#!/bin/sh
# (This file is public domain.)
# This file is part of the Eplain macro package.

help ()
{
    cat <<EOF
Usage:  trimsee [-i IS] [-o OS] [-s SEE]
        trimsee {-h|--help|-v|--version}
Remove commas (or other page list separators) in front
of see / see also commands in the output of MakeIndex.
Input is read from stdin, output is directed to stdout.

-i IS           use IS as a regular expression matching separator
                in front of see / see also commands in the input
                (default: '$DEFAULT_IS')
-o OS           use OS as a separator to replace IS in front of
                see / see also commands (default: '$DEFAULT_OS')
-s SEE          use SEE as a regular expression matching see /
                see also commands (default: '$DEFAULT_SEE')
-h, --help      show this help message
-v, --version   show version
EOF
}

check_missing_arg ()
{
    if test "$1" -lt 2; then
        echo "Missing argument to option '$2'" 1>&2
        exit 1
    fi
}

VERSION='0.1'

DEFAULT_SEE='\\indexsee'
DEFAULT_IS=', \+'
DEFAULT_OS=' '

SEE=$DEFAULT_SEE
IS=$DEFAULT_IS
OS=$DEFAULT_OS

while [ $# != 0 ]
do
  case "$1" in
      -i)
          check_missing_arg $# "$1"
          IS=$2
          shift
          ;;
      -o)
          check_missing_arg $# "$1"
          OS=$2
          shift
          ;;
      -s)
          check_missing_arg $# "$1"
          SEE=$2
          shift
          ;;
      -h | --help)
          help
          exit 0
          ;;
      -v | --version)
          echo "trimsee version $VERSION"
          exit 0
          ;;
      *)
          echo "Unknown option '$1'" 1>&2
          exit 1
          ;;
  esac
  shift
done


# The idea is to implement line output delayed by one line.  When we
# read next line, we check if it starts with a see/see also entry, and
# if it does, we remove the comma at the end of the previous line
# before printing it.  We keep previous lines in the hold buffer.

sed -n '

# Remove all commas in front of see/see also inside each line.
s/'"$IS$SEE/$OS$SEE"'/g

# If this line does not start with see/see also, we will print the
# previous line intact.  NOTE:  There are two characters inside the
# brackets:  a space and a tab.
/^[ 	]*'"$SEE"'/! { x; b PRINT; }

# This line starts with see/see also, so remove comma at the end of
# the previous line before we print it.
x
s/'"$IS"'$/'"$OS"'/

# Print the previous line.
:PRINT
1! p

# At the end of the input, print the last line.
$ { x; p; }

'