#!/bin/bash
#
# grubeditor.sh -- conveniently edit grub{test}.cfg files by automating their
# extraction with cbfstool and the user's editor of choice.
#
#  Copyright (C) 2017 Zyliwax <zyliwax@protonmail.com>
#
#    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 <http://www.gnu.org/licenses/>.
#

# Usage:
# ./grubeditor.sh [options] romimage
#
# Supported options:
#
# -h | --help: show usage help
#
# -r | --realcfg: generate grub.cfg instead of grubtest.cfg
#
# -i | --inplace: do not create a .modified romfile, instead modify the
# existing file
#
# -e | --editor /path/to/editor: open the cfg file with /path/to/editor instead
# of $EDITOR
#
# -s | --swapcfg: swap grub.cfg and grubtest.cfg, incompatible with other
# options besides -i
#
# -x | --extractcfg: extract either grub.cfg or grubtest.cfg depending on
# whether -r is set
#
# -d | --diffcfg: diff grub.cfg and grubtest.cfg, incompatible with other
# options besides -D
#
# -D | --differ [/path/to/]differ: use /path/to/differ instead of "diff", can
# be an interactive program like vimdiff

# THIS BLOCK IS EXPERIMENTAL
# Allow debugging by running DEBUG= ${0}.
[[ "x${DEBUG+set}" = 'xset' ]] && set -v
# -u kills the script if any variables are unassigned
# -e kills the script if any function returns not-zero
#set -u

# Define the list of available option in both short and long form.
shortopts="hrie:sdD:"
longopts="help,realcfg,inplace,editor:,swapcfgs,diffcfgs,differ:"

# Variables for modifying the program's operation
edit_realcfg=0
edit_inplace=0
do_swapcfgs=0
do_diffcfgs=0
# Path to cbfstool, filled by detect_architecture
# (Possible to provide explicitly and disclaim warranty?)
cbfstool=""
# Editor variables
use_editor=""
default_editor="vi"
editor_rawarg=""
# Differ variables
use_differ=""
default_differ="diff"
differ_rawarg=""
# Last but not least, the rom file itself
romfile=""

# This program works primarily from a cascade of functions. Let's define them.

get_options() {
    # Test for enhanced getopt.
    getopt --test > /dev/null
    if [[ $? -ne 4 ]]; then
        echo "Your environment lacks enhanced getopt, so you cannot run this script properly."
        exit 205
    fi

    # Parse the command line options based on the previously defined values. 
    parsedopts=$(getopt --options ${shortopts} --longoptions ${longopts} --name "${0}" -- "$@")
    if [[ $? -ne 0 ]]; then # getopt didn't approve of your arguments
        echo "Unrecognized options."
        exit 206
    fi

    # Use eval set to properly quote the arguments
    eval set -- "$parsedopts"

    # Interpret the arguments one-by-one until you run out.
    while [[ 1 ]]; do
        case "$1" in
            -h|--help)
                show_help
                # I return non-zero here just so nobody thinks we successfully edited grub.cfg
                exit 200
                ;;
            -r|--realcfg)
                edit_realcfg=1
                shift
                ;;
            -i|--inplace)
                edit_inplace=1
                shift
                ;;
            -e|--editor)
                editor_rawarg="$2" 
                shift 2
                ;;
            -s|--swapcfgs)
                do_swapcfgs=1
                shift
                ;;
            -d|--diffcfgs)
                do_diffcfgs=1
                shift
                ;;
            -D|--differ)
                differ_rawarg="$2" 
                shift 2
                ;;
            --)
                # Stop interpreting arguments magically.
                shift
                break
                ;;
            *)
                echo "Something went wrong while interpreting the arguments!"
                echo "I hit \"${1}\" and don't know what to do with it."
                exit 209
                ;;
        esac
    done
    
    # The only option remaining should be the input file. Ensure it was
    # provided before proceeding with the rest of the script and capture it if
    # it was.
    if [[ $# -ne 1 ]]; then
        echo "You have specified multiple (or no) input files, which is unsupported."
        echo "Please rerun this command with just a single filename to remove any chance for ambiguity."
        exit 210
    fi
    romfile="$1"
}

determine_architecture() {
    # The cbfstool in _util is packed only for i686, x86_64, and armv7l. This
    # procedure is necessary for this process to not fail. After this process
    # is over, the variable $cbfstool gets filled with the appropriate value
    # for use by the rest of the script.
    arch="$(uname -m)"
    case "${arch}" in
        armv7l|i686|x86_64)
            echo "Supported architecture \"${arch}\" detected. You may proceed."
            cbfstool="${0%/*}/cbfstool/${arch}/cbfstool"
            ;;
        *) 
            echo "Unsupported architecture \"${arch}\" detected! You may not proceed."
            exit 230
            ;;
    esac
}

determine_operation() {
    if [[ $do_swapcfgs -eq 1 ]]; then
        swap_configs
        exit $?
    elif [[ $do_diffcfgs -eq 1 ]]; then
        diff_configs
        exit $?
    else
        edit_config
        exit $?
    fi
}

# These functions are not part of the primary function cascade but are
# referenced within them either directly or indirectly from other helper
# functions depending on the operations requested by the user.

