#!/bin/sh
#
# Copyright (c) 2015 Ryan Stone. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# $FreeBSD$

usage()
{
	echo "Usage: importgit <-c commit | -r c1..c2> -g /path/to/git/repo [-n]" >&2
}

error()
{
	local print_usage

	if [ "$1" = "-u" ]
	then
		shift
		print_usage=1
	else
		print_usage=
	fi

	echo "$@" >&2
	if [ -n "$print_usage" ]
	then
		usage
	fi
	exit 1
}

unset git_repo range commit dry_run

while getopts ":c:g:nr:" o
do
	case "$o" in
	c)
		range="${OPTARG}~..${OPTARG}"
		;;
	g)
		git_repo=$OPTARG
		;;
	n)
		dry_run=1
		;;
	r)
		range=$OPTARG
		;;
	*)
		error -u "Unrecognized argument '-$OPTARG'"
        esac
done

shift $((OPTIND - 1))
OPTIND=1

if [ -n "$1" ]
then
	error -u "Unrecognized argument $1"
fi

if [ -z "$range" ]
then
	error -u "-c or -r argument is mandatory"
fi

if ! echo "$range" | egrep -qs '^[^.]+\.\.[^.]*$'
then
	error -u "$range is not a range of commits.  Did you mean '-c $range'?"
fi

if [ -z "$git_repo" ]
then
	error -u "-g <repo> argument is mandatory"
fi

if ! type git > /dev/null 2> /dev/null
then
	error "Install devel/git first"
fi

GIT="git -C $git_repo"

if ! $GIT rev-parse --git-dir 2> /dev/null > /dev/null
then
	error "$git_repo does not seem to be a git repo"
fi

if ! type svn > /dev/null 2> /dev/null
then
	error "Install devel/subversion first"
fi

if [ -n "$(svn status)" ]
then
	error "Working tree is not clean"
fi

if ! svn --non-interactive ls > /dev/null
then
	error "Could not communicate with svn server.  Is your ssh key loaded?"
fi

$GIT log --format=%H $range | tail -r | while read -r commit
do
	echo "Applying `$GIT show -s --oneline $commit`"

	if [ -n "$($GIT show --diff-filter=CDRTUXB $commit)" ]
	then
		error "Commit performed unsupported change (e.g. delete/rename)"
	fi

	if [ "$($GIT show -s --format=%P $commit | wc -w)" -ne 1 ]
	then
		error "Cannot import merge commits"
	fi

	$GIT diff --diff-filter=A --name-only \
	    ${commit}~..$commit | while read -r newfile
	do
		if [ -f "$newfile" ]
		then
			error "New file $newfile already exists in tree"
		fi
	done

	# The previous while loop ran in a subshell, so we have to check if it
	# exited with an error and bail out if so.
	ret=$?
	if [ "$ret" -ne 0 ]
	then
		exit $ret
	fi

	if [ -n "$dry_run" ]
	then
		continue
	fi

	$GIT show $commit | patch -p 1 -s || \
	    error "Failed to apply patch"

	$GIT diff --diff-filter=A --name-only \
	    ${commit}~..$commit | while read -r newfile
	do
		svn add --parents --depth=infinity $newfile || \
		    error "Failed to add new file"
	done

	# The previous while loop ran in a subshell, so we have to check if it
	# exited with an error and bail out if so.
	ret=$?
	if [ "$ret" -ne 0 ]
	then
		exit $ret
	fi

	$GIT show -s --format='%B' $commit | svn commit -F - || \
	    error "Failed to commit"
done