Merge branch 'feature-withdrawal-fee'

2 files changed, 68 insertions, 2 deletions

diff --git a/routes/liquid/receive.js b/routes/liquid/receive.js
index d2864872..0eed35fd 100644
--- a/routes/liquid/receive.js
+++ b/routes/liquid/receive.js
@@ -13,6 +13,9 @@ const network =
     config.liquid.network === "mainnet" ? "liquid" : config.liquid.network
   ];
 
+// used to calculate how many credits to give
+const withdrawalFeeMultiplier = 0.01;
+
 const getAccount = async (params, transaction) => {
   let account = await db.Account.findOne({
     where: params,
@@ -341,6 +344,7 @@ setInterval(async () => {
             { pending: Math.min(p.account.pending, total) },
             { transaction }
           );
+          await account.increment({ fee_credits: Math.floor(total * withdrawalFeeMultiplier) }, { transaction });
           await p.account.reload({ transaction });
 
           await p.save({ transaction });
diff --git a/routes/liquid/send.js b/routes/liquid/send.js
index 6f3616e8..fcb05942 100644
--- a/routes/liquid/send.js
+++ b/routes/liquid/send.js
@@ -84,6 +84,11 @@ sendLiquid = async ({ asset, amount, user, address, memo, tx, limit }) => {
           total += fee - covered;
         }
 
+        // get withdrawal fee
+        // 'total' refers to the total before the withdrawal fee
+        // (i.e. the total liquid bitcoin that leaves this server)
+        var withdrawalFee = Math.floor(amount * withdrawalFeeMultiplier);
+
         if (limit && total > limit + fee)
           throw new Error("Tx amount exceeds authorized amount");
 
@@ -112,11 +117,67 @@ sendLiquid = async ({ asset, amount, user, address, memo, tx, limit }) => {
                 account.ticker === "BTC" ? "SAT" : account.ticker
               }, have ${account.balance}`
             );
+          } else if (total + withdrawalFee > account.balance) {
+            l.warn("amount plus withdrawal fee exceeds balance", {
+              total,
+              fee,
+              withdrawalFee,
+              balance: account.balance
+            });
+            throw new Error(
+              `Insufficient funds, need ${total + withdrawalFee} ${
+                account.ticker === "BTC" ? "SAT" : account.ticker
+              }, have ${account.balance}`
+            );
+          }
+
+          // use user's credits to reduce fee, if available
+          console.log(account.fee_credits);
+          let withdrawalFeeDeduction = Math.min(account.fee_credits, withdrawalFee);
+          if (withdrawalFeeDeduction) {
+            await account.decrement({ fee_credits: withdrawalFeeDeduction }, { transaction });
+            await account.reload({ transaction });
+            withdrawalFee -= withdrawalFeeDeduction;
           }
 
-          await account.decrement({ balance: total }, { transaction });
+          await account.decrement({ balance: (total + withdrawalFee)}, { transaction });
           await account.reload({ transaction });
 
+          let receiverAccount = await db.Account.findOne({
+            where: {
+              "$user.username$": withdrawalFeeReceiver
+            },
+            include: [
+              {
+                model: db.User,
+                as: "user"
+              },
+            ],
+            lock: transaction.LOCK.UPDATE,
+            transaction
+          });
+
+          let fee_payment_id = null;
+          if (withdrawalFee) {
+            await receiverAccount.increment({ balance: withdrawalFee }, { transaction });
+            await receiverAccount.reload({ transaction });
+            let fee_payment = {
+              amount: withdrawalFee,
+              fee: 0,
+              memo: "Liquid withdrawal fee",
+              account_id: receiverAccount.id,
+              user_id: receiverAccount.user_id,
+              rate: app.get("rates")[receiverAccount.user.currency],
+              currency: receiverAccount.user.currency,
+              confirmed: true,
+              received: true,
+              network: "COINOS"
+            };
+            fee_payment.account = receiverAccount;
+            payments.push(fee_payment);
+            fee_payment_id = fee_payment.id;
+          }
+
           let payment = {
             amount: -amount,
             account_id: account.id,
@@ -128,7 +189,8 @@ sendLiquid = async ({ asset, amount, user, address, memo, tx, limit }) => {
             address,
             confirmed: true,
             received: false,
-            network: "liquid"
+            network: "liquid",
+            fee_payment_id: fee_payment_id
           };
 
           payment.account = account;