extension: BeforeMessageStored event to rewrite envelope (#417)

* extension: add InboundMessage type
* manager: fires BeforeMessageStored event
* manager: Reacts to BeforeMessageStored event response
* manager: Apply BeforeMessageStored response fields to message

Signed-off-by: James Hillyerd <james@hillyerd.com>

pkg/message/manager_test.go

@@ -1,10 +1,12 @@
 package message_test
 
 import (
+	"net/mail"
 	"testing"
 
 	"github.com/inbucket/inbucket/v3/pkg/config"
 	"github.com/inbucket/inbucket/v3/pkg/extension"
+	"github.com/inbucket/inbucket/v3/pkg/extension/event"
 	"github.com/inbucket/inbucket/v3/pkg/message"
 	"github.com/inbucket/inbucket/v3/pkg/policy"
 	"github.com/inbucket/inbucket/v3/pkg/test"
@@ -48,16 +50,140 @@ func TestDeliverRespectsRecipientPolicy(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// Expect empty mailbox for nostore domain.
 	assertMessageCount(t, sm, "u1@nostore.com", 0)
 	assertMessageCount(t, sm, "u2@example.com", 1)
 }
 
+func TestDeliverEmitsBeforeMessageStoredEvent(t *testing.T) {
+	sm, extHost := testStoreManager()
+
+	// Register function to receive event.
+	var got *event.InboundMessage
+	extHost.Events.BeforeMessageStored.AddListener(
+		"test",
+		func(msg event.InboundMessage) *event.InboundMessage {
+			got = &msg
+			return nil
+		})
+
+	// Deliver a message to trigger event.
+	origin, _ := sm.AddrPolicy.ParseOrigin("from@example.com")
+	recip1, _ := sm.AddrPolicy.NewRecipient("u1@example.com")
+	recip2, _ := sm.AddrPolicy.NewRecipient("u2@example.com")
+	if err := sm.Deliver(
+		origin,
+		[]*policy.Recipient{recip1, recip2},
+		"Received: xyz\n",
+		[]byte("From: from@example.com\nSubject: tsub\n\ntest email"),
+	); err != nil {
+		t.Fatal(err)
+	}
+
+	require.NotNil(t, got, "BeforeMessageStored listener did not receive InboundMessage")
+	assert.Equal(t, []string{"u1@example.com", "u2@example.com"}, got.Mailboxes, "Mailboxes not equal")
+	assert.Equal(t, mail.Address{Name: "", Address: "from@example.com"}, got.From, "From not equal")
+	assert.Equal(t, []mail.Address{
+		{Name: "", Address: "u1@example.com"},
+		{Name: "", Address: "u2@example.com"},
+	}, got.To, "To not equal")
+	assert.Equal(t, "tsub", got.Subject, "Subject not equal")
+	assert.Equal(t, int64(48), got.Size, "Size not equal")
+}
+
+func TestDeliverUsesBeforeMessageStoredEventResponseMailboxes(t *testing.T) {
+	sm, extHost := testStoreManager()
+
+	// Register function to receive event.
+	extHost.Events.BeforeMessageStored.AddListener(
+		"test",
+		func(msg event.InboundMessage) *event.InboundMessage {
+			// Listener rewrites destination mailboxes.
+			resp := msg
+			resp.Mailboxes = []string{"new1@example.com", "new2@nostore.com"}
+			return &resp
+		})
+
+	// Deliver a message to trigger event.
+	origin, _ := sm.AddrPolicy.ParseOrigin("from@example.com")
+	recip1, _ := sm.AddrPolicy.NewRecipient("u1@example.com")
+	recip2, _ := sm.AddrPolicy.NewRecipient("u2@example.com")
+	if err := sm.Deliver(
+		origin,
+		[]*policy.Recipient{recip1, recip2},
+		"Received: xyz\r\n",
+		[]byte("From: from@example.com\nSubject: tsub\n\ntest email"),
+	); err != nil {
+		t.Fatal(err)
+	}
+
+	// Expect messages in only the mailboxes in the event response, and for the DiscardDomains
+	// policy to be ignored.
+	assertMessageCount(t, sm, "u1@example.com", 0)
+	assertMessageCount(t, sm, "u2@example.com", 0)
+	assertMessageCount(t, sm, "new1@example.com", 1)
+	assertMessageCount(t, sm, "new2@nostore.com", 1)
+}
+
+func TestDeliverUsesBeforeMessageStoredEventResponseFields(t *testing.T) {
+	sm, extHost := testStoreManager()
+
+	// Register function to receive event.
+	extHost.Events.BeforeMessageStored.AddListener(
+		"test",
+		func(msg event.InboundMessage) *event.InboundMessage {
+			// Listener rewrites destination mailboxes.
+			msg.Subject = "event subj"
+			msg.From = mail.Address{Address: "from@event.com", Name: "From Event"}
+
+			// Changing To does not affect destination mailbox(es).
+			msg.To = []mail.Address{
+				{Address: "to@event.com", Name: "To Event"},
+				{Address: "to2@event.com", Name: "To 2 Event"},
+			}
+
+			// Size is read only, should have no effect.
+			msg.Size = 12345
+
+			return &msg
+		})
+
+	// Deliver a message to trigger event.
+	origin, _ := sm.AddrPolicy.ParseOrigin("from@example.com")
+	recip1, _ := sm.AddrPolicy.NewRecipient("u1@example.com")
+	if err := sm.Deliver(
+		origin,
+		[]*policy.Recipient{recip1},
+		"Received: xyz\r\n",
+		[]byte("From: from@example.com\nSubject: tsub\n\ntest email"),
+	); err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify single message stored.
+	metadata, err := sm.GetMetadata("u1@example.com")
+	require.NoError(t, err)
+	require.Len(t, metadata, 1, "mailbox has incorrect # of messages")
+	got := metadata[0]
+
+	// Verify metadata fields were overridden by event response values.
+	assert.Equal(t, "event subj", got.Subject, "Subject didn't match")
+	assert.Equal(t, "from@event.com", got.From.Address, "From Address didn't match")
+	assert.Equal(t, "From Event", got.From.Name, "From Name didn't match")
+	require.Len(t, got.To, 2)
+	assert.Equal(t, "to@event.com", got.To[0].Address, "To Address didn't match")
+	assert.Equal(t, "To Event", got.To[0].Name, "To Name didn't match")
+	assert.Equal(t, "to2@event.com", got.To[1].Address, "To Address didn't match")
+	assert.Equal(t, "To 2 Event", got.To[1].Name, "To Name didn't match")
+	assert.NotEqual(t, 12345, got.Size, "Size is read only")
+}
+
 func TestDeliverEmitsAfterMessageStoredEvent(t *testing.T) {
 	sm, extHost := testStoreManager()
 
