Link parsing (#120)

* add link parsing + formatting functionality

* refinement + docs

* add missing test

* credit url library

internal/text/link_test.go

@@ -0,0 +1,155 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package text_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/text"
+)
+
+const text1 = `
+This is a text with some links in it. Here's link number one: https://example.org/link/to/something#fragment
+
+Here's link number two: http://test.example.org?q=bahhhhhhhhhhhh
+
+https://another.link.example.org/with/a/pretty/long/path/at/the/end/of/it
+
+really.cool.website <-- this one shouldn't be parsed as a link because it doesn't contain the scheme
+
+https://example.orghttps://google.com <-- this shouldn't work either, but it does?! OK
+`
+
+const text2 = `
+this is one link: https://example.org
+
+this is the same link again: https://example.org
+
+these should be deduplicated
+`
+
+const text3 = `
+here's a mailto link: mailto:whatever@test.org
+`
+
+const text4 = `
+two similar links:
+
+https://example.org
+
+https://example.org/test
+`
+
+const text5 = `
+what happens when we already have a link within an href?
+
+<a href="https://example.org">https://example.org</a>
+`
+
+type TextTestSuite struct {
+	suite.Suite
+}
+
+func (suite *TextTestSuite) TestParseURLsFromText1() {
+	urls, err := text.FindLinks(text1)
+
+	assert.NoError(suite.T(), err)
+
+	assert.Equal(suite.T(), "https://example.org/link/to/something#fragment", urls[0].String())
+	assert.Equal(suite.T(), "http://test.example.org?q=bahhhhhhhhhhhh", urls[1].String())
+	assert.Equal(suite.T(), "https://another.link.example.org/with/a/pretty/long/path/at/the/end/of/it", urls[2].String())
+	assert.Equal(suite.T(), "https://example.orghttps://google.com", urls[3].String())
+}
+
+func (suite *TextTestSuite) TestParseURLsFromText2() {
+	urls, err := text.FindLinks(text2)
+	assert.NoError(suite.T(), err)
+
+	// assert length 1 because the found links will be deduplicated
+	assert.Len(suite.T(), urls, 1)
+}
+
+func (suite *TextTestSuite) TestParseURLsFromText3() {
+	urls, err := text.FindLinks(text3)
+	assert.NoError(suite.T(), err)
+
+	// assert length 0 because `mailto:` isn't accepted
+	assert.Len(suite.T(), urls, 0)
+}
+
+func (suite *TextTestSuite) TestReplaceLinksFromText1() {
+	replaced := text.ReplaceLinks(text1)
+	assert.Equal(suite.T(), `
+This is a text with some links in it. Here's link number one: <a href="https://example.org/link/to/something#fragment" rel="noopener">example.org/link/to/something#fragment</a>
+
+Here's link number two: <a href="http://test.example.org?q=bahhhhhhhhhhhh" rel="noopener">test.example.org?q=bahhhhhhhhhhhh</a>
+
+<a href="https://another.link.example.org/with/a/pretty/long/path/at/the/end/of/it" rel="noopener">another.link.example.org/with/a/pretty/long/path/at/the/end/of/it</a>
+
+really.cool.website <-- this one shouldn't be parsed as a link because it doesn't contain the scheme
+
+<a href="https://example.orghttps://google.com" rel="noopener">example.orghttps//google.com</a> <-- this shouldn't work either, but it does?! OK
+`, replaced)
+}
+
+func (suite *TextTestSuite) TestReplaceLinksFromText2() {
+	replaced := text.ReplaceLinks(text2)
+	assert.Equal(suite.T(), `
+this is one link: <a href="https://example.org" rel="noopener">example.org</a>
+
+this is the same link again: <a href="https://example.org" rel="noopener">example.org</a>
+
+these should be deduplicated
+`, replaced)
+}
+
+func (suite *TextTestSuite) TestReplaceLinksFromText3() {
+	// we know mailto links won't be replaced with hrefs -- we only accept https and http
+	replaced := text.ReplaceLinks(text3)
+	assert.Equal(suite.T(), `
+here's a mailto link: mailto:whatever@test.org
+`, replaced)
+}
+
+func (suite *TextTestSuite) TestReplaceLinksFromText4() {
+	replaced := text.ReplaceLinks(text4)
+	assert.Equal(suite.T(), `
+two similar links:
+
+<a href="https://example.org" rel="noopener">example.org</a>
+
+<a href="https://example.org/test" rel="noopener">example.org/test</a>
+`, replaced)
+}
+
+func (suite *TextTestSuite) TestReplaceLinksFromText5() {
+	// we know this one doesn't work properly, which is why html should always be sanitized before being passed into the ReplaceLinks function
+	replaced := text.ReplaceLinks(text5)
+	assert.Equal(suite.T(), `
+what happens when we already have a link within an href?
+
+<a href="<a href="https://example.org" rel="noopener">example.org</a>"><a href="https://example.org" rel="noopener">example.org</a></a>
+`, replaced)
+}
+
+func TestTextTestSuite(t *testing.T) {
+	suite.Run(t, new(TextTestSuite))
+}