Persist, renew and delete sessions, refactor storage package, move reusable packages to pkg

pkg/linkmeta/linkmeta.go

@@ -0,0 +1,132 @@
+package linkmeta
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"golang.org/x/net/html"
+	"golang.org/x/net/html/atom"
+)
+
+var (
+	Client = &http.Client{
+		Timeout: 15 * time.Second,
+	}
+
+	ErrContentType = errors.New("Unsupported Content-Type")
+)
+
+type Meta struct {
+	URL         string `json:"URL"`
+	SiteName    string `json:"siteName,omitempty"`
+	Color       string `json:"color,omitempty"`
+	Title       string `json:"title"`
+	Description string `json:"description"`
+	ImageURL    string `json:"imageURL,omitempty"`
+	VideoURL    string `json:"videoURL,omitempty"`
+}
+
+func Fetch(url string) (*Meta, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	// TODO: Image links
+	if !strings.HasPrefix(resp.Header.Get("Content-Type"), "text/html") {
+		return nil, ErrContentType
+	}
+
+	return ExtractMeta(resp.Body, url)
+}
+
+func ExtractMeta(body io.Reader, url string) (*Meta, error) {
+	meta := Meta{URL: url}
+	var currentNode atom.Atom
+
+	z := html.NewTokenizer(body)
+	for {
+		tt := z.Next()
+		switch tt {
+		case html.ErrorToken:
+			if z.Err() == io.EOF {
+				return &meta, nil
+			}
+			return nil, z.Err()
+
+		case html.TextToken:
+			if currentNode == atom.Title && meta.Title == "" {
+				meta.Title = string(z.Text())
+			}
+
+		case html.StartTagToken, html.SelfClosingTagToken, html.EndTagToken:
+			name, hasAttr := z.TagName()
+			node := atom.Lookup(name)
+
+			if node == atom.Meta && hasAttr {
+				var key, val []byte
+				var name, content string
+				for hasAttr {
+					key, val, hasAttr = z.TagAttr()
+					switch atom.String(key) {
+					case "name":
+						name = string(val)
+
+					case "property":
+						name = string(val)
+
+					case "content":
+						content = string(val)
+					}
+				}
+
+				if content != "" {
+					switch name {
+					case "og:site_name":
+						meta.SiteName = content
+
+					case "theme-color", "msapplication-TileColor":
+						meta.Color = content
+
+					case "og:title", "twitter:title", "title":
+						meta.Title = content
+
+					case "og:description", "twitter:description":
+						meta.Description = content
+
+					case "description":
+						if meta.Description == "" {
+							meta.Description = content
+						}
+
+					case "og:image", "og:image:secure_url", "twitter:image":
+						if !strings.HasPrefix(meta.ImageURL, "https:") {
+							meta.ImageURL = content
+						}
+
+					case "og:video:url", "og:video:secure_url", "twitter:player":
+						if !strings.HasPrefix(meta.VideoURL, "https:") {
+							meta.VideoURL = content
+						}
+					}
+				}
+
+				continue
+			}
+
+			if tt == html.StartTagToken {
+				currentNode = node
+			} else {
+				currentNode = 0
+			}
+
+			if (node == atom.Head && tt == html.EndTagToken) || node == atom.Body {
+				return &meta, nil
+			}
+		}
+	}
+}