#!/usr/bin/env ksh

#
# This script lets you recursively diff the CVS directories you have
# checked out.  To use, just pass in an optional revision levels and
# an optional file directory name.  This script then will show you the
# differences you're interested in.
#
#                                             -- Paul Serice
#

CVSMGDIFF_VERSION=1.1

: ${MGDIFF:=@PREFIX@/bin/mgdiff}
: ${TMP:=/tmp}

function usage {
    if [ $# -ne 1 ] ; then
        echo "progname: Error: Invalid args for usage: \"$@\"" >&2
        exit 1
    fi
    cmd=
    cmd="$cmd echo >&2 ;"
    cmd="$cmd echo \"Usage: $progname [-h] [-v]"
    cmd="$cmd [-g <gui>] [[-r <rev1>] [-r <rev2>]] file\" >&$1 ;"
    cmd="$cmd echo >&2"
    eval "$cmd"
    if [ $1 -eq 1 ] ; then
        exit 0
    fi
    exit 1
}

function verify_exec {
    if [ $# -ne 1 ] ; then
        echo "$progname: Error: Invalid args for verify_exec: \"$@\"" >&2
        exit 1
    fi
    if ! type "$1" >/dev/null 2>&1 ; then
        echo "$progname: Error: Unable to find executable for \"$1\"." >&2
        exit 1
    fi
}

tmp_base="cvsmgdiff-$$."
function clean_up {
    # These signal handlers are rough.  It is, as far as I can tell,
    # impossible to pass in the name of the currently active temporary
    # files.  A reasonable alternative is to scan $TMP for files that
    # match the pattern we use being careful not to allow a malicious
    # user to trick us into deleting some other file.
    find "$TMP" -maxdepth 1 \
                -type f \
                -links 1 \
                -uid `id -u` \
                -name "$tmp_base"'*' \
                -print0 \
    | xargs -r0 rm -f
    exit 0
}

#
# getunique() -- Finds two unique temporary file names.
#
getunique()
{
    old_umask=`umask`
    umask 077
    if ! tmp_file_1=$(mktemp -q "$TMP/${tmp_base}XXXXXX") ; then
        echo "Error: Unable to allocate a necessary temporary file." >&2
        exit 1
    fi
    
    if ! tmp_file_2=$(mktemp -q "$TMP/${tmp_base}XXXXXX") ; then
        echo "Error: Unable to allocate a necessary temporary file." >&2
        exit 1
    fi
    umask $old_umask
}

#
# Script Starts Here !!!
#

progname="cvsmgdiff.sh"
verify_exec "basename"
progname=`basename $0`

# Signal Trap handler to clean up temporary files in "$TMP".
if ! trap 'clean_up' HUP INT QUIT TERM ; then
    echo "$progname: Unable to register signal handler." >&2
    exit 1
fi

# Get cvs revision(s) to use.
cnt=0
while getopts "g:hr:v" OPT ; do
    case "$OPT" in
        g)  MGDIFF="$OPTARG"
            ;;
        h)  usage 1
            ;;
        r)  rev[$cnt]="-r$OPTARG"
            cnt=`expr $cnt + 1`
            ;;
        v)  echo "$progname: ${CVSMGDIFF_VERSION}"
            exit 0
            ;;
        \?) usage 2
            ;;
    esac
done
shift `expr $OPTIND - 1`

verify_exec "cut"
verify_exec "cvs"
verify_exec "echo"
verify_exec "expr"
verify_exec "find"
verify_exec "grep"
verify_exec "$MGDIFF"
verify_exec "mktemp"
verify_exec "sleep"
verify_exec "xargs"

mgdiff_basename=`basename "$MGDIFF"`

# Portability issues.
if [ "$mgdiff_basename" = "mgdiff" ] ; then
    QUIET_OPT="-quit"
    FNAME_OPT="-file"
elif [ "$mgdiff_basename" = "xdiff" ] ; then
    QUIET_OPT="-D"
    FNAME_OPT="-N"
elif [ "$mgdiff_basename" = "xxdiff" ] ; then
    QUIET_OPT="-D"
    FNAME_OPT="-N"
    TITLE_1_OPT="--title1"
    TITLE_2_OPT="--title2"
fi

