#!/bin/sh

# Copyright (C) 2014-2022 Internet Systems Consortium, Inc. ("ISC")
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

# This is kea-admin script that conducts administrative tasks on the Kea
# installation. Currently supported operations are:
#
# - database init
# - database version check
# - database version upgrade
# - lease database dump
# - lease upload to the database
# - lease database recount

# shellcheck disable=SC1091
# SC1091: Not following: ... was not specified as input (see shellcheck -x).

# shellcheck disable=SC2039
# SC2039: In POSIX sh, 'local' is undefined.

# shellcheck disable=SC2086
# SC2086: Double quote to prevent globbing and word splitting.
# Reason for disable: explicitly don't quote extra_arguments so it is
# considered multiple arguments instead of one.

# Exit with error if commands exit with non-zero and if undefined variables are
# used.
set -eu

# Shell ${variables} derived from autoconf @variables@. Some depend on others, so mind the order.
prefix="@prefix@"
export prefix
exec_prefix="@exec_prefix@"
export exec_prefix
SCRIPTS_DIR_DEFAULT="@datarootdir@/@PACKAGE@/scripts"
scripts_dir="${SCRIPTS_DIR_DEFAULT}"
VERSION="@PACKAGE_VERSION@"

assume_yes=0

# lease dump parameters
dhcp_version=0
dump_file=""
dump_qry=""

# Include the installed admin-utils.sh if available. Fallback to sources otherwise.
if test -d "@datarootdir@/@PACKAGE_NAME@"; then
    . "@datarootdir@/@PACKAGE_NAME@/scripts/admin-utils.sh"
else
    . "@abs_top_srcdir@/src/bin/admin/admin-utils.sh"
fi

# Find the installed kea-lfc if available. Fallback to sources otherwise.
if test -d "@sbindir@"; then
    kea_lfc="@sbindir@/kea-lfc"
else
    kea_lfc="@abs_top_srcdir@/src/bin/lfc/kea-lfc"
fi

# Prints out usage version.
usage() {
  printf \
'
kea-admin %s

This is a kea-admin script that conducts administrative tasks on
the Kea installation.

Usage: %s COMMAND BACKEND [parameters]

COMMAND: Currently supported operations are:

 - db-init: Initializes new database. Useful for first time installation.
 - db-version: Checks version of the existing database schema. Useful
 -             for checking database version when preparing for an upgrade.
 - db-upgrade: Upgrades your database schema.
 - lease-dump: Dumps current leases to a memfile-ready CSV file.
 - lease-upload: Uploads leases from a CSV file to the database.
 - stats-recount: Recounts lease statistics.

BACKEND - one of the supported backends: memfile|mysql|pgsql

PARAMETERS: Parameters are optional in general, but may be required
            for specific operations.
 -h or --host hostname - specifies a hostname of a database to connect to
 -P or --port port - specifies the TCP port to use for the database connection
 -u or --user name - specifies username when connecting to a database
 -p or --password [password] - specifies a password for the database connection;
                               if omitted from the command line,
                               then the user will be prompted for a password
 -n or --name database - specifies a database name to connect to
 -d or --directory - path to upgrade scripts (default: %s)
 -v or --version - print kea-admin version and quit.
 -x or --extra - specifies extra argument(s) to pass to the database command

 Parameters specific to lease-dump, lease-upload:
     -4 to dump IPv4 leases to file
     -6 to dump IPv6 leases to file
     -i or --input to specify the name of file from which leases will be uploaded
     -o or --output to specify the name of file to which leases will be dumped
     -y or --yes - assume yes on overwriting temporary files
' "${VERSION}" "${0}" "${SCRIPTS_DIR_DEFAULT}"
}

### Logging functions ###

# Logs message at the error level.
# Takes one parameter that is printed as is.
log_error() {
    printf "ERROR/kea-admin: %s\n" "${1}"
}

# Logs message at the warning level.
# Takes one parameter that is printed as is.
log_warning() {
    printf "WARNING/kea-admin: %s\n" "${1}"
}

# Logs message at the info level.
# Takes one parameter that is printed as is.
log_info() {
    printf "INFO/kea-admin: %s\n" "${1}"
}

