#!/bin/bash

USAGE="$0 file1 file2"
TMPDIR="/tmp"

TMPFILE1="$TMPDIR/inidiff.tmp.1"
TMPFILE2="$TMPDIR/inidiff.tmp.2"

SECTIONRE='^[[:space:]]*\[([^]]*)\][[:space:]]*$'
SECTIONRE2='^[[:space:]]*\[[^]]*\][[:space:]]*$'

set -e

if [ ! -f "$1" ] || [ ! -f "$2" ]; then
        echo "$USAGE" >&2
fi

echo -n > "$TMPFILE1"
echo -n > "$TMPFILE2"

cat "$1" \
        | sed -nr "s/$SECTIONRE/\1/p" \
        | sort -u \
        | while read section; do
                echo "[$section]" >> "$TMPFILE1"
                cat "$1" \
                | sed -nr "/\[$section\]/,/$SECTIONRE/p" | grep -v "$SECTIONRE2" | grep -v '^$' | sort >> "$TMPFILE1"
        done

cat "$2" \
        | sed -nr "s/$SECTIONRE/\1/p" \
        | sort -u \
        | while read section; do
                echo "[$section]" >> "$TMPFILE2"
                cat "$2" \
                | sed -nr "/\[$section\]/,/$SECTIONRE/p" | grep -v "$SECTIONRE2" | grep -v '^$' | sort >> "$TMPFILE2"
        done

diff "$TMPFILE1" "$TMPFILE2"