Don't return pointer from NewImageAttachment()

Add (forceful) Reset function to memo

activitystreams/activity.go

@@ -117,6 +117,7 @@ type Object struct {
 	Content      string            `json:"content"`
 	ContentMap   map[string]string `json:"contentMap,omitempty"`
 	Tag          []Tag             `json:"tag"`
+	Attachment   []Attachment      `json:"attachment,omitempty"`
 
 	// Extensions
 	// NOTE: add extensions here

activitystreams/attachment.go

@@ -0,0 +1,33 @@
+package activitystreams
+
+import (
+	"mime"
+	"strings"
+)
+
+type Attachment struct {
+	Type      AttachmentType `json:"type"`
+	URL       string         `json:"url"`
+	MediaType string         `json:"mediaType"`
+	Name      string         `json:"name"`
+}
+
+type AttachmentType string
+
+const AttachImage AttachmentType = "Image"
+
+// NewImageAttachment creates a new Attachment from the given URL, setting the
+// correct type and automatically detecting the MediaType based on the file
+// extension.
+func NewImageAttachment(url string) Attachment {
+	var imgType string
+	extIdx := strings.LastIndexByte(url, '.')
+	if extIdx > -1 {
+		imgType = mime.TypeByExtension(url[extIdx:])
+	}
+	return Attachment{
+		Type:      AttachImage,
+		URL:       url,
+		MediaType: imgType,
+	}
+}

activitystreams/attachment_test.go

@@ -0,0 +1,40 @@
+package activitystreams
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestNewImageAttachment(t *testing.T) {
+	type args struct {
+		url string
+	}
+	tests := []struct {
+		name string
+		args args
+		want *Attachment
+	}{
+		{name: "good svg", args: args{"https://writefreely.org/img/writefreely.svg"}, want: &Attachment{
+			Type:      "Image",
+			URL:       "https://writefreely.org/img/writefreely.svg",
+			MediaType: "image/svg+xml",
+		}},
+		{name: "good png", args: args{"https://i.snap.as/12345678.png"}, want: &Attachment{
+			Type:      "Image",
+			URL:       "https://i.snap.as/12345678.png",
+			MediaType: "image/png",
+		}},
+		{name: "no extension", args: args{"https://i.snap.as/12345678"}, want: &Attachment{
+			Type:      "Image",
+			URL:       "https://i.snap.as/12345678",
+			MediaType: "",
+		}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := NewImageAttachment(tt.args.url); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("NewImageAttachment() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

activitystreams/tag.go

@@ -10,5 +10,5 @@ type TagType string
 
 const (
 	TagHashtag TagType = "Hashtag"
-	TagMention         = "Mention"
+	TagMention TagType = "Mention"
 )

memo/memo.go

@@ -67,3 +67,13 @@ func (memo *Memo) Get() (value interface{}, err error) {
 	}
 	return memo.cache.res.value, memo.cache.res.err
 }
+
+// Reset forcibly resets the cache to nil without checking if the cache
+// duration has elapsed.
+func (memo *Memo) Reset() {
+	defer memo.mu.Unlock()
+	memo.mu.Lock()
+
+	memo.cache = nil
+	memo.lastCache = time.Now()
+}