 	listener := extHost.Events.AfterMessageStored.AsyncTestListener("manager", 1)
 
-	// Attempt to deliver a message to generate event.
+	// Deliver a message to trigger event.
 	origin, _ := sm.AddrPolicy.ParseOrigin("from@example.com")
 	recip, _ := sm.AddrPolicy.NewRecipient("to@example.com")
 	if err := sm.Deliver(
@@ -75,6 +201,46 @@ func TestDeliverEmitsAfterMessageStoredEvent(t *testing.T) {
 	assertMessageCount(t, sm, "to@example.com", 1)
 }
 
+func TestDeliverBeforeAndAfterMessageStoredEvents(t *testing.T) {
+	sm, extHost := testStoreManager()
+
+	// Register function to receive Before event.
+	extHost.Events.BeforeMessageStored.AddListener(
+		"test",
+		func(msg event.InboundMessage) *event.InboundMessage {
+			// Listener rewrites destination mailboxes.
+			resp := msg
+			resp.Mailboxes = []string{"new1@example.com", "new2@example.com"}
+			return &resp
+		})
+
+	// After event listener.
+	listener := extHost.Events.AfterMessageStored.AsyncTestListener("manager", 2)
+
+	// Deliver a message to trigger events.
+	origin, _ := sm.AddrPolicy.ParseOrigin("from@example.com")
+	recip1, _ := sm.AddrPolicy.NewRecipient("u1@example.com")
+	recip2, _ := sm.AddrPolicy.NewRecipient("u2@example.com")
+	if err := sm.Deliver(
+		origin,
+		[]*policy.Recipient{recip1, recip2},
+		"Received: xyz\r\n",
+		[]byte("From: from@example.com\nSubject: tsub\n\ntest email"),
+	); err != nil {
+		t.Fatal(err)
+	}
+
+	// Confirm mailbox names overriden by Before were sent to After event.  Order is
+	// not guaranteed.
+	got1, err := listener()
+	require.NoError(t, err)
+	got2, err := listener()
+	require.NoError(t, err)
+	got := []string{got1.Mailbox, got2.Mailbox}
+	assert.Contains(t, got, "new1@example.com")
+	assert.Contains(t, got, "new2@example.com")
+}
+
 // Returns an empty StoreManager and extension Host pair, configured for testing.
 func testStoreManager() (*message.StoreManager, *extension.Host) {
 	extHost := extension.NewHost()