Add difficulty chart timespan selection

backend/src/api/mining.ts

@@ -69,6 +69,19 @@ class Mining {
       emptyBlocks: emptyBlocks,
     };
   }
+
+  /**
+   * Return the historical difficulty adjustments and oldest indexed block timestamp
+   */
+  public async $getHistoricalDifficulty(interval: string | null): Promise<object> {
+    const difficultyAdjustments = await BlocksRepository.$getBlocksDifficulty(interval);
+    const oldestBlock = new Date(await BlocksRepository.$oldestBlockTimestamp());
+
+    return {
+      adjustments: difficultyAdjustments,
+      oldestIndexedBlockTimestamp: oldestBlock.getTime(),
+    }
+  }
 }
 
 export default new Mining();

backend/src/repositories/BlocksRepository.ts

@@ -232,7 +232,7 @@ class BlocksRepository {
 
     const connection = await DB.pool.getConnection();
 
-    let query = `SELECT MIN(blockTimestamp) as timestamp, difficulty, height
+    let query = `SELECT MIN(UNIX_TIMESTAMP(blockTimestamp)) as timestamp, difficulty, height
       FROM blocks`;
 
     if (interval) {

backend/src/routes.ts

@@ -577,7 +577,7 @@ class Routes {
 
   public async $getHistoricalDifficulty(req: Request, res: Response) {
     try {
-      const stats = await BlocksRepository.$getBlocksDifficulty(req.params.interval ?? null);
+      const stats = await mining.$getHistoricalDifficulty(req.params.interval ?? null);
       res.header('Pragma', 'public');
       res.header('Cache-control', 'public');
       res.setHeader('Expires', new Date(Date.now() + 1000 * 300).toUTCString());