#!/bin/bash

echo -e "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nThis script should be run as root on a clean install of a Linux x64 system."
echo "It should work by default on most Linux distributions, and is tested on Debian."
echo "You can choose to do a full install, or update a server which was previously"
echo "installed with the same script."
echo -e "\nNOTICE: The Minecraft Fabric installer supports versions from 1.14 to latest."
echo "        For another Minecraft server version, download the desired server.jar"
echo "        file and move it to '/home/minecraft/server.jar'."
echo "NOTICE: The available options for Java are: 8/16/17/21, for Linux x64."
echo "        For another Java version, download the desired build archive manually."
echo "        I recommend selecting a JRE release from Adoptium here:"
echo "          https://adoptium.net/temurin/releases/"
echo "        To install it, download and extract the archive to '/home/minecraft/',"
echo "        verify the Java binary can be found at '/home/minecraft/jdk*/bin/java'."
while true; do
echo ""
read -p "  Do you want to proceed? [Y/n] " proceed
case $proceed in
	[yY]|"" ) break;;
	[nN] ) echo "=> Exiting."; exit;;
	* ) echo "=> Invalid response.";;
esac
done

echo -e "\n=> Running compatibility checks..."

echo -n "=> Checking curl... "
curl --version &> /dev/null && echo "DONE" || chk1="failed"
if [ "$chk1" == "failed" ]; then echo "FAIL"; fi
echo -n "=> Checking systemd... "
systemd-notify --booted && echo "DONE" || chk2="failed"
if [ "$chk2" == "failed" ]; then echo "FAIL"; fi
echo -n "=> Checking root privileges... "
if [ "$EUID" == 0 ]; then echo "DONE"; else chk3="failed"; echo "FAIL"; fi
echo -n "=> Checking /etc/systemd/system/ permissions... "
touch /etc/systemd/system/permission.test &> /dev/null && rm /etc/systemd/system/permission.test &> /dev/null && echo "DONE" || chk4="failed"
if [ "$chk4" == "failed" ]; then echo "FAIL"; fi
echo -n "=> Checking internet connection... "
ping -c 1 8.8.8.8 &> /dev/null && echo "DONE" || chk5="failed"
if [ "$chk5" == "failed" ]; then echo "FAIL"; fi
echo -n "=> Checking DNS resolution... "
ping -c 1 google.com &> /dev/null && echo "DONE" || chk6="failed"
if [ "$chk6" == "failed" ]; then echo "FAIL"; fi

if [ "$chk1" == "failed" ]; then echo "WARNING: curl command error, downloads will fail."; fi
if [ "$chk2" == "failed" ]; then echo "WARNING: this system is not using systemd, please skip creating unit files."; fi
if [ "$chk3" == "failed" ]; then echo "WARNING: root privileges are not detected, creating a user will fail."; fi
if [ "$chk4" == "failed" ]; then echo "WARNING: cannot write to systemd directory, please skip creating unit files."; fi
if [ "$chk5" == "failed" ]; then echo "WARNING: cannot connect to the internet, downloads will fail."; fi
if [ "$chk6" == "failed" ]; then echo "WARNING: cannot resolve domain names, downloads will fail."; fi

if [[ "$chk1"&&"$chk2"&&"$chk3"&&"$chk4"&&"$chk5" != "failed" ]]; then echo -e "All checks complete.\n"; fi
if [[ "$chk1"||"$chk2"||"$chk3"||"$chk4"||"$chk5" == "failed" ]]; then
while true; do
	echo ""
	read -p "  At least one check failed, are you sure you want to proceed? [y/N] " skipwarn
	case $skipwarn in
		[yY] ) echo "=> Ignoring warnings..."; break;;
		[nN]|"" ) echo "=> Exiting."; exit;;
		* ) echo "=> Invalid response.";;
	esac
done
fi