# External command finders.
find_differ() {
    found_differ=0

    if [[ -n "${differ_rawarg}" ]]; then
        which "${differ_rawarg}" &> /dev/null
        if [[ $? -eq 0 ]]; then
            echo "Using differ \"${differ_rawarg}\"..."
            use_differ="${differ_rawarg}"
            found_differ=1
        else
            echo "The provided \"${differ_rawarg}\" is not a valid command!"
            echo "Defaulting to ${default_differ}..."
            use_differ="${default_differ}"
        fi
    fi
    
    if [[ $found_differ -eq 1 ]]; then 
        return
    else
        echo "Defaulting to ${default_differ}..."
        use_differ="${default_differ}"
    fi
}

find_editor() {
    found_editor=0

    if [[ -n "${editor_rawarg}" ]]; then
        which "${editor_rawarg}" &> /dev/null
        if [[ $? -eq 0 ]]; then
            echo "Using editor \"${editor_rawarg}\"..."
            use_editor="${editor_rawarg}"
            found_editor=1
        else
            echo "The provided \"${editor_rawarg}\" is not a valid command!"
            echo "Defaulting to ${default_editor}..."
            use_editor="${default_editor}"
        fi
    fi
    
    if [[ $found_editor -eq 1 ]]; then 
        return
    else
        if [[ -n "${EDITOR}" ]]; then
            which "${EDITOR}" &> /dev/null
            if [[ $? -ne 0 ]]; then
                echo "Your \$EDITOR is defined as ${EDITOR}, but is not a valid command!"
                echo "(This is bad. I highly suggest fixing this in your ~/.bashrc.)"
                echo "Defaulting to ${default_editor}..."
                use_editor="${default_editor}"
            else
                echo "Using your defined \$EDITOR \"$EDITOR\"..."
                use_editor="${EDITOR}"
            fi
        else
            echo "\$EDITOR blank, defaulting to ${default_editor}..."
            use_editor="${default_editor}"
        fi
    fi
}

# Filename randomizer.
random_filer() {
    # Inputs:
    # $1 is a descriptive label for the file
    # $2 is directory (becomes /tmp if not set)
    [[ -n "${1}" ]] && label="${1}" || label="tempfile"
    [[ -n "${2}" ]] && savedir="${2%/}" || savedir="/tmp"

    # Hardcoded string size for multiple good reasons (no processing weird
    # input, prevent malicious overflows, etc.)
    size=5

    # Loop forever until a free filename is found.
    while [[ 1 ]]; do

        # Read data from /dev/urandom and convert into random ASCII strings.
        rand=$(cat /dev/urandom | tr -dc 'a-zA-Z' | fold -w $size | head -n 1)

        # Build a complete filename with a hardcoded extension.
        possible="${savedir}/${label}_${rand}.tmp.cfg"

        # See if file doesn't exist and return it as string or keep going.
        if [[ ! -f "${possible}" ]]; then
            echo "${possible}" 
            break
        fi

    done
}

# Primary command functions.
show_help() {
    cat << HELPSCREEN
"${0}" -- conveniently edit grub{test}.cfg files in Libreboot ROM image files by automating their extraction with cbfstool and the user's editor of choice.

Usage:

"${0}" [OPTIONS] [ROMFILE]

Options:

-h | --help: show usage help

-r | --realcfg: generate grub.cfg instead of grubtest.cfg

-i | --inplace: do not create a .modified romfile, instead modify the
existing file

-e | --editor [/path/to/]editor: open the cfg file with /path/to/editor instead of the value of \$EDITOR

-s | --swapcfg: swap grub.cfg and grubtest.cfg

-d | --diffcfg: diff grub.cfg and grubtest.cfg

-D | --differ [/path/to/]differ: use /path/to/differ instead of "diff", can be an interactive program like vimdiff
HELPSCREEN
}

swap_configs() {
    # Procedure:
    # 1. Call cbfstool twice, once each to extract grub.cfg and grubtest.cfg.
    # 2. If --inplace not specified, copy ${romfile} to ${romfile}.modified and
    # implement remaining steps on this copy. Otherwise, implement remaining
    # steps on ${romfile}.
    # 3. Call cbfstool twice, once each to delete grub.cfg and grubtest.cfg
    # from romfile.
    # 4. Call cbfstool twice, once to embed grubtest.cfg as grub.cfg into
    # romfile and again to embed grub.cfg as grubtest.cfg into romfile.
    # 5. Delete the extracted grub.cfg and grubtest.cfg files.
    # 6. You're done!

