go.tools/cmd/godoc: include the blog server

Defer parsing of blog content until accessed for faster startup.
Fall back on redirect if blog content unavailable locally.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/13335052

cmd/godoc/blog.go

@@ -0,0 +1,68 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"go/build"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sync"
+
+	"code.google.com/p/go.tools/godoc/blog"
+)
+
+const (
+	blogRedirect = false
+	blogRepo     = "code.google.com/p/go.blog"
+	blogURL      = "http://blog.golang.org/"
+)
+
+var (
+	blogServer   http.Handler // set by blogInit
+	blogInitOnce sync.Once
+)
+
+func init() {
+	// Initialize blog only when first accessed.
+	http.HandleFunc("/blog/", func(w http.ResponseWriter, r *http.Request) {
+		blogInitOnce.Do(blogInit)
+		blogServer.ServeHTTP(w, r)
+	})
+}
+
+func blogInit() {
+	// Binary distributions will include the blog content in "/blog".
+	root := filepath.Join(runtime.GOROOT(), "blog")
+
+	// Prefer content from go.blog repository if present.
+	if pkg, err := build.Import(blogRepo, "", build.FindOnly); err == nil {
+		root = pkg.Dir
+	}
+
+	// If content is not available fall back to redirect.
+	if fi, err := os.Stat(root); err != nil || !fi.IsDir() {
+		fmt.Fprintf(os.Stderr, "Blog content not available locally. "+
+			"To install, run \n\tgo get %v\n", blogRepo)
+		blogServer = makePrefixRedirectHandler("/blog/", blogURL)
+		return
+	}
+
+	s, err := blog.NewServer(blog.Config{
+		BaseURL:      "/blog/",
+		BasePath:     "/blog",
+		ContentPath:  filepath.Join(root, "content"),
+		TemplatePath: filepath.Join(root, "template"),
+		HomeArticles: 5,
+		PlayEnabled:  *showPlayground,
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	blogServer = s
+}

cmd/godoc/handlers.go

@@ -126,7 +126,7 @@ var cmdRedirects = map[string]string{
 }
 
 var redirects = map[string]string{
-	"/blog":       "http://blog.golang.org",
+	"/blog":       "/blog/",
 	"/build":      "http://build.golang.org",
 	"/change":     "https://code.google.com/p/go/source/list",
 	"/cl":         "https://gocodereview.appspot.com/",
@@ -163,7 +163,6 @@ var redirects = map[string]string{
 }
 
 var prefixHelpers = map[string]string{
-	"blog":   "http://blog.golang.org/",
 	"change": "https://code.google.com/p/go/source/detail?r=",
 	"cl":     "https://codereview.appspot.com/",
 	"issue":  "https://code.google.com/p/go/issues/detail?id=",