#!/bin/bash

# Specify text file with cron-style schedule, and commands
# Like the following example
# * * * * *     /path/to/some/command
# */15 * * * *  /path/to/another/command
# * 2,15 * * *  /path/to/yet/another/command
# Or pass text via STDIN
CRONFILE="$1"

# Use GNU `date` binary instead of default macOS one
DATE="/usr/local/Cellar/coreutils/8.26/bin/gdate"

# Path to Python; make sure the module
# `croniter` is installed using `pip install croniter`
PYTHON="/usr/local/bin/python"

BEGINDATE="2017-01-13 23:00:00"
ENDDATE="2017-01-14 03:00:00"

BEGINYEAR=$(${DATE} --date="${BEGINDATE}" +%Y)
BEGINMONTH=$(${DATE} --date="${BEGINDATE}" +%m)
BEGINDAY=$(${DATE} --date="${BEGINDATE}" +%d)
BEGINHOUR=$(${DATE} --date="${BEGINDATE}" +%H)
BEGINMINUTE=$(${DATE} --date="${BEGINDATE}" +%M)
BEGINUNIX=$(${DATE} --date="${BEGINDATE}" +%s)

ENDYEAR=$(${DATE} --date="${ENDDATE}" +%Y)
ENDMONTH=$(${DATE} --date="${ENDDATE}" +%m)
ENDDAY=$(${DATE} --date="${ENDDATE}" +%d)
ENDHOUR=$(${DATE} --date="${ENDDATE}" +%H)
ENDMINUTE=$(${DATE} --date="${ENDDATE}" +%M)
ENDUNIX=$(${DATE} --date="${ENDDATE}" +%s)

OUTPUTFILE="crons-${BEGINHOUR}-${ENDHOUR}.txt"

while read line; do

    cronminute=$(echo "${line}" | awk '{print $1}')
    cronhour=$(echo "${line}" | awk '{print $2}')
    cronday=$(echo "${line}" | awk '{print $3}')
    cronmonth=$(echo "${line}" | awk '{print $4}')
    crondow=$(echo "${line}" | awk '{print $5}')

    NEXTRUN=$(${PYTHON} -c "from croniter import croniter;from datetime import datetime;base = datetime(${BEGINYEAR}, ${BEGINMONTH}, ${BEGINDAY}, ${BEGINHOUR}, ${BEGINMINUTE});iter = croniter('${cronminute} ${cronhour} ${cronday} ${cronmonth} ${crondow}', base);print iter.get_next(datetime)")

    NEXTRUNUNIX=$(${DATE} --date="${NEXTRUN}" +%s)

    if [[ ${NEXTRUNUNIX} -ge ${BEGINUNIX} && ${NEXTRUNUNIX} -le ${ENDUNIX} ]]; then

        echo "${line}" >> "${OUTPUTFILE}"

    fi

# done < <(cat ${CRONFILE})
done < "${CRONFILE:-/dev/stdin}"