#!/bin/bash

set -eu

# working path
wp=$(dirname $0)
wp=$(readlink -f ${wp})

# config
config=${wp}/cluster.list

# return 1 if string argument is natural number 0 otherwise
function is_natural_number ()
{
    case "$1" in
        ''|*[!0-9]*) return 1 ;;
        *)           return 0 ;;
    esac
}

# return 1 if string argument is number and 0 otherwise
function is_number ()
{
    local string="$1"
    if [[ "$string" == "" ]]; then
    return 1
    fi
    if is_natural_number $string; then
    return 0
    fi
    # first symbol from string
    local first="${string:0:1}"
    # string without first symbol
    string="${string:1:${#string}-1}"
    if [[ $first == "-" ]]; then
    if is_natural_number "$string"; then
        return 0
    fi
    fi
    return 1
}

# Usage: <input> | drop <first|last> [-]<count>
#
# if count natural, drop first lines from <input> (<last> not supported)
# if count negative, drop all except first or last <count> lines from <input>
function drop ()
{
    case $1 in
    first|last) ;;
    *)
        echo "drop: expected 'first' or 'last' as first argument. You provided '$1'"
        return 1
        ;;
    esac
    local order=$1
    if ! is_number $2; then
    echo "drop: expected number as second argument. You provided '$2'"
    return 1
    fi;
    local count=$2
    if [[ $count -eq 0 ]] ; then
    while read line; do
        echo $line
    done
    elif is_natural_number $count; then
    # drop all except $count
    case $order in
        first)
        # drop $count lines from begin
        while read line; do
            if [[ $count -eq 0 ]]; then
            echo $line
            else
            count=$((count-1))
            fi
        done
        ;;
        last)
        echo "last with natural count not supported yet"
        return 1
        ;;
    esac
    else
    # drop $count
    case $order in
        first)
        # drop all except $count lines from begin
        tail -n+$((-count+1))
        ;;
        last)
        # drop all except $count lines from end
        head -n-$((-count))
        ;;
    esac
    fi
    return 0
}

# Usage: <input> | join <delimeter>
# Combine lines from <input> and insert <delimeter> between every pair
function join ()
{
    local delimeter="$1"
    sed -e "s/^/${delimeter}\n/g" | drop first 1 | xargs
}

function config_get_column ()
{
    local column=$1
    cat ${config} | drop "first" 1 | grep -v "#" | awk "{ print \$${column} }"
}

function config_get_column_as_list ()
{
    config_get_column $1 | sort -u | join "${2-,}" | tr -d ' '
}

function print_usage ()
{
    echo "Script print machine names according to config file ${config}

Usage ${0} <platform> <cluster_number> <vm_number>

  - platform can be
        'c6' - CentOS 6.3
        'r6' - RedHat 6.3
        'u1204' - Ubuntu 12.04
    'all' - all platforms
  - cluster_number is [$(config_get_column_as_list 3)] or 'all'
  - vm_number is [$(config_get_column_as_list 2)] or 'all'
"
    if [ "${1-}" != "" ]; then
    local message="${1}"
    echo "error: ${message}"
    fi
    exit 1
}

function check_platform ()
{
    case ${platform} in
    c6|r6|u1204|all) ;;
    *) print_usage "expected 'c6', 'r6', 'u1204' or 'all' for <platform>, you provided '${platform}'";;
    esac
}

function check_number ()
{
    local column=${1}
    local actual=${2}
    local name=${3}
    local found=0
    for expected in $(config_get_column ${column} | sort -u); do
    if [[ "$expected" == "$actual" ]]; then
        found=1
        break
    fi
    done
    if [[ $found -ne 1 ]]; then
    print_usage "expected all|$(config_get_column_as_list ${column} \|) as '${3}', you provided '${2}'"
    fi
}

function check_cluster ()
{
    if [ "${cluster}" != "all" ]; then
    check_number 2 "${cluster}" "cluster_number"
    fi;
}

function check_vm ()
{
    if [ "${vm}" != "all" ]; then
    check_number 3 "${vm}" "vm_number"
    fi;
}

if [ $# -eq 0 ]; then
    print_usage
fi;

if [ $# -ne 3 ]; then
    print_usage "invalid argument count, expected 4, you provided $#"
fi;

platform=${1}
check_platform
cluster=${2}
check_cluster
vm=${3}
check_vm

awk_script='{ if ('
if [ "$platform" == "all" ]; then
    awk_script="${awk_script}1"
else
    awk_script="${awk_script}(\"$platform\" == \$1)"
fi;
awk_script="${awk_script} && "
if [ "$cluster" == "all" ]; then
    awk_script="${awk_script}1"
else
    awk_script="${awk_script}($cluster == \$2)"
fi;
awk_script="${awk_script} && "
if [ "$vm" == "all" ]; then
    awk_script="${awk_script}1"
else
    awk_script="${awk_script}($vm == \$3)"
fi;
awk_script="${awk_script}) print \$4 }"
cat ${config} | tail -n+2 | grep -v "#" | awk "${awk_script}"