First implementation of an atom feed

feed.go

@@ -0,0 +1,174 @@
+package atomfeed
+
+import (
+	"encoding/xml"
+	"errors"
+	"fmt"
+)
+
+type Feed struct {
+	XMLName xml.Name `xml:"http://www.w3.org/2005/Atom feed"`
+	*CommonAttributes
+	Authors      []*Person           `xml:"author,omitempty"`
+	Categories   []*Category         `xml:"category,omitempty"`
+	Contributors []*Person           `xml:"contributor,omitempty"`
+	Generator    *Generator          `xml:"generator,omitempty"`
+	Icon         *Icon               `xml:"icon,omitempty"`
+	ID           *ID                 `xml:"id"`
+	Links        []*Link             `xml:"link,omitempty"` // There should be one link with rel "self"
+	Logo         *Logo               `xml:"logo,omitempty"`
+	Rights       *Text               `xml:"rights,omitempty"`
+	Subtitle     *Text               `xml:"subtitle,omitempty"`
+	Title        *Text               `xml:"title"`
+	Updated      *Date               `xml:"updated"`
+	Extensions   []*ExtensionElement `xml:",any"`
+	Entries      []*Entry            `xml:"entry,omitempty"`
+}
+
+func (f *Feed) Check() error {
+	if f.ID == nil {
+		return errors.New("no id element of feed")
+	} else {
+		if err := f.ID.Check(); err != nil {
+			return fmt.Errorf("id element of feed: %v", err)
+		}
+	}
+
+	if f.Authors == nil {
+		for _, e := range f.Entries {
+			if err := e.checkAuthors(); err != nil {
+				return fmt.Errorf("no authors set in feed %v: %v", f.ID.URI, err)
+			}
+		}
+	} else {
+		for i, a := range f.Authors {
+			if err := a.Check(); err != nil {
+				return fmt.Errorf("author element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	if f.Categories != nil {
+		for i, c := range f.Categories {
+			if err := c.Check(); err != nil {
+				return fmt.Errorf("category element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	if f.Contributors != nil {
+		for i, c := range f.Contributors {
+			if err := c.Check(); err != nil {
+				return fmt.Errorf("contributor element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	if f.Generator != nil {
+		if err := f.Generator.Check(); err != nil {
+			return fmt.Errorf("generator element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Icon != nil {
+		if err := f.Icon.Check(); err != nil {
+			return fmt.Errorf("icon element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Links != nil {
+		for i, l := range f.Links {
+			if err := l.Check(); err != nil {
+				return fmt.Errorf("link element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	if f.Logo != nil {
+		if err := f.Logo.Check(); err != nil {
+			return fmt.Errorf("logo element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Rights != nil {
+		if err := (*f.Rights).Check(); err != nil {
+			return fmt.Errorf("rights element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Subtitle != nil {
+		if err := (*f.Subtitle).Check(); err != nil {
+			return fmt.Errorf("subtitle element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Title == nil {
+		return fmt.Errorf("no title element of feed %v", f.ID.URI)
+	} else {
+		if err := (*f.Title).Check(); err != nil {
+			return fmt.Errorf("title element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Updated == nil {
+		return fmt.Errorf("no updated element of feed %v", f.ID)
+	} else {
+		if err := f.Updated.Check(); err != nil {
+			return fmt.Errorf("updated element of feed %v: %v", f.ID.URI, err)
+		}
+	}
+
+	if f.Extensions != nil {
+		for i, x := range f.Extensions {
+			if err := x.Check(); err != nil {
+				return fmt.Errorf("extension element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	if f.Entries != nil {
+		for i, n := range f.Entries {
+			if err := n.Check(); err != nil {
+				return fmt.Errorf("entry element %v of feed %v: %v", i, f.ID.URI, err)
+			}
+		}
+	}
+
+	return nil
+}
+
+// TODO: Create complete link or delete
+func (f *Feed) Standardize() {
+	if f.Links == nil {
+		f.Links = make([]*Link, 1)
+		f.Links[0] = &Link{Rel: "self"}
+	} else {
+		selfExists := false
+		for _, l := range f.Links {
+			if l.Rel == "self" {
+				selfExists = true
+				break
+			}
+		}
+		if !selfExists {
+			f.Links = append(f.Links, &Link{Rel: "self"})
+		}
+	}
+}
+
+func (f *Feed) AddExtension(name string, value any) {
+	f.Extensions = append(f.Extensions, &ExtensionElement{XMLName: xml.Name{Local: name}, Value: value})
+}
+
+func (f *Feed) ToXML(encoding string) (string, error) {
+	if err := f.Check(); err != nil {
+		return "", fmt.Errorf("error checking feed: %v", err)
+	}
+
+	xml, err := xml.MarshalIndent(f, "", "  ")
+	if err != nil {
+		return "", fmt.Errorf("error xml encoding feed: %v", err)
+	}
+
+	return fmt.Sprintln(`<?xml version="1.0" encoding="`+encoding+`"?>`) + string(xml), nil
+}