refactor: Refactor to remove streams and match js reader api changes

Removes streams for massive code reduction. Entire utils gone. About a million lines from main file
gone. All gone. No one is left. There all dead dave.

BREAKING CHANGE: API is now a single async function. Input changed to an array of feed objects.
Output changed to a string bundle.

Author: digitalsadhu

lib/reader.js

@@ -1,82 +1,28 @@
 'use strict';
 
-const { Readable, PassThrough, Stream } = require('readable-stream');
-const { parse } = require('JSONStream');
-const mergeStream = require('merge-stream');
-const { dedupe, sort, setOrder } = require('./util');
 const assert = require('assert');
 
-module.exports = class Reader extends Readable {
-    constructor(streams) {
-        super();
-
-        assert(
-            streams instanceof Stream || Array.isArray(streams),
-            `Expected first argument to new Reader() to be a stream or array of streams. 
-            Instead got ${typeof stream}`
-        );
-
-        if (!Array.isArray(streams)) {
-            streams = [streams];
-        }
-
-        assert(
-            streams.every(stream => stream instanceof Stream),
-            'Expected any/all arguments given to Reader constructor to be subclasses of Stream.'
-        );
-
-        assert(
-            streams.length,
-            'Expected at least one stream to be provided to new Reader(). Got none.'
-        );
-
-        const merged = mergeStream();
-
-        let count = 0;
-        streams.forEach((readStream, index) => {
-            const tmpStream = new PassThrough({ objectMode: true });
-            merged.add(tmpStream);
-
-            readStream.on('file found', file => {
-                this.emit('file found', file);
-                readStream
-                    .pipe(parse('*'))
-                    .on('error', err => {
-                        this.emit('error', err);
-                    })
-                    .pipe(setOrder(index))
-                    .pipe(tmpStream);
-
-                count++;
-                if (count === streams.length) {
-                    this.emit('pipeline ready');
-                }
-            });
-
-            readStream.on('file not found', file => {
-                this.emit('file not found', file);
-                tmpStream.end();
-
-                count++;
-                if (count === streams.length) {
-                    this.emit('pipeline ready');
-                }
-            });
-        });
-
-        this.data = merged.pipe(sort()).pipe(dedupe());
-        this.data.pause();
-
-        this.data.on('data', chunk => {
-            this.push(`${chunk.content.trim()}\n\n`);
-        });
-
-        this.data.on('end', () => {
-            this.push(null);
-        });
-    }
-
-    _read() {
-        return this.data.resume();
-    }
+module.exports = async function reader(feeds = []) {
+    assert(
+        feeds.length,
+        `Expected at least 1 feed to be given. Instead got "${feeds.length}"`
+    );
+    assert(
+        feeds.every(Array.isArray),
+        `Expected every feed to be an array. Instead got "${feeds.join(', ')}"`
+    );
+
+    feeds = feeds.reduce((prev, current) => prev.concat(current), []);
+
+    const map = new Map();
+    feeds.forEach(feed => {
+        // because map preserves order, when we get a duplicate we actually
+        // need to append to the end of the map. We do that by deleting
+        // first and then adding to the map
+        map.delete(feed.id);
+        map.set(feed.id, feed);
+    });
+    return Array.from(map.values())
+        .map(feed => feed.content.trim())
+        .join('\n\n');
 };