bkpr: separate the invoice_fees from the invoice paid

For income events, break out the amount paid in routing fees vs the
total amount of the *invoice* that is paid.

Also printout these fees, when available, on listaccountevents

plugins/bkpr/account_entry.c

@@ -7,6 +7,7 @@
 static const char *tags[] = {
 	"journal_entry",
 	"penalty_adj",
+	"invoice_fee",
 };
 
 const char *account_entry_tag_str(enum account_entry_tag tag)

plugins/bkpr/account_entry.h

@@ -2,10 +2,11 @@
 #define LIGHTNING_PLUGINS_BKPR_ACCOUNT_ENTRY_H
 #include "config.h"
 
-#define NUM_ACCOUNT_ENTRY_TAGS (JOURNAL_ENTRY + 1)
+#define NUM_ACCOUNT_ENTRY_TAGS (INVOICEFEE + 1)
 enum account_entry_tag {
 	JOURNAL_ENTRY = 0,
 	PENALTY_ADJ = 1,
+	INVOICEFEE = 2,
 };
 
 /* Convert an enum into a string */

plugins/bkpr/channel_event.c

@@ -39,6 +39,8 @@ void json_add_channel_event(struct json_stream *out,
 	json_add_string(out, "tag", ev->tag);
 	json_add_amount_msat_only(out, "credit", ev->credit);
 	json_add_amount_msat_only(out, "debit", ev->debit);
+	if (!amount_msat_zero(ev->fees))
+		json_add_amount_msat_only(out, "fees", ev->fees);
 	json_add_string(out, "currency", ev->currency);
 	if (ev->payment_id)
 		json_add_sha256(out, "payment_id", ev->payment_id);

plugins/bkpr/incomestmt.c

@@ -190,6 +190,16 @@ static struct income_event *maybe_chain_income(const tal_t *ctx,
 	return NULL;
 }
 
+static struct income_event *paid_invoice_fee(const tal_t *ctx,
+					     struct channel_event *ev)
+{
+	struct income_event *iev;
+	iev = channel_to_income(ctx, ev, AMOUNT_MSAT(0), ev->fees);
+	iev->tag = tal_free(ev->tag);
+	iev->tag = (char *)account_entry_tag_str(INVOICEFEE);
+	return iev;
+}
+
 static struct income_event *maybe_channel_income(const tal_t *ctx,
 						 struct channel_event *ev)
 {
@@ -203,7 +213,17 @@ static struct income_event *maybe_channel_income(const tal_t *ctx,
 	}
 
 	if (streq(ev->tag, "invoice")) {
-		/* FIXME: add a sub-category for fees paid */
+		/* If it's a payment, we note fees separately */
+		if (!amount_msat_zero(ev->debit)) {
+			struct amount_msat paid;
+			bool ok;
+			ok = amount_msat_sub(&paid, ev->debit, ev->fees);
+			assert(ok);
+			return channel_to_income(ctx, ev,
+						 ev->credit,
+						 paid);
+		}
+
 		return channel_to_income(ctx, ev,
 					 ev->credit,
 					 ev->debit);
@@ -338,6 +358,13 @@ struct income_event **list_income_events(const tal_t *ctx,
 			if (ev)
 				tal_arr_expand(&evs, ev);
 
+			/* Breakout fees on sent payments */
+			if (streq(chan->tag, "invoice")
+			    && !amount_msat_zero(chan->debit)) {
+				ev = paid_invoice_fee(evs, chan);
+				tal_arr_expand(&evs, ev);
+			}
+
 			j++;
 			continue;
 		}

tests/test_pay.py

@@ -1303,6 +1303,21 @@ def test_forward_pad_fees_and_cltv(node_factory, bitcoind):
     l1.rpc.waitsendpay(rhash)
     assert only_one(l3.rpc.listinvoices('test_forward_pad_fees_and_cltv')['invoices'])['status'] == 'paid'
 
+    # Do some checks of the bookkeeper's records
+    def _income_tagset(node, tagset):
+        incomes = node.rpc.listincome()['income_events']
+        return [e for e in incomes if e['tag'] in tagset]
+
+    tags = ['invoice', 'invoice_fee']
+    wait_for(lambda: len(_income_tagset(l1, tags)) == 2)
+    incomes = _income_tagset(l1, tags)
+    # the balance on l3 should equal the invoice
+    bal = only_one(only_one(l3.rpc.listbalances()['accounts'])['balances'])['balance']
+    assert incomes[0]['tag'] == 'invoice'
+    assert bal == incomes[0]['debit']
+    inve = only_one([e for e in l1.rpc.listaccountevents()['events'] if e['tag'] == 'invoice'])
+    assert Millisatoshi(inve['debit']) == Millisatoshi(incomes[0]['debit']) + Millisatoshi(incomes[1]['debit'])
+
 
 @pytest.mark.developer("needs DEVELOPER=1 for dev_ignore_htlcs")
 def test_forward_stats(node_factory, bitcoind):