#!/bin/bash
#
# fbopt version 0.4.1
#
# Written in 2018 by Franco Masotti/frnmst <franco.masotti@live.com>
#
# To the extent possible under law, the author(s) have dedicated all 
# copyright and related and neighboring rights to this software to the public 
# domain worldwide. This software is distributed without any warranty.
#
# You should have received a copy of the CC0 Public Domain Dedication along 
# with this software. If not, see 
# <http://creativecommons.org/publicdomain/zero/1.0/>. 
#
#
# See also https://frnmst.gitlab.io/notes/my-bash-option-parsing-template.html
#

show_help()
{
    cat <<-EOF
Usage: spectrscan [OPTION] OUTFILE
An unintrusive frontend of scanimage which acts as a
paper to pdf converter suitable for texts.

If the ouput file exists then the new scanned documents will be added
as the tail of the existing one.

The default system scanner is used.

Mandatory arguments to long options are mandatory for short options too.
Options:
    -h, --help                          print this help
    -i, --imagemagick=OPTIONS           pass options to ImageMagick
                                        to post-process the documents
    --list-modes                        list all possible scan modes
    --list-resolutions                  list all possible resolutions
    --list-sources                      list all possible sources
    -m, --mode=MODE                     scan in Color, Lineart, Gray or whatever
                                        supported method
    --print-flags                       print the enabled options. This can also
                                        be used to print the default options
    -r, --resolution=RESOLUTION         page resolution in DPI
    -s, --source=SOURCE                 scan from the ADF, Flatbed or whatever
                                        supported method
    -t, --two-sided                     toggle preserve the order in
                                        double sided paper: scan a batch of
                                        papers one side, then the other
    --two-sided-reverse                 same as '--two-sided' but with the need of
                                        reversing every single paper. This
                                        option conflicts with '--two-sided'
    -u, --unpaper[=OPTIONS]             enable unpaper. You may pass
                                        options to unpaper


Exit status:
 0  if OK,
 1  if an error occurred.

This  is  free  software: you are free to change and redistribute it.  There
is NO WARRANTY, to the extent  permitted by law.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
Copyright  ©  2017  Franco Masotti.
EOF
}

# A function that prints the variable name and value of all
# the flags enabled by the user. This is useful to check that
# all the flags are correct, as kind of a dry run.
show_flags()
{

    local flags="${*}"

    for flag in ${flags}; do
            printf "%s='%s'\n" "${flag}" "${!flag}"
    done
}

getopt_error()
{
    local program_name="${0}"

    printf "%s\n" "Try '"${program_name}" --help' for more information"
} 1>&2 2>&-

main()
{
    # Create a new array from the reference of the input one.
    # See https://stackoverflow.com/questions/1063347/passing-arrays-as-parameters-in-bash
    # See some comments below.
    declare -a argc=("${!1}")

    local getopt_short_options='hi:m:r:s:tu::'
    local getopt_long_options='help,imagemagick:,list-modes,list-resolutions,list-sources,mode:,print-flags,resolution:,source:,two-sided,two-sided-reverse,unpaper::'

    # Set the default values for the flags.
    local imagemagick="${IMAGEMAGICK}"
    local mode="${MODE}"
    local resolution="${RESOLUTION}"
    local source="${SOURCE}"
    local unpaper="${UNPAPER}"
    local two_sided="${TWO_SIDED}"

    local program_name="${0}"
    opts="$(getopt \
        --name "${program_name}" \
        --shell bash \
        --options "${getopt_short_options}" \
        --longoptions "${getopt_long_options}" \
        -- \
        "${argc[@]}")"
    getopt_retval=${?}
    # Check that getopt works and that some kind of argument
    # is passed to the script. This is "quotation hell".
    a="'"${argc[@]}"'"
    { [ ${getopt_retval} -ne 0 ] || [ -z "${a}" ]; } && getopt_error && return 1
    eval set -- "${opts}"

    # Option parsing.
    while [ "${1}" != '--' ]; do
        case "${1}" in

            -h | --help )           help='true' ;;

            -i | --imagemagick )    imagemagick="${2}";
                                    shift 1 ;;

            --list-modes )          list_modes='true' ;;

            --list-sources )        list_sources='true' ;;

            --list-resolutions )    list_resolutions='true' ;;

            -m | --mode )           mode="${2}";
                                    shift 1 ;;

            --print-flags )         print_flags='true' ;;

            -r | --resolution )     resolution="${2}";
                                    shift 1 ;;

            -s | --source )         source="${2}";
                                    shift 1 ;;

            -t | --two-sided )      two_sided='true' ;;

            --two-sided-reverse )   two_sided_reverse='true' ;;

            -u | --unpaper )        unpaper="${2}";
                                    shift 1 ;;

        esac
        # Iterate through all arguments.
        shift 1
    done

    shift 1
    # Everything else after '--' is an argument.
    argc="${*}"

    # Override values of optional parameters.
    # This must be done before showing the flags.
    [ -z "${unpaper}" ] && unpaper='true'

    # Check that the flags that must be non empty are actually not empty.
    # A user might infact circumvent getopt's mechanisms like this
    # ./program -flag ''
    # This can also be done inside the option parser loop but to avoid nestings
    # I prefer it done here.
    { [ -z "${imagemagick}" ] \
        || [ -z "${mode}" ] \
        || [ -z "${resolution}" ] \
        || [ -z "${source}" ]; } \
        && getopt_error && return 1
    [ "${print_flags}" = 'true' ] \
        && show_flags \
            'imagemagick' \
            'mode' \
            'list_modes' \
            'resolution' \
            'list_resolutions' \
            'source' \
            'list_sources' \
            'two_sided' \
            'two_sided_reverse' \
            'unpaper' \
        && return 0
    [ "${help}" = 'true' ] && show_help && return 0

    # From now on you should call a function or an external program
    # using the values of the flag variables.
    [ "${two_sided}" = 'true' ] \
        && [ "${two_sided_reverse}" = 'true' ] \
        && getopt_error \
        && return 1
    [ "${list_modes}" = 'true' ] \
        && supported_params="$(get_supported_parameters)" \
        && get_supported_modes \
        && return ${?}
    [ "${list_resolutions}" = 'true' ] \
        && supported_params="$(get_supported_parameters)" \
        && get_supported_resolutions \
        && return ${?}
    [ "${list_sources}" = 'true' ] \
        && supported_params="$(get_supported_parameters)" \
        && get_supported_sources \
        && return ${?}
    # Override two_sided value if necessary.
    [ "${two_sided_reverse}" = 'true' ] && two_sided='reverse'

    local output_file="${1}"
    [ -z "${output_file}" ] && getopt_error && return 1

    preliminary_checks \
        "${imagemagick}" \
        "${mode}" \
        "${resolution}" \
        "${source}" \
        "${unpaper}" \
        "${two_sided}" \
        "${output_file}"
}

# Test dependencies and versions.
# getopt must return 4 to be fully compatible. See getopt's manual.
which bash getopt 1>/dev/null 2>/dev/null && { getopt -T; [ ${?} -eq 4 ]; }

# Get and pass argc to the main function.
# All this work with an array must be done to preserve
# quotations for arguments that have whitespaces.
# See https://lists.debian.org/debian-user/2007/12/msg01244.html
declare -a opts=()
for opt in "${@}"; do
    opts=("${opts[@]}" "${opt}")
done
main 'opts[@]'