Add atom feed to the go website

1 files changed, 216 insertions, 0 deletions

diff --git a/cmd/server/feed.go b/cmd/server/feed.go
new file mode 100644
index 0000000..2d4a75b
--- /dev/null
+++ b/cmd/server/feed.go
@@ -0,0 +1,216 @@
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/gorilla/mux"
+	"riedstra.dev/mitch/go-website/page"
+)
+
+type Author struct {
+	Name  string `xml:"name"` // Required
+	Uri   string `xml:"uri,omitempty"`
+	Email string `xml:"email,omitempty"`
+}
+
+type Link struct {
+	Href   string `xml:"href,attr,omitempty"`
+	Rel    string `xml:"rel,attr,omitempty"`
+	Type   string `xml:"type,attr,omitempty"`
+	Title  string `xml:"Title,attr,omitempty"`
+	Length string `xml:"Length,attr,omitempty"`
+}
+
+type Content struct {
+	Type string `xml:"type,attr"`
+	Data string `xml:",chardata"`
+}
+
+type Entry struct {
+	// Spec requires this, autogenerated from Title and updated if otherwise
+	// left empty
+	Id string `xml:"id"`
+
+	Title     string     `xml:"title"`   // Required
+	Updated   *time.Time `xml:"updated"` // Required
+	Author    *Author    `xml:"author,omitempty"`
+	Published *time.Time `xml:"published,omitempty"`
+	Links     []Link     `xml:"link,omitempty"`
+	Content   *Content   `xml:"content,omitempty"`
+}
+
+func (i Entry) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	type Alias Entry
+
+	errs := []string{}
+	if i.Title == "" {
+		errs = append(errs, "Title Cannot be empty")
+	}
+	if i.Updated == nil {
+		errs = append(errs, "Updated cannot be nil")
+	}
+
+	if len(errs) > 0 {
+		return errors.New(strings.Join(errs, ","))
+	}
+
+	if i.Id == "" {
+		i.Id = fmt.Sprintf("%s::%d", i.Title, i.Updated.Unix())
+	}
+
+	i2 := (*Alias)(&i)
+
+	return e.EncodeElement(i2, start)
+}
+
+type Atom struct {
+	Ns        string     `xml:"xmlns,attr"`
+	Title     string     `xml:"title"`            // Required
+	Id        string     `xml:"id"`               // Required
+	Author    Author     `xml:"author,omitempty"` // Required
+	Updated   *time.Time `xml:"updated"`          // Required
+	Published *time.Time `xml:"published,omitempty"`
+	Subtitle  string     `xml:"subtitle,omitempty"`
+	Entries   []Entry    `xml:"entry"`
+}
+
+func (a Atom) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	type Alias Atom
+
+	a.Ns = "http://www.w3.org/2005/Atom"
+	errs := []string{}
+	if a.Id == "" {
+		errs = append(errs, "ID Cannot be empty")
+	}
+	if a.Author.Name == "" {
+		errs = append(errs, "Author Name cannot be empty")
+	}
+	if a.Updated == nil {
+		errs = append(errs, "Updated cannot be empty")
+	}
+
+	if len(errs) > 0 {
+		return errors.New(strings.Join(errs, ","))
+	}
+
+	start.Name = xml.Name{Local: "feed"}
+
+	a2 := (*Alias)(&a)
+
+	return e.EncodeElement(a2, start)
+}
+
+// FeedHandler takes care of pulling from the index all of the relevant posts
+// and dumping them into an Atom feed.
+//
+// Relevant query parameters are:
+//
+// "content" if unset, or set to false content is omitted from the feed
+// "limit=n" stop at "n" and return the feed
+//
+func (a *App) FeedHandler(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	var addContent bool
+	var limit int
+
+	if _, ok := r.URL.Query()["content"]; ok {
+		if r.URL.Query().Get("content") != "false" {
+			addContent = true
+		}
+	}
+
+	if l := r.URL.Query().Get("limit"); l != "" {
+		i, err := strconv.Atoi(l)
+		if err == nil {
+			limit = i
+		}
+	}
+
+	tag, ok := vars["tag"]
+	if !ok {
+		http.Error(w, "Tag not found or supplied", http.StatusNotFound)
+		return
+	}
+
+	p := page.NewPage("index")
+	index, err := p.Index()
+	if err != nil {
+		log.Println(err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	pages, ok := index[tag]
+	if !ok {
+		http.Error(w, "Invalid tag", http.StatusNotFound)
+		return
+	}
+
+	pages, dateless := pages.RemoveDateless()
+	for _, p := range dateless {
+		log.Printf("Warning, page %s has no Date field. Skipping inclusion on feed", p)
+	}
+	pages.SortDate()
+
+	feed := &Atom{
+		Author:   a.Author,
+		Title:    a.Title,
+		Id:       a.FeedId,
+		Updated:  &a.Updated.Time,
+		Subtitle: a.Description,
+	}
+
+	entries := []Entry{}
+
+	for n, p := range pages {
+		if limit != 0 && n >= limit {
+			break
+		}
+
+		content := &bytes.Buffer{}
+		err := p.Render(content)
+		if err != nil {
+			log.Println(err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+
+		entry := Entry{
+			Title:   p.Title,
+			Updated: &p.Date.Time,
+			Links:   []Link{Link{Href: strings.Join([]string{a.SiteURL, p.Path()}, "/")}},
+		}
+
+		if addContent {
+			entry.Content = &Content{Type: "html", Data: content.String()}
+		}
+
+		entries = append(entries, entry)
+
+	}
+
+	feed.Entries = entries
+
+	w.Header().Add("Content-type", "application/xml")
+	w.Write([]byte(xml.Header))
+
+	enc := xml.NewEncoder(w)
+	enc.Indent("", "  ")
+
+	err = enc.Encode(feed)
+	if err != nil {
+		log.Println(err)
+		// Headers probably already sent, but we'll try anyway
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+	}
+
+	return
+}