#!/bin/bash

p="#"
a1="=>"
a2=" ->"

set -euo pipefail

# Introduction.

clear -x
echo "This script is able to: create a user, install Java, download and run an"
echo "installer, update an existing server, create a launch script, create a systemd"
echo "service unit, and create a shortcut command to run commands directly on the"
echo "Minecraft console and view the output."
echo ""
echo "This script should be run as root on an unused installation of Arch Linux."
echo "Before starting, have a directory prepared to store game data."
echo ""
echo "If you plan to manually install a Java version or use your own server installer,"
echo "make sure to prepare them before starting this script. In the case of a server"
echo "installer, just make sure to know the file path."
echo ""
echo "It is safe to abort/stop the script via Ctrl+C at any input prompt, and you can"
echo "get back to any point just by skipping most steps and redoing a couple."
echo ""
echo "NOTICE: The Minecraft Fabric installer supports versions from 1.14 to latest."
echo "        For other Minecraft versions, download the desired server installer file"
echo "        manually before running this script."
echo "NOTICE: The available options for Java are: 8, 11, 17, 21, and 25, or anything"
echo "        else available from the Arch repositories."
echo "        For other Java versions, install it manually. The AUR has many."
while true; do
	echo ""
	read -rp "$p Are you ready to proceed? [Y/n] " proceed
	case "$proceed" in
		[Yy]|"" )
			break;;
		[Nn] )
			echo "$a1 Exiting."; exit;;
		* )
			echo "$a1 Invalid response.";;
	esac
done

# Compatibility tests.

echo ""
echo "$a1 Running compatibility tests..."

test1=""
test2=""
test3=""
test4=""
test5=""
test6=""
tests_failed=""

echo -n "$a2 Checking curl... "
if curl --version &> /dev/null; then
	echo "PASS"; else test1="fail"; echo "FAIL"; fi

echo -n "$a2 Checking for systemd... "
if [ -d "/run/systemd/system" ]; then
	echo "PASS"; else test2="fail"; echo "FAIL"; fi

echo -n "$a2 Checking root privileges... "
if [ "$EUID" = "0" ]; then
	echo "PASS"; else test3="fail"; echo "FAIL"; fi

echo -n "$a2 Checking /etc/systemd/system/ permissions... "
if touch "/etc/systemd/system/permission.test" &> /dev/null && rm "/etc/systemd/system/permission.test" &> /dev/null; then
	echo "PASS"; else test4="fail"; echo "FAIL"; fi

echo -n "$a2 Checking connection... "
if [ "$(curl -o /dev/null -ILsw "%{response_code}" https://archlinux.org/)" -eq 200 ]; then
	echo "PASS"; else test5="fail"; echo "FAIL"; fi

echo -n "$a2 Checking fabricmc.net connection... "
if [ "$(curl -o /dev/null -ILsw "%{response_code}" https://maven.fabricmc.net/)" -eq 200 ]; then
	echo "PASS"; else test6="fail"; echo "FAIL"; fi

if [ "$test1" = "fail" ]; then
	echo "WARNING: curl command error, please skip the Fabric installer."
	tests_failed="true"; fi
if [ "$test2" = "fail" ]; then
	echo "WARNING: this system is not using systemd, please skip creating unit files."
	tests_failed="true"; fi
if [ "$test3" = "fail" ]; then
	echo "WARNING: root privileges are not detected, please run again as root."
	tests_failed="true"; fi
if [ "$test4" = "fail" ]; then
	echo "WARNING: cannot write to systemd directory, please skip creating unit files."
	tests_failed="true"; fi
if [ "$test5" = "fail" ]; then
	echo "WARNING: cannot connect to archlinux.org, downloads will likely fail. If you can"
	echo "         verify that you can install packages, then it's safe to proceed."
	tests_failed="true"; fi
if [ "$test6" = "fail" ]; then
	echo "WARNING: cannot connect to maven.fabricmc.net, please skip the Fabric installer."
	tests_failed="true"; fi

if [ "$tests_failed" = "true" ]; then
	while true; do
		echo ""
		read -rp "$p At least one test failed, are you sure you want to proceed? [y/N] " skip_warn
		case "$skip_warn" in
			[Yy] ) echo "$a1 Ignoring warnings..."; break;;
			[Nn]|"" ) echo "$a1 Exiting."; exit;;
			* ) echo "$a1 Invalid response.";;
		esac
	done
else
	echo ""
	echo "$a1 All tests completed successfully."
fi

# Create/select a user.

while true; do
	echo ""
	read -rp "$p Do you want to create a new user? [y/N] " create_user
	case "$create_user" in
		[Yy] )
			echo "$a1 Creating a user..."

