#!/bin/bash

# 2 args:
#	libxfs-apply <repo> <commit ID or patchfile>

usage()
{
	echo $*
	echo
	echo "Usage:"
	echo "	libxfs-apply [--verbose] --sob <name/email> --source <repodir> --commit <commit_id>"
	echo "	libxfs-apply --patch <patchfile>"
	echo
	echo "libxfs-apply should be run in the destination git repository."
	exit
}

cleanup()
{
	rm -f $PATCH
}

# output to stderr so it is not caught by file redirects
fail()
{
	>&2 echo "Fail:"
	>&2 echo $*
	cleanup
	exit
}

# filterdiff 0.3.4 is the first version that handles git diff metadata (almost)
# correctly. It just doesn't work properly in prior versions, so those versions
# can't be used to extract the commit message prior to the diff. Hence just
# abort and tell the user to upgrade if an old version is detected. We need to
# check against x.y.z version numbers here.
_version=`filterdiff --version | cut -d " " -f 5`
_major=`echo $_version | cut -d "." -f 1`
_minor=`echo $_version | cut -d "." -f 2`
_patch=`echo $_version | cut -d "." -f 3`
if [ $_major -eq 0 ]; then
	if [ $_minor -lt 3 ]; then
		fail "filterdiff $_version found. 0.3.4 or greater is required."
	fi
	if [ $_minor -eq 3 -a $_patch -le 3 ]; then
		fail "filterdiff $_version found. 0.3.4 or greater is required."
	fi
fi

# We should see repository contents we recognise, both at the source and
# destination. Kernel repositorys will have fs/xfs/libxfs, and xfsprogs
# repositories will have libxcmd.
SOURCE="kernel"
check_repo()
{
	if [ ! -d "fs/xfs/libxfs" -a ! -d "libxcmd" ]; then
		usage "$1 repository contents not recognised!"
	fi
	if [ -d "$REPO/libxcmd" ]; then
		SOURCE="xfsprogs"
	fi
}

REPO=
PATCH=
COMMIT_ID=
VERBOSE=
GUILT=0
STGIT=0

while [ $# -gt 0 ]; do
	case "$1" in
	--source)	REPO=$2 ; shift ;;
	--patch)	PATCH=$2; shift ;;
	--commit)	COMMIT_ID=$2 ; shift ;;
	--sob)		SIGNED_OFF_BY=$2 ; shift ;;
	--verbose)	VERBOSE=true ;;
	*)		usage ;;
	esac
	shift
done

if [ -n "$PATCH" ]; then
	if [ -n "$REPO" -o -n "$COMMIT_ID" ]; then
		usage "Need to specify either patch or source repo/commit"
	fi
	VERBOSE=true
elif [ -z "$REPO" -o -z "$COMMIT_ID" ]; then
	usage "Need to specify both source repo and commit id"
fi

check_repo Destination

# Are we using guilt? This works even if no patch is applied.
guilt top &> /dev/null
if [ $? -eq 0 ]; then
	GUILT=1
fi

# Are we using stgit? This works even if no patch is applied.
stg top &> /dev/null
if [ $? -eq 0 ]; then
	STGIT=1
fi

#this is pulled from the guilt code to handle commit ids sanely.
# usage: munge_hash_range <hash range>
#
# this means:
#	<hash>			- one commit
#	<hash>..		- hash until head (excludes hash, includes head)
#	..<hash>		- until hash (includes hash)
#	<hash1>..<hash2>	- from hash to hash (inclusive)
#
# The output of this function is suitable to be passed to "git rev-list"
munge_hash_range()
{
	case "$1" in
		*..*..*|*\ *)
			# double .. or space is illegal
			return 1;;
		..*)
			# e.g., "..v0.10"
			echo ${1#..};;
		*..)
			# e.g., "v0.19.."
			echo ${1%..}..HEAD;;
		*..*)
			# e.g., "v0.19-rc1..v0.19"
			echo ${1%%..*}..${1#*..};;
		?*)
			# e.g., "v0.19"
			echo $1^..$1;;
		*)  # empty
			return 1;;
	esac
	return 0
}

# Filter the patch into the right format & files for the other tree
filter_kernel_patch()
{
	local _patch=$1
	local _libxfs_files=""

	# The files we will try to apply to
	_libxfs_files=`mktemp`
	ls -1 fs/xfs/libxfs/*.[ch] | sed -e "s%.*/\(.*\)%*\1%" > $_libxfs_files

	# Create the new patch
	# filterdiff will have screwed up files that source/sink /dev/null.
	# fix that up with some sed magic.
	filterdiff \
			--verbose \
			-I $_libxfs_files \
			--strip=1 \
			--addoldprefix=a/fs/xfs/ \
			--addnewprefix=b/fs/xfs/ \
			$_patch | \
		sed -e 's, [ab]\/fs\/xfs\/\(\/dev\/null\), \1,' \
		    -e '/^diff --git/d'


	rm -f $_libxfs_files
}

filter_xfsprogs_patch()
{
	local _patch=$1
	local _libxfs_files=""

