#!/usr/bin/env bash

# yadm - Yet Another Dotfiles Manager
# Copyright (C) 2015-2019 Tim Byrne and Martin Zuther

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.


YADM_CHECKSUMS="$YADM_HOOK_DIR/files.checksums"
WARNING_MESSAGE="No checksums were created"

# unpack exported array; filenames including a newline character (\n)
# are NOT supported
OLD_IFS="$IFS"
IFS=$'\n'
YADM_ENCRYPT_INCLUDE_FILES=( $YADM_ENCRYPT_INCLUDE_FILES )
IFS="$OLD_IFS"


function get_checksum_command {
    # check if "shasum" exists and supports the algorithm (which is
    # tested by sending an empty string to "shasum")
    if command -v "shasum" > /dev/null && echo -n | shasum --algorithm "256" &> /dev/null; then
        echo "shasum --algorithm 256"
    # check if "sha256sum" exists
    elif command -v "sha256sum" > /dev/null; then
        echo "sha256sum"
    # check if "gsha256sum" exists
    elif command -v "gsha256sum" > /dev/null; then
        echo "gsha256sum"
    else
        # display warning in bright yellow
        echo -e "\033[1;33m" >&2
        echo -n "WARNING: \"shasum\", \"sha256sum\" and \"gsha256sum\" not found.   $WARNING_MESSAGE." >&2

        # reset output color
        echo -e "\033[0m" >&2

        # signal error
        return 1
    fi
}


# get checksum command
CHECKSUM_COMMAND=$(get_checksum_command)
ERROR_CODE=$?

# no command found
if [ $ERROR_CODE -ne 0 ]; then
    # return original exit status of yadm command
    exit "$YADM_HOOK_EXIT"
fi

# empty (or create) checksum file
echo -n > "$YADM_CHECKSUMS"

# calculate checksums for encrypted files
for included in ${YADM_ENCRYPT_INCLUDE_FILES[*]}; do
    # highlight any errors in red
    echo -en "\033[0;31m"

    # calculate checksums
    $CHECKSUM_COMMAND "$included" >> "$YADM_CHECKSUMS"
    ERROR_CODE=$?

    # reset output color
    echo -ne "\033[0m"

    # handle errors
    if [ $ERROR_CODE -ne 0 ]; then
        # display warning in bright yellow
        echo -e "\033[1;33m" >&2
        echo -n "WARNING: an error occurred.  Please inspect the checksum file." >&2

        # reset output color
        echo -e "\033[0m" >&2

        # exit and signal error
        exit $ERROR_CODE
    fi
done

# announce success and return original exit status of yadm command
echo "Wrote SHA-256 checksums: $YADM_CHECKSUMS"
exit "$YADM_HOOK_EXIT"