From 0e680cb17a0e654cea38590b382aab91f478668f Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@gmail.com>
Date: Fri, 18 Jun 2021 10:53:08 +0100
Subject: [PATCH] Meta: Ensure long messages fit in commit tweet

Abbreviating the commit message to 240 characters was not always enough.
As a bonus, we now add an ellipsis to abbreviated messages.
---
 Meta/tweet-commits.js | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/Meta/tweet-commits.js b/Meta/tweet-commits.js
index 581eafe3941..cb601f7f9b1 100644
--- a/Meta/tweet-commits.js
+++ b/Meta/tweet-commits.js
@@ -1,6 +1,9 @@
 const fs = require("fs");
 const Twit = require("twit");
 const { CONSUMER_KEY, CONSUMER_SECRET, ACCESS_TOKEN, ACCESS_TOKEN_SECRET } = process.env;
+const tweetLength = 280;
+// Twitter always considers t.co links to be 23 chars, see https://help.twitter.com/en/using-twitter/how-to-tweet-a-link
+const twitterLinkLength = 23;
 
 const T = new Twit({
     consumer_key: CONSUMER_KEY,
@@ -13,11 +16,14 @@ const T = new Twit({
     const githubEvent = JSON.parse(fs.readFileSync(0).toString());
     const tweets = [];
     for (const commit of githubEvent["commits"]) {
-        tweets.push(
-            `${commit["message"].substring(0, 240)}\nAuthor: ${commit["author"]["name"]}\n${
-                commit["url"]
-            }`
-        );
+        const authorLine = `Author: ${commit["author"]["name"]}`;
+        const maxMessageLength = tweetLength - authorLine.length - twitterLinkLength - 2; // -2 for newlines
+        const commitMessage =
+            commit["message"].length > maxMessageLength
+                ? commit["message"].substring(0, maxMessageLength - 2) + "…" // Ellipsis counts as 2 characters
+                : commit["message"];
+
+        tweets.push(`${commitMessage}\n${authorLine}\n${commit["url"]}`);
     }
     for (const tweet of tweets) {
         try {