API method for node fee histogram data

backend/src/api/explorer/nodes.api.ts

@@ -129,6 +129,56 @@ class NodesApi {
     }
   }
 
+  public async $getFeeHistogram(node_public_key: string): Promise<unknown> {
+    try {
+      const inQuery = `
+        SELECT CASE WHEN fee_rate <= 10.0 THEN CEIL(fee_rate)
+                    WHEN (fee_rate > 10.0 and fee_rate <= 100.0) THEN CEIL(fee_rate / 10.0) * 10.0
+                    WHEN (fee_rate > 100.0 and fee_rate <= 1000.0) THEN CEIL(fee_rate / 100.0) * 100.0
+                    WHEN fee_rate > 1000.0 THEN CEIL(fee_rate / 1000.0) * 1000.0
+               END as bucket,
+               count(short_id) as count,
+               sum(capacity) as capacity
+        FROM (
+          SELECT CASE WHEN node1_public_key = ? THEN node2_fee_rate WHEN node2_public_key = ? THEN node1_fee_rate END as fee_rate,
+                 short_id as short_id,
+                 capacity as capacity
+          FROM channels
+          WHERE status = 1 AND (channels.node1_public_key = ? OR channels.node2_public_key = ?)
+        ) as fee_rate_table
+        GROUP BY bucket;
+      `;
+      const [inRows]: any[] = await DB.query(inQuery, [node_public_key, node_public_key, node_public_key, node_public_key]);
+
+      const outQuery = `
+        SELECT CASE WHEN fee_rate <= 10.0 THEN CEIL(fee_rate)
+                    WHEN (fee_rate > 10.0 and fee_rate <= 100.0) THEN CEIL(fee_rate / 10.0) * 10.0
+                    WHEN (fee_rate > 100.0 and fee_rate <= 1000.0) THEN CEIL(fee_rate / 100.0) * 100.0
+                    WHEN fee_rate > 1000.0 THEN CEIL(fee_rate / 1000.0) * 1000.0
+               END as bucket,
+               count(short_id) as count,
+               sum(capacity) as capacity
+        FROM (
+          SELECT CASE WHEN node1_public_key = ? THEN node1_fee_rate WHEN node2_public_key = ? THEN node2_fee_rate END as fee_rate,
+                 short_id as short_id,
+                 capacity as capacity
+          FROM channels
+          WHERE status = 1 AND (channels.node1_public_key = ? OR channels.node2_public_key = ?)
+        ) as fee_rate_table
+        GROUP BY bucket;
+      `;
+      const [outRows]: any[] = await DB.query(outQuery, [node_public_key, node_public_key, node_public_key, node_public_key]);
+
+      return {
+        incoming: inRows.length > 0 ? inRows : [],
+        outgoing: outRows.length > 0 ? outRows : [],
+      };
+    } catch (e) {
+      logger.err(`Cannot get node fee distribution for ${node_public_key}. Reason: ${(e instanceof Error ? e.message : e)}`);
+      throw e;
+    }
+  }
+
   public async $getAllNodes(): Promise<any> {
     try {
       const query = `SELECT * FROM nodes`;

backend/src/api/explorer/nodes.routes.ts

@@ -20,6 +20,7 @@ class NodesRoutes {
       .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/rankings/connectivity', this.$getTopNodesByChannels)
       .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/rankings/age', this.$getOldestNodes)
       .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/:public_key/statistics', this.$getHistoricalNodeStats)
+      .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/:public_key/fees/histogram', this.$getFeeHistogram)
       .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/:public_key', this.$getNode)
       .get(config.MEMPOOL.API_URL_PREFIX + 'lightning/nodes/group/:name', this.$getNodeGroup)
     ;
@@ -95,6 +96,22 @@ class NodesRoutes {
     }
   }
 
+  private async $getFeeHistogram(req: Request, res: Response) {
+    try {
+      const node = await nodesApi.$getFeeHistogram(req.params.public_key);
+      if (!node) {
+        res.status(404).send('Node not found');
+        return;
+      }
+      res.header('Pragma', 'public');
+      res.header('Cache-control', 'public');
+      res.setHeader('Expires', new Date(Date.now() + 1000 * 60).toUTCString());
+      res.json(node);
+    } catch (e) {
+      res.status(500).send(e instanceof Error ? e.message : e);
+    }
+  }
+
   private async $getNodesRanking(req: Request, res: Response): Promise<void> {
     try {
       const topCapacityNodes = await nodesApi.$getTopCapacityNodes(false);

frontend/src/app/lightning/lightning-api.service.ts

@@ -53,6 +53,10 @@ export class LightningApiService {
     return this.httpClient.get<any>(this.apiBasePath + '/api/v1/lightning/nodes/' + publicKey + '/statistics');
   }
 
+  getNodeFeeHistogram$(publicKey: string): Observable<any> {
+    return this.httpClient.get<any>(this.apiBasePath + '/api/v1/lightning/nodes/' + publicKey + '/fees/histogram');
+  }
+
   getNodesRanking$(): Observable<INodesRanking> {
     return this.httpClient.get<INodesRanking>(this.apiBasePath + '/api/v1/lightning/nodes/rankings');
   }