Allow outputting RSS, Atom, and JSON feeds

README.md

@@ -2,13 +2,15 @@
 
 [![Build Status](https://travis-ci.org/mmcdole/gofeed.svg?branch=master)](https://travis-ci.org/mmcdole/gofeed) [![Coverage Status](https://coveralls.io/repos/github/mmcdole/gofeed/badge.svg?branch=master)](https://coveralls.io/github/mmcdole/gofeed?branch=master) [![Go Report Card](https://goreportcard.com/badge/github.com/mmcdole/gofeed)](https://goreportcard.com/report/github.com/mmcdole/gofeed) [![](https://godoc.org/github.com/mmcdole/gofeed?status.svg)](http://godoc.org/github.com/mmcdole/gofeed) [![License](http://img.shields.io/:license-mit-blue.svg)](http://doge.mit-license.org)
 
-# Gofeed: A Robust Feed Parser for Golang
+# Gofeed: A Robust Feed Library for Golang
 
 <img src="https://github.com/mmcdole/gofeed/assets/3767096/ab4e7b0e-1472-4249-880c-c6784000ed31" width="150" height="150"> 
 <br /><br />
 
 `gofeed` is a powerful and flexible library designed for parsing **RSS**, **Atom**, and **JSON** feeds across various formats and versions. It effectively manages non-standard elements and known extensions, and demonstrates resilience against common feed issues.
 
+`gofeed` allows you to render a feed to RSS, Atom, or JSON, allowing for conversion between feed types, creation of new feeds, or postprocessing of an existing feed. 
+
 ## Table of Contents
 - [Features](#features)
 - [Overview](#overview)
@@ -26,7 +28,9 @@
 - JSON (1.0, 1.1)
 
 ### Handling Invalid Feeds
+
 `gofeed` takes a best-effort approach to deal with broken or invalid XML feeds, capable of handling issues like:
+
 - Unescaped markup
 - Undeclared namespace prefixes
 - Missing or illegal tags
@@ -42,12 +46,15 @@ For added convenience, gofeed includes native support for parsing certain well-k
 
 - Dublin Core: Accessible via `Feed.DublinCoreExt` and `Item.DublinCoreExt`
 - Apple iTunes: Accessible via `Feed.ITunesExt` and `Item.ITunesExt`
+
+### Feed Rendering
+
+Whether a feed is created by parsing an existing feed or creating a feed from scratch, `gofeed` can render the feed to JSON Feed 1.1, RSS 2.0, or Atom 1.0.
 
 ## Overview
 
 In `gofeed`, you have two primary choices for feed parsing: a universal parser for handling multiple feed types seamlessly, and specialized parsers for more granular control over individual feed types.
 
