From a5c472e815e1e945ffdb216adac2dfe86207edd5 Mon Sep 17 00:00:00 2001
From: George Tankersley <george.tankersley@gmail.com>
Date: Wed, 22 May 2019 16:22:23 -0400
Subject: [PATCH] swag/server: implement z_sendmany call

---
 swag/server.go | 104 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 96 insertions(+), 8 deletions(-)

diff --git a/swag/server.go b/swag/server.go
index 0b9377e..e55c68f 100644
--- a/swag/server.go
+++ b/swag/server.go
@@ -2,23 +2,111 @@ package swag
 
 import (
 	"context"
+	"encoding/json"
+	"errors"
+	"strconv"
+	"strings"
 
 	"github.com/btcsuite/btcd/rpcclient"
 	"github.com/zcash-hackworks/zcon1-swag-api/api"
 )
 
+const (
+	swagFromAddress   = "TODO HARDCODED FROM ADDRESS"
+	swagDefaultAmount = 1
+)
+
 type Server struct {
+	rpc *rpcclient.Client
 }
 
-func NewServer(dbPath string, zc *rpcclient.Client) (api.SwagAPIServer, error) {
-	return &Server{}, nil
-}
-
-func (s *Server) Redeem(ctx context.Context, req *api.Request) (*api.Response, error) {
-	return &api.Response{
-		Success: true,
-		Msg:     "hello",
+func NewServer(dbPath string, rpc *rpcclient.Client) (api.SwagAPIServer, error) {
+	// TODO: CREATE AND POPULATE THE DATABASE
+	return &Server{
+		rpc: rpc,
 	}, nil
 }
 
+func (s *Server) Redeem(ctx context.Context, req *api.Request) (*api.Response, error) {
+
+	// TODO: QUERY THE DATABASE
+
+	return s.TriggerSend(ctx, req)
+}
+
 func (s *Server) GracefulStop() {}
+
+type zSendManyDest struct {
+	Address string `json:"address"`
+	Amount  int64  `json:"amount"`
+}
+
+func (s *Server) TriggerSend(ctx context.Context, req *api.Request) (*api.Response, error) {
+	// z_sendmany "fromaddress" [{"address":... ,"amount":...},...] ( minconf ) ( fee )
+	//
+	// Send multiple times. Amounts are decimal numbers with at most 8 digits of precision.
+	// Change generated from a taddr flows to a new taddr address, while change generated from a zaddr returns to itself.
+	// When sending coinbase UTXOs to a zaddr, change is not allowed. The entire value of the UTXO(s) must be consumed.
+	// Before Sapling activates, the maximum number of zaddr outputs is 54 due to transaction size limits.
+	//
+	// Arguments:
+	// 1. "fromaddress"         (string, required) The taddr or zaddr to send the funds from.
+	// 2. "amounts"             (array, required) An array of json objects representing the amounts to send.
+	//     [{
+	//       "address":address  (string, required) The address is a taddr or zaddr
+	//       "amount":amount    (numeric, required) The numeric amount in ZEC is the value
+	//       "memo":memo        (string, optional) If the address is a zaddr, raw data represented in hexadecimal string format
+	//     }, ... ]
+	// 3. minconf               (numeric, optional, default=1) Only use funds confirmed at least this many times.
+	// 4. fee                   (numeric, optional, default=0.0001) The fee amount to attach to this transaction.
+	//
+	// Result:
+	// "operationid"          (string) An operationid to pass to z_getoperationstatus to get the result of the operation.
+	//
+	// Examples:
+	// > zcash-cli z_sendmany "t1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd" '[{"address": "ztfaW34Gj9FrnGUEf833ywDVL62NWXBM81u6EQnM6VR45eYnXhwztecW1SjxA7JrmAXKJhxhj3vDNEpVCQoSvVoSpmbhtjf" ,"amount": 5.0}]'
+	// > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "z_sendmany", "params": ["t1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd", [{"address": "ztfaW34Gj9FrnGUEf833ywDVL62NWXBM81u6EQnM6VR45eYnXhwztecW1SjxA7JrmAXKJhxhj3vDNEpVCQoSvVoSpmbhtjf" ,"amount": 5.0}]] }' -H 'content-type: text/plain;' http://127.0.0.1:8232/
+
+	// Construct raw JSON-RPC params. This is VERY UGLY because the btcd library lacks direct support for our RPC calls.
+
+	zDests := make([]zSendManyDest, 1)
+	zDests[0] = zSendManyDest{
+		Address: req.Address,
+		Amount:  swagDefaultAmount,
+	}
+
+	encodedDests, err := json.Marshal(zDests)
+	if err != nil {
+		return &api.Response{
+			Success: false,
+			Msg:     "Couldn't initiate transaction successfully.",
+		}, err
+	}
+
+	params := make([]json.RawMessage, 2)
+	params[0] = json.RawMessage("\"" + swagFromAddress + "\"")
+	params[1] = json.RawMessage(encodedDests)
+	result, rpcErr := s.rpc.RawRequest("z_sendmany", params)
+
+	// For some reason, the error responses are not JSON
+	if rpcErr != nil {
+		errParts := strings.SplitN(rpcErr.Error(), ":", 2)
+		errMsg := strings.TrimSpace(errParts[1])
+		_, err = strconv.ParseInt(errParts[0], 10, 32)
+		if err != nil {
+			// This should never happen. We can't panic here, but it's that class of error.
+			// This is why we need integration testing to work better than regtest currently does. TODO.
+			return nil, errors.New("SendTransaction couldn't parse error code")
+		}
+
+		return &api.Response{
+			Success: false,
+			Msg:     errMsg,
+		}, rpcErr
+	}
+
+	return &api.Response{
+		Success: true,
+		Msg:     string(result),
+	}, nil
+}