add prefix helpers + tests

Author: Benjamin Forster

lib/prefixes.js

@@ -0,0 +1,46 @@
+const PREFIX_KEY = '@prefix/'
+const PREFIX_REGEX = /^(\w+):/
+const DEFAULT_PREFIXES = {
+  _: 'hg://',
+  foaf: 'http://xmlns.com/foaf/0.1/'
+}
+
+function toKey (prefix) {
+  return PREFIX_KEY + prefix
+}
+function fromKey (key) {
+  return key.replace(PREFIX_KEY, '')
+}
+
+function fromNodes (nodes) {
+  return {
+    prefix: fromKey(nodes[0].key),
+    uri: nodes[0].value
+  }
+}
+
+function toPrefixed (uri, prefixes) {
+  if (!prefixes) return uri
+  const prefix = Object.keys(prefixes).find(v => uri.startsWith(prefixes[v]))
+  if (!prefix) return uri
+  return uri.replace(prefixes[prefix], prefix + ':')
+}
+
+function fromPrefixed (uri, prefixes) {
+  if (!prefixes) return uri
+  const match = uri.match(PREFIX_REGEX)
+  if (match && prefixes[match[1]]) {
+    return uri.replace(PREFIX_REGEX, prefixes[match[1]])
+  }
+  return uri
+}
+
+module.exports = {
+  DEFAULT_PREFIXES,
+  PREFIX_KEY,
+  toKey,
+  fromKey,
+  fromNodes,
+  toPrefixed,
+  fromPrefixed
+}

test/prefixes.spec.js

@@ -0,0 +1,67 @@
+/* eslint-env mocha */
+const expect = require('chai').expect
+const prefixes = require('../lib/prefixes')
+
+describe('prefix utilities', () => {
+  describe('toKey', () => {
+    it('converts a prefix to a key', () => {
+      expect(prefixes.toKey('this')).to.eql('@prefix/this')
+    })
+  })
+
+  describe('fromKey', () => {
+    it('converts a key to its prefix', () => {
+      expect(prefixes.fromKey('@prefix/this')).to.eql('this')
+    })
+  })
+
+  describe('fromNodes', () => {
+    it('converts hyperdb nodes to prefix/uri object', () => {
+      const dummyNodes = [{ key: '@prefix/this', value: 'http://this.example.com' }]
+      expect(prefixes.fromNodes(dummyNodes)).to.eql({ uri: 'http://this.example.com', prefix: 'this' })
+    })
+    it('ignores conflicts', () => {
+      const dummyNodes = [
+        { key: '@prefix/this', value: 'http://this.example.com' },
+        { key: '@prefix/this', value: 'http://conflict.example.com' }
+      ]
+      expect(prefixes.fromNodes(dummyNodes)).to.eql({ uri: 'http://this.example.com', prefix: 'this' })
+    })
+  })
+
+  describe('toPrefixed', () => {
+    it('returns unmodified string if prefix is undefined', () => {
+      const str = 'http://test.com/this/ok#wow'
+      const prefixed = prefixes.toPrefixed(str)
+      expect(prefixed).to.eql(str)
+    })
+    it('returns unmodified string if prefix is not set', () => {
+      const str = 'http://test.com/this/ok#wow'
+      const prefixed = prefixes.toPrefixed(str, { 'wow': 'http://wow.com/' })
+      expect(prefixed).to.eql(str)
+    })
+    it('returns prefix string if prefix is present', () => {
+      const str = 'http://wow.com/now/this#and_hashed'
+      const prefixed = prefixes.toPrefixed(str, { 'wow': 'http://wow.com/' })
+      expect(prefixed).to.eql('wow:now/this#and_hashed')
+    })
+  })
+
+  describe('fromPrefixed', () => {
+    it('returns unmodified string if prefix is undefined', () => {
+      const str = 'some:thing'
+      const prefixed = prefixes.fromPrefixed(str)
+      expect(prefixed).to.eql(str)
+    })
+    it('returns unmodified string if prefix is not set', () => {
+      const str = 'some:thing'
+      const prefixed = prefixes.fromPrefixed(str, { 'wow': 'http://wow.com/' })
+      expect(prefixed).to.eql(str)
+    })
+    it('returns prefix string if prefix is present', () => {
+      const str = 'wow:now'
+      const prefixed = prefixes.fromPrefixed(str, { 'wow': 'http://wow.com/' })
+      expect(prefixed).to.eql('http://wow.com/now')
+    })
+  })
+})