-
 ### Universal Feed Parser 
 
 The universal `gofeed.Parser` is designed to make it easy to work with various types of feeds—RSS, Atom, JSON—by converting them into a unified `gofeed.Feed` model. This is especially useful when you're dealing with multiple feed formats and you want to treat them the same way.
@@ -150,6 +157,47 @@ jsonFeed, _ := fp.Parse(strings.NewReader(feedData))
 fmt.Println(jsonFeed.HomePageURL)
 ```
 
+### Feed Creation
+
+#### From Scratch
+
+The following example demonstrates building a feed and outputting it as Atom to standard output:
+
+```go
+feed := &Feed{
+    Title:   "Test Feed",
+    ID:      "http://example.com/feed",
+    Updated: "2024-01-01T12:00:00Z",
+	Entries: []*Entry{
+        Title:   "Simple Entry",
+        ID:      "http://example.com/entry2",
+        Updated: "2024-01-01T11:30:00Z",
+        Summary: "A simple Atom entry",
+        Content: &Content{
+            Type:  "text",
+            Value: "Plain text content",
+        },
+    },
+}
+_ = feed.RenderAtom(os.Stdout, nil)
+```
+
+#### From an Existing Feed
+
+The following example will convert a feed from RSS to Atom, printing the result to standard output:
+
+```go
+feedData := `<rss version="2.0">
+<channel>
+<webMaster>example@site.com (Example Name)</webMaster>
+</channel>
+</rss>`
+fp := gofeed.NewParser()
+feed, _ := fp.ParseString(feedData)
+
+_ = feed.RenderAtom(os.Stdout, nil)
+```
+
 ## Advanced Usage
 
 #### With Basic Authentication
@@ -240,3 +288,4 @@ This project is licensed under the [MIT License](https://raw.githubusercontent.c
 * [Matt Jibson](https://mattjibson.com/) for his date parsing function in the [goread](https://github.com/mjibson/goread) project.
 * [Jim Teeuwen](https://github.com/jteeuwen) for his method of representing arbitrary feed extensions in the [go-pkg-rss](https://github.com/jteeuwen/go-pkg-rss) library.
 * [Sudhanshu Raheja](https://revolt.ist) for supporting JSON Feed parser
+* [Chris Dzombak](https://github.com/cdzombak) for adding feed rendering

atom/feed.go

@@ -2,30 +2,32 @@ package atom
 
 import (
 	"encoding/json"
+	"encoding/xml"
 	"time"
 
 	"github.com/mmcdole/gofeed/extensions"
 )
 
 // Feed is an Atom Feed
 type Feed struct {
-	Title         string         `json:"title,omitempty"`
-	ID            string         `json:"id,omitempty"`
-	Updated       string         `json:"updated,omitempty"`
-	UpdatedParsed *time.Time     `json:"updatedParsed,omitempty"`
-	Subtitle      string         `json:"subtitle,omitempty"`
-	Links         []*Link        `json:"links,omitempty"`
-	Language      string         `json:"language,omitempty"`
-	Generator     *Generator     `json:"generator,omitempty"`
-	Icon          string         `json:"icon,omitempty"`
-	Logo          string         `json:"logo,omitempty"`
-	Rights        string         `json:"rights,omitempty"`
-	Contributors  []*Person      `json:"contributors,omitempty"`
-	Authors       []*Person      `json:"authors,omitempty"`
-	Categories    []*Category    `json:"categories,omitempty"`
-	Entries       []*Entry       `json:"entries"`
-	Extensions    ext.Extensions `json:"extensions,omitempty"`
-	Version       string         `json:"version"`
+	XMLName       xml.Name       `xml:"http://www.w3.org/2005/Atom feed" json:"-"`
+	Title         string         `json:"title,omitempty" xml:"title"`
+	ID            string         `json:"id,omitempty" xml:"id"`
+	Updated       string         `json:"updated,omitempty" xml:"updated"`
+	UpdatedParsed *time.Time     `json:"updatedParsed,omitempty" xml:"-"`
+	Subtitle      string         `json:"subtitle,omitempty" xml:"subtitle,omitempty"`
+	Links         []*Link        `json:"links,omitempty" xml:"link"`
+	Language      string         `json:"language,omitempty" xml:"lang,attr,omitempty"`
+	Generator     *Generator     `json:"generator,omitempty" xml:"generator"`
