From fb0b1540096a2014db71c374d3147d6c2143f491 Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Tue, 19 May 2020 19:10:27 -0700
Subject: [PATCH] lmno: Be forgiving in game ID values received from the user

Most significantly, we now accept a lowercase version of the ID.

But also, game ID values are intentionally chosen not to have
ambiguous character in them, (such as "M"/"N" or "S"/"F"), which might
sound similar when someone says a game ID aloud. So on the input side
we accept either form and canonicalize to the only letter which can
possibly exist in a game ID.
---
 lmno.js | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/lmno.js b/lmno.js
index f79da3a..64a106b 100644
--- a/lmno.js
+++ b/lmno.js
@@ -46,6 +46,24 @@ LMNO.letters = "BCDFGHJKLMQRTVWXYZ";
 
 const lmno = new LMNO();
 
+/* Force a game ID into a canonical form as described above. */
+function lmno_canonize(id) {
+  /* Capitalize */
+  id = id.toUpperCase();
+
+  /* Replace unused letters with nearest phonetic match. */
+  id = id.replace(/N/g, 'M');
+  id = id.replace(/P/g, 'B');
+  id = id.replace(/S/g, 'F');
+
+  /* Replace unused numbers nearest visual match. */
+  id = id.replace(/0/g, 'O');
+  id = id.replace(/1/g, 'I');
+  id = id.replace(/5/g, 'S');
+
+  return id;
+}
+
 app.post('/new/:game_engine', (request, response) =>  {
   const game_engine = request.params.game_engine;
   const game_id = lmno.create_game(game_engine);
@@ -60,6 +78,13 @@ app.post('/new/:game_engine', (request, response) =>  {
  */
 app.get('/[a-zA-Z0-9]{4}', (request, response) => {
   const game_id = request.path.replace(/\//g, "");
+  const canon_id = lmno_canonize(game_id);
+
+  /* Redirect user to page with the canonical ID in it. */
+  if (game_id !== canon_id) {
+    response.redirect(301, `/${canon_id}/`);
+    return;
+  }
 
   const game = lmno.ids[game_id];
   if (game === undefined) {
@@ -71,7 +96,18 @@ app.get('/[a-zA-Z0-9]{4}', (request, response) => {
 
 /* LMNO middleware to lookup the game. */
 app.use('/empires/:game_id([a-zA-Z0-9]{4})', (request, response, next) => {
-  request.game = lmno.ids[request.params.game_id].game;
+  const game_id = request.params.game_id;
+  const canon_id = lmno_canonize(game_id);
+
+  /* Redirect user to page with the canonical ID in it. */
+  if (game_id !== canon_id) {
+    const new_url = request.originalUrl.replace("/empires/" + game_id,
+                                                "/empires/" + canon_id);
+    response.redirect(301, new_url);
+    return;
+  }
+
+  request.game = lmno.ids[game_id].game;
   if (request.game === undefined) {
     response.sendStatus(404);
     return;
-- 
2.43.0