plugins: minimal 'pay' plugin.

I wrote this sync first, then rewrote async, then developed libplugin.
But committing all that just wastes reviewer time, so I present it as
if it was always asnc and using the library helper.

Currently the command it registers is 'pay2', but when it's complete
we'll remove the internal 'pay' and rename it. This does a single
'getroute/sendpay' call.  No retries, no options.

Shockingly, this by itself is almost sufficient to pass our current test
suite with `pay`->`pay2`.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

plugins/.gitignore

@@ -0,0 +1 @@
+pay

plugins/Makefile

@@ -1,3 +1,6 @@
+PLUGIN_PAY_SRC := plugins/pay.c
+PLUGIN_PAY_OBJS := $(PLUGIN_PAY_SRC:.c=.o)
+
 PLUGIN_LIB_SRC := plugins/libplugin.c
 PLUGIN_LIB_HEADER := plugins/libplugin.h
 PLUGIN_LIB_OBJS := $(PLUGIN_LIB_SRC:.c=.o)
@@ -28,10 +31,19 @@ PLUGIN_COMMON_OBJS :=				\
 	wire/fromwire.o				\
 	wire/towire.o
 
+plugins/pay: $(PLUGIN_PAY_OBJS) $(PLUGIN_LIB_OBJS) $(PLUGIN_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS)
+
+$(PLUGIN_PAY_OBJS) $(PLUGIN_LIB_OBJS): $(PLUGIN_LIB_HEADER)
+
 # Make sure these depend on everything.
-ALL_OBJS += $(PLUGIN_LIB_OBJS)
+ALL_PROGRAMS += plugins/pay
+ALL_OBJS += $(PLUGIN_PAY_OBJS) $(PLUGIN_LIB_OBJS)
+
+check-source: $(PLUGIN_PAY_SRC:%=check-src-include-order/%)
+check-source-bolt: $(PLUGIN_PAY_SRC:%=bolt-check/%)
+check-whitespace: $(PLUGIN_PAY_SRC:%=check-whitespace/%)
 
 clean: plugin-clean
 
 plugin-clean:
-	$(RM) $(PLUGIN_LIB_OBJS)
+	$(RM) $(PLUGIN_PAY_OBJS) $(PLUGIN_LIB_OBJS)

plugins/pay.c

@@ -0,0 +1,125 @@
+#include <ccan/array_size/array_size.h>
+#include <ccan/intmap/intmap.h>
+#include <ccan/tal/str/str.h>
+#include <common/bolt11.h>
+#include <common/type_to_string.h>
+#include <plugins/libplugin.h>
+
+struct pay_command {
+	/* Payment hash, as text. */
+	const char *payment_hash;
+
+	/* Description, if any. */
+	const char *desc;
+};
+
+static struct command_result *sendpay_done(struct command *cmd,
+					   const char *buf,
+					   const jsmntok_t *result,
+					   struct pay_command *pc)
+{
+	return send_outreq(cmd, "waitsendpay",
+			   forward_result, forward_error, pc,
+			   "'payment_hash': '%s', 'timeout': 60",
+			   pc->payment_hash);
+}
+
+static struct command_result *getroute_done(struct command *cmd,
+					    const char *buf,
+					    const jsmntok_t *result,
+					    struct pay_command *pc)
+{
+	const jsmntok_t *t = json_get_member(buf, result, "route");
+	char *json_desc;
+	if (!t)
+		plugin_err("getroute gave no 'route'? '%.*s'",
+			   result->end - result->start, buf);
+
+	if (pc->desc)
+		json_desc = tal_fmt(pc, ", 'description': '%s'", pc->desc);
+	else
+		json_desc = "";
+
+	return send_outreq(cmd, "sendpay", sendpay_done, forward_error, pc,
+			   "'route': %.*s, 'payment_hash': '%s'%s",
+			   t->end - t->start, buf + t->start,
+			   pc->payment_hash,
+			   json_desc);
+}
+
+static struct command_result *handle_pay(struct command *cmd,
+					 const char *buf,
+					 const jsmntok_t *params)
+{
+	u64 *msatoshi;
+	struct bolt11 *b11;
+	const char *b11str;
+	char *fail;
+	double *riskfactor;
+	struct pay_command *pc = tal(cmd, struct pay_command);
+
+	/* FIXME! */
+	double *maxfeepercent;
+	unsigned int *retryfor;
+	unsigned int *maxdelay;
+	unsigned int *exemptfee;
+
+	setup_locale();
+
+	if (!param(cmd, buf, params,
+		   p_req("bolt11", param_string, &b11str),
+		   p_opt("msatoshi", param_u64, &msatoshi),
+		   p_opt("description", param_string, &pc->desc),
+		   p_opt_def("riskfactor", param_double, &riskfactor, 1.0),
+		   p_opt_def("maxfeepercent", param_percent, &maxfeepercent, 0.5),
+		   p_opt_def("retry_for", param_number, &retryfor, 60),
+		   p_opt_def("maxdelay", param_number, &maxdelay,
+			     /* FIXME! */
+			     14 * 24 * 6),
+		   p_opt_def("exemptfee", param_number, &exemptfee, 5000),
+		   NULL))
+		return NULL;
+
+	b11 = bolt11_decode(cmd, b11str, pc->desc, &fail);
+	if (!b11) {
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "Invalid bolt11: %s", fail);
+	}
+
+	if (b11->msatoshi) {
+		if (msatoshi) {
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "msatoshi parameter unnecessary");
+		}
+	} else {
+		if (!msatoshi) {
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "msatoshi parameter required");
+		}
+		b11->msatoshi = tal_steal(b11, msatoshi);
+	}
+
+	pc->payment_hash = type_to_string(pc, struct sha256,
+					  &b11->payment_hash);
+
+	/* OK, ask for route to destination */
+	return send_outreq(cmd, "getroute", getroute_done, forward_error, pc,
+			   "'id': '%s',"
+			   "'msatoshi': %"PRIu64","
+			   "'riskfactor': %f",
+			   type_to_string(tmpctx, struct pubkey, &b11->receiver_id),
+			   *b11->msatoshi, *riskfactor);
+}
+
+static const struct plugin_command commands[] = { {
+		"pay2",
+		"Send payment specified by {bolt11} with {msatoshi}",
+		"Try to send a payment, retrying {retry_for} seconds before giving up",
+		handle_pay
+	}
+};
+
+int main(int argc, char *argv[])
+{
+	plugin_main(argv, NULL, commands, ARRAY_SIZE(commands));
+}

tests/test_plugin.py

@@ -108,3 +108,11 @@ def test_failing_plugins():
                 '--plugin={}'.format(p),
                 '--help',
             ])
+
+
+def test_pay_plugin(node_factory):
+    l1, l2 = node_factory.line_graph(2)
+    inv = l2.rpc.invoice(123000, 'label', 'description', 3700)
+
+    res = l1.rpc.pay2(bolt11=inv['bolt11'])
+    assert res['status'] == 'complete'