+	Icon          string         `json:"icon,omitempty" xml:"icon,omitempty"`
+	Logo          string         `json:"logo,omitempty" xml:"logo,omitempty"`
+	Rights        string         `json:"rights,omitempty" xml:"rights,omitempty"`
+	Contributors  []*Person      `json:"contributors,omitempty" xml:"contributor"`
+	Authors       []*Person      `json:"authors,omitempty" xml:"author"`
+	Categories    []*Category    `json:"categories,omitempty" xml:"category"`
+	Entries       []*Entry       `json:"entries" xml:"entry"`
+	Extensions    ext.Extensions `json:"extensions,omitempty" xml:"-"`
+	Version       string         `json:"version" xml:"-"`
 }
 
 func (f Feed) String() string {
@@ -35,80 +37,80 @@ func (f Feed) String() string {
 
 // Entry is an Atom Entry
 type Entry struct {
-	Title           string         `json:"title,omitempty"`
-	ID              string         `json:"id,omitempty"`
-	Updated         string         `json:"updated,omitempty"`
-	UpdatedParsed   *time.Time     `json:"updatedParsed,omitempty"`
-	Summary         string         `json:"summary,omitempty"`
-	Authors         []*Person      `json:"authors,omitempty"`
-	Contributors    []*Person      `json:"contributors,omitempty"`
-	Categories      []*Category    `json:"categories,omitempty"`
-	Links           []*Link        `json:"links,omitempty"`
-	Rights          string         `json:"rights,omitempty"`
-	Published       string         `json:"published,omitempty"`
-	PublishedParsed *time.Time     `json:"publishedParsed,omitempty"`
-	Source          *Source        `json:"source,omitempty"`
-	Content         *Content       `json:"content,omitempty"`
-	Extensions      ext.Extensions `json:"extensions,omitempty"`
+	Title           string         `json:"title,omitempty" xml:"title"`
+	ID              string         `json:"id,omitempty" xml:"id"`
+	Updated         string         `json:"updated,omitempty" xml:"updated"`
+	UpdatedParsed   *time.Time     `json:"updatedParsed,omitempty" xml:"-"`
+	Summary         string         `json:"summary,omitempty" xml:"summary"`
+	Authors         []*Person      `json:"authors,omitempty" xml:"author"`
+	Contributors    []*Person      `json:"contributors,omitempty" xml:"contributor"`
+	Categories      []*Category    `json:"categories,omitempty" xml:"category"`
+	Links           []*Link        `json:"links,omitempty" xml:"link"`
+	Rights          string         `json:"rights,omitempty" xml:"rights,omitempty"`
+	Published       string         `json:"published,omitempty" xml:"published"`
+	PublishedParsed *time.Time     `json:"publishedParsed,omitempty" xml:"-"`
+	Source          *Source        `json:"source,omitempty" xml:"source"`
+	Content         *Content       `json:"content,omitempty" xml:"content"`
+	Extensions      ext.Extensions `json:"extensions,omitempty" xml:"-"`
 }
 
 // Category is category metadata for Feeds and Entries
 type Category struct {
-	Term   string `json:"term,omitempty"`
-	Scheme string `json:"scheme,omitempty"`
-	Label  string `json:"label,omitempty"`
+	Term   string `json:"term,omitempty" xml:"term,attr"`
+	Scheme string `json:"scheme,omitempty" xml:"scheme,attr"`
+	Label  string `json:"label,omitempty" xml:"label,attr"`
 }
 
 // Person represents a person in an Atom feed
 // for things like Authors, Contributors, etc
 type Person struct {
-	Name  string `json:"name,omitempty"`
-	Email string `json:"email,omitempty"`
-	URI   string `json:"uri,omitempty"`
+	Name  string `json:"name,omitempty" xml:"name"`
+	Email string `json:"email,omitempty" xml:"email"`
+	URI   string `json:"uri,omitempty" xml:"uri"`
 }
 
 // Link is an Atom link that defines a reference
 // from an entry or feed to a Web resource
 type Link struct {
-	Href     string `json:"href,omitempty"`
-	Hreflang string `json:"hreflang,omitempty"`
