#!/bin/sh

# Run with no arguments to find out what this does.

ENCRYPTED="${1}"
WORK_AREA="${2}"

ENCRYPTION_SUFFIX=".asc"
BASENAME=`basename ${ENCRYPTED} ${ENCRYPTION_SUFFIX}`
THIS_ENCRYPTED=this-${BASENAME}.${ENCRYPTION_SUFFIX}
PREV_ENCRYPTED=prev-${BASENAME}.${ENCRYPTION_SUFFIX}
THIS_PLAINTEXT=this-${BASENAME}
PREV_PLAINTEXT=prev-${BASENAME}

EARLY_EXIT="no"

if [ "${ENCRYPTED}x" = "x" ]; then
  echo "ERROR: ENCRYPTED_FILE argument required"
  EARLY_EXIT="yes"
fi

if [ "${WORK_AREA}x" = "x" ]; then
  echo "ERROR: WORK_AREA argument required"
  EARLY_EXIT="yes"
fi

if [ ! -f "${ENCRYPTED}" ]; then
  echo "ERROR: '${ENCRYPTED}' must exist and be under version control"
  EARLY_EXIT="yes"
elif ! svn info "${ENCRYPTED}" > /dev/null 2>&1; then
  echo "ERROR: '${ENCRYPTED}' must be under Subversion version control"
  echo "       (no git support yet, sorry; patches welcome)"
  EARLY_EXIT="yes"
fi
# TBD: The next test in the chain should be that ENCRYPTED is,
#      in fact, encrypted with GnuPG.  Since gpg doesn't appear
#      to have a --test option for this express purpose, some
#      other gpg subcommand will have to be used instead.

if [ "${EARLY_EXIT}" = "yes" ]; then
  echo ""
  echo "Get plaintext diffs for all revisions of a GnuPG-encrypted file."
  echo "Put the diffs in a designated folder (such as a ramdisk)."
  echo ""
  echo "Usage: ${0} ENCRYPTED_FILE WORK_AREA"
  exit 1
fi

for REV in `svn log -q ${ENCRYPTED} | grep -v -- "---------" | cut -d " " -f 1 | cut -c 2-`;
do
  PREV_REV=`dc -e "${REV} 1 - p"`
  svn cat -r${REV} ${ENCRYPTED} > /${WORK_AREA}/${THIS_ENCRYPTED}
  svn cat -r${PREV_REV} ${ENCRYPTED} > /${WORK_AREA}/${PREV_ENCRYPTED}
  gpg -d /${WORK_AREA}/${THIS_ENCRYPTED} > /${WORK_AREA}/${THIS_PLAINTEXT}
  gpg -d /${WORK_AREA}/${PREV_ENCRYPTED} > /${WORK_AREA}/${PREV_PLAINTEXT}
  diff -u /${WORK_AREA}/${PREV_PLAINTEXT} /${WORK_AREA}/${THIS_PLAINTEXT} \
      > /${WORK_AREA}/${BASENAME}-r${REV}-diff.out
  # Clean up afterwards.
  rm /${WORK_AREA}/${THIS_ENCRYPTED} \
     /${WORK_AREA}/${THIS_PLAINTEXT} \
     /${WORK_AREA}/${PREV_ENCRYPTED} \
     /${WORK_AREA}/${PREV_PLAINTEXT}
done