			echo ""
			read -rp "$p Enter the user name: " user

			echo "$a2 Checking if user exists."
			if id "$user" &> /dev/null; then
				echo "$a2 User '$user' already exists."
				continue
			fi

			echo ""
			echo "The home directory must be specified as an absolute file path."
			echo "Using an asterisk ('*') takes the first match."
			while true; do
				echo ""
				read -rp "$p Enter the home directory path (ENTER for '/home/$user'): " home_dir_pattern
				if [ ! "$home_dir_pattern" ]; then
					home_dir_pattern="/home/$user"
				fi
				mapfile -t files < <(compgen -G "${home_dir_pattern%/}")
				home="${files[0]}"
				if [ ! -d "$home" ]; then
					home="$home_dir_pattern"
					echo "$a2 Directory not found: '$home'."
					while true; do
						echo ""
						read -rp "$p Do you want to create this directory? [Y/n] " create_home
						case "$create_home" in
							[Yy]|"" )
								echo "$a2 Creating home directory: '$home'."
								mkdir -p "$home" || exit 1
								echo "$a2 Selected home directory."
								break 2;;
							[Nn] ) break;;
							* ) echo "$a2 Invalid response.";;
						esac
					done
				else
					echo "$a2 Found directory: '$home'."
					while true; do
						echo ""
						read -rp "$p Do you want to continue with this directory? [Y/n] " use_home
						case "$use_home" in
							[Yy]|"" )
								echo "$a2 Selected home directory: '$home'."
								break 2;;
							[Nn] ) break;;
							* ) echo "$a2 Invalid response.";;
						esac
					done
				fi
			done

			echo "$a2 Creating user."
			if useradd -d "$home" "$user" &> /dev/null; then
				echo "$a2 Setting ownership."
				chown -R "$user:$user" "$home"
				echo "$a2 Set a password for user '$user':"
				passwd "$user"
				echo "$a1 Created user '$user' with home directory: '$home'."
			else
				echo "$a1 Failed to create user '$user'."
			fi
			break;;
		[Nn]|"" ) echo "$a1 Skipping..."; break;;
		* ) echo "$a1 Invalid response.";;
	esac
done

echo ""
echo "This user will own the data directory and will run the Minecraft server (i.e."
echo "execute Java). Ensure that the selected user will have the ability to do so."
while true; do
	echo ""
	read -rp "$p Enter a user: " user

	echo "$a1 Checking for user '$user'..."
	if id "$user" &> /dev/null; then
		echo "$a2 Found user: '$user'."
		while true; do
			echo ""
			read -rp "$p Do you want to continue with this user? [Y/n] " use_user
			case "$use_user" in
				[Yy]|"" )
					echo "$a1 Selected user '$user'."
					break 2;;
				[Nn] ) break;;
				* ) echo "$a1 Invalid response.";;
			esac
		done
	else
		echo "$a2 Could not find user: '$user'."
	fi
done

# Data directory.

echo ""
echo "The data directory stores the minecraft directories (minecraft/ and sometimes"
echo "minecraft.bak/) and some generated scripts. The minecraft directories store the"
echo "server itself and all of the game data."
echo "All server files (excluding systemd units and command symlinks) will be within"
echo "the specified data directory. This does NOT allow having multiple servers,"
echo "especially when separate Java versions or systemd units are needed."
echo "Running multiple servers would require changing various names, commands, and"
echo "file paths, which goes beyond the scope of this script. Instead, using separate"
echo "machines via a hypervisor is recommended and is the intended use of this script."
echo ""
echo "The data directory can be specified as any directory on the system, but must be"
echo "specified as an absolute file path. Using a relative file path will cause issues"
echo "later on."
echo "Using an asterisk ('*') takes the first match."
while true; do
	echo ""
	read -rp "$p Enter the data directory path: " data_dir_pattern
	mapfile -t files < <(compgen -G "${data_dir_pattern%/}")
	data_dir="${files[0]}"
	if [ ! -d "$data_dir" ]; then
		data_dir="$data_dir_pattern"
		echo "$a1 Directory not found: '$data_dir'."
		while true; do
			echo ""
			read -rp "$p Do you want to create this directory? [Y/n] " create_data_dir
			case "$create_data_dir" in
				[Yy]|"" )
					echo "$a2 Creating data directory: '$data_dir'."
					mkdir -p "$data_dir" || break
					echo "$a2 Selected data directory."
					break 2;;
				[Nn] ) break;;
				* ) echo "$a2 Invalid response.";;
			esac
		done
	else
		echo "$a1 Found directory: '$data_dir'."
		echo "NOTICE: Keep in mind that multiple steps involve removing directories based on"
		echo "        this file path. A malformed or incorrect value could be very bad."
		while true; do
			echo ""
			read -rp "$p Do you want to continue with this directory? [Y/n] " use_dir
			case "$use_dir" in
				[Yy]|"" )
					echo "$a1 Selected data directory: '$data_dir'."
					break 2;;
				[Nn] ) break;;
				* ) echo "$a1 Invalid response.";;
			esac
		done
	fi
done
echo "$a2 Setting ownership."
chown "$user:$user" "$data_dir"