-	Rel      string `json:"rel,omitempty"`
-	Type     string `json:"type,omitempty"`
-	Title    string `json:"title,omitempty"`
-	Length   string `json:"length,omitempty"`
+	Href     string `json:"href,omitempty" xml:"href,attr"`
+	Hreflang string `json:"hreflang,omitempty" xml:"hreflang,attr,omitempty"`
+	Rel      string `json:"rel,omitempty" xml:"rel,attr"`
+	Type     string `json:"type,omitempty" xml:"type,attr"`
+	Title    string `json:"title,omitempty" xml:"title,attr,omitempty"`
+	Length   string `json:"length,omitempty" xml:"length,attr,omitempty"`
 }
 
 // Content either contains or links to the content of
 // the entry
 type Content struct {
-	Src   string `json:"src,omitempty"`
-	Type  string `json:"type,omitempty"`
-	Value string `json:"value,omitempty"`
+	Src   string `json:"src,omitempty" xml:"src,attr"`
+	Type  string `json:"type,omitempty" xml:"type,attr"`
+	Value string `json:"value,omitempty" xml:",chardata"`
 }
 
 // Generator identifies the agent used to generate a
 // feed, for debugging and other purposes.
 type Generator struct {
-	Value   string `json:"value,omitempty"`
-	URI     string `json:"uri,omitempty"`
-	Version string `json:"version,omitempty"`
+	Value   string `json:"value,omitempty" xml:",chardata"`
+	URI     string `json:"uri,omitempty" xml:"uri,attr"`
+	Version string `json:"version,omitempty" xml:"version,attr"`
 }
 
 // Source contains the feed information for another
 // feed if a given entry came from that feed.
 type Source struct {
-	Title         string         `json:"title,omitempty"`
-	ID            string         `json:"id,omitempty"`
-	Updated       string         `json:"updated,omitempty"`
-	UpdatedParsed *time.Time     `json:"updatedParsed,omitempty"`
-	Subtitle      string         `json:"subtitle,omitempty"`
-	Links         []*Link        `json:"links,omitempty"`
-	Generator     *Generator     `json:"generator,omitempty"`
-	Icon          string         `json:"icon,omitempty"`
-	Logo          string         `json:"logo,omitempty"`
-	Rights        string         `json:"rights,omitempty"`
-	Contributors  []*Person      `json:"contributors,omitempty"`
-	Authors       []*Person      `json:"authors,omitempty"`
-	Categories    []*Category    `json:"categories,omitempty"`
-	Extensions    ext.Extensions `json:"extensions,omitempty"`
+	Title         string         `json:"title,omitempty" xml:"title"`
+	ID            string         `json:"id,omitempty" xml:"id"`
+	Updated       string         `json:"updated,omitempty" xml:"updated"`
+	UpdatedParsed *time.Time     `json:"updatedParsed,omitempty" xml:"-"`
+	Subtitle      string         `json:"subtitle,omitempty" xml:"subtitle,omitempty"`
+	Links         []*Link        `json:"links,omitempty" xml:"link"`
+	Generator     *Generator     `json:"generator,omitempty" xml:"generator"`
+	Icon          string         `json:"icon,omitempty" xml:"icon,omitempty"`
+	Logo          string         `json:"logo,omitempty" xml:"logo,omitempty"`
+	Rights        string         `json:"rights,omitempty" xml:"rights,omitempty"`
+	Contributors  []*Person      `json:"contributors,omitempty" xml:"contributor"`
+	Authors       []*Person      `json:"authors,omitempty" xml:"author"`
+	Categories    []*Category    `json:"categories,omitempty" xml:"category"`
+	Extensions    ext.Extensions `json:"extensions,omitempty" xml:"-"`
 }

atom/render.go

@@ -0,0 +1,23 @@
+package atom
+
+import (
+	"encoding/xml"
+	"io"
+)
+
+// Render writes the Atom feed as Atom 1.0 XML to the provided io.Writer
+func (f *Feed) Render(w io.Writer) error {
+	if f == nil {
+		return nil
+	}
+
+	// Write XML declaration
+	if _, err := w.Write([]byte(xml.Header)); err != nil {
+		return err
+	}
+
+	// Create XML encoder and encode the feed
+	encoder := xml.NewEncoder(w)
+	encoder.Indent("", "  ")
+	return encoder.Encode(f)
+}