feat(2020-day-06): stream handler utility for generating checksums

Author: developher-net

2020/day-06/streamHandler.js

@@ -0,0 +1,41 @@
+const fs = require('fs')
+const split2 = require('split2')
+
+const defaultProcessor = (data) => {
+  console.info('Data chunk:')
+  console.debug(data)
+  console.info('-----------')
+  return 1
+}
+
+const streamHandler = ({ filePath, processor = defaultProcessor }) => {
+  let checksum = 0
+  let buffer = ''
+
+  return new Promise((resolve, reject) => {
+    return fs.createReadStream(filePath)
+      .pipe(split2())
+      .on('data', (data) => {
+        // Emmpty line indicates record separator
+        if (data.trim() === '') {
+          checksum += processor(buffer)
+          // flush buffer
+          buffer = ''
+          return
+        }
+        // Add the line to the buffer
+        buffer += data.trim() + '\n'
+      })
+      .on('end', (data) => {
+        // get the final record from the buffer
+        checksum += processor(buffer)
+        console.debug('Finished stream. Checksum:', checksum)
+        resolve({ checksum })
+      })
+      .on('error', reject)
+  })
+}
+
+module.exports = {
+  streamHandler
+}

2020/day-06/streamHandler.test.js

@@ -0,0 +1,29 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const path = require('path')
+// const { groupChecksum } = require('./questions')
+const { streamHandler } = require('./streamHandler')
+
+const filePath = path.join(__dirname, 'testData.txt')
+
+describe('--- Day 6: Custom Customs ---', () => {
+  describe('Part 1', () => {
+    describe('streamHandler()', () => {
+      it('parses a stream processing a running checksum', (done) => {
+        streamHandler({ filePath })
+          .then(({ checksum }) => {
+            expect(checksum).to.equal(5)
+            done()
+          })
+      })
+      it('accepts a custom function to calculate checksums', (done) => {
+        const processor = () => { return 2 }
+        streamHandler({ filePath, processor })
+          .then(({ checksum }) => {
+            expect(checksum).to.equal(5 * 2)
+            done()
+          })
+      })
+    })
+  })
+})

2020/day-06/testData.txt

@@ -0,0 +1,15 @@
+abc
+
+a
+b
+c
+
+ab
+ac
+
+a
+a
+a
+a
+
+b