# Install/update a server.

echo ""
echo "Choose 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 minecraft.bak/ directory."
while true; do
	echo ""
	read -rp "$p Update an existing server? [y/N] " update
	case "$update" in
		[Yy] )
			update="true"
			echo "$a1 Updating..."
			break;;
		[Nn]|"" )
			update="false"
			echo "$a1 Skipping..."
			break;;
		* )
			echo "$a1 Invalid response.";;
	esac
done

echo "$a1 Changing working directory to '$data_dir'."
cd "$data_dir" || exit 1

if [ "$update" = "true" ]; then
	req_failed=""
	some_failed=""

	if [ -d "minecraft.bak" ]; then
		echo -n "$a2 Removing previous minecraft.bak directory... "
		if rm -rf "minecraft.bak/"; then
			echo "DONE"; else echo "FAIL"; req_failed="true"; fi
	fi

	echo -n "$a2 Backing up current minecraft directory... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif mv "minecraft/" "minecraft.bak/"; then
		echo "DONE"; else echo "FAIL"; req_failed="true"; fi

	echo -n "$a2 Creating new minecraft directory... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif mkdir -p "minecraft"; then
		echo "DONE"; else echo "FAIL"; req_failed="true"; fi

	echo -n "$a2 Copying world... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif cp -R "minecraft.bak/world/" "minecraft/world/"; then
		echo "DONE"; else echo "FAIL"; some_failed="true"; fi

	echo -n "$a2 Copying mods... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif cp -R "minecraft.bak/mods/" "minecraft/mods/"; then
		echo "DONE"; else echo "FAIL"; some_failed="true"; fi

	echo -n "$a2 Copying config... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif cp -R "minecraft.bak/config/" "minecraft/config/"; then
		echo "DONE"; else echo "FAIL"; some_failed="true"; fi

	echo -n "$a2 Copying defaultconfigs... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif cp -R "minecraft.bak/defaultconfigs/" "minecraft/defaultconfigs/"; then
		echo "DONE"; else echo "FAIL"; some_failed="true"; fi

	echo -n "$a2 Copying properties and player/IP lists... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif cp "minecraft.bak/banned-ips.json" "minecraft.bak/banned-players.json" "minecraft.bak/ops.json" "minecraft.bak/server.properties" "minecraft.bak/whitelist.json" "minecraft/"; then
		echo "DONE"; else echo "FAIL"; some_failed="true"; fi

	echo -n "$a2 Updating ownership... "
	if [ "$req_failed" = "true" ]; then echo "SKIPPED"
	elif chown -R "$user:$user" "minecraft"; then
		echo "DONE"; else echo "FAIL"; req_failed="true"; fi

	if [ "$req_failed" = "true" ] || [ "$some_failed" = "true" ]; then
		while true; do
			echo ""
			read -rp "$p At least one step failed, do you want to proceed anyway? [y/N] " skip_fail
			case "$skip_fail" in
				[Yy] ) echo "$a1 Ignoring failures..."; break;;
				[Nn]|"" ) echo "$a1 Exiting. Please try again or resolve failures manually."; exit;;
				* ) echo "$a1 Invalid response.";;
			esac
		done
	fi
	echo "$a1 Finished copying data."
	echo "NOTICE: After completing the installation, please check for other config files"
	echo "        or directories that you may want to keep such as logs, configurations,"
	echo "        mod-specific directories, etc."
	echo "NOTICE: Mods must be updated manually, please do so before starting the server."

	echo "$a1 Changing working directory to '$data_dir/minecraft'."
	cd "$data_dir/minecraft" || exit 1
else
	existing_dir=""

	echo "$a1 Creating minecraft directory..."
	if [ -d "minecraft" ]; then
		echo "$a2 The minecraft directory already exists in: '$data_dir'."
		echo ""
		echo "If this directory is already backed up or is no longer needed and you plan to"
		echo "set up the server again or use a new server, then it should be removed. You will"
		echo "have a few seconds to stop the script if you choose to remove the directory."
		while true; do
			echo ""
			read -rp "$p Remove directory before continuing? [y/N] " rm_dir
			case "$rm_dir" in
				[Yy] )
					echo "$a2 Removing: '$data_dir/minecraft' in 10 seconds."
					sleep 5
					echo "$a2 5."; sleep 1
					echo "$a2 4."; sleep 1
					echo "$a2 3."; sleep 1
					echo "$a2 2."; sleep 1
					echo "$a2 1."; sleep 1
					echo "$a2 Removing minecraft directory."
					rm -rf "minecraft" || exit 1
					break;;
				[Nn]|"" )
					echo "$a2 Using existing minecraft directory."
					existing_dir="true"
					break;;
				* )
					echo "$a1 Invalid response.";;
			esac
		done
	fi
	if [ "$existing_dir" = "true" ]; then
		echo "$a2 Updating ownership."
	else
		echo "$a2 Creating minecraft directory."
		mkdir -p "$data_dir/minecraft"
		echo "$a2 Setting ownership."
	fi
	chown "$user:$user" "$data_dir/minecraft"
	echo "$a2 Changing working directory to '$data_dir/minecraft'."
	cd "$data_dir/minecraft" || exit 1
	if [ "$existing_dir" = "true" ]; then
		echo "$a1 Using minecraft directory."
	else
		echo "$a1 Created minecraft directory."
	fi
fi

