1  /*!
 2   * lib/bitcoind-rpc/headers.js
 3   * Copyright © 2019 – Katana Cryptographic Ltd. All Rights Reserved.
 4   */
 5  
 6  
 7  import QuickLRU from 'quick-lru'
 8  
 9  import errors from '../errors.js'
10  import { createRpcClient } from './rpc-client.js'
11  
12  
13  /**
14   * A singleton providing information about block headers
15   */
16  class Headers {
17  
18      constructor() {
19          // Cache
20          this.headers = new QuickLRU({
21              // Maximum number of headers to store in cache
22              maxSize: 2016,
23              // Maximum age for items in the cache. Items do not expire
24              maxAge: Number.POSITIVE_INFINITY
25          })
26  
27          // Initialize the rpc client
28          this.rpcClient = createRpcClient()
29      }
30  
31      /**
32       * Get the block header for a given hash
33       * @param {string} hash - block hash
34       * @returns {Promise}
35       */
36      async getHeader(hash) {
37          if (this.headers.has(hash))
38              return this.headers.get(hash)
39  
40          try {
41              const header = await this.rpcClient.getblockheader({ blockhash: hash, verbose: true })
42              const fmtHeader = JSON.stringify(header, null, 2)
43              this.headers.set(hash, fmtHeader)
44              return fmtHeader
45          } catch {
46              throw errors.generic.GEN
47          }
48      }
49  
50  }
51  
52  export default new Headers()