### Convenience functions ###

# Checks if the value is in the list. An example usage of this function
# is to determine whether the kea-admin command belongs to the list of
# supported commands.
is_in_list() {
    local member="${1-}"  # Value to be checked
    local list="${2-}"    # Comma separated list of items
    _inlist=0             # Return value: 0 if not in list, 1 otherwise.
    if [ -z "${member}" ]; then
        log_error "missing member (need to specify a string as first param)"
    fi
    # Iterate over all items on the list and compare with the member.
    # If they match, return, otherwise log error and exit.
    for item in ${list}
    do
        if [ "${item}" = "${member}" ]; then
            _inlist=1
            return
        fi
    done
}

### Functions that implement database initialization commands

memfile_init() {
    # Useless as Kea converts CSV versions at startup.
    log_error "NOT IMPLEMENTED"
    exit 1
}

# Validates that the MySQL db_users's permissions are sufficient to
# create the schema.
mysql_can_create() {

    # Let's grab the version for possible debugging issues.  It also
    # determines basic functional access to db.
    run_command \
        mysql_execute "select @@global.version;"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql_can_create: get MySQL version failed, mysql status = ${EXIT_CODE}"
        exit 1
    fi

    # shellcheck disable=SC2153
    # SC2153: Possible misspelling: ... may not be assigned, but ... is.
    # Reason for disable: OUTPUT is assigned in run_command.
    printf "MySQL Version is: %s\n" "${OUTPUT}"

    # SQL to drop our test table and trigger
    cleanup_sql="DROP TABLE IF EXISTS kea_dummy_table; DROP PROCEDURE IF EXISTS kea_dummy_trigger;"

    # SQL to create our test table
    table_sql="CREATE TABLE kea_dummy_table(dummy INT UNSIGNED PRIMARY KEY NOT NULL);"

    # SQL to create our test trigger
    trigger_sql="\
CREATE TRIGGER kea_dummy_trigger BEFORE insert ON kea_dummy_table FOR EACH ROW\n \
BEGIN\n \
END;"

    # Let's clean up just in case.
    run_command \
        mysql_execute "$cleanup_sql"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql_can_create cannot run pre cleanup, mysql status = ${EXIT_CODE}"
        exit 1;
    fi

    # Now make the dummy table.
    perms_ok=1
    run_command \
        mysql_execute "$table_sql"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql_can_create cannot create table, check user permissions, mysql status = ${EXIT_CODE}"
        perms_ok=0;
    else
        # Now attempt to make trigger
        run_command \
            mysql_execute "$trigger_sql"
        if [ "${EXIT_CODE}" -ne 0 ]
        then
            log_error "mysql_can_create cannot trigger, check user permissions, mysql status = ${EXIT_CODE}"
            perms_ok=0;
        fi
    fi

    # Try to cleanup no matter what happened above
    run_command \
        mysql_execute "$cleanup_sql"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql_can_create cannot run post cleanup, mysql status = ${EXIT_CODE}"
        exit 1;
    fi

    if [ $perms_ok -ne 1 ]
    then
        log_error "Create failed, the user, $db_user, has insufficient privileges."
        exit 1;
    fi
}

# Initializes a new, empty MySQL database.
# It essentially calls scripts/mysql/dhcpdb_create.mysql script, with
# some extra sanity checks. It will refuse to use it if there are any
# existing tables. It's better safe than sorry.
mysql_init() {
    printf 'Checking if there is a database initialized already...\n'

    # Let's try to count the number of tables. Anything above 0 means that there
    # is some database in place. If there is anything, we abort. Note that
    # mysql may spit out connection or access errors to stderr, we ignore those.
    # We should not hide them as they may give hints to user what is wrong with
    # his setup.
    run_command \
        mysql_execute "SHOW TABLES;"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql_init table query failed, mysql status = ${EXIT_CODE}"
        exit 1
    fi

    count=$(printf '%s' "${OUTPUT}" | wc -w)
    if [ "${count}" -gt 0 ]; then
        # Let's start with a new line. mysql could have printed something out.
        printf '\n'
        log_error "Expected empty database ${db_name}. Aborting, the following tables are present:
        ${OUTPUT}"
        exit 1
    fi

