#!/bin/bash
#############################################################################################################
#                                Auto Update & Run PaperMC server script                                    #
#                                              by jiriks74                                                  #
#                             https://github.com/jiriks74/start_papermc.sh                                  #
#  This script is under GPLv3, if you want to distribute changes you have to do so under the same license   #
#                            and acknowledge the original script and author.                                #
#############################################################################################################

############
# Settings #
############

# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #
# This script is not made for migrating versions.                  #
# If you're migrating versions, delete your old server's .jar file #
# and change the version below.                                    #
# I am not responsible for any loss of data                        #
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #
# If enough people request it (or someone creates a PR) I'll add the functionality to migrate versions
version="1.12.2"
# Leave blank to use the latest build (auto updates on every run)
select_build=""

#
# Memory settings
#
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #
# Do not allocate all of your available memory on a shared host! #
# Minecraft (and Java) needs to have more memory than the Xmx    #
# parameter (maxMem below). You should set it at least 1500M     #
# lower than your available memory if you're running just the    #
# minecraft server.                                              #
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #
mem="2000M"


# ------------------------------------------------
# You shouldn't need to change anything below this
# ------------------------------------------------

# Options for the server
mc_launchoptions="-nogui"

if [[ "${mem%M}" -gt 12000 ]]; then
  G1NewSize=40
  G1MaxNewSize=50
  G1HeapRegionSize=16M
  G1Reserve=15
  InitiatingHeapOccupancy=20
else
  G1NewSize=30
  G1MaxNewSize=40
  G1HeapRegionSize=8M
  G1Reserve=20
  InitiatingHeapOccupancy=15
fi

# Aikar's flags are used by default
# See https://docs.papermc.io/paper/aikars-flags
java_launchoptions="-Xms$mem -Xmx$mem -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=$G1NewSize -XX:G1MaxNewSizePercent=$G1MaxNewSize -XX:G1HeapRegionSize=$G1HeapRegionSize -XX:G1ReservePercent=$G1Reserve -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=$InitiatingHeapOccupancy -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true"

# Api url
url="https://api.papermc.io/v2/projects/paper/versions/$version/builds"

##########
# Checks #
##########

# Check if selected version exists
if curl -s "$url" | grep -q '{"error":"Version not found."}'; then
  echo "Error: Invalid version selected: $version"
  exit 1
else
  # Check if selected build exists
  if [ ! -z "$select_build" ]; then
    if curl -Is "https://api.papermc.io/v2/projects/paper/versions/$version/builds/$select_build/downloads/paper-$version-$select_build.jar" | grep "HTTP/2 404" >/dev/null; then
      echo "Error: Invalid build selected: $select_build"
      exit 1
    fi
  fi
fi

# Check if curl is installed
if ! command -v curl &> /dev/null
then
    echo "Error: Curl is not installed"
    exit 1
fi

# Check if jq is installed
if ! command -v jq &> /dev/null
then
    echo "Error: jq is not installed"
    exit 1
fi

# Check if awk is installed
if ! command -v awk &> /dev/null
then
    echo "Error: awk is not installed"
    exit 1
fi

# Check if java is installed
if ! command -v java &> /dev/null
then
    echo "Error: Java is not installed"
    java_version="0"
fi

#####################################################
# Check if the correct version of Java is installed #
#####################################################
#

# Extract the middle number of the Minecraft version
minecraft_middle=$(echo "$version" | awk -F '.' '{print $2}')

# If java is installed, get the version (the java_version won't be 0)
if [[ $java_version != "0" ]]; then
  # Get the current Java version and extract the build number
  java_version=$(java -version 2>&1 | awk -F '"' '/version/ {print $2}' | awk -F '.' '{print $1}')
fi

# Ask if the user wants to continue anyway
# If the user doesn't answer in 15 seconds, the script will exit
function ask_continue {
  if [[ $java_version_override != true ]]; then
    answer=""
    echo "You have 15 seconds to respond before the script exits."
    read -t 15 -p "Do you want to continue anyway? [y/N]: " answer
    if [[ $answer != "y" ]] || [[ $answer != "Y" ]]; then
        echo "Exiting..."
        exit 1
    fi
  fi
}