# Install Java.

echo ""
echo "Choose a valid version of Java."
echo "Here is a table of Minecraft versions and their minimum Java requirements:"
echo "        Minecraft | Java"
echo "         <= 1.5.2 | 5 (1.5.0)"
echo "   1.6.1 - 1.11.2 | 6 (1.6.0)"
echo "    1.12 - 1.16.5 | 8 (1.8.0)"
echo "    1.17 - 1.17.1 | 16"
echo "    1.18 - 1.20.4 | 17"
echo " 1.20.5 - 1.21.11 | 21"
echo "             26.1 | 25"
echo "Running Java versions newer than the requirements is possible but may result in"
echo "instability, especially with the oldest versions. It is not recommended."
echo ""
echo "Ensure the version is available as a jdk(version)-openjdk package at"
echo "https://archlinux.org/packages/?q=jdk, or it must be installed manually."
echo "Make sure to check out the AUR for more versions."
while true; do
	echo ""
	read -rp "$p Enter a valid version (ENTER to skip): " java
	case "$java" in
		"" )
			echo "$a1 Skipping installation..."
			break;;
		*[!0-9]* )
			echo "$a1 Invalid response.";;
		* )
			echo "$a1 Installing Java $java via the OpenJDK package..."
			echo "$a2 Installing jdk$java-openjdk."
			if pacman -Sy --noconfirm "jdk$java-openjdk"; then
				echo "$a1 Installed OpenJDK $java."
				break
			else
				echo "$a1 Failed to install OpenJDK $java."
			fi ;;
	esac
done

# Installer.

echo ""
echo "Choose if you want to install a Fabric server. You should still choose 'Y' if"
echo "you are re-running this script. Downloading and running the installer can still"
echo "be skipped in the next step."
echo "If you are installing a Fabric server with your own installer, then choose 'N'"
echo "and proceed like any other manual installation."
echo "The Fabric installer supports Minecraft 1.14 and later."
while true; do
	echo ""
	read -rp "$p Install a Fabric server? [Y/n] " use_fabric
	case "$use_fabric" in
		[Yy]|"" )
			install="fabric"
			break;;
		[Nn] )
			echo "$a1 Skipping Fabric installer."
			echo ""
			echo "Choose if you want to use an existing server installer."
			echo "This requires an existing and accessible .jar file."
			while true; do
				echo ""
				read -rp "$p Use other server installer? [Y/n] " use_other
				case "$use_other" in
					[Yy]|"" )
						install="manual"
						break;;
					[Nn] )
						install="none"
						runjar=""
						echo "$a1 Skipping installation."
						break;;
					* )
						echo "$a1 Invalid response.";;
				esac
			done
			break;;
		* )
			echo "$a1 Invalid response.";;
	esac
done

# Installation.

if [ "$install" != "none" ]; then
	if [ "$install" = "fabric" ]; then
		while true; do
			echo ""
			read -rp "$p Download the Fabric installer? [Y/n] " get_installer
			case "$get_installer" in
				[Yy]|"" )
					get_installer="true"
					break;;
				[Nn] )
					echo "$a1 Skipping..."
					break;;
				* )
					echo "$a1 Invalid response.";;
			esac
		done
		if [ "$get_installer" = "true" ]; then
			echo "$a1 Getting Fabric installer..."
			echo "$a2 Checking latest installer version."
			installer_ver=$(curl -s https://maven.fabricmc.net/net/fabricmc/fabric-installer/maven-metadata.xml | grep -oPm1 '(?<=<latest>)[^<]+')
			echo "$a2 Got installer version: '$installer_ver'."
			echo "$a2 Downloading file."
			curl -s -o 'fabric-installer.jar' "https://maven.fabricmc.net/net/fabricmc/fabric-installer/$installer_ver/fabric-installer-$installer_ver.jar"
			echo "$a1 Downloaded installer."