    # Beginning with MySQL 8.0, the db user needs additional settings or SUPER
    # privileges to create triggers and or functions. Call mysql_can_create to find
    # out if we're good to go.  If not, it will exit.
    printf "Verifying create permissions for %s\n" "$db_user"
    mysql_can_create

    printf "Initializing database using script %s\n" $scripts_dir/mysql/dhcpdb_create.mysql
    mysql -B --host="${db_host}" --user="${db_user}" \
    --password="${db_password}" \
    "${db_name}" ${extra_arguments} < "${scripts_dir}/mysql/dhcpdb_create.mysql"

    printf "mysql returned status code %s\n" "${EXIT_CODE}"

    if [ "${EXIT_CODE}" -eq 0 ]; then
        printf "Database version reported after initialization: "
        checked_mysql_version
        printf '\n'
    fi

    exit "${EXIT_CODE}"
}

pgsql_init() {
    printf 'Checking if there is a database initialized already...\n'

    # Let's try to count the number of tables. Anything above 0 means that there
    # is some database in place. If there is anything, we abort.
    run_command \
        pgsql_execute "\d"
    if [ "${EXIT_CODE}" -ne 0 ]; then
        log_error "pgsql_init: table query failed, status code: ${EXIT_CODE}?"
        exit 1
    fi

    count=$(printf '%s' "${OUTPUT}" | wc -w)
    if [ "${count}" -gt 0 ]; then
        # Let's start with a new line. pgsql could have printed something out.
        printf '\n'
        log_error "Expected empty database ${db_name}. Aborting, the following tables are present:
        ${OUTPUT}"
        exit 2
    fi

    init_script="$scripts_dir/pgsql/dhcpdb_create.pgsql"
    printf "Initializing database using script %s\n" $init_script
    run_command \
        pgsql_execute_script $init_script
    if [ "${EXIT_CODE}" -ne 0 ]; then
        log_error "Database initialization failed, status code: ${EXIT_CODE}?"
        exit 1
    fi

    version=$(checked_pgsql_version)
    printf "Database version reported after initialization: %s\n" "$version"
    exit 0
}

### Functions that implement database version checking commands
memfile_version() {
    # @todo Implement this?
    log_error "NOT IMPLEMENTED"
    exit 1
}

### Functions used for upgrade
memfile_upgrade() {
    # Useless as Kea converts CSV versions at startup.
    log_error "NOT IMPLEMENTED"
    exit 1
}

# Upgrades existing MySQL database installation. The idea is that
# it will go over all upgrade scripts from (prefix)/share/kea/scripts/mysql
# and run them one by one. They will be named properly, so they will
# be run in order.
#
# This function prints version before and after upgrade.
mysql_upgrade() {

    printf "Database version reported before upgrade: "
    checked_mysql_version
    printf '\n'

    # Check if the scripts directory exists at all.
    if [ ! -d ${scripts_dir}/mysql ]; then
        log_error "Invalid scripts directory: ${scripts_dir}/mysql"
        exit 1
    fi

    # Check if there are any files in it
    num_files=$(find "${scripts_dir}/mysql" -name 'upgrade*.sh' -type f | wc -l)
    if [ "$num_files" -eq 0 ]; then
        log_error "No scripts in ${scripts_dir}/mysql or the directory is not readable or does not have any upgrade* scripts."
        exit 1
    fi

    # Beginning with MySQL 8.0, the db user needs additional settings or SUPER
    # privileges to create triggers and or functions. Call mysql_can_create to find
    # out if we're good to go.  If not, it will exit.
    printf "Verifying upgrade permissions for %s\n" "$db_user"
    mysql_can_create

    for script in "${scripts_dir}"/mysql/upgrade*.sh
    do
        echo "Processing $script file..."
        "${script}" --host="${db_host}" --user="${db_user}" \
        --password="${db_password}" "${db_name}" ${extra_arguments}
    done

    printf "Database version reported after upgrade: "
    checked_mysql_version
    printf '\n'
}

pgsql_upgrade() {
    version=$(checked_pgsql_version)
    printf "Database version reported before upgrade: %s\n" "$version"

    # Check if the scripts directory exists at all.
    if [ ! -d ${scripts_dir}/pgsql ]; then
        log_error "Invalid scripts directory: ${scripts_dir}/pgsql"
        exit 1
    fi

    # Check if there are any files in it
    num_files=$(find "${scripts_dir}/pgsql" -name 'upgrade*.sh' -type f | wc -l)
    if [ "$num_files" -eq 0 ]; then
        log_error "No scripts in ${scripts_dir}/pgsql or the directory is not readable or does not have any upgrade* scripts."
        exit 1
    fi

