feat: add button to auto-balance LN channels

Solves #831.

NOTE: work in progress, implementation not ready yet.

src/components/designer/AutoBalanceButton.tsx

@@ -0,0 +1,25 @@
+import React from 'react';
+import styled from '@emotion/styled';
+import { Button } from 'antd';
+import { useStoreActions } from 'store';
+import { Network } from 'types';
+
+const Styled = {
+  Button: styled(Button)`
+    margin-left: 8px;
+  `,
+};
+
+interface Props {
+  network: Network;
+}
+
+const AutoBalanceButton: React.FC<Props> = ({ network }) => {
+  const { autoBalanceChannels } = useStoreActions(s => s.network);
+
+  const handleClick = async () => autoBalanceChannels({ id: network.id });
+
+  return <Styled.Button onClick={handleClick}>Auto Balance channels</Styled.Button>;
+};
+
+export default AutoBalanceButton;

src/components/network/NetworkActions.tsx

@@ -20,6 +20,7 @@ import { Status } from 'shared/types';
 import { useStoreState } from 'store';
 import { Network } from 'types';
 import { getNetworkBackendId } from 'utils/network';
+import AutoBalanceButton from 'components/designer/AutoBalanceButton';
 
 const Styled = {
   Button: styled(Button)`
@@ -130,6 +131,7 @@ const NetworkActions: React.FC<Props> = ({
           </Button>
           <AutoMineButton network={network} />
           <SyncButton network={network} />
+          <AutoBalanceButton network={network} />
           <Divider type="vertical" />
         </>
       )}

src/store/models/network.ts

@@ -13,7 +13,17 @@ import {
   TapdNode,
   TapNode,
 } from 'shared/types';
-import { AutoMineMode, CustomImage, Network, StoreInjections } from 'types';
+import { clightningService } from 'lib/lightning/clightning';
+import { eclairService } from 'lib/lightning/eclair';
+import { lndService } from 'lib/lightning/lnd';
+import { LightningNodeChannel } from 'lib/lightning/types';
+import {
+  AutoMineMode,
+  CustomImage,
+  LightningService,
+  Network,
+  StoreInjections,
+} from 'types';
 import { delay } from 'utils/async';
 import { initChartFromNetwork } from 'utils/chart';
 import { APP_VERSION, DOCKER_REPO } from 'utils/constants';
@@ -178,6 +188,9 @@ export interface NetworkModel {
   setAutoMineMode: Action<NetworkModel, { id: number; mode: AutoMineMode }>;
   setMiningState: Action<NetworkModel, { id: number; mining: boolean }>;
   mineBlock: Thunk<NetworkModel, { id: number }, StoreInjections, RootModel>;
+
+  /* */
+  autoBalanceChannels: Thunk<NetworkModel, { id: number }, StoreInjections, RootModel>;
 }
 
 const networkModel: NetworkModel = {
@@ -922,6 +935,95 @@ const networkModel: NetworkModel = {
 
     actions.setAutoMineMode({ id, mode });
   }),
+  autoBalanceChannels: thunk(async (actions, { id }, { getState, getStoreState }) => {
+    const { networks } = getState();
+    const network = networks.find(n => n.id === id);
+    if (!network) throw new Error(l('networkByIdErr', { id }));
+
+    const getNodeLightningService = (node: LightningNode): LightningService => {
+      switch (node.implementation) {
+        case 'LND':
+          return lndService;
+        case 'c-lightning':
+          return clightningService;
+        case 'eclair':
+          return eclairService;
+        default:
+          throw new Error('unknown implementation');
+      }
+    };
+
+    const balanceChannel = async (
+      channel: LightningNodeChannel,
+      localNode: LightningNode,
+      remoteNode: LightningNode,
+      satsTolerance = 150,
+    ) => {
+      if (channel.status !== 'Open') {
+        // TODO: warn about channel not opened.
+        return;
+      }
+
+      if (remoteNode === undefined || remoteNode === null) {
+        // TODO: warn about remote node being null.
+        return;
+      }
+
+      const localBalance = Number(channel.localBalance);
+      const remoteBalance = Number(channel.remoteBalance);
+      const toPay = Math.floor(Math.abs(localBalance - remoteBalance) / 2);
+
+      // If the balance difference in satoshis is too small, we ignore it.
+      if (toPay < satsTolerance) {
+        return;
+      }
+
+      // The source node pays an invoice to the target node, in order to balance the channel.
+      const src = localBalance > remoteBalance ? localNode : remoteNode;
+      const target = localBalance > remoteBalance ? remoteNode : localNode;
+
+      console.log(
+        '[AUTO BALANCE]: ',
+        'paying from ' + src.name + ' to ' + target.name + ' the amount ' + toPay,
+      );
+
+      const invoice = await getNodeLightningService(target).createInvoice(target, toPay);
+
+      await getNodeLightningService(src).payInvoice(src, invoice);
+    };
+
+    interface ChannelInfo {
+      channel: LightningNodeChannel;
+      fromNode: LightningNode;
+      toNode: LightningNode;
+    }
+
+    const lnNodes = network.nodes.lightning;
+    const channels = [] as LightningNodeChannel[];
+    const id2Node = {} as Record<string, LightningNode>;
+
+    for (const node of lnNodes) {
+      const lightningService = getNodeLightningService(node);
+      const nodeChannels = await lightningService.getChannels(node);
+      channels.push(...nodeChannels);
+      id2Node[node.name] = node;
+    }
+
+    const links = getStoreState().designer.activeChart.links;
+    const channelsInfo = [] as ChannelInfo[];
+
+    for (const channel of channels) {
+      const id = channel.uniqueId;
+      const { to, from } = links[id];
+      const fromNode = id2Node[from.nodeId as string];
+      const toNode = id2Node[to.nodeId as string];
+      channelsInfo.push({ channel, fromNode, toNode });
+    }
+
+    for (const { channel, fromNode, toNode } of channelsInfo) {
+      await balanceChannel(channel, fromNode, toNode);
+    }
+  }),
 };
 
 export default networkModel;