echo -e "\nChoose to install a new server or update an existing one."
echo "WARNING: Only update an existing server if it was initially installed using this"
echo "         script, or if you know that it's been set up in the same way."
echo "NOTICE: This will replace any existing /home/minecraft-old/ directory."
while true; do
echo ""
read -p "  Update an existing server? [y/N] " update
case $update in
	[yY] ) update="true"; echo "=> Updating..."; break;;
	[nN]|"" ) echo "=> Skipping..."; break;;
	* ) echo "=> Invalid response.";;
esac
done
if [ "$update" == "true" ]; then
	echo -n "=> Removing previous minecraft-old directory... "
	rm -rf /home/minecraft-old/ && echo "DONE"
	echo -n "=> Backing up current minecraft home directory... "
	mv /home/minecraft/ /home/minecraft-old/ && echo "DONE"
	echo -n "=> Creating new minecraft home directory... "
	mkdir -p /home/minecraft && echo "DONE"
	echo -n "=> Copying world... "
	cp -R /home/minecraft-old/world/ /home/minecraft/world/ && echo "DONE"
	echo -n "=> Copying mods... "
	cp -R /home/minecraft-old/mods/ /home/minecraft/mods/ && echo "DONE"
	echo -n "=> Copying config... "
	cp -R /home/minecraft-old/config/ /home/minecraft/config/ && echo "DONE"
	echo -n "=> Copying defaultconfigs... "
	cp -R /home/minecraft-old/defaultconfigs/ /home/minecraft/defaultconfigs/ && echo "DONE"
	echo -n "=> Copying properties and player lists... "
	cp /home/minecraft-old/banned-ips.json /home/minecraft-old/banned-players.json /home/minecraft-old/ops.json /home/minecraft-old/server.properties /home/minecraft-old/whitelist.json /home/minecraft/ && echo "DONE"
	echo "=> Finished copying data."
	echo "NOTICE: After completing the installation, please check for other config files"
	echo "        that you may want to keep such as mod-specific folders, logs, etcetera."
	echo "NOTICE: Mods must be updated manually, please do so before starting the server."
else
	echo -e "\n=> Creating 'minecraft' user..."
	mkdir -p /home/minecraft
	useradd -d /home/minecraft/ minecraft &> /dev/null &&
	( echo "  Please set a password for the user:"; passwd minecraft )
fi

cd /home/minecraft/
echo -e "\nChoose a valid version of Java."
echo "Minecraft requires Java 8 for 1.16.5 and earlier, Java 16 for 1.17-1.17.1,"
echo "Java 17 for 1.18-1.20.4, and Java 21 for 1.20.5 and later."
while true; do
	echo ""
	read -p "  Enter version [8,16,17,21] (press ENTER to skip): " java
	case $java in
		16 )
			echo "=> Downloading Java $java (Adoptium Eclipse Temurin)..."
			API_URL="https://api.adoptium.net/v3/binary/latest/$java/ga/linux/x64/jdk/hotspot/normal/eclipse"
			FETCH_URL=$(curl -s -w %{redirect_url} "${API_URL}")
			curl -o "jdk-$java.tar.gz" -Ls "${FETCH_URL}"
			tar -xf jdk-$java.tar.gz
			rm jdk-$java.tar.gz
			echo "=> Downloaded Java $java."
			break;;
		8|17|21 )
			echo "=> Downloading Java $java (Adoptium Eclipse Temurin)..."
			API_URL="https://api.adoptium.net/v3/binary/latest/$java/ga/linux/x64/jre/hotspot/normal/eclipse"
			FETCH_URL=$(curl -s -w %{redirect_url} "${API_URL}")
			curl -o "jdk-$java-jre.tar.gz" -Ls "${FETCH_URL}"
			tar -xf jdk-$java-jre.tar.gz
			rm jdk-$java-jre.tar.gz
			echo "=> Downloaded Java $java."
			break;;
		"" ) echo "=> Skipping installation..."; break;;
		* ) echo "=> Invalid response.";;
	esac
done

echo -e "\nChoose if you want to use the Fabric server installer."
echo "The Fabric installer supports Minecraft 1.14 to latest."
echo "Skip if you have a server.jar, make sure it's at '/home/minecraft/server.jar'."
while true; do
	echo ""
	read -p "  Use Fabric server installer? [Y/n] " fabric
	case $fabric in
		[yY]|"" ) fabric="install"; break;;
		[nN] ) echo "=> Skipping Fabric installer..."; break;;
		* ) echo "=> Invalid response.";;
	esac
done
if [ "$fabric" == "install" ]; then
	serverjar="fabric-server-launch.jar"
	echo "=> Downloading Fabric installer..."
	curl -s -o 'fabric-installer.jar' https://maven.fabricmc.net/net/fabricmc/fabric-installer/1.0.1/fabric-installer-1.0.1.jar

	while true; do
		echo ""
		read -p "  Select valid Minecraft version to install (press ENTER for latest): " mc
		case $mc in
			"" )
				echo "=> Installing latest Fabric server..."
				/home/minecraft/jdk*/bin/java -jar fabric-installer.jar server -downloadMinecraft && break;;
			* )
				echo "=> Installing $mc Fabric server..."
				/home/minecraft/jdk*/bin/java -jar fabric-installer.jar server -mcversion $mc -downloadMinecraft && break || echo "=> Invalid version.";;
		esac
	done
	echo "=> Running server once to generate files..."
	/home/minecraft/jdk*/bin/java -jar fabric-server-launch.jar
	echo "=> Server files created."
	echo "=> Installed $mc Fabric server."
else
	serverjar="server.jar"
	while true; do
		echo ""
		read -p "  Is the server.jar available at '/home/minecraft/server.jar'? [Y/n] " mc
		case $mc in
			[yY]|"" )
				echo "=> Installing server..."
				/home/minecraft/jdk*/bin/java -jar server.jar;;
			[nN] ) echo "=> Can't install, exiting."; exit;;
			* ) echo "=> Invalid response.";;
		esac
	done
fi

