#!/bin/sh

usage()
{
	cat <<EOF
Usage:
  $0 -o difference.zip -f from.zip -t to.zip
  $0 -f from.zip -t to.zip
EOF
	exit 1
}

output=
from=
to=
excludes=

while [ $# -gt 0 ]; do
	o=$1
	shift
	case "$o" in
		-o)
			output=$1
			shift
			;;
		-f)
			from=$1
			shift
			;;
		-t)
			to=$1
			shift
			;;
		-x)
			excludes="$excludes $1"
			shift
			;;
		*)
			usage
			;;
	esac
done

[ -n "$from" ] || usage
[ -n "$to" ] || usage

found()
{
	type=$1
	source=$2
	echo >&2 "$type: $source"
	case "$type" in
		new|changed|deleted)
			echo "$source"
			;;
		excluded)
			;;
		deleted|*)
			echo >&2 " * Sorry, can't handle deletion of $source."
			;;
	esac
}

tempdir=`mktemp -d -t zipdiff.XXXXXX`

newline="
"
fromlist="$(zipinfo -1 "$from" | grep -v /\$)"
tolist="$(zipinfo -1 "$to" | grep -v /\$)"

diffit()
{
	echo "$fromlist" | while IFS= read -r line; do
		case "$newline$tolist$newline" in
			*$newline$line$newline*)
				;;
			*)
				found deleted "$line"
				;;
		esac
	done
	echo "$tolist" | while IFS= read -r line; do
		case "$newline$fromlist$newline" in
			*$newline$line$newline*)
				# check if equal
				isexcluded=false

				for P in $excludes; do
					case "$line" in
						$P)
							found excluded "$line"
							isexcluded=true
							break
							;;
					esac
				done

				if ! $isexcluded; then
					unzip -p "$from" "$line" > "$tempdir/v1"
					unzip -p "$to" "$line" > "$tempdir/v2"
					if ! diff --brief "$tempdir/v1" "$tempdir/v2" >/dev/null 2>&1; then
						found changed "$line"
					fi
					rm "$tempdir/v1"
					rm "$tempdir/v2"
				fi
				;;
			*)
				found new "$line"
				;;
		esac
	done
}

result=`diffit`

case "$output" in
	'')
		;;
	*)
		rm -f "$output"
		echo "$result" | while IFS= read -r line; do
			echo >&2 "extracting $line..."
			dline=./$line
			mkdir -p "$tempdir/${dline%/*}"
			unzip -p "$to" "$line" > "$tempdir/$line" # this may create an empty file - don't care, DP handles this as deletion
		done
		case "$output" in
			/*)
				;;
			*)
				output=`pwd`/$output
				;;
		esac
		cd "$tempdir"
		#zip -9r "$output" .
		7za a -tzip -mx=9 "$output" .
		cd ..
		;;
esac

rm -rf "$tempdir"