			while true; do
				echo ""
				read -rp "$p Select valid Minecraft version to install (ENTER for latest): " mc
				case "$mc" in
					"" )
						mc="latest"
						echo "$a1 Installing latest Fabric server..."
						echo "$a2 Running installer."
						if sudo -u "$user" java -jar "fabric-installer.jar" server -downloadMinecraft; then
							break
						else
							echo "$a1 Failed to install server."
						fi ;;
					* )
						echo "$a1 Installing $mc Fabric server..."
						echo "$a2 Running installer."
						if sudo -u "$user" java -jar "fabric-installer.jar" server -mcversion "$mc" -downloadMinecraft; then
							break
						else
							echo "$a1 Failed to install server."
						fi ;;
				esac
			done
			echo "$a1 Installed $mc Fabric server."
			echo "$a2 Removing installer."
			rm "fabric-installer.jar"
		fi
	elif [ "$install" = "manual" ]; then
		echo ""
		echo "Enter the server installer file path."
		echo "Working directory is '$data_dir/minecraft' for relative file paths."
		echo "Using an asterisk ('*') takes the first match."
		while true; do
			echo ""
			read -rp "$p Enter the server installer path: " serverjar_pattern
			mapfile -t files < <(compgen -G "$serverjar_pattern")
			serverjar="${files[0]}"
			if [ ! -f "$serverjar" ]; then
				serverjar="$serverjar_pattern"
				echo "$a1 File not found: '$serverjar'."
			else
				echo "$a1 Found file: '$serverjar'."
				while true; do
					echo ""
					read -rp "$p Do you want to continue with this installer? [Y/n] " use_installer
					case "$use_installer" in
						[Yy]|"" )
							echo "$a1 Selected server installer: '$serverjar'."
							break 2;;
						[Nn] ) break;;
						* ) echo "$a1 Invalid response.";;
					esac
				done
			fi
		done
		echo ""
		echo "Choose server installer arguments. These are NOT the runtime arguments and will"
		echo "have no effect after the installation is complete."
		echo "Forge should use 'nogui --installServer' args."
		echo "You can and should use '--nogui' on newer versions."
		while true; do
			echo ""
			read -rp "$p Enter any installer arguments (ENTER for 'nogui'): " server_args
			if [ ! "$server_args" ]; then
				server_args="nogui"
			fi
			echo ""
			echo "Server installer arguments: '$server_args'"
			while true; do
				echo ""
				read -rp "$p Do you want to continue with these arguments? [Y/n] " use_install_args
				case "$use_install_args" in
					[Yy]|"" )
						use_install_args="true"
						echo "$a1 Selected server installer arguments: '$server_args'."
						break;;
					[Nn] ) break;;
					* ) echo "$a1 Invalid response.";;
				esac
			done
			if [ "$use_install_args" = "true" ]; then
				echo "$a1 Installing server..."
				echo "$a2 Launching executable."
				if sudo -u "$user" bash -c "java -jar \"$serverjar\" $server_args"; then
					echo "$a1 Finished installing the server."
					break
				else
					echo "$a1 Failed to install the server."
				fi
			fi
		done
		echo "$a2 Removing installer."
		rm "$serverjar"
	fi

	# File generation.

	while true; do
		echo ""
		echo "Normally, the server would be run once to generate a eula.txt and other config"
		echo "files to help set up the server. However, this is entirely optional."
		while true; do
			echo ""
			read -rp "$p Do you want to launch the server once? [Y/n] " launch_once
			case "$launch_once" in
				[Yy]|"" ) break;;
				[Nn] ) echo "$a1 Skipping..."; break 2;;
				* ) echo "$a1 Invalid response.";;
			esac
		done

		different_exec=""

		if [ "$install" = "fabric" ]; then
			runjar="fabric-server-launch.jar"
			echo "$a2 Checking for '$runjar'."
			if [ ! -f "$runjar" ]; then
				echo ""
				echo "The Fabric server launch file could not be found. Either specify an existing"
				echo "launch file or skip the first launch and continue until an executable is needed,"
				echo "like if you are going to generate a run script."
				while true; do
					echo ""
					read -rp "$p Do you want to specify a different executable? [y/N] " different_exec
					case "$different_exec" in
						[Yy] )
							different_exec="true"
							break;;
						[Nn]|"" )
							echo "$a1 Skipping first launch..."
							break 2;;
						* ) echo "$a1 Invalid response.";;
					esac
				done
				
			fi
		fi
		if [ "$install" = "manual" ] || [ "$different_exec" = "true" ]; then
			echo ""
			echo "Enter the server executable file path (not the installer)."
			echo "Working directory is '$data_dir/minecraft' for relative file paths."
			echo "Using an asterisk ('*') takes the first match."
			while true; do
				echo ""
				read -rp "$p Enter the .jar file that runs the server (ENTER for *.jar): " runjar_pattern
				if [ ! "$runjar_pattern" ]; then
					runjar_pattern="*.jar"
				fi
				mapfile -t files < <(compgen -G "$runjar_pattern")
				runjar="${files[0]}"
				if [ ! -f "$runjar" ]; then
					runjar="$runjar_pattern"
					echo "$a2 File not found: '$runjar'."
				else
					echo "$a2 Found file: '$runjar'."
					while true; do
						echo ""
						read -rp "$p Do you want to continue with this executable? [Y/n] " use_exec
						case "$use_exec" in
							[Yy]|"" )
								echo "$a2 Selected server executable: '$runjar'."
								break 2;;
							[Nn] ) break;;
							* ) echo "$a2 Invalid response.";;
						esac
					done
				fi
			done
		fi

