#!/bin/bash

# relative to ./patch/
PATCHFILE="cx231xx-Add-support-for-OTG102-aka-EZGrabber2.patch"

if [ "`pwd`" = "$HOME" ]; then
 echo "error: do not run this script in your home directory" >&2
 exit 1
fi

# set up directory structure
mkdir -p rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS} tmp

# target kernel version; this is used instead of `uname -r`
# If this script is successful, the target version is saved to tmp/UNAME_R,
# which is read by ./build and ./install
UNAME_R_FILE="tmp/UNAME_R"
UNAME_R="`rpm -q kernel --last | head -n1 | sed -e 's/^kernel-//g' -e 's/\s.*//g'`"

# remove $UNAME_R_FILE for now so that ./build and ./install will fail
rm -f "$UNAME_R_FILE"

# set up rpmbuild
rm -rf rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS}  # keep SRPMS
mkdir -p rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS}

# check to see if the source for the latest installed kernel is available
yumdownloader --urls --source kernel  # run once so the user can see repo download progress
PKGNAME="kernel-`egrep -o '^.*\.fc[0-9]+' <<< "$UNAME_R"`"
URLBASENAME="$(basename "`yumdownloader --urls --source "$PKGNAME" | tail -n1`")"
SRPMBASENAME="$(sed "s/\\.`uname -m`$//" <<< "$URLBASENAME")"
if [ "$URLBASENAME" != "$SRPMBASENAME" ]; then
 echo "error: you do not have the latest kernel installed.  Please fix that first." >&2
 exit 1
fi

# download kernel SRPM if necessary and prepare the source tree
SRPM="rpmbuild/SRPMS/$SRPMBASENAME"
TOPDIR="`pwd`/rpmbuild"
if [ ! -e "$SRPM" ]; then
 # use a tmp directory first so that existing partial downloads will be ignored/overwritten
 yumdownloader --destdir=tmp --source "$PKGNAME"
 mv tmp/"$SRPMBASENAME" "$SRPM"
fi
sudo yum-builddep "$SRPM"
rpm --define "_topdir $TOPDIR" -Uvh "$SRPM"
cd rpmbuild/SPECS
rpmbuild --define "_topdir $TOPDIR" -bp --target=`uname -m` kernel.spec
cd ../BUILD/kernel-`egrep -o '^[0-9]+\.[0-9]+' <<< "$UNAME_R"`.`egrep -o 'fc[0-9]+' <<< "$UNAME_R"`
cd linux-"$UNAME_R"

# apply the patch and configure the kernel
patch -p1 -F1 -s < ../../../../patch/"$PATCHFILE"
R=$?
if [ $R -ne 0 ]; then
 echo "error: problem applying patch" >&2
 exit $R
fi
cp -a /boot/config-"$UNAME_R" .config
cp -a /lib/modules/"$UNAME_R"/build/Module.symvers .
sed -i.bak -r "s/^EXTRAVERSION ?= ?$/EXTRAVERSION = `grep -o -- '-.*$' <<< "$UNAME_R"`/" Makefile
make oldconfig
make scripts
make prepare

# write out the target version to $UNAME_R_FILE
R=$?
[ $R -eq 0 ] && echo -n "$UNAME_R" > ../../../../"$UNAME_R_FILE" || exit $R