Add sync service

api/reader.go

@@ -0,0 +1,92 @@
+package vex
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/mmcdole/gofeed"
+)
+
+type Reader struct {
+	feedReader *gofeed.Parser
+	client     *http.Client
+}
+
+func NewRssReader(client *http.Client) Reader {
+	return Reader{
+		feedReader: gofeed.NewParser(),
+		client:     client,
+	}
+}
+
+type GoFeed struct {
+	*gofeed.Feed
+
+	ETag         string
+	LastModified time.Time
+}
+
+func (r *Reader) ReadFeed(url string, etag string, lastModified *time.Time) (*GoFeed, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("User-Agent", "Gofeed/1.0")
+
+	if etag != "" {
+		req.Header.Set("If-None-Match", fmt.Sprintf(`"%s"`, etag))
+	}
+	if lastModified != nil {
+		req.Header.Set("If-Modified-Since", lastModified.Format(time.RFC1123))
+	}
+
+	resp, err := r.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp != nil {
+		defer func() {
+			ce := resp.Body.Close()
+			if ce != nil {
+				err = ce
+			}
+		}()
+	}
+
+	if resp.StatusCode == http.StatusNotModified {
+		return nil, nil
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return nil, gofeed.HTTPError{
+			StatusCode: resp.StatusCode,
+			Status:     resp.Status,
+		}
+	}
+
+	feed := &GoFeed{}
+
+	feedBody, err := r.feedReader.Parse(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	feed.Feed = feedBody
+
+	if eTag := resp.Header.Get("Etag"); eTag != "" {
+		feed.ETag = eTag
+	}
+
+	if lastModified := resp.Header.Get("Last-Modified"); lastModified != "" {
+		parsed, err := time.ParseInLocation(time.RFC1123, lastModified, time.UTC)
+		if err == nil {
+			feed.LastModified = parsed
+		}
+	}
+
+	return feed, nil
+}