Changed Post struct. Added NewPost() func and PostID() method.

pkg/mindflow/post.go

@@ -1,12 +1,31 @@
 package mindflow
 
 import (
+	"errors"
+	"fmt"
+	"strings"
 	"time"
 )
 
 type Post struct {
-	Category string
+	ID       int64
+	Category Category
 	Date     time.Time
 	Title    string
 	Body     string
 }
+
+func NewPost(category Category, title, body string) (*Post, error) {
+	if title == "" || body == "" {
+		return nil, errors.New("empty title or body is not allowed")
+	}
+	return &Post{
+		Category: category,
+		Date:     time.Now().UTC(),
+		Title:    title,
+		Body:     body}, nil
+}
+
+func (p *Post) PostID() string {
+	return fmt.Sprint(strings.ToLower(p.Category.Name), "-", p.Date.Format("20060102-1504"))
+}