1 files changed, 188 insertions, 0 deletions
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..945b30b
--- /dev/null
+++ b/main.go
@@ -0,0 +1,188 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strings"
+
+	"github.com/beevik/etree"
+)
+
+type ErrorRequestHandler func(w http.ResponseWriter, r *http.Request) error
+
+var RegexCollection = map[string]string{
+	"nerdcast":     "NerdCast [0-9]+[a-c]* -",
+	"empreendedor": "Empreendedor [0-9]+ -",
+	"mamicas":      "Caneca de Mamicas [0-9]+ -",
+	"english":      "Speak English [0-9]+ -",
+	"nerdcash":     "NerdCash [0-9]+ -",
+	"bunker":       "Lá do Bunker [0-9]+ -",
+	"tech":         "NerdTech [0-9]+ -",
+	"genera":       "Generacast [0-9]+ -",
+}
+
+const (
+	FeedUrl = "https://api.jovemnerd.com.br/feed-nerdcast/"
+)
+
+func getSeries(r *http.Request) []string {
+	query := r.URL.Query().Get("q")
+
+	var series []string
+
+	for _, q := range strings.Split(query, ",") {
+		if _, ok := RegexCollection[q]; ok {
+			series = append(series, q)
+		}
+	}
+
+	if len(series) > 0 {
+		return series
+	}
+
+	return []string{"nerdcast"}
+}
+
+func match(title string, series []string) bool {
+	for _, s := range series {
+		if ok, err := regexp.MatchString(RegexCollection[s], title); err == nil && ok {
+			return true
+		}
+	}
+
+	return false
+}
+
+func fetchXML(_ context.Context) ([]byte, error) {
+	res, err := http.Get(FeedUrl)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode == http.StatusOK {
+		return io.ReadAll(res.Body)
+	}
+
+	return nil, errors.New("Invalid http code")
+}
+
+func appendTag(tag *etree.Element, ap string) {
+	text := tag.Text()
+	tag.SetText(text + ap)
+}
+
+func filterBySeries(series []string, xml []byte, temper bool) ([]byte, error) {
+	doc := etree.NewDocument()
+	err := doc.ReadFromBytes(xml)
+	if err != nil {
+		return nil, err
+	}
+
+	channel := doc.FindElement("//channel")
+
+	if temper {
+		tmp := strings.ToUpper(strings.Join(series, ","))
+		tmp = fmt.Sprintf(" [%s]", tmp)
+		appendTag(channel.FindElement("title"), tmp)
+		appendTag(channel.FindElement("description"), tmp)
+		appendTag(channel.FindElement("link"), "?"+tmp)
+		appendTag(channel.FindElement("author[namespace-prefix()='itunes']"), tmp)
+		appendTag(channel.FindElement("subtitle[namespace-prefix()='itunes']"), tmp)
+		appendTag(channel.FindElement("summary[namespace-prefix()='itunes']"), tmp)
+		appendTag(channel.FindElement("author[namespace-prefix()='googleplay']"), tmp)
+
+	}
+
+	for _, tag := range channel.FindElements("item") {
+		title := tag.FindElement("title").Text()
+		if !match(title, series) {
+			channel.RemoveChild(tag)
+		}
+	}
+
+	return doc.WriteToBytes()
+}
+
+func wrap(next ErrorRequestHandler) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if err := next(w, r); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
+	}
+}
+
+func titles(w http.ResponseWriter, r *http.Request) error {
+	xml, err := fetchXML(r.Context())
+	if err != nil {
+		return err
+	}
+
+	doc := etree.NewDocument()
+	err = doc.ReadFromBytes(xml)
+	if err != nil {
+		return err
+	}
+
+	series := getSeries(r)
+
+	els := doc.FindElements("//channel/item")
+	for _, e := range els {
+		txt := e.FindElement("title").Text() + "\n"
+		if match(txt, series) {
+			_, err = w.Write([]byte(txt))
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func podcast(w http.ResponseWriter, r *http.Request) error {
+	xml, err := fetchXML(r.Context())
+	if err != nil {
+		return err
+	}
+
+	series := getSeries(r)
+	filterdXML, err := filterBySeries(series, xml, true)
+	if err != nil {
+		return err
+	}
+
+	_, err = w.Write(filterdXML)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	var (
+		addr = flag.String("addr", ":8080", "Server address")
+	)
+
+	flag.Parse()
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/titles", wrap(titles))
+	mux.HandleFunc("/", wrap(podcast))
+
+	server := http.Server{
+		Handler: mux,
+		Addr:    *addr,
+	}
+
+	err := server.ListenAndServe()
+	if err != nil {
+		fmt.Printf("Server error: %s", err.Error())
+	}
+}