From e92f59fc7ff48a65582fc03e192ac0b8d27aebec Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Sat, 21 May 2022 10:50:42 -0600
Subject: [PATCH] Redirect legacy URL path

---
 srv/src/http/index.go | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/srv/src/http/index.go b/srv/src/http/index.go
index aa606d6..a392361 100644
--- a/srv/src/http/index.go
+++ b/srv/src/http/index.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"path/filepath"
+	"regexp"
 	"strings"
 
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/http/apiutil"
@@ -12,12 +13,24 @@ import (
 
 func (a *api) renderIndexHandler() http.Handler {
 
+	legacyPostPathRegexp := regexp.MustCompile(
+		`^/[0-9]{4}/[0-9]{2}/[0-9]{2}/([^/.]+)\.html$`,
+	)
+
 	tpl := a.mustParseBasedTpl("index.html")
 	const pageCount = 10
 
 	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 
-		if path := r.URL.Path; !strings.HasSuffix(path, "/") && filepath.Base(path) != "index.html" {
+		path := r.URL.Path
+
+		if matches := legacyPostPathRegexp.FindStringSubmatch(path); len(matches) == 2 {
+			id := matches[1]
+			http.Redirect(rw, r, filepath.Join("/posts", id), http.StatusMovedPermanently)
+			return
+		}
+
+		if !strings.HasSuffix(path, "/") && filepath.Base(path) != "index.html" {
 			http.Error(rw, "Page not found", 404)
 			return
 		}