while true; do
	echo ""
	read -p "  Agree to the EULA? [Y/n] " eula
	case $eula in
		[yY]|"" ) sed -i '3s/.*/eula=true/' eula.txt && echo "=> EULA set to true."; break;;
		[nN] ) echo "=> Skipping..."; break;;
		* ) echo "=> Invalid response.";;
	esac
done

echo "=> Creating run script with Java arguments..."
touch /home/minecraft/run.sh
chmod +x /home/minecraft/run.sh
echo -e "\nChoose allocated server memory in GB"
echo "You should leave roughly 2GB available for the host/OS, e.g. use up to 6GB if"
echo "the system has 8GB. I recommend using 2-6 for best performance, and avoiding >8"
echo "unless there are many players."
while true; do
	echo ""
	read -p "  Enter allocated memory [1-16] (press ENTER to use 4GB): " mem
	case $mem in
		[1-9]|1[0-6] ) echo "=> Allocating ${mem}GB"...; break;;
		"" ) echo "=> Allocating 4GB..."; mem="4"; break;;
		* ) echo "=> Invalid response.";;
	esac
done
cat > /home/minecraft/run.sh << EOF
/home/minecraft/jdk*/bin/java -Xmx${mem}G -Xms${mem}G -XX:+UseG1GC -Dsun.rmi.dgc.server.gcInterval=2147483646 -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M -jar $serverjar nogui
EOF
echo "=> Created run script in home directory."

if [ "$update" != "true" ]; then
	echo -e "\nThis step allows you to set up autostart by creating systemd unit files."
	echo "This would allow you to start/stop the server with systemctl, view logs with"
	echo "journalctl, and send commands to Minecraft's console in the background."
	while true; do
		echo ""
		read -p "  Do you want to set up autostart? [Y/n] " sysd
		case $sysd in
			[yY]|"" ) sysd="install"; break;;
			[nN] ) sysd="skip"; echo "=> Skipping..."; break;;
			* ) echo "=> Invalid response.";;
		esac
	done
fi

if [ "$sysd" == "install" ]; then
echo "=> Creating systemd unit files..."

cat > /etc/systemd/system/minecraft.service << EOF
[Unit]
Description=A dedicated Minecraft server
After=network.target

[Service]
User=minecraft
Type=simple
KillSignal=SIGCONT
Sockets=minecraft.socket
WorkingDirectory=/home/minecraft/
ExecStart=/bin/sh -c "/home/minecraft/run.sh < /run/minecraft.control"
ExecStop=/bin/sh -c "echo '/stop' > /run/minecraft.control"
Type=exec
Restart=on-failure

[Install]
WantedBy=multi-user.target
EOF

cat > /etc/systemd/system/minecraft.socket << EOF
[Unit]
BindsTo=minecraft.service

[Socket]
ListenFIFO=/run/minecraft.control
FileDescriptorName=control
RemoveOnStop=true
SocketMode=0660
SocketUser=minecraft
EOF

echo "=> Created systemd unit files."
systemctl enable minecraft.service &> /dev/null
echo "=> Enabled systemd service."
echo "=> The server is set up to autostart and restart automatically."

cat > /home/minecraft/console.sh << EOF
echo "$*" > /run/minecraft.control
EOF
chmod +x /home/minecraft/console.sh
echo "=> Created executable console script in home directory."
fi

chown -R minecraft /home/minecraft
echo "=> User 'minecraft' now owns all files in home directory."

echo -e "\nInstallation complete, server is not running."
echo "NOTICE: Please configure server.properties before starting the server."
if [ "$fabric" == "install" ]; then
	echo "NOTICE: It's recommended to download performance mods such as Lithium,"
	echo "        FerriteCore, and ModernFix."
fi
if [ "$sysd" == "skip" ]; then
	echo -e "\nStart the server with the run script, or set up a user crontab for autostart."
	echo "  $ ./run.sh"
fi
if [ "$sysd" == "install" ]; then
	echo -e "\nSystemd is in use, the server will automatically start on boot."
	echo "NOTICE: The server can be stopped by using either systemd, the /stop command,"
	echo "        or shutting down the host. Each method performs a clean shutdown, so the"
	echo "        server won't lose data. You may notice a delay shutting down the host as"
	echo "        the Minecraft server stops."

	echo -e "\nMany commands are available with systemd, some important ones are:"
	echo "Executing commands in the Minecraft server console using a script:"
	echo "  $ ./console.sh '/<command here>'"
	echo "View server messages with journalctl: (Shift+G jumps to the end)"
	echo "  # journalctl -u minecraft"
	echo "Or follow them as they update with:"
	echo "  # journalctl -f -u minecraft"
	echo "And easily perform a clean start/stop of the server with:"
	echo "  # systemctl {start,stop} minecraft"
fi