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linkpreview pkg

This commit is contained in:
Sergey Cherepanov 2019-10-28 14:03:05 +03:00
parent 0ad2ccc431
commit 319eb5e591
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4 changed files with 191 additions and 0 deletions

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package linkpreview
import (
"context"
"net/http"
"path/filepath"
"strings"
"github.com/otiai10/opengraph"
)
func New() LinkPreview {
return &linkPreview{}
}
type LinkType string
const (
LinkTypeHtml LinkType = "html"
LinkTypeImage LinkType = "image"
LinkTypeVideo LinkType = "video"
LinkTypeText LinkType = "text"
LinkTypeUnexpected LinkType = "unexpected"
// read no more than 400 kb
maxBytesToRead = 400000
)
type LinkPreview interface {
Fetch(ctx context.Context, url string) (Info, error)
}
type Info struct {
Title string
Description string
ImageUrl string
Type LinkType
}
type linkPreview struct{}
func (l *linkPreview) Fetch(ctx context.Context, url string) (Info, error) {
rt := &proxyRoundTripper{RoundTripper: http.DefaultTransport}
client := &http.Client{Transport: rt}
og, err := opengraph.FetchWithContext(ctx, url, client)
if err != nil {
if resp := rt.lastResponse; resp != nil && resp.StatusCode == http.StatusOK {
return l.makeNonHtml(url, resp)
}
return Info{}, err
}
return l.convertOGToInfo(og), nil
}
func (l *linkPreview) convertOGToInfo(og *opengraph.OpenGraph) (i Info) {
i = Info{
Title: og.Title,
Description: og.Description,
Type: LinkTypeHtml,
}
if len(og.Image) != 0 {
i.ImageUrl = og.Image[0].URL
}
return
}
func (l *linkPreview) makeNonHtml(url string, resp *http.Response) (i Info, err error) {
ct := resp.Header.Get("Content-Type")
i.Title = filepath.Base(url)
if strings.HasPrefix(ct, "image/") {
i.Type = LinkTypeImage
i.ImageUrl = url
} else if strings.HasPrefix(ct, "text/") {
i.Type = LinkTypeText
} else {
i.Type = LinkTypeUnexpected
}
return
}
type proxyRoundTripper struct {
http.RoundTripper
lastResponse *http.Response
}
func (p *proxyRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
resp, err := p.RoundTripper.RoundTrip(req)
if err == nil {
p.lastResponse = resp
resp.Body = http.MaxBytesReader(nil, resp.Body, maxBytesToRead)
}
return resp, err
}

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package linkpreview
import (
"context"
"io"
"net/http"
"net/http/httptest"
"strings"
"testing"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)
var ctx = context.Background()
func TestLinkPreview_Fetch(t *testing.T) {
t.Run("html page", func(t *testing.T) {
ts := newTestServer("text/html", strings.NewReader(tetsHtml))
defer ts.Close()
lp := New()
info, err := lp.Fetch(ctx, ts.URL)
require.NoError(t, err)
assert.Equal(t, Info{
Title: "Title",
Description: "Description",
ImageUrl: "http://site.com/images/example.jpg",
Type: LinkTypeHtml,
}, info)
})
t.Run("binary image", func(t *testing.T) {
tr := testReader(0)
ts := newTestServer("image/jpg", &tr)
defer ts.Close()
url := ts.URL + "/filename.jpg"
lp := New()
info, err := lp.Fetch(ctx, url)
require.NoError(t, err)
assert.Equal(t, Info{
Title: "filename.jpg",
ImageUrl: url,
Type: LinkTypeImage,
}, info)
assert.True(t, int(tr) <= maxBytesToRead)
})
t.Run("binary", func(t *testing.T) {
tr := testReader(0)
ts := newTestServer("binary/octed-stream", &tr)
defer ts.Close()
url := ts.URL + "/filename.jpg"
lp := New()
info, err := lp.Fetch(ctx, url)
require.NoError(t, err)
assert.Equal(t, Info{
Title: "filename.jpg",
Type: LinkTypeUnexpected,
}, info)
assert.True(t, int(tr) <= maxBytesToRead)
})
}
func newTestServer(contentType string, data io.Reader) *httptest.Server {
return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", contentType)
io.Copy(w, data)
}))
}
const tetsHtml = `<html><head>
<title>Title</title>
<meta name="description" content="Description">
<meta property="og:image" content="http://site.com/images/example.jpg" />
</head></html>`
type testReader int
func (t *testReader) Read(p []byte) (n int, err error) {
*t += testReader(len(p))
return len(p), nil
}