if [ $cnt -gt 2 ] ; then
    echo
    echo "Error: Too many revisions."
    echo
    exit 1
fi

if [ ! -d `pwd`"/CVS" ] && [ ! -d `pwd`"/$1/CVS" ] ; then
    echo
    echo "Warning: \"$1\" does not appear to be a CVS directory." 1>&2
    echo "Trying to diff \"$1\" with CVS repository anyway."
    echo
    sleep 5
fi

# Run CVS recursively on the entire directory.
cvs diff "${rev[@]}" "$@" 2>/dev/null \
| grep '^Index:' \
| cut -d ' ' -f 2 \
| while read fname ; do

      echo -n "Processing $fname . . . "

      # tkdiff CVS access built-in.
      if [ "$mgdiff_basename" = "tkdiff" ] ; then

          "$MGDIFF" ${rev[0]+"${rev[@]}"} "$fname"

      # The others require a little bit of scripting.
      elif [ $cnt -eq 2 ] ; then

          getunique

          \cvs update -p "${rev[0]}" "$fname" > "$tmp_file_1" 2> /dev/null
          \cvs update -p "${rev[1]}" "$fname" > "$tmp_file_2" 2> /dev/null

          "$MGDIFF" ${QUIET_OPT+"$QUIET_OPT"} \
                    ${TITLE_1_OPT+"$TITLE_1_OPT" "$fname (rev ${rev[0]#-r})"} \
                    ${TITLE_2_OPT+"$TITLE_2_OPT" "$fname (rev ${rev[1]#-r})"} \
                    "$tmp_file_1" "$tmp_file_2"

          \rm -f "$tmp_file_1" > /dev/null 2>&1
          \rm -f "$tmp_file_2" > /dev/null 2>&1
          
      elif [ $cnt -le 1 ] ; then

         if [ $cnt -eq 1 ] ; then
             title_rev="${rev[0]#-r}"
         else
             title_rev=`cvs status "$fname" \
                        | grep 'Working revision:' \
                        | awk '{print $3;}'`
         fi
              
          # For some reason, xxdiff does not like to work with pipes
          # despite its saying otherwise.
          if [ "$TITLE_1_OPT" ] ; then

              getunique

              # The convention that "diff" uses is that the old file is on
              # the left and the new file is on the right.  We use this to
              # display the files for all but "mgdiff" which has a
              # "File->Save As..." menu option that works better the other
              # way around.
              file_first="$tmp_file_1"
              file_second="$fname"
              if [ "$mgdiff_basename" = "mgdiff" ] ; then
                  file_first="$fname"
                  file_second="$tmp_file_1"
              fi

              cvs update -p ${rev[0]+"${rev[0]}"} "$fname" \
                     > "$tmp_file_1" 2>/dev/null
              
              "$MGDIFF" ${QUIET_OPT+"$QUIET_OPT"} \
                        ${TITLE_1_OPT+"$TITLE_1_OPT" "$fname (rev $title_rev)"}\
                        "$file_first" "$file_second"
              
              \rm -f "$tmp_file_1" > /dev/null 2>&1
              \rm -f "$tmp_file_2" > /dev/null 2>&1

          else

              # See comment above.
              file_first="-"
              file_second="$fname"
              if [ "$mgdiff_basename" = "mgdiff" ] ; then
                  file_first="$fname"
                  file_second="-"
              fi

              cvs update -p ${rev[0]+"${rev[0]}"} "$fname" 2>/dev/null \
              | "$MGDIFF" ${QUIET_OPT+"$QUIET_OPT"} \
                          ${FNAME_OPT+"$FNAME_OPT" "$fname (rev $title_rev)"} \
                          "$file_first" "$file_second"

          fi
          
      fi

      echo "Done."

  done