"""Illustrative cost worksheet. Inputs are assumptions, not market quotes."""
import json,math
from pathlib import Path
SCENARIOS=[
 {'name':'Modest workload','paas_infra':900,'paas_ops_hours':4,'custom_infra':600,'custom_ops_hours':16,'hourly_cost':80,'migration_cost':6000},
 {'name':'Scaled workload','paas_infra':6500,'paas_ops_hours':6,'custom_infra':3100,'custom_ops_hours':24,'hourly_cost':80,'migration_cost':24000},
 {'name':'More operations','paas_infra':6500,'paas_ops_hours':6,'custom_infra':3100,'custom_ops_hours':36,'hourly_cost':80,'migration_cost':24000},
]
def evaluate(s):
 p=s['paas_infra']+s['paas_ops_hours']*s['hourly_cost']
 c=s['custom_infra']+s['custom_ops_hours']*s['hourly_cost']
 savings=p-c
 return {**s,'paas_monthly':p,'custom_monthly':c,'monthly_savings':savings,'break_even_months':round(s['migration_cost']/savings,2) if savings>0 else None,'first_nonnegative_month':math.ceil(s['migration_cost']/savings) if savings>0 else None,'net_at_12_months':12*savings-s['migration_cost'],'net_by_month':[m*savings-s['migration_cost'] for m in range(25)]}
def run():
 rows=[evaluate(s) for s in SCENARIOS]
 assert [(r['paas_monthly'],r['custom_monthly'],r['monthly_savings']) for r in rows]==[(1220,1880,-660),(6980,5020,1960),(6980,5980,1000)]
 assert [r['net_at_12_months'] for r in rows]==[-13920,-480,-12000]
 assert [r['first_nonnegative_month'] for r in rows]==[None,13,24]
 assert rows[1]['net_by_month'][12]<0 and rows[1]['net_by_month'][13]>0
 return {'currency':'USD','scope':'Assumed constant monthly inputs; no vendor pricing, tax, discounting or measured customer data','scenarios':rows}
if __name__=='__main__':
 output=run();assert output==run()
 Path(__file__).with_name('results.json').write_text(json.dumps(output,indent=2)+'\n')
 print([(r['name'],r['monthly_savings'],r['break_even_months'],r['net_at_12_months']) for r in output['scenarios']])