		echo ""
		echo "Choose server executable arguments. These are NOT saved and will only be used"
		echo "this one time to launch the server so that config files are generated."
		echo "You can and should use '--nogui' on newer versions."
		while true; do
			echo ""
			read -rp "$p Enter any executable arguments (ENTER for 'nogui'): " run_args
			if [ ! "$run_args" ]; then
				run_args="nogui"
			fi
			echo ""
			echo "Server executable arguments: '$run_args'"
			while true; do
				echo ""
				read -rp "$p Do you want to continue with these arguments? [Y/n] " use_run_args
				case "$use_run_args" in
					[Yy]|"" )
						echo "$a2 Selected server executable arguments: '$run_args'."
						break 2;;
					[Nn] ) break;;
					* ) echo "$a2 Invalid response.";;
				esac
			done
		done

		echo "$a2 Running server..."
		sudo -u "$user" bash -c "java -jar \"$runjar\" $run_args"
		echo "$a2 Finished running server."

		echo ""
		echo "If there were any errors (other than the expected EULA notice), you may want to"
		echo "stop here and make some changes. You can press Ctrl+C if you need to exit this"
		echo "script, or enter 'Y' to just re-enter the executable path and arguments."
		echo "Keep in mind that you do not want the server to launch fully, (which it won't"
		echo "as long as eula.txt is left alone,) as the only purpose of this is to generate"
		echo "files like a eula.txt, and ideally other configs for you to modify later."
		while true; do
			echo ""
			read -rp "$p Do you want to retry the installation? [y/N] " do_retry
			case "$do_retry" in
				[Yy] )
					echo "$a1 Retrying..."
					break;;
				[Nn]|"" )
					echo "$a1 First server launch completed."
					break 2;;
				* ) echo "$a1 Invalid response.";;
			esac
		done
	done

	# EULA.

	echo "$a1 Setting EULA..."
	echo ""
	echo "If no EULA file exists, one will be created with a single line: 'eula=true'."
	while true; do
		echo ""
		read -rp "$p Agree to the EULA? [Y/n] " eula
		case "$eula" in
			[Yy]|"" )
				if [ ! -f "eula.txt" ]; then
					echo "$a2 Created eula.txt."
					echo "eula=true" > "eula.txt"
				else
					echo "$a2 Modified eula.txt to set: 'eula=true'."
					sed -i 's/^eula=.*/eula=true/' "eula.txt"
				fi
				echo "$a1 EULA set to true."
				break;;
			[Nn] )
				echo "$a1 Skipping..."
				break;;
			* )
				echo "$a1 Invalid response.";;
		esac
	done
fi

# Run script.

echo ""
echo "Do you want to create a script which launches the server with set arguments?"
echo "It will be stored in the minecraft directory. Modify that file to change the"
echo "arguments that are used every time the server is launched."
echo "Skipping both its creation and usage will prevent systemd unit creation."
while true; do
	echo ""
	read -rp "$p Create run.sh script? [Y/n] " make_script
	case "$make_script" in
		[Yy]|"" )
			run_script="install"
			break;;
		[Nn] )
			echo ""
			echo "For a run script to be \"existing\", it must be named 'run.sh' and be within the"
			echo "minecraft directory. Ensure this is true if it must be used."
			while true; do
				echo ""
				read -rp "$p Use existing run.sh script? [Y/n] " use_script
				case "$use_script" in
					[Yy]|"" )
						run_script="existing"
						break;;
					[Nn] )
						run_script="skip"
						echo "$a1 Skipping..."
						break;;
					* )
						echo "$a2 Invalid response.";;
				esac
			done
			break;;
		* )
			echo "$a2 Invalid response.";;
	esac
done

if [ "$run_script" = "install" ]; then
	echo "$a1 Creating run script with Java arguments..."
	echo ""
	echo "Choose allocated server memory in GB"
	echo "You should leave roughly 1-2GB available for the host. E.g. use up to 6-7GB if"
	echo "the system has 8GB. I recommend using 3-6 for best performance, and avoiding >8"
	echo "unless there are many players or mods."
	while true; do
		echo ""
		read -rp "$p Enter allocated memory [1-99] (ENTER to use 4GB): " mem
		case "$mem" in
			[1-9]|[1-9][0-9] )
				echo "$a2 Allocating ${mem}GB."
				break;;
			"" )
				echo "$a2 Allocating 4GB."
				mem="4"
				break;;
			* )
				echo "$a2 Invalid response.";;
		esac
	done

