Backref basics

backref.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type Refs map[string][]string
+
+func processBackrefs(fp *FilePages) error {
+	pages, err := fp.AllPages()
+
+	refs := make(Refs)
+
+	if err != nil {
+		return err
+	}
+
+	for _, page := range pages {
+		links, err := ParseLinks(page.Content)
+
+		if err != nil {
+			return err
+		}
+
+		for _, link := range links {
+			refs[link.PageName] = append(refs[link.PageName], page.Name)
+		}
+	}
+
+	f, err := os.Create(filepath.Join(fp.dirname, "backrefs.json"))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	err = json.NewEncoder(f).Encode(&refs)
+
+	return err
+}
+
+func loadBackrefs(fp *FilePages, p string) ([]string, error) {
+	refs := make(Refs)
+	p = strings.Replace(p, " ", "_", -1)
+
+	f, err := os.Open(filepath.Join(fp.dirname, "backrefs.json"))
+	if err != nil {
+		return nil, err
+	}
+
+	defer f.Close()
+
+	err = json.NewDecoder(f).Decode(&refs)
+	if err != nil {
+		return nil, err
+	}
+
+	return refs[p], nil
+}

file.go

@@ -27,8 +27,9 @@ func NewFilePages(dirname string) PagesRepository {
 	return fp
 }
 
-func (fp *FilePages) Get(p string) Page {
-	f, err := os.Open(filepath.Join(fp.dirname, strings.Replace(p, " ", "_", -1)))
+func (fp *FilePages) Get(title string) Page {
+	name := strings.Replace(title, " ", "_", -1)
+	f, err := os.Open(filepath.Join(fp.dirname, name))
 	if err != nil {
 		return Page{}
 	}
@@ -37,7 +38,16 @@ func (fp *FilePages) Get(p string) Page {
 	if err != nil {
 		return Page{}
 	}
-	return Page{Content: string(body)}
+	refs, err := loadBackrefs(fp, name)
+	if err != nil {
+		return Page{}
+	}
+	return Page{
+		Name:    name,
+		Title:   title,
+		Content: string(body),
+		Refs:    refs,
+	}
 }
 
 func (fp *FilePages) Save(p string, page Page, summary, author string) error {
@@ -61,6 +71,11 @@ func (fp *FilePages) Save(p string, page Page, summary, author string) error {
 		f.WriteString(strings.Replace(page.Content, "\r\n", "\n", -1))
 	}
 
+	err = processBackrefs(fp)
+	if err != nil {
+		return fmt.Errorf("while processing backrefs: %v", err)
+	}
+
 	return saveWithGit(fp, p, summary, author)
 }
 
@@ -247,3 +262,17 @@ func (fp *FilePages) RecentChanges() ([]Change, error) {
 
 	return changes, nil
 }
+
+func (fp *FilePages) AllPages() ([]Page, error) {
+	files, err := ioutil.ReadDir(fp.dirname)
+	if err != nil {
+		return nil, err
+	}
+
+	var pages []Page
+	for _, file := range files {
+		pages = append(pages, fp.Get(file.Name()))
+	}
+
+	return pages, nil
+}

main.go

@@ -29,7 +29,15 @@ const (
 
 // Page
 type Page struct {
+	// Name is the filename of the page
+	Name string
+
+	// Title is the human-readable title of the page
+	Title string
+
 	Content string
+
+	Refs []string
 }
 
 type DiffPage struct {
@@ -63,10 +71,11 @@ type PagesRepository interface {
 }
 
 type indexPage struct {
-	Session *Session
-	Title   string
-	Name    string
-	Content template.HTML
+	Session  *Session
+	Title    string
+	Name     string
+	Content  template.HTML
+	Backrefs []string
 }
 
 type editPage struct {
@@ -395,7 +404,8 @@ func (h *indexHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		page = "Home"
 	}
 
-	pageText := mp.Get(page).Content
+	mpPage := mp.Get(page)
+	pageText := mpPage.Content
 	if pageText == "" {
 		http.Redirect(w, r, "/edit/"+page, 302)
 		return
@@ -438,10 +448,11 @@ func (h *indexHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	data := indexPage{
-		Session: sess,
-		Title:   strings.Replace(page, "_", " ", -1),
-		Content: template.HTML(pageText),
-		Name:    page,
+		Session:  sess,
+		Title:    strings.Replace(page, "_", " ", -1),
+		Content:  template.HTML(pageText),
+		Name:     page,
+		Backrefs: mpPage.Refs,
 	}
 
 	t, err := template.ParseFiles("templates/layout.html", "templates/view.html")

templates/view.html

@@ -3,6 +3,15 @@
     <div class="content">
         {{ .Content }}
     </div>
+
+    <div class="backrefs">
+        <h3>Backrefs</h3>
+        <ul>
+        {{ range $ref := .Backrefs }}
+        <li><a href="/{{ $ref }}">{{ $ref }}</a></li>
+        {{ end }}
+        </ul>
+    </div>
 {{ end }}
 
 {{ define "navbar" }}

util.go

@@ -2,9 +2,16 @@ package main
 
 import (
 	"math/rand"
+	"regexp"
+	"strings"
 	"time"
 )
 
+type ParsedLink struct {
+	Name     string
+	PageName string
+}
+
 var random *rand.Rand
 
 func init() {
@@ -20,3 +27,28 @@ func RandStringBytes(n int) string {
 	}
 	return string(b)
 }
+
+func ParseLinks(content string) ([]ParsedLink, error) {
+	hrefRE := regexp.MustCompile(`#?\[\[\s*([\w.\- ]+)\s*\]\]`)
+
+	links := hrefRE.FindAllStringSubmatch(content, -1)
+
+	var result []ParsedLink
+
+	for _, matches := range links {
+		link := matches[0]
+
+		if link[0] == '#' {
+			link = strings.TrimPrefix(link, "#[[")
+		} else {
+			link = strings.TrimPrefix(link, "[[")
+		}
+
+		link = strings.TrimSuffix(link, "]]")
+		link = strings.TrimSpace(link)
+		l := strings.Replace(link, " ", "_", -1)
+		result = append(result, ParsedLink{link, l})
+	}
+
+	return result, nil
+}