update links to support custom URL hash

models/link.js

@@ -1,40 +1,47 @@
+const mongoose = require('../lib/mongoose')
+const Sequence = require('./sequence')
+
 const { URL } = require('url')
 const normalizeUrl = require('normalize-url')
 const HashIds = require('hashids/cjs')
 const hash = new HashIds(process.env.DOMAIN, process.env.HASH_MIN_LENGTH - 0)
 
-const mongoose = require('../lib/mongoose')
-const AutoIncrement = require('mongoose-sequence')(mongoose)
-
-const schema = new mongoose.Schema(
-  {
-    _id: {
-      type: Number,
-      immutable: true,
-      get: id => hash.encode(id)
+const schema = new mongoose.Schema({
+  url: {
+    type: String,
+    required: true,
+    unique: true,
+    trim: true,
+    validate: {
+      validator: url => new URL(url).host !== process.env.DOMAIN,
+      msg: `Cannot shorten ${process.env.DOMAIN} URLs`
     },
-    url: {
-      type: String,
-      required: true,
-      trim: true,
-      minlength: process.env.HASH_MIN_LENGTH,
-      maxlength: process.env.HASH_MAX_LENGTH,
-      validate: [
-        {
-          validator: url => new URL(url).host !== process.env.DOMAIN,
-          msg: `Cannot shorten ${process.env.DOMAIN} URLs`
-        }
-      ],
-      set: url => normalizeUrl(url, { forceHttps: true }),
-      unique: true
-    }
+    set: url => normalizeUrl(url, { forceHttps: true })
   },
-  { _id: false }
-)
+  hash: {
+    type: String,
+    unique: true,
+    trim: true,
+    minlength: process.env.HASH_MIN_LENGTH,
+    maxlength: process.env.HASH_MAX_LENGTH,
+    validate: [
+      {
+        validator: hash => /^\w+$/.test(hash),
+        msg: 'Hashes must be alphanumeric'
+      },
+      {
+        validator: val => !hash.decode(val).length,
+        msg: 'Cannot use this hash'
+      }
+    ]
+  }
+})
 
-schema.plugin(AutoIncrement)
-schema.statics.findByHashId = function(hashId) {
-  return this.findById(hash.decode(hashId)[0])
-}
+schema.pre('save', async function() {
+  if (!this.hash) this.hash = hash.encode(await Sequence.next())
+})
+schema.virtual('redirectTo').get(function() {
+  return `${process.env.DOMAIN}/${this.hash}`
+})
 
 module.exports = mongoose.model('Link', schema)

models/link.test.js

@@ -0,0 +1,37 @@
+require('dotenv-defaults').config()
+
+const Link = require('./link')
+const HashIds = require('hashids/cjs')
+const hashIds = new HashIds(process.env.DOMAIN, process.env.HASH_MIN_LENGTH - 0)
+
+describe('Link model', () => {
+  const url = 'www.nodejs.org'
+  const normalizedURL = 'https://nodejs.org'
+  let hash
+
+  beforeAll(async () => {
+    return Link.deleteMany({})
+  })
+
+  test('shorten URL', async () => {
+    const doc = await Link.create({ url })
+    hash = doc.hash
+
+    expect(typeof doc.hash).toBe('string')
+    expect(doc.hash.length).toBeGreaterThanOrEqual(6)
+  })
+
+  test('fetch URL', async () => {
+    const doc = await Link.findOne({ hash })
+
+    expect(doc.url).toBe(normalizedURL)
+    expect(doc.redirectTo.startsWith(process.env.DOMAIN)).toBe(true)
+  })
+
+  test('set custom hash', async () => {
+    await Link.create({ url: 'example.com', hash: 'FooBar' })
+
+    // eslint-disable-next-line no-unused-expressions
+    expect(new Link({ url, hash: hashIds.encode(500) }).validate()).rejects
+  })
+})

models/sequence.js

@@ -0,0 +1,17 @@
+const mongoose = require('../lib/mongoose')
+
+const schema = new mongoose.Schema({
+  _id: { type: String, required: true },
+  i: { type: Number, default: 0 }
+})
+
+schema.static('next', async function() {
+  const doc = await this.findOneAndUpdate(
+    { _id: 'ctr' },
+    { $inc: { i: 1 } },
+    { new: true, upsert: true, setDefaultsOnInsert: true, lean: true }
+  )
+  return doc.i
+})
+
+module.exports = mongoose.model('Sequence', schema, 'sequence')