#
# Takes a given human readable time string representation
# and converts it into a number of seconds e.g. time_t
#
# Input format is XX:YYz where `XX' is a number of `z'
# units and `YY' is a number of the next lowest time units.
# note that XX or YY can be any number of digits.  Also note
# that both negative and positive values are supported for
# XX (which negates the entire number) and the sign will be
# returned by this function.
#

source ~/lib/sh/include

require fsetvar
require freturn

readable_to_time_t ()
{
        local +i strtime=$1
        local +i divset
        local +i unit
        local +i lastunit
        local +i threshold1

        local -i time
        local -i divisor
        local -i threshold
        local -i thisdivisor
        local -i dividend
        local -i remainder

        local +i pattern
        local +i majorval
        local +i minorval
        local +i unit
        local -i value

        if [[ ${strtime:0:1} == '-' ]]; then
                local -i negative
                strtime=${strtime:1}
        elif [[ ${strtime:0:1} == '+' ]]; then
                unset negative
                strtime=${strtime:1}
        fi

        pattern='^'
        pattern+='([[:digit:]]+):'
        pattern+='([[:digit:]]+)'
        pattern+='([[:alpha:]])'
        pattern+='$'
        if ! [[ $strtime =~ $pattern ]]; then
                false
                freturn ""
        fi

        majorval=${BASH_REMATCH[1]}
        minorval=${BASH_REMATCH[2]}

        # strip leading zeros, otherwise bash thinks we're
        # trying to give it an octal
        #
        majorval=${majorval#0*}
        minorval=${minorval#0*}

        unit=${BASH_REMATCH[3]}

        case $unit in
        (s) value=$((majorval + minorval));;
        (m) value=$((majorval*60 + minorval));;
        (h) value=$((majorval*60*60 + minorval*60));;
        (d) value=$((majorval*60*60*24 + minorval*60*60));;
        (M) value=$((majorval*60*60*24*30 + minorval*60*60*24));;
        (*) false; freturn ""; false; return; ;;
        esac

        [[ ${negative+unset} ]] && value=-$value

        true
        freturn $value
}
# vim:syn=sh:ft=sh