From c28fe49a7a303ef0440ccffd830e4949a1f2381f Mon Sep 17 00:00:00 2001
From: Joel Kronqvist <work.joelkronqvist@gmail.com>
Date: Tue, 18 Oct 2022 21:41:31 +0300
Subject: Enhanced robustness in retrieving the example input and in the init
 (at reboot) script.

The server errored out if the database was empty and there came a request, as it didn't check for empty arrays in dbparse.js in the function getRandomIndex. Fixed by adding handling & recursion limit. Added in init.sh a check to see if logging in to MySQL is possible to prevent errors at startup.
---
 dbparse.js | 10 +++++++---
 init.sh    |  8 ++++++++
 server.js  |  2 ++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/dbparse.js b/dbparse.js
index 29b9cb7..eddfdc8 100644
--- a/dbparse.js
+++ b/dbparse.js
@@ -173,10 +173,14 @@ function randInt(start, stop)
 	return start + Math.floor(Math.random() * (stop - start));
 }
 
-async function getRandomIndex(day, DB)
+async function getRandomIndex(day, DB, depth=0)
 {
+	if (depth > 10)
+		return null;
+
 	let indexes = await DB.execute("SELECT course, teacher, class FROM shifts WHERE day = ? ORDER BY RAND() LIMIT 1", [day]);
-	indexes = Object.values(indexes[0]);
+	
+	indexes = Object.values(indexes[0] || [null, null, null]); /// ERROR HERE!!!
 	let start = randInt(0, indexes.length);
 	for (let test = 0; test < 3; test++)
 	{
@@ -185,7 +189,7 @@ async function getRandomIndex(day, DB)
 			return indexes[i];
 	}
 	console.log("Warning: row without class/teacher/course in database!");
-	return getRandomIndex(day, DB);
+	return getRandomIndex(day, DB, depth + 1);
 }
 
 
diff --git a/init.sh b/init.sh
index 55be6ee..2fc915d 100755
--- a/init.sh
+++ b/init.sh
@@ -13,6 +13,14 @@ echo "# Connected to internet!"
 
 echo ""
 
+echo "# Testing DB availability"
+while ! echo 'exit' | mysql; do
+	sleep 5
+done
+echo "# Database seems to be available (ignore error messages above)"
+
+echo ""
+
 cd "$BASE_DIR/LYLLRuoka"
 echo "# node server.js:"
 node server.js
diff --git a/server.js b/server.js
index fcfa1ea..c180b71 100644
--- a/server.js
+++ b/server.js
@@ -252,6 +252,8 @@ async function buildMain(args)
 
 	// get the example input
 	res["example-input"] = await DBPARSE.randomIndex(day, SQLDB);
+	if (res["example-input"] === null)
+		res["example-input"] = "";
 
 	// get the day
 	let weekdays = ["ma", "ti", "ke", "to", "pe", "la", "su"];
-- 
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