	# The files we will try to apply to. We need to pull this from the
	# patch, as the may be libxfs files added in this patch and so we
	# need to capture them.
	_libxfs_files=`mktemp`
	#ls -1 libxfs/*.[ch] | sed -e "s%.*/\(.*\)%*libxfs/\1%" > $_libxfs_files
	lsdiff $_patch | sed -e "s%.*/\(.*\)%*libxfs/\1%" > $_libxfs_files

	# Create the new patch
	# filterdiff will have screwed up files that source/sink /dev/null.
	# fix that up with some sed magic.
	filterdiff \
			--verbose \
			-I $_libxfs_files \
			--strip=3 \
			--addoldprefix=a/ \
			--addnewprefix=b/ \
			$_patch | \
		sed -e 's, [ab]\/\(\/dev\/null\), \1,' \
		    -e '/^diff --git/d'

	rm -f $_libxfs_files
}

fixup_header_format()
{
	local _source=$1
	local _patch=$2
	local _hdr=`mktemp`
	local _diff=`mktemp`
	local _new_hdr=$_hdr.new

	# there's a bug in filterdiff that leaves a line at the end of the
	# header in the filtered git show output like:
	#
	# difflibxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
	#
	# split the header on that (convenient!)
	sed -e /^difflib/q $_patch > $_hdr
	cat $_patch | awk '
		BEGIN { difflib_seen = 0; index_seen = 0 }
		/^difflib/ { difflib_seen++; next }
		/^index/ { if (++index_seen == 1) { next } }
		// { if (difflib_seen) { print $0 } }' > $_diff

	# the header now has the format:
	# commit 0d5a75e9e23ee39cd0d8a167393dcedb4f0f47b2
	# Author: Eric Sandeen <sandeen@sandeen.net>
	# Date:   Wed Jun 1 17:38:15 2016 +1000
	# 
	#     xfs: make several functions static
	#....
	#     Signed-off-by: Dave Chinner <david@fromorbit.com>
	#
	#difflibxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
	#
	# We want to format it like a normal patch with a line to say what repo
	# and commit it was sourced from:
	#
	# xfs: make several functions static
	#
	# From: Eric Sandeen <sandeen@sandeen.net>
	#
	# Source kernel commit: 0d5a75e9e23ee39cd0d8a167393dcedb4f0f47b2
	#
	# <body>
	#
	# To do this, use sed to first strip whitespace, then pass it into awk
	# to rearrange the headers.
	sed -e 's/^ *//' $_hdr | awk -v src=$_source '
		BEGIN {
			date_seen=0
			subject_seen=0
		}
		/^commit/ {
			commit=$2
			next;
		}
		/^Author:/ {
			split($0, a, ":")
			from=a[2]
			next;
		}
		/^Date:/ { date_seen=1; next }
		/^difflib/ { next }

		// {
			if (date_seen == 0)
				next;
			if (subject_seen == 0) {
				if (length($0) != 0) {
					subject_seen=1
					subject=$0;
				}
				next;
			}
			if (subject_seen == 1) {
				print subject
				print
				print "From:" from
				print
				print "Source " src " commit: " commit
				subject_seen=2
			}
			print $0
		}' > $_hdr.new

	# Remove the last line if it contains only whitespace
	sed -i '${/^[[:space:]]*$/d;}' $_hdr.new

	# Add Signed-off-by: header if specified
	if [ ! -z ${SIGNED_OFF_BY+x} ]; then 
		echo "Signed-off-by: $SIGNED_OFF_BY" >> $_hdr.new
	else	# get it from git config if present
		SOB_NAME=`git config --get user.name`
		SOB_EMAIL=`git config --get user.email`
		if [ ! -z ${SOB_NAME+x} ]; then
			echo "Signed-off-by: $SOB_NAME <$SOB_EMAIL>" >> $_hdr.new
		fi
	fi

	# now output the new patch
	cat $_hdr.new $_diff

	rm -f $_hdr* $_diff

}

apply_patch()
{
	local _patch=$1
	local _patch_name=$2
	local _current_commit=$3
	local _new_patch=`mktemp`
	local _source="kernel"
	local _target="xfsprogs"

	# filter just the libxfs parts of the patch
	if [ $SOURCE == "xfsprogs" ]; then

		[ -n "$VERBOSE" ] || lsdiff $_patch | grep -q "[ab]/libxfs/"
		if [ $? -ne 0 ]; then
			echo "Doesn't look like an xfsprogs patch with libxfs changes"
			echo "Skipping commit $_current_commit"
			return
		fi

		filter_kernel_patch $_patch > $_new_patch
		_source="xfsprogs"
		_target="kernel"
	elif [ $SOURCE == "kernel" ]; then

