#!/bin/sh

set -euo pipefail

if [ $# -ne 1 ]; then
    printf 'usage: %s <path/to/VintagestoryLib.dll>\n' "$(basename "$0")" 1>&2
    exit 1
fi

einfo() {
    printf ' \033[32;1m*\033[m %s\n' "$1"
}

eerror() {
    printf ' \033[31;1m*\033[m %s\n' "$1"
}

ebegin() {
    printf ' \033[32;1m*\033[m %s ...' "$1"
}

eend() {
    if [ "$1" -eq 0 ]; then
        printf '\033[1000C\033[5D\033[34;1m[ \033[32mok \033[34m]\033[m\n'
    else
        printf '\n \033[31;1m*\033[m %s\033[1000C\033[5D\033[34;1m[ \033[31m!! \033[34m]\033[m\n' "$2"
    fi
    return "$1"
}

if [ -r "$1.bak" -a ! -r "$1" ]; then
    einfo "Seems like the script broke last time you ran it :("
    ebegin "Restoring the backup file to its original location"
    if ! mv -n "$1.bak" "$1"; then
        eend 1 "Couldn't move the file"
    fi
    eend 0
fi

if [ -e "$1.bak" ]; then
    eerror 'Backed-up file already exists, it seems likely you already ran the'
    eerror 'patcher? If not (or you really want to run it again, which may'
    eerror 'break things), please rename the file:'
    eerror "  $1.bak"
    eerror 'to something else.'
    exit 1
fi

if [ ! -r "$1" ]; then
    eerror "File $1 does not exist or is not a regular readable file"
    exit 1
fi

mv "$1" "$1.bak"
ORIGINAL="$1.bak"
TARGET="$1"

extract-original-rsa() {
    xxd -ps -c 0 "$1" | grep -Eo '3c00520053004100.{1628}6c00750065003e00' | head -n1 | sed -E 's/([a-z0-9]{2})00/\1/g' | xxd -r -p
}

a2utf16() {
    sed -E 's/([A-Za-z0-9]{2})/\100/g'
}

ebegin 'Extracting original RSA key'
ORIGINAL_RSA="$(extract-original-rsa "$ORIGINAL")"
NEW_RSA='<RSAKeyValue><Modulus>s9/kwnOq8bfUr8NfN7LN6y+e+crm+Ik2qkYqTt8LZ23j1o7LnBtIjWPRehEXguPn9tqNZ/XrBKGRtrUqBP3FpiqI9/7EfKvBUO+H3Q0imdnL8eYF70CGQInx2HQCAEDPiLPphmsEXxjLWVbVNbdrPz2GNMm63mX2SNq9VcT9AZNpmmpOR1YOTHZ4SVnZbNqZ2Y0P6b3g3yR/cm6lxJxHYKCGtC+nmBWWaHhUMn87bNXhPHu4MPuPNn147dS6iEJKEECJLjXKmXc71J4BD1giw/TmYPkkIM+Y509M/1/RNDSIEn4pw4WWBvtg2MXzPyGvimzuCjvJUX4ljap239F2pw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>'

if [ "$(printf '%s' "$ORIGINAL_RSA" | wc -c)" -ne "$(printf '%s' "$NEW_RSA" | wc -c)" ]; then
    eend 1 'Original and new RSA keys are not the same length'
fi
eend 0

ebegin 'Checking server domains'
ORIGINAL_DOMAIN='auth3.vintagestory.at'
NEW_DOMAIN='vsauth.xn--80andq.net'
if [ "$(printf '%s' "$ORIGINAL_DOMAIN" | wc -c)" -ne "$(printf '%s' "$NEW_DOMAIN" | wc -c)" ]; then
    eend 1 'Original and new domains are not the same length'
fi
eend 0

einfo 'Preparing patch values'
ORSA="$(printf '%s' "$ORIGINAL_RSA" | xxd -p -c 0 | a2utf16)"
NRSA="$(printf '%s' "$NEW_RSA" | xxd -p -c 0 | a2utf16)"
ODOMAIN="$(printf '%s' "$ORIGINAL_DOMAIN" | xxd -p -c 0 | a2utf16)"
NDOMAIN="$(printf '%s' "$NEW_DOMAIN" | xxd -p -c 0 | a2utf16)"

ebegin 'Patching'
if xxd -p -c 0 "$ORIGINAL" | sed "s/$ORSA/$NRSA/g;s/$ODOMAIN/$NDOMAIN/g" | xxd -r -p > "$TARGET"; then
    eend 0
else
    eend $? 'Patch failed :('
fi

ebegin 'Verifying'
if [ "$(wc -c < "$ORIGINAL")" -ne "$(wc -c < "$TARGET")" ]; then
    eend 1 'Original and patched files are not the same size'
fi
eend 0

einfo 'All done! ^w^'