    # Postgres psql does not accept pw on command line, but can do it
    # thru an env
    export PGPASSWORD=$db_password

    for script in "${scripts_dir}"/pgsql/upgrade*.sh
    do
        echo "Processing $script file..."
        "${script}" -U "${db_user}" -h "${db_host}" \
        -d "${db_name}" ${extra_arguments}
    done

    version=$(checked_pgsql_version)
    printf "Database version reported after upgrade: %s\n" "$version"
    exit 0
}

# Remove a file if it exists
remove_file () {
    local file="${1}"
    if [ -e "${file}" ]
    then
        log_info "Removing file ${file}..."
        rm -f "${file}"
    fi
}

# Utility function which tests if the given file exists and
# if so notifies the user and provides them the opportunity
# to abort the current command.
check_file_overwrite () {
    local file="${1}"
    if [ $assume_yes -eq 1 ]
    then
        remove_file "${file}"
    elif [ -e "${file}" ]
    then
        echo "Output file, $file, exists and will be overwritten."
        echo "Do you wish to continue? (y/N)"

        # Ask for an answer only on an interactive shell to prevent blocking in
        # automated or non-interactive scenarios where the answer defaults to no.
        if test -t 0; then
            read -r ans
        else
            log_warning 'Non-interactive tty detected. Assuming no.'
            ans='N'
        fi

        if [ "${ans}" != "y" ]
        then
            echo "$command aborted by user."
            exit 1
        fi
    fi
}

### Functions used for dump

# Sets the global variable, dump_qry, to the schema-version specific
# SQL text needed to dump the lease data for the current backend
# and protocol
get_dump_query() {
    local version="${1}"

    case ${backend} in
    mysql)
        invoke="call"
        ;;
    pgsql)
        invoke="select * from"
        ;;
    *)
        log_error "unsupported backend ${backend}"
        usage
        exit 1
        ;;
    esac

    dump_qry="${invoke} lease${dhcp_version}DumpHeader();${invoke} lease${dhcp_version}DumpData();";
}

memfile_dump() {
    log_error "lease-dump is not supported for memfile"
    exit 1
}

mysql_dump() {

    # Check the lease type was given
    if [ ${dhcp_version} -eq 0 ]; then
        log_error "lease-dump: lease type ( -4 or -6 ) needs to be specified"
        usage
        exit 1
    fi

    # get the correct dump query
    run_command \
        mysql_version
    version="${OUTPUT}"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "lease-dump: mysql_version failed, exit code ${EXIT_CODE}"
        exit 1
    fi

    # Fetch the correct SQL text. Note this function will exit
    # if it fails.
    get_dump_query "$version"

    # Make sure they specified a file
    if [ "$dump_file" = "" ]; then
        log_error "you must specify an output file for lease-dump"
        usage
        exit 1

    fi

    # If output file exists, notify user, allow them a chance to bail
    check_file_overwrite "$dump_file"

    # Check the temp file too
    tmp_file="/tmp/$(basename "${dump_file}").tmp"
    check_file_overwrite $tmp_file

    # Run the sql to output tab-delimited lease data to a temp file.
    # By using a temp file we can check for MySQL errors before using
    # 'tr' to translate tabs to commas.  We do not use MySQL's output
    # to file as that requires linux superuser privileges to execute
    # the select.
    if ! mysql_execute "${dump_qry}" > $tmp_file; then
        log_error "lease-dump: mysql_execute failed, exit code ${EXIT_CODE}"
        exit 1
    fi

    # Now translate tabs to commas.
    if ! tr '\t' ',' < "${tmp_file}" > "${dump_file}"; then
        log_error "lease-dump: reformatting failed";
        exit 1
    fi

    # Clean up the temporary file.
    rm -f "${tmp_file}"
    log_info "Removed temporary file ${tmp_file}."

    log_info "Successfully dumped lease${dhcp_version} to ${dump_file}."
    exit 0
}

### Functions used for dump
pgsql_dump() {
    # Check the lease type was given
    if [ ${dhcp_version} -eq 0 ]; then
        log_error "lease-dump: lease type ( -4 or -6 ) needs to be specified"
        usage
        exit 1
    fi

    version=$(pgsql_version)
    get_dump_query "$version"