		[ -n "$VERBOSE" ] || lsdiff $_patch | grep -q "[ab]/fs/xfs/libxfs/"
		if [ $? -ne 0 ]; then
			echo "Doesn't look like a kernel patch with libxfs changes"
			echo "Skipping commit $_current_commit"
			return
		fi

		filter_xfsprogs_patch $_patch > $_new_patch
	else
		fail "Unknown source repo type: $SOURCE"
	fi

	grep -q "Source $_target commit: " $_patch
	if [ "$?" -eq "0" ]; then
		echo "$_patch_name already synced up"
		echo "$_skipping commit $_current_commit"
		return
	fi

	# now munge the header to be in the correct format.
	fixup_header_format $_source $_new_patch > $_new_patch.2

	if [ -n "$VERBOSE" ]; then
		echo "Filtered patch from $REPO contains:"
		lsdiff $_new_patch.2
	fi

	# Ok, now apply with guilt or patch; either may fail and require a force
	# and/or a manual reject fixup
	if [ $GUILT -eq 1 ]; then
		[ -n "$VERBOSE" ] || echo "$REPO looks like a guilt directory."
		PATCHES=`guilt applied | wc -l`
		if [ -n "$VERBOSE" -a $PATCHES -gt 0 ]; then
			echo -n "Top patch is: "
			guilt top
		fi

		guilt import -P $_patch_name $_new_patch.2
		guilt push
		if [ $? -eq 0 ]; then
			guilt refresh
		else
			echo "Guilt push of $_current_commit $_patch_name failed!"
			read -r -p "Skip or Fail [s|F]? " response
			if [ -z "$response" -o "$response" != "s" ]; then
				echo "Force push patch, fix and refresh."
				echo "Restart from commit $_current_commit"
				fail "Manual cleanup required!"
			else
				echo "Skipping."
				guilt delete -f $_patch_name
			fi
		fi
	elif [ $STGIT -eq 1 ]; then
		[ -n "$VERBOSE" ] || echo "$REPO looks like a stgit directory."
		PATCHES=`stg series | wc -l`
		if [ -n "$VERBOSE" -a $PATCHES -gt 0 ]; then
			echo -n "Top patch is: "
			stg top
		fi

		stg import -n $_patch_name $_new_patch.2
		if [ $? -ne 0 ]; then
			echo "stgit push failed!"
			read -r -p "Skip or Fail [s|F]? " response
			if [ -z "$response" -o "$response" != "s" ]; then
				echo "Force push patch, fix and refresh."
				echo "Restart from commit $_current_commit"
				fail "Manual cleanup required!"
			else
				echo "Skipping. Manual series file cleanup needed!"
			fi
		fi
	else
		echo "Applying with patch utility:"
		patch -p1 < $_new_patch.2
		echo "Patch was applied in $REPO; check for rejects, etc"
	fi

	rm -f $_new_patch*
}

# name a guilt patch. Code is lifted from guilt import-commit.
name_patch()
{
	s=`git log --no-decorate --pretty=oneline -1 $1 | cut -c 42-`

	# Try to convert the first line of the commit message to a
	# valid patch name.
	fname=`printf %s "$s" |  \
			sed -e "s/&/and/g" -e "s/[ :]/_/g" -e "s,[/\\],-,g" \
			    -e "s/['\\[{}]//g" -e 's/]//g' -e 's/\*/-/g' \
			    -e 's/\?/-/g' -e 's/\.\.\.*/./g' -e 's/^\.//' \
			    -e 's/\.patch$//' -e 's/\.$//' | tr A-Z a-z`

	# Try harder to make it a legal commit name by
	# removing all but a few safe characters.
	fname=`echo $fname|tr -d -c _a-zA-Z0-9---/\\n`

	echo $fname
}

# single patch is easy.
if [ -z "$COMMIT_ID" ]; then
	apply_patch $PATCH
	cleanup
	exit 0
fi

# switch to source repo and get individual commit IDs
#
# git rev-list gives us a list in reverse chronological order, so we need to
# reverse that to give us the order we require.
pushd $REPO > /dev/null
check_repo Source
hashr=`munge_hash_range $COMMIT_ID`
if [ $SOURCE == "kernel" ]; then
	hashr="$hashr -- fs/xfs/libxfs"
else
	hashr="$hashr -- libxfs"
fi

# grab and echo the list of commits for confirmation
echo "Commits to apply:"
commit_list=`git rev-list $hashr | tac`
git log --oneline $hashr |tac
read -r -p "Proceed [y|N]? " response
if [ -z "$response" -o "$response" != "y" ]; then
	fail "Aborted!"
fi
popd > /dev/null

PATCH=`mktemp`
for commit in $commit_list; do

	# switch to source repo and pull commit into a patch file
	pushd $REPO > /dev/null
	git show $commit > $PATCH || usage "Bad source commit ID!"
	patch_name=`name_patch $commit`
	popd > /dev/null

	apply_patch $PATCH $patch_name $commit
done


cleanup