#!/usr/bin/env bash
# 2017-03-10: algorithm to correct for leap years in logsum program
# 2017-03-11: Converted leap_test_algorithm to leap_test_function which is called in build_epoch_list
# 2017-03-12: Replaced original work with leap_test_function code with working leap_test_function
# code and tweaked to return leaps and the corrected leap for printing.

function format_date () {
# Retruns the date format requested in $1
    case "$1" in
        as_epoch)
            date -d "$2" +%s
            ;;
        as_day)
            date -d @"$2" +%F
            ;;
        as_day_time)
            date +%F_%T
            ;;
        get_year)
            date -d @"$2" +%Y;;
    esac
return 0
}

reg_date='([0-9]{2}(([02468][048])|([13579][26]))-((02-((0[1-9])|([12][0-9])))|((0[469]|11)-((0[1-9])|([12][0-9])|30))|((0[13578]|1[02])-((0[1-9])|([12][0-9])|3[01]))))|([0-9]{4}-((02-((0[1-9])|(1[0-9])|(2[0-8])))|((0[469]|11)-((0[1-9])|([12][0-9])|30))|((0[13578]|1[02])-((0[1-9])|([12][0-9])|3[01]))))'
default_ranges="30 60 90 180 365 730 1460 1825 3650 7300"
RECENT_RANGES=( $default_ranges )
_SEC_IN_DAY=$((60 * 60 * 24))
leap_list=()

function leap_test () {
# Determines the number of leap days in a RECENT_RANGES epoch and corrects epoch accordingly.
# Returns leaps and leap_corrected_epoch.

    test_epoch="$1"
    year_test_epoch=$(format_date get_year "$test_epoch")
    year_epoch_now=$(format_date get_year "$_EPOCH_NOW")

    leaps=0
    for (( test_year="$year_epoch_now"; test_year>="$year_test_epoch"; test_year-- )); do
        if [[  "$test_year-02-29" =~ $reg_date ]]; then
            test_year_leap_day_epoch=$(format_date as_epoch "$test_year-02-29")

            if [[ "$_EPOCH_NOW" -ge "$test_year_leap_day_epoch" && "$test_epoch" -le "$test_year_leap_day_epoch" ]]; then
                let leaps leaps+=1
            fi
        fi
    done

    echo "$leaps" "$((test_epoch -  leaps * _SEC_IN_DAY))"
return 0
}

# ENTER A DATE TO CHECK BELOW
my_date="2016-02-27"
_EPOCH_NOW=$(format_date as_epoch "$my_date")
function build_epoch_list () {
# Calculate epoch_value for day-range & add to EPOCH_LIST array
for range in "${RECENT_RANGES[@]}"; do
    if_leap=( $(leap_test $((_EPOCH_NOW - range * _SEC_IN_DAY )) ) )
    leap_list+=( "${if_leap[0]}" )
    EPOCH_LIST+=( "${if_leap[1]}" )
done
return 0
}
build_epoch_list

printf "%s\n" "Current Search Start Date: $(format_date as_day "$_EPOCH_NOW")"
printf "%-10s %-9s %-10s\n" "Range" "Leaps" "Start Date"
printf "%s\n" "--------------------------------------"
for i in "${!RECENT_RANGES[@]}"; do
    printf " %-10s %-9s %-12s\n" "${RECENT_RANGES[$i]}" "${leap_list[$i]}" "$(format_date as_day "${EPOCH_LIST[$i]}")"
done
printf "%s\n\n\n" "--------------------------------------"