#!/usr/bin/env bash

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

CONFIGDIR="/etc/kernelconf"

declare -a OUT

umask 022

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

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

if [[ "$1" == "--force" ]] ; then
  FORCE="1"
fi

for config in "/proc/config.gz" "$CONFIGDIR/latest" ; do
  if [[ -f "$config" ]] ; then
    OLDCONFIG="$config"
  fi
done

if [ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]; then
  CHROOTED=1
fi

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

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

  if [[ "$NOCONFIG" ]] ; then
    if [[ -n "$OLDCONFIG" ]] ; then
      OUT+=("********** Using old config ************")
      echo "${OUT[-1]}"
      zcat -f "$OLDCONFIG"  > .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

  CORES="$(getconf _NPROCESSORS_ONLN)"
  (nice make -j$((CORES-2)) -l$((CORES-2)) CC="ccache gcc") > "buildlog-$TIMESTAMP" || tail -n 20 "buildlog-$TIMESTAMP"
  SUCCESS=$?
  if [[ $SUCCESS == 0 ]] && [[ $CHROOTED == 1 ]] ; then
    ( make tarxz-pkg ) >> "buildlog-$TIMESTAMP"
  elif [[ $SUCCESS == 0 ]] ; then
    ( make install ; make modules_install ) >> "buildlog-$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
  fi
  echo
  echo
  echo Summary:
  IFS=$'\n' echo -e "${OUT[*]}"
  echo diff between current running und last build config:
  diff .config <(zcat -f "${OLDCONFIG}" )

  if [[ -d "$CONFIGDIR" ]] ; then
    VERSIONSTRING=$(basename $(realpath $(pwd)))
    TARGET="$CONFIGDIR/${VERSIONSTRING}_$(date --iso=minutes)"
    cp .config "$TARGET"
    ln -f -rs "$TARGET" "$CONFIGDIR/latest"
  fi

  emerge --getbinpkg=n --usepkg=n @module-rebuild
fi

cd "${LWD}" || exit 1