NPI check digit validator / registry query

npi

#!/usr/bin/env bash

# npi - A tool I wrote while working for Stratice Healthcare, a former company 
#       developing a software solution for DME ordering. I no longer have any 
#       need for this tool but am keeping it around for posterity. JsonQuery (jq)
#       is required for the query functionality.

# Usage:
# npi [-c <count>] [-v] [-f] [<digits>]
#     Can be run with zero, nine, or ten digits. When run with zero digits,
#     a random npi with a valid check digit is generated, with nine digits,
#     the calculated check digit is displayed, and with ten digits, the check
#     digit is validated.
#     
#     -c #  Can be used with zero digits to generate <count> NPIs. There is no
#           programmatic upper bound so, if you run with a very large number,
#           this can tie up your computer for a while.
#     -v    Attempts to verify the NPI with the the US Department of Health &
#           Human services. Required jq.
#     -f    A valid NPI starts with a 1 or a 2. This forces a check digit to 
#           be generated even if the first digit is something other than 1 or
#           2.

# Copyright (C) 2017 Joel Murphy
# All rights reserved

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

NUM_RE='^-?[0-9]+$'
NPI_RE='^[12][0-9]{8,9}$'

SUM=0
CHD=0
COUNT=1
VERIFY=0
FORCE=0
NPI=''

check_digit() {
    # Compute check digit
    SUM=0
    for (( idx=$((${#ARG}-1)); idx>=0; idx-- )); do
        DIGIT="${ARG:idx:1}"
        if [[ $((${idx}%2)) -eq 0 ]]; then
            DIGIT="$((${DIGIT}*2/10+${DIGIT}*2%10))"
        fi
        SUM="$((${SUM}+${DIGIT}))"
    done
    SUM="$((${SUM}+24))"
    CHD="$((${SUM}*9%10))"
}

process_args() {
    while [[ $# -ge 1 ]]; do
        case "${1}" in
            -c)
                if [[ ${2} =~ $NUM_RE ]]; then
                    COUNT="${2}"
                    shift 2
                else
                    echo "Invalid argument: count ${2}"
                    exit
                fi
                ;;
            -v)
                VERIFY=1
                shift 1
                ;;
            -f)
                FORCE=1
                shift 1
                ;;
            *)
                if [[ ${1} =~ ${NUM_RE} ]]; then
                    COUNT=1
                    NPI="${1}"
                else
                    echo "Invalid argument: ${1}"
                    exit
                fi
                shift 1
                ;;
        esac
    done
}

main() {
    for I in $(seq 1 ${COUNT}); do

        ARG=${NPI:-$((${RANDOM}${RANDOM}%200000000+100000000))}
        if [[ ${FORCE} -eq 0 && ! ${ARG} =~ ${NPI_RE} ]]; then
            echo "First digit must be 1 or 2"
            exit
        fi

        if [[ ${#ARG} -eq 9 ]]; then
            # Compute check digit
            check_digit

            echo "${ARG}${CHD}"

        elif [[ ${#ARG} -eq 10 ]]; then
            # Verify check digit
            T_CHD=$((${ARG}%10))
            ARG=$((${ARG}/10))

            check_digit
            if [[ CHD -eq T_CHD ]]; then
                echo -e "NPI check digit is \033[1;32mvalid\033[0m"

                if [[ VERIFY -eq 1 ]]; then
                    GET=$(curl https://npiregistry.cms.hhs.gov/api/?number=${NPI} 2>/dev/null)
                    if [[ $(echo "${GET}" | jq -r ".result_count") -ge 1 ]]; then
                        echo "${GET}" | jq -r ".results[0].basic"
                    else
                        echo "Cannot verify NPI"
                    fi
                fi
            else
                echo -e "NPI check digit is \033[1;31minvalid\033[0m, should be ${CHD}"
            fi
        fi
    done
}

process_args $@
main