Initial commit.

.gitignore

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+.DS_Store
+node_modules/

README.md

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+# URL helper
+
+A URL helper for use with design systems at The Grid.

package.json

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+{
+  "name": "url-helper",
+  "version": "0.1.0",
+  "description": "A URL helper for use with design systems at The Grid.",
+  "main": "lib/url-helper.js",
+  "scripts": {
+    "test": "grunt test --stack"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/design-systems/url-helper"
+  },
+  "author": "Paul Young",
+  "license": "proprietary",
+  "bugs": {
+    "url": "https://github.com/design-systems/url-helper/issues"
+  },
+  "homepage": "https://github.com/design-systems/url-helper",
+  "dependencies": {
+    "URIjs": "^1.16.0",
+    "url": "^0.10.3"
+  },
+  "devDependencies": {
+    "chai": "^3.2.0",
+    "coffee-script": "^1.9.3",
+    "mocha": "^2.2.5"
+  },
+  "scripts": {
+    "build": "npm run clean; ./node_modules/.bin/coffee --compile --output lib/ src/",
+    "clean": "mkdir -p lib; rm -r lib; mkdir lib",
+    "test": "npm run build; ./node_modules/.bin/mocha 'spec/**/*.coffee' --compilers coffee:coffee-script/register --reporter spec"
+  }
+}

spec/url-helper.coffee

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+chai = require "chai"
+{expect} = chai
+
+urlHelper = require "../lib/url-helper"
+
+describe "url helper", ->
+
+  describe "relative", ->
+
+    context "absolute URL", ->
+      it "should pass through unchanged", ->
+        to = "https://twitter.com/thegrid"
+        from = "index.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal "https://twitter.com/thegrid"
+
+
+    context "URL relative to index", ->
+      it "should resolve to the correct URL", ->
+        to = "index.html"
+        from = "faq/index.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal "../"
+
+
+    context "URL relative to named page", ->
+      it "should resolve to the correct URL", ->
+        to = "foo.html"
+        from = "bar/baz.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal "../foo.html"
+
+
+    context "URL relative to itself", ->
+      it "should resolve to the correct URL", ->
+        to = "faq/index.html"
+        from = "faq/index.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal ""
+
+
+    context "URL relative to another URL", ->
+      it "should resolve to the correct URL", ->
+        to = "blog/foo/index.html"
+        from = "categories/noflo/index.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal "../../blog/foo/"
+
+
+    context "Sibling page URL relative to index", ->
+      it "should resolve to the correct URL", ->
+        to = "index.html"
+        from = "index.abcde.html"
+        resolved = urlHelper.resolveRelativeUrl to, from
+        expect(resolved).to.equal "./"
+
+
+  describe "absolute", ->
+
+    context "without a URL", ->
+      it "should be invalid", ->
+        isValid = urlHelper.validateAbsoluteUrl null
+        expect(isValid).to.equal false
+
+    context "empty URL", ->
+      it "should be invalid", ->
+        isValid = urlHelper.validateAbsoluteUrl ""
+        expect(isValid).to.equal false
+
+    context "relative URL", ->
+      it "should be invalid", ->
+        isValid = urlHelper.validateAbsoluteUrl "../index.html"
+        expect(isValid).to.equal false
+
+    context "protocol-relative URL", ->
+      it "should be invalid", ->
+        isValid = urlHelper.validateAbsoluteUrl "//thegrid.io"
+        expect(isValid).to.equal false
+
+    context "URL with a file:// protocol", ->
+      it "should be invalid", ->
+        isValid = urlHelper.validateAbsoluteUrl "file://thegrid.png"
+        expect(isValid).to.equal false
+
+    context "URL with http:// protocol", ->
+      it "should be valid", ->
+        isValid = urlHelper.validateAbsoluteUrl "http://thegrid.io"
+        expect(isValid).to.equal true
+
+    context "URL with https:// protocol", ->
+      it "should be valid", ->
+        isValid = urlHelper.validateAbsoluteUrl "https://thegrid.io"
+        expect(isValid).to.equal true

src/url-helper.coffee

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+url = require "url"
+URI = require "URIjs"
+
+urlHelper =
+  isAbsoluteUrl: (uri) ->
+    (new URI(uri)).is "absolute"
+
+  resolveRelativeUrl: (to, from) ->
+    return to if module.exports.isAbsoluteUrl to
+    uri = new URI("/#{to}").relativeTo("/#{from}")
+    if uri.filename() is "index.html"
+      uri = uri.directory(".") if uri.directory() is ""
+      uri = uri.filename("")
+    uri.toString()
+
+  validateAbsoluteUrl: (remoteUrl) ->
+    return false unless remoteUrl?
+    {protocol} = url.parse remoteUrl
+    protocol is "http:" or protocol is "https:"
+
+  normalizeUrl: (uri, pagePath) ->
+    if urlHelper.isAbsoluteUrl uri
+      return uri if urlHelper.validateAbsoluteUrl uri
+      return null
+    urlHelper.resolveRelativeUrl uri, pagePath
+
+module.exports = urlHelper