    # Make sure they specified a file
    if [ "$dump_file" = "" ]; then
        log_error "you must specify an output file for lease-dump"
        usage
        exit 1

    fi

    # If output file exists, notify user, allow them a chance to bail
    check_file_overwrite "$dump_file"

    # psql does not accept password as a parameter but will look in the environment
    export PGPASSWORD=$db_password

    # Call psql and redirect output to the dump file. We don't use psql "to csv"
    # as it can only be run as db superuser. Check for errors.
    if ! (
        echo "${dump_qry}" | \
            psql --set ON_ERROR_STOP=1 -t -h "${db_host}" -q --user="${db_user}" \
            --dbname="${db_name}" -w --no-align --field-separator=',' \
            ${extra_arguments} > "${dump_file}"
    ); then
        log_error "lease-dump: psql call failed, exit code: ${?}"
        exit 1
    fi

    echo lease${dhcp_version} successfully dumped to "${dump_file}"
    exit 0
}

######################## functions used in lease-upload ########################

# Finds the position of a column by name, starting with 1.
get_column_position() {
    local column_name="${1}"; shift

    # Look only in the header, count the number of commas up to the column.
    position=$(head -n 1 "${input_file}" | grep -Eo ",|${column_name}" | uniq -c | \
        head -n 1 | grep ',' | tr -s ' ' | cut -d ' ' -f 2)

    if test -z "${position}"; then
        # If no commas, that means position 1.
        printf '1'
    else
        # Else increment, so that it starts at 1.
        printf '%s' "$((position + 1))"
    fi
}

# Adds quotes around values at given positions starting with 1 in a CSV line.
stringify_positions_in_line() {
    local positions="${1}"; shift
    local line="${1}"; shift

    i=1
    output=
    for p in ${positions}; do
        # Get everything up to position p.
        if test "${i}" -lt "${p}"; then
            up_until_p=$(printf '%s' "${line}" | cut -d ',' -f "${i}-$((p - 1))")
        else
            up_until_p=''
        fi

        # Get value at position p.
        p_word=$(printf '%s' "${line}" | cut -d ',' -f "${p}")

        # Add comma unless we're doing the first append.
        if test "${i}" != 1; then
            output="${output},"
        fi

        # Append everything up to position p.
        output="${output}${up_until_p}"

        # Add comma if we're not stringifying position 1 and if there is
        # anything up to position p. In the second case, the comma was already
        # added at a previous step.
        if test "${p}" != 1 && test -n "${up_until_p}"; then
            output="${output},"
        fi

        # Add value at position p.
        output="${output}'${p_word}'"

        # Skip position p when getting the values between positions next time.
        i=$((p + 1))
    done

    # The last position might be somewhere in the middle, so add everything
    # until the end.
    the_rest=$(printf '%s' "${line}" | cut -d ',' -f ${i}-)

    # Add comma unless we're adding the whole line or nothing.
    if test "${i}" != 1 && test -n "${the_rest}"; then
        output="${output},"
    fi

    # Append.
    output="${output}${the_rest}"

    # Print back to the caller.
    printf '%s' "${output}"
}

# Entry point for the lease-upload command.
lease_upload() {
    # Check that an input file was specified.
    if test -z "${input_file-}"; then
        log_error 'you must specify an input file with -i or --input for lease-upload'
        usage
        exit 1
    fi

    # Check that the input file has at least one row of values.
    input_file_line_length=$(wc -l < "${input_file}")
    if test "${input_file_line_length}" -le 1; then
        log_error 'CSV file has no leases'
        exit 1
    fi

    # Invoke LFC on the input file.
    log_info "Looking at ${input_file_line_length} lines of CSV in ${input_file}..."
    cleaned_up_csv="/tmp/$(basename "${input_file}").tmp"
    check_file_overwrite "${cleaned_up_csv}"
    cp "${input_file}" "${cleaned_up_csv}"
    "${kea_lfc}" "-${dhcp_version}" -x "${cleaned_up_csv}" \
        -i "${cleaned_up_csv}.1" -o "${cleaned_up_csv}.output" \
        -f "${cleaned_up_csv}.completed" -p "${cleaned_up_csv}.pid" \
        -cignored-path
    cleaned_up_csv_line_length=$(wc -l < "${cleaned_up_csv}")
    log_info "Reduced to ${cleaned_up_csv_line_length} lines in ${cleaned_up_csv}."

