add rss service (#117)

* add rss service

* git ignore rss

* update readme

* go fmt

* maintain map by url

* make rss service multi-tenant

rss/parser/parser.go

@@ -0,0 +1,63 @@
+package parser
+
+import (
+	"errors"
+	"net/http"
+	"net/url"
+
+	"github.com/PuerkitoBio/goquery"
+)
+
+var (
+	parsers = map[string]Parser{
+		"a16z.com":     a16zParser,
+		"cnbc.com":     cnbcParser,
+		"www.cnbc.com": cnbcParser,
+	}
+)
+
+type Parser func(string) (string, error)
+
+func Parse(uri string) (string, error) {
+	u, err := url.Parse(uri)
+	if err != nil {
+		return "", err
+	}
+
+	if v, ok := parsers[u.Host]; ok {
+		return v(uri)
+	}
+	return "", errors.New("no parser for url")
+}
+
+func classParser(class string) Parser {
+	return func(url string) (string, error) {
+		// Request the HTML page.
+		res, err := http.Get(url)
+		if err != nil {
+			return "", err
+		}
+
+		defer res.Body.Close()
+
+		if res.StatusCode != 200 {
+			return "", errors.New("bad status code")
+		}
+
+		// Load the HTML document
+		doc, err := goquery.NewDocumentFromReader(res.Body)
+		if err != nil {
+			return "", err
+		}
+
+		return doc.Find(class).Html()
+	}
+}
+
+func a16zParser(url string) (string, error) {
+	return classParser(".blog-content")(url)
+}
+
+func cnbcParser(url string) (string, error) {
+	return classParser(".PageBuilder-col-9")(url)
+}