    # Extract config files from provided romfile.
    real2test="$(random_filer "real2test")"
    test2real="$(random_filer "test2real")"
    "${cbfstool}" "${romfile}" extract -n grub.cfg -f "${real2test}"
    "${cbfstool}" "${romfile}" extract -n grubtest.cfg -f "${test2real}"

    # Determine whether to edit inplace or make a copy.
    if [[ $edit_inplace -eq 1 ]]; then
        outfile="${romfile}"
    else
        cp "${romfile}" "${romfile}.modified"
        outfile="${romfile}.modified"
    fi

    # Remove config files from the output file.
    "${cbfstool}" "${outfile}" remove -n grub.cfg
    "${cbfstool}" "${outfile}" remove -n grubtest.cfg

    # Embed new configs into the output file.
    "${cbfstool}" ${outfile} add -t raw -n grub.cfg -f "${test2real}"
    "${cbfstool}" ${outfile} add -t raw -n grubtest.cfg -f "${real2test}"
    
    # Delete the tempfiles.
    rm "${test2real}" "${real2test}"
}

diff_configs() {
    # Procedure:
    # 1. Call cbfstool twice, once to extract grub.cfg and grubtest.cfg.
    # 2. Execute ${use_differ} grub.cfg grubtest.cfg #.
    # 3. Delete the extracted grub.cfg and grubtest.cfg files.
    # 4. You're done!

    # Determine the differ command to use.
    find_differ

    # Extract config files from provided romfile.
    "${cbfstool}" "${romfile}" extract -n grub.cfg -f /tmp/grub_tmpdiff.cfg
    "${cbfstool}" "${romfile}" extract -n grubtest.cfg -f /tmp/grubtest_tmpdiff.cfg

    # Run the differ command with real as first option, test as second option.
    "${use_differ}" /tmp/grub_tmpdiff.cfg /tmp/grubtest_tmpdiff.cfg
}

edit_config() {
    # Procedure:
    # 1. If --realcfg specified, set ${thisconfig} to "grub.cfg". Otherwise,
    # set ${thisconfig} to "grubtest.cfg".
    # 2. Call cbfstool once to extract ${thisconfig} from ${romfile}.
    # 3. Run ${use_editor} ${thisconfig}.
    # 4. If ${use_editor} returns zero, proceed with update procedure:
    # 5. Call cbfstool once to extract ${thisconfig} from ${romfile}.
    # 6. Quietly diff the extracted file with the edited file. If diff returns
    # zero, take no action: warn the user that the files were the same, delete
    # both files, then skip the remaining steps (you're done)! Otherwise, the
    # files are different and you must continue with the update procedure.
    # 7. If --inplace not specified, copy ${romfile} to ${romfile}.modified and
    # implement remaining steps on this copy. Otherwise, implement remaining
    # steps on ${romfile}.
    # 8. Call cbfstool once to delete internal pre-update ${thisconfig} from
    # the rom file.
    # 9. Call cbfstool once to embed the updated ${thisconfig} that was just
    # edited into the rom file.
    # 10. Alert the user of success (either explicitly or by not saying
    # anything, either way return zero).
    # 11. You're done!

    # Determine the editor command to use.
    find_editor

    # Determine whether we are editing the real config or the test config.
    if [[ $edit_realcfg -eq 1 ]]; then
        thisconfig="grub.cfg"
    else
        thisconfig="grubtest.cfg"
    fi

    # Extract the desired configuration file from the romfile.
    tmp_editme="$(random_filer "${thisconfig%.cfg}")"
    "${cbfstool}" "${romfile}" extract -n "${thisconfig}" -f "${tmp_editme}"

    # Launch the editor!
    "${use_editor}" "${tmp_editme}"

    # Did the user commit the edit?
    if [[ $? -eq 0 ]]; then
        # See if it actually changed from what exists in the cbfs.
        tmp_refcfg="/tmp/${thisconfig%.cfg}_ref.cfg"
        "${cbfstool}" "${romfile}" extract -n "${thisconfig}" -f "${tmp_refcfg}"
        # Diff the files as quietly as possible.
        diff -q "${tmp_editme}" "${tmp_refcfg}" &> /dev/null
        if [[ $? -ne 0 ]]; then
            # The files differ, so it won't be frivolous to update the config.
            # See if the user wants to edit the file in place.
            # (This code should really be genericized and placed in a function
            # to avoid repetition.)
            if [[ $edit_inplace -eq 1 ]]; then
                outfile="${romfile}"
            else
                cp "${romfile}" "${romfile}.modified"
                outfile="${romfile}.modified"
            fi
            # Remove the old config, add in the new one.
            "${cbfstool}" "${outfile}" remove -n "${thisconfig}"
            "${cbfstool}" "${outfile}" add -t raw -n "${thisconfig}" -f "${tmp_editme}"
        else
            echo "No changes to config file. Not updating the ROM image."
        fi
        # We are done with the config files. Delete them.
        rm "${tmp_editme}"
        rm "${tmp_refcfg}"
    fi
}

# Run through the primary function cascade.
get_options $@
determine_architecture
determine_operation