    # Determine the columns whose values need to be stringified to avoid syntax
    # errors in the MySQL client. These are columns which are VARCHARs or need
    # to be further processed by a procedure.
    if test "${dhcp_version}" = '4'; then
        string_columns='address hwaddr client_id hostname user_context'
    elif test "${dhcp_version}" = '6'; then
        string_columns='address duid hostname hwaddr user_context'
    else
        log_error "lease-upload: lease type -4 or -6 needs to be specified"
        usage
        exit 1
    fi

    # Get positions of string columns.
    string_positions=
    for i in ${string_columns}; do
        string_positions="${string_positions} $(get_column_position "${i}")"
    done

    # Construct the SQL insert statements.
    header_parsed=false
    sql_statement='START TRANSACTION;'
    while read -r line; do
        if "${header_parsed}"; then
            line=$(stringify_positions_in_line "${string_positions}" "${line}")
            if test "${backend}" = 'mysql'; then
                sql_statement="${sql_statement} CALL lease${dhcp_version}Upload(${line}); "
            elif test "${backend}" = 'pgsql'; then
                sql_statement="${sql_statement} SELECT lease${dhcp_version}Upload(${line}); "
            else
                log_error "lease-upload not implemented for ${backend}"
                exit 1
            fi
        else
            header_parsed=true
        fi
    done < "${cleaned_up_csv}"
    sql_statement="${sql_statement} COMMIT;"

    # Execute the SQL insert statements.
    if test "${backend}" = 'mysql'; then
        output="$(mysql_execute "${sql_statement}")"
    elif test "${backend}" = 'pgsql'; then
        output="$(pgsql_execute "${sql_statement}")"
    else
        log_error "lease-upload not implemented for ${backend}"
        exit 1
    fi

    # Clean up the temporary CSV.
    rm -f "${cleaned_up_csv}"
    log_info "Removed temporary file ${cleaned_up_csv}."

    # Print a confirmation message.
    log_info "Successfully updated table lease${dhcp_version}."
}

### Functions used for recounting statistics
mysql_recount() {
    printf "Recount lease statistics from database\n"

    run_command \
        mysql_execute "$_RECOUNT4_QUERY"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql failed to recount IPv4 leases, mysql status = ${EXIT_CODE}"
        exit 1
    fi

    run_command \
        mysql_execute "$_RECOUNT6_QUERY"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "mysql failed to recount IPv6 leases, mysql status = ${EXIT_CODE}"
        exit 1
    fi
}

pgsql_recount() {
    printf "Recount lease statistics from database\n"

    run_command \
        pgsql_execute "$_RECOUNT4_QUERY"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "pgsql failed to recount IPv4 leases, pgsql status = ${EXIT_CODE}"
        exit 1
    fi

    run_command \
        pgsql_execute "$_RECOUNT6_QUERY"
    if [ "${EXIT_CODE}" -ne 0 ]
    then
        log_error "pgsql failed to recount IPv6 leases, pgsql status = ${EXIT_CODE}"
        exit 1
    fi
}

### Script starts here ###

# First, find what the command is
command=${1-}
if [ -z "${command}" ]; then
    log_error "missing command"
    usage
    exit 1
fi

# Check if this is a simple question about version.
if test "${command}" = "-v" || test "${command}" = "--version" ; then
    echo "${VERSION}"
    exit 0
fi

is_in_list "${command}" "db-init db-version db-upgrade lease-dump lease-upload stats-recount"
if [ "${_inlist}" -eq 0 ]; then
    log_error "invalid command: ${command}"
    usage
    exit 1
fi
shift

# Second, check what's the backend
backend=${1-}
if [ -z "${backend}" ]; then
    log_error "missing backend"
    usage
    exit 1
fi
is_in_list "${backend}" "memfile mysql pgsql"
if [ "${_inlist}" -eq 0 ]; then
    log_error "invalid backend: ${backend}"
    exit 1
fi
shift

