#!/usr/bin/env bash

SRC_TREE="/usr/src/linux"
SRC_CONFIG=".config"

declare -a OUT

LWD="$PWD"
cd "$SRC_TREE" || exit 1

if [[ ! -f $SRC_CONFIG ]] ; then
  NOCONFIG="1"
fi
if [[ "$1" == "--force" ]] ; then
  FORCE="1"
fi

if [[ -f /proc/config.gz ]] ; then
  OLDCONFIG="1"
fi


if [[ "$NOCONFIG" || "$FORCE" ]]  ; then
  echo "**************** building kernel  ***********"

  TIMESTAMP=$(date +%F-%H_%M_%S)

  if [[ "$NOCONFIG" ]] ; then
    if [[ "$OLDCONFIG" ]] ; then
      OUT+=("********** Using old config ************")
      echo "${OUT[-1]}"
      zcat /proc/config.gz > .config
    else
      OUT+=("********** WARNING! No old config has been found! Using defconfig! ************")
      echo "${OUT[-1]}"
      make defconfig
    fi
  else
    OUT+=("Found kernel config in source tree!")
    echo "${OUT[-1]}"
  fi

  make olddefconfig

  echo mounting boot if not yet mounted
  mount /boot 2> /dev/null

  (make -j17 -l15 CC="ccache gcc" && make install && make modules_install && make firmware_install) > "buildlog-$TIMESTAMP" || tail -n 20 "buildlog-$TIMESTAMP"

  GRUBMKONFIG="$(which grub2-mkconfig 2> /dev/null)"
  if [[ -z "$GRUBMKONFIG" ]] ; then
    GRUBMKONFIG="$(which grub-mkconfig)"
  fi

  if [[ -f /boot/grub2/grub.cfg && -n "$GRUBMKONFIG" ]] ; then
    "$GRUBMKONFIG" -o /boot/grub2/grub.cfg
  elif [[ -f /boot/grub/grub.cfg && -n "$GRUBMKONFIG" ]] ; then
    "$GRUBMKONFIG" -o /boot/grub/grub.cfg
  else
    echo "please update bootloader manually!"
  fi
  echo
  echo
  echo Summary:
  IFS=$'\n' echo -e "${OUT[*]}"
  echo diff between current running und last build config:
  diff .config <(zcat /proc/config.gz )

fi

 cd "${LWD}" || exit 1