should accept all")
+	}
+}
+
+func TestWhitelistRule_SenderInList_Accepts(t *testing.T) {
+	r := NewWhitelistRule([]string{"allowed@test.com"})
+	result := r.Evaluate(EmailContext{Sender: "allowed@test.com"})
+	if !result.Accepted {
+		t.Fatal("expected accept for whitelisted sender")
+	}
+}
+
+func TestWhitelistRule_SenderNotInList_Rejects(t *testing.T) {
+	r := NewWhitelistRule([]string{"allowed@test.com"})
+	result := r.Evaluate(EmailContext{Sender: "unknown@test.com"})
+	if result.Accepted {
+		t.Fatal("expected reject for non-whitelisted sender")
+	}
+}
+
+func TestWhitelistRule_CaseInsensitive(t *testing.T) {
+	r := NewWhitelistRule([]string{"Allowed@Test.com"})
+	result := r.Evaluate(EmailContext{Sender: "allowed@test.com"})
+	if !result.Accepted {
+		t.Fatal("whitelist should be case-insensitive")
+	}
+}
+
+// stubs
+
+type stubRule struct {
+	name   string
+	result RuleResult
+}
+
+func (s *stubRule) Name() string                  { return s.name }
+func (s *stubRule) Evaluate(_ EmailContext) RuleResult { return s.result }
+
+type trackingRule struct {
+	called bool
+}
+
+func (t *trackingRule) Name() string                  { return "tracker" }
+func (t *trackingRule) Evaluate(_ EmailContext) RuleResult { t.called = true; return Accept() }