# Ok, let's process parameters (if there are any)
while test "${#}" -gt 0
do
    option=${1}
    case ${option} in
        # Specify database host
        -h|--host)
            shift
            db_host=${1-}
            if [ -z "${db_host}" ]; then
                log_error "-h or --host requires a parameter"
                usage
                exit 1
            fi
            ;;
        # Specify database port
        -P|--port)
            shift
            if test -z "${1+x}"; then
                log_error '-P or --port requires a parameter'
                usage
                exit 1
            fi
            db_port=${1}
            export db_port_full_parameter="--port=${db_port}"
            ;;
        # Specify database user
        -u|--user)
            shift
            db_user=${1-}
            if [ -z "${db_user}" ]; then
                log_error "-u or --user requires a parameter"
                usage
                exit 1
            fi
            ;;
        # Specify database password
        -p|--password)
            password_parameter_passed=true
            # If there is at least one more parameter following...
            if test "${#}" -gt 1; then
                # Then take it as password.
                shift
                db_password=${1}
            else
                # If it's an interactive shell...
                if test -t 0; then
                    # Read from standard input while hiding feedback to the terminal.
                    printf 'Password: '
                    stty -echo
                    read -r db_password
                    stty echo
                    printf '\n'
                else
                    log_warning 'Non-interactive tty detected. Assuming empty password.'
                    db_password=''
                fi
            fi
            ;;
        # Specify database name
        -n|--name)
            shift
            db_name=${1-}
            if [ -z "${db_name}" ]; then
                log_error "-n or --name requires a parameter"
                usage
                exit 1
            fi
            ;;
        -d|--directory)
            shift
            scripts_dir=${1-}
            if [ -z "${scripts_dir}" ]; then
                log_error "-d or --directory requires a parameter"
                usage
                exit 1
            fi
            ;;
        # specify DHCPv4 lease type
        -4)
            if [ ${dhcp_version} -eq 6 ]; then
                log_error "you may not specify both -4 and -6"
                usage
                exit 1
            fi
            dhcp_version=4
            ;;
        # specify DHCPv6 lease type
        -6)
            if [ ${dhcp_version} -eq 4 ]; then
                log_error "you may not specify both -4 and -6"
                usage
                exit 1
            fi
            dhcp_version=6
            ;;
        # specify input file, used by lease-upload
        -i|--input)
            shift
            input_file=${1-}
            if [ -z "${input_file}" ]; then
                log_error '-i or --input requires a parameter'
                usage
                exit 1
            fi
            ;;
        # specify output file, currently only used by lease dump
        -o|--output)
            shift
            dump_file=${1-}
            if [ -z "${dump_file}" ]; then
                log_error "-o or --output requires a parameter"
                usage
                exit 1
            fi
            ;;
        # specify extra arguments to pass to the database command
        -x|--extra)
            shift
            if [ -z "${1-}" ]; then
                log_error "-x or --extra requires a parameter"
                usage
                exit 1
            fi
            if [ -z "${extra_arguments}" ]; then
                extra_arguments=${1}
            else
                extra_arguments="${extra_arguments} ${1}"
            fi
            ;;
        -y|--yes)
            assume_yes=1
            ;;
        *)
            log_error "invalid option: ${option}"
            usage
            exit 1
    esac
    shift
done

# After all the parameters have been parsed, check environment variables.
if test -z "${password_parameter_passed+x}"; then
    if test -n "${KEA_ADMIN_DB_PASSWORD+x}"; then
        printf 'Using the value of KEA_ADMIN_DB_PASSWORD for authentication...\n'
        db_password="${KEA_ADMIN_DB_PASSWORD}"
    fi
fi

case ${command} in
    # Initialize the database
    db-init)
        case ${backend} in
            memfile)
                memfile_init
                ;;
            mysql)
                mysql_init
                ;;
            pgsql)
                pgsql_init
                ;;
            esac
        ;;
    db-version)
        case ${backend} in
            memfile)
                memfile_version
                ;;
            mysql)
                checked_mysql_version
                printf '\n'
                ;;
            pgsql)
                checked_pgsql_version
                ;;
            esac
        ;;
    db-upgrade)
        case ${backend} in
            memfile)
                memfile_upgrade
                ;;
            mysql)
                mysql_upgrade
                ;;
            pgsql)
                pgsql_upgrade
                ;;
            esac
        ;;
    lease-dump)
        case ${backend} in
            memfile)
                memfile_dump
                ;;
            mysql)
                mysql_dump
                ;;
            pgsql)
                pgsql_dump
                ;;
            esac
        ;;
    lease-upload)
        case ${backend} in
            memfile)
                log_error 'lease-upload is not supported for memfile'
                exit 1
                ;;
            mysql)
                lease_upload
                ;;
            pgsql)
                lease_upload
                ;;
            esac
        ;;
    stats-recount)
        case ${backend} in
            memfile)
                log_info "memfile does not keep lease statistics"
                ;;
            mysql)
                mysql_recount
                ;;
            pgsql)
                pgsql_recount
                ;;
            esac
        ;;
esac

exit 0