SLA 영업일 계산으로 서비스 수준 계약 위반 타이머 운영하기

curl -s -H "Authorization: Bearer $NARWHAL_API_KEY" \
  "https://api.narwhalapi.com/v1/calendars/holidays/SGP/2026"

{
  "country": "SGP",
  "coverage": [
    {
      "scope": "national_public",
      "subdivision_codes": []
    }
  ],
  "holidays": [
    {
      "date": "2026-11-08",
      "name": "Deepavali",
      "holiday_key": "deepavali",
      "scope": "national_public",
      "subdivision_codes": []
    },
    {
      "date": "2026-11-09",
      "name": "Deepavali (Observed)",
      "holiday_key": "deepavali",
      "scope": "national_public",
      "subdivision_codes": [],
      "observed": true
    }
  ]
}

import json, os, urllib.request
from datetime import date, datetime, timedelta
from zoneinfo import ZoneInfo

def get(path):
    req = urllib.request.Request("https://api.narwhalapi.com" + path,
                                 headers={"Authorization": "Bearer " + os.environ["NARWHAL_API_KEY"]})
    with urllib.request.urlopen(req, timeout=30) as r:
        return json.load(r)

def holiday_dates(country, years):
    return {date.fromisoformat(h["date"]) for y in years for h in get(f"/v1/calendars/holidays/{country}/{y}")["holidays"]}

def is_working_day(d, off):
    return d.weekday() < 5 and d not in off

def due_date(opened, working_days, off):
    d, left = opened, working_days
    while left:
        d += timedelta(1)
        left -= is_working_day(d, off)
    return d

def elapsed_working_days(opened, resolved, off):
    return sum(is_working_day(opened + timedelta(n), off) for n in range(1, (resolved - opened).days + 1))

off = holiday_dates("SGP", (2026,))
sg = ZoneInfo("Asia/Singapore")

# Clock start: the ticket timestamp becomes a date in the contract's time zone.
created = datetime(2026, 11, 5, 20, 0, tzinfo=ZoneInfo("America/New_York"))
opened = created.astimezone(sg).date()
print("created", created.date(), "in New York is", opened, "in Singapore")
print("3 working days from the Singapore date:", due_date(opened, 3, off))
print("3 working days from the New York date: ", due_date(created.date(), 3, off))

# Breach test: compare the resolution date with the due date.
opened, resolved = date(2026, 2, 13), date(2026, 2, 27)
due = due_date(opened, 5, off)
late = elapsed_working_days(opened, resolved, off) - 5
print("5 working days from", opened, "is due", due, "; resolved", resolved, "so", late, "working days late")

created 2026-11-05 in New York is 2026-11-06 in Singapore
3 working days from the Singapore date: 2026-11-12
3 working days from the New York date:  2026-11-11
5 working days from 2026-02-13 is due 2026-02-24 ; resolved 2026-02-27 so 3 working days late