#!/bin/bash
#
# Look up the given filename in the description file and confirm that
# the checksum matches
#
# FIXME
# - the description file is expected to be in the current dir
# - does not handle description file entries with more than just the sha1 tag

DESCRIPTIONS='Descriptions.txt'

if [ "$1" == "--rm_on_fail" ]; then
    RM_ON_FAIL=yes
    shift
fi

FILE="$1"
if [ -z "$FILE" ]; then
    echo "Need filename" 2>&1
    exit 1
fi
shift

# The name of the Descriptions.txt entry to use
CHECKNAME="$1"
if [ -z "$CHECKNAME" ]; then
    # default to the same as the filename
    CHECKNAME="$FILE"
fi

do_exit_fail() {
    if [ "$RM_ON_FAIL" ]; then
        rm -f "$FILE"
    fi
    exit 1
}

LINE=$(egrep "^$CHECKNAME " "$DESCRIPTIONS")

if [ $? -ne 0 ]; then
    echo "Unknown file $CHECKNAME" 2>&1
    do_exit_fail
fi

if [ ! -e "$FILE" ]; then
    echo "File $FILE does not exist" 2>&1
    do_exit_fail
fi

SUM_FIELD=$(echo "$LINE" | awk -- '{print $2}')

TYPE=$(echo "$SUM_FIELD" | cut -d: -f1)
EXPECT=$(echo "$SUM_FIELD" | cut -d: -f2)

case "$TYPE" in
    sha1)
        GOT=$(sha1sum "$FILE" | cut -d" " -f1)
        ;;
    sha256)
        GOT=$(sha256sum "$FILE" | cut -d" " -f1)
        ;;
    *)
        echo "Unknown checksum type $TYPE for $CHECKNAME" 2>&1
        do_exit_fail
        ;;
esac

if [ "$EXPECT" != "$GOT" ]; then
    echo "File $FILE failed checksum check" 2>&1

    do_exit_fail
fi

exit 0