# Check if the correct version of java is installed
# For version 1.8 to 1.11 use java 8
# For version 1.12 to 1.16.4 use java 11
# For version 1.16.5 use java 16
# For version 1.17.1 to 1.18.1+ use java 17
if (( 8 <= minecraft_middle && minecraft_middle <= 11 )); then
  if ! [[ $java_version -eq 8 ]]; then
    echo "Java 8 is required for Minecraft version $version. Please install Java 8."
    if [[ $java_version == 0 ]]; then
      exit 1
    fi
    ask_continue
  fi
elif (( 12 <= minecraft_middle && minecraft_middle <= 16 )); then
  if ! [[ $java_version -eq 11 ]]; then
    if [[ $java_version == 0 ]]; then
      exit 1
    fi
    echo "Java 11 is required for Minecraft version $version. Please install Java 11."
    ask_continue
  fi
elif (( minecraft_middle == 17 )); then
  if ! [[ $java_version -eq 16 ]]; then
    echo "Java 16 is required for Minecraft version $version. Please install Java 16."
    if [[ $java_version == 0 ]]; then
      exit 1
    fi
    ask_continue
  fi
elif (( 18 <= minecraft_middle )); then
  if ! [[ $java_version -eq 17 ]]; then
    echo "Java 17 is required for Minecraft version $version. Please install Java 17."
    if [[ $java_version == 0 ]]; then
      exit 1
    fi
    ask_continue
  fi
else
  echo "Unsupported Minecraft version $version."
  if [[ $java_version == 0 ]]; then
    exit 1
  fi
  ask_continue
fi

# Check if some server already exists
if ls paper-*.jar 1> /dev/null 2>&1; then
  # Get the current server file name
  server_file=$(basename ./paper-*.jar)

  # Extract the build number using cut command
  current_build=$(echo "$server_file" | cut -d'-' -f3)
  current_build="${current_build%.jar}"

  # Check if select_build variable is set
  if [ -z "$select_build" ]; then
    echo "Checking for newer build..."
    json_response=$(curl -s "$url") # Get all the versions from the paper api

    # Get the latest build number
    latest_build=$(curl -s $url | jq '.builds[-1].build')

      # Check if the latest build is newer than the current build
      if [ "$latest_build" -gt "$current_build" ]; then
          echo "Newer build available: $latest_build"

          # Ask the user if they want to download and install the new build
          echo
          echo
          echo "You have 15 seconds to answer, then the new build will be downloaded automatically"
          read -t 15 -p "Do you want to download and install the new build? (Y/n) " answer
          # If the user doesn't answer set the answer to "y"
          if [ -z "$answer" ]; then
              answer="y"
          fi
          if [ "$answer" == "y" ]; then
              # Download the new build
              echo "Downloading the new build..."
              curl -s "https://api.papermc.io/v2/projects/paper/versions/$version/builds/$latest_build/downloads/paper-$version-$latest_build.jar" -o "./paper-$version-$latest_build.jar"
              echo "Download complete"

              # Remove the old server file
              echo "Removing the old server file..."
              rm "$server_file"
              echo "Old server file removed"

              server_file=$(basename ./paper-*.jar) 
          else
              echo "Skipping download and installation"
          fi
          
      else
          echo "Server is up to date"
      fi

  else
    if [ "$current_build" -ne "$select_build" ]; then
      echo "The current build is not the selected build"
      echo "Downloading the selected build..."
      curl -s "https://api.papermc.io/v2/projects/paper/versions/$version/builds/$select_build/downloads/paper-$version-$select_build.jar" -o "./paper-$version-$select_build.jar"
      echo "Download complete"

      echo "Removing the old server file..."
      rm "$server_file"
      echo "Old server file removed"
      server_file=$(basename ./paper-*.jar)
    fi
  fi

# If no server file exists
else
  # Check if select_build variable is set
  if [ -z "$select_build" ]; then
    echo "Downloading the latest build of version $version..."
    json_response=$(curl -s "$url")
    # Get the latest build number
    latest_build=$(curl -s $url | jq '.builds[-1].build')

    curl -s "https://api.papermc.io/v2/projects/paper/versions/$version/builds/$latest_build/downloads/paper-$version-$latest_build.jar" -o "./paper-$version-$latest_build.jar"
    echo "Download complete"

  else
    echo "Downloading version $version build $select_build..."
    curl -s "https://api.papermc.io/v2/projects/paper/versions/$version/builds/$select_build/downloads/paper-$version-$select_build.jar" -o "./paper-$version-$select_build.jar"
    echo "Download complete"
  fi
fi

if test "$(cat eula.txt 2>/dev/null)" != "eula=true"; then
  echo
  echo
  echo "'eula.txt' does not exist or is not accepted"
  echo "Please agree to the Minecraft EULA by entering 'y'"
  echo "By entering 'y' you are indicating your agreement to Minecraft's EULA (https://aka.ms/MinecraftEULA)."
  echo "You have 15 seconds to respond, or the script will exit"
  read -t 15 -p "Do you agree to the Minecraft EULA? [y/N] " eula_agreed

  if [ "$eula_agreed" == "y" ]; then
    if [ ! -f eula.txt ]; then
      # Write eula_agreed to eula.txt
      echo "eula=true" > eula.txt
    else
      rm eula.txt
      echo "eula=true" > eula.txt
    fi
    echo
    echo
    echo "EULA accepted"
  else
    echo
    echo
    echo "You did not agree to the Minecraft EULA"
    echo "Exiting..."
    exit 1
  fi
fi

# Run the server
echo
echo
echo "Starting the server..."
java $java_launchoptions -jar "$(basename ./paper-*.jar)" $mc_launchoptions