	if [ ! "$runjar" ]; then
		echo "$a2 No .jar file has been selected to run the server."
		echo ""
		echo "Enter the server executable file path (not the installer)."
		echo "Working directory is '$data_dir/minecraft' for relative file paths."
		echo "Using an asterisk ('*') takes the first match."
		while true; do
			echo ""
			read -rp "$p Enter the .jar file that runs the server (ENTER for *.jar): " runjar_pattern
			if [ ! "$runjar_pattern" ]; then
				runjar_pattern="*.jar"
			fi
			mapfile -t files < <(compgen -G "$runjar_pattern")
			runjar="${files[0]}"
			if [ ! -f "$runjar" ]; then
				runjar="$runjar_pattern"
				echo "$a2 File not found: '$runjar'."
			else
				echo "$a2 Found file: '$runjar'."
			fi
			while true; do
				echo ""
				read -rp "$p Do you want to continue with this executable path? [Y/n] " use_exec
				case "$use_exec" in
					[Yy]|"" )
						echo "$a2 Selected server executable: '$runjar'."
						break 2;;
					[Nn] ) break;;
					* ) echo "$a2 Invalid response.";;
				esac
			done
		done
	fi

	echo ""
	echo "You can and should use '--nogui' on newer versions."
	while true; do
		echo ""
		read -rp "$p Do you want to use '--nogui' instead of 'nogui' in the launch script? [y/N] " new_nogui
		case "$new_nogui" in
			[Yy] )
				nogui_arg="--nogui"
				break;;
			[Nn]|"" )
				nogui_arg="nogui"
				break;;
			* ) echo "$a1 Invalid response.";;
		esac
	done
	echo "$a2 Using '$nogui_arg' argument in launch script."

	echo "$a2 Writing script."
	cat > "$data_dir/minecraft/run.sh" <<- EOF
		cd "$data_dir/minecraft"
		java -Xmx${mem}G -Xms${mem}G -XX:+UseG1GC -Dsun.rmi.dgc.server.gcInterval=2147483646 -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M -jar "$runjar" $nogui_arg
	EOF
	echo "$a2 Setting ownership."
	chown "$user:$user" "$data_dir/minecraft/run.sh"
	echo "$a2 Marking executable flag."
	chmod +x "$data_dir/minecraft/run.sh"
	echo "$a1 Created launch script in the minecraft directory."
fi

# Systemd units.

sysd=""

if [ "$update" != "true" ] && [ "$run_script" != "skip" ]; then
	echo ""
	echo "Choose 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 server console in the background."
	while true; do
		echo ""
		read -rp "$p Do you want to set up a systemd unit? [Y/n] " sysd
		case "$sysd" in
			[Yy]|"" )
				sysd="install"
				break;;
			[Nn] )
				sysd="skip"
				echo "$a1 Skipping..."
				break;;
			* )
				echo "$a1 Invalid response.";;
		esac
	done
fi

if [ "$sysd" = "install" ] && [ "$run_script" != "skip" ]; then
	echo "$a1 Creating systemd unit files..."

	echo "$a2 Creating service file."
	cat > "/etc/systemd/system/minecraft.service" <<- EOF
		[Unit]
		Description=Dedicated Minecraft server
		After=network.target minecraft.socket
		Requires=minecraft.socket

		[Service]
		User=$user
		Type=exec
		WorkingDirectory=$data_dir/minecraft
		ExecStart=/usr/bin/sh -c "$data_dir/minecraft/run.sh < /run/minecraft.control"
		ExecStop=/usr/bin/sh -c "echo '/stop' > /run/minecraft.control"
		Restart=on-failure
		RestartSec=5

		[Install]
		WantedBy=multi-user.target
	EOF

	echo "$a2 Creating socket file."
	cat > "/etc/systemd/system/minecraft.socket" <<- EOF
		[Unit]
		Description=Minecraft control FIFO
		PartOf=minecraft.service

		[Socket]
		ListenFIFO=/run/minecraft.control
		SocketMode=0660
		SocketUser=$user
		RemoveOnStop=true

		[Install]
		WantedBy=multi-user.target
	EOF

	echo "$a1 Created systemd unit files."
	echo "$a2 Reloading systemd daemon."
	systemctl daemon-reload
	echo "$a2 Enabling socket for FIFO creation."
	systemctl enable minecraft.socket &> /dev/null
	echo "$a2 Enabling service."
	systemctl enable minecraft.service &> /dev/null
	echo "$a1 Enabled systemd service."
	echo "INFO: The server is set up to start and restart automatically."

	echo "$a1 Creating mcc (Minecraft console) script in the data directory..."
	echo "$a2 Creating script."
	cat > "$data_dir/mcc.sh" <<- EOF
		#!/bin/bash

		if [ ! -p /run/minecraft.control ]; then
		    echo "FIFO does not exist."
		    exit 1
		fi

		timestamp="\$(date +"%F %T.%N")"
		journalctl -o cat -fu minecraft.service --since "\$timestamp" &
		journal_pid=\$!
		printf "%s\n" "\$*" > /run/minecraft.control
		wait \$journal_pid
	EOF
	echo "$a2 Setting ownership."
	chown "$user:$user" "$data_dir/mcc.sh"
	echo "$a2 Marking executable flag."
	chmod +x "$data_dir/mcc.sh"
	echo "$a1 Created console script in data directory."
	echo "INFO: The console script passes all arguments to the server, and returns the"
	echo "      output until stopped with Ctrl+C."

	add_cmd=""

	echo ""
	echo "Choose to install an mcc.sh link in /usr/bin/."
	echo "Creates a link to ~/mcc.sh, allowing you to run server commands from anywhere"
	echo "using just that command. E.g. 'mcc /gamerule keepInventory true'."
	echo "You will choose the command name."
	while true; do
		echo ""
		read -rp "$p Add mcc.sh link in /usr/bin? [Y/n] " add_cmd
		case "$add_cmd" in
			[Yy]|"" )
				while true; do
					echo ""
					read -rp "$p Enter the name of the command (ENTER for 'mcc'): " mcc_cmd
					if [ ! "$mcc_cmd" ]; then
						mcc_cmd="mcc"
					fi
					if command -v "$mcc_cmd" &> /dev/null; then
						echo "$a2 Command '$mcc_cmd' already exists."
						if [ "$(command -v "$mcc_cmd")" = "/usr/bin/$mcc_cmd" ]; then
							echo ""
							echo "The command '$mcc_cmd' appears to be the file: '/usr/bin/$mcc_cmd'."
							if [ -L "/usr/bin/$mcc_cmd" ]; then
								echo "It links to '$(readlink "/usr/bin/$mcc_cmd")'."
							else
								echo "It is not a symbolic link. It was not created by this script."
							fi
							while true; do
								echo ""
								read -rp "$p Do you want to replace it? [y/N] " rm_cmd
								case "$rm_cmd" in
									[Yy] )
										echo "$a2 Removing: '/usr/bin/$mcc_cmd'."
										rm -f "/usr/bin/$mcc_cmd"
										break 2;;
									[Nn]|"" ) break;;
									* ) echo "$a1 Invalid response.";;
								esac
							done
						else
							echo ""
							echo "It is not a file in the /usr/bin directory. It was not created by this script."
							echo "The path is: $(command -v "$mcc_cmd")"
							while true; do
								echo ""
								read -rp "$p Do you want to create a link in /usr/bin anyway? [y/N] " do_conflict
								case "$do_conflict" in
									[Yy] ) break 2;;
									[Nn]|"" ) break;;
									* ) echo "$a1 Invalid response.";;
								esac
							done
						fi
						continue 2
					else
						echo "$a2 Command '$mcc_cmd' is available."
						while true; do
							echo ""
							read -rp "$p Do you want to continue with this name? [Y/n] " use_cmd
							case "$use_cmd" in
								[Yy]|"" )
									echo "$a1 Selected command: '$mcc_cmd'."
									break 2;;
								[Nn] ) break;;
								* ) echo "$a1 Invalid response.";;
							esac
						done
					fi
				done
				add_cmd="true"
				echo "$a2 Creating symlink."
				ln -s "$data_dir/mcc.sh" "/usr/bin/$mcc_cmd"
				echo "$a1 Created '$mcc_cmd' link."
				break;;
			[Nn] )
				add_cmd="false"
				echo "$a1 Skipping..."
				break;;
			* )
				echo "$a1 Invalid response.";;
		esac
	done
fi

if [ "$install" != "none" ]; then
	echo ""
	echo "Installation complete, the server is not running."
	echo "NOTICE: Please configure server.properties before starting the server."
	if [ "$install" = "fabric" ]; then
		echo "NOTICE: It's recommended to download performance mods such as Lithium,"
		echo "        FerriteCore, ModernFix, and possibly others."
	fi
	if [ "$run_script" != "skip" ]; then
		if [ "$sysd" = "install" ]; then
			echo ""
			echo "Systemd is in use, the server will automatically start after 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 ""
			echo "Many commands are available with systemd, some important ones are:"
			echo "Executing commands in the Minecraft server console using a script:"
			echo "  $ ./mcc.sh <command here>"
			if [ "$add_cmd" = "true" ]; then
				echo "Or by using the '$mcc_cmd' command:"
				echo "  # $mcc_cmd <minecraft command here>"
			fi
			echo "View the server logs with journalctl: (Shift+G jumps to the end)"
			echo "  $ journalctl -u minecraft"
			echo "Or follow them as they update with:"
			echo "  $ journalctl -fu minecraft"
			echo "And easily perform a clean start/stop of the server with:"
			echo "  # systemctl {start,stop,restart} minecraft"
		else
			echo ""
			echo "Start the server with the run script, or set up a user crontab for autostart."
			echo "  $ ./run.sh"
		fi
	fi
fi
echo "$a1 Finished."