"""Reproduce SpaceTRC9.0 length/unit/light-interval calculations with stdlib only.
Usage: python reproduce-scale.py.txt scales.json
This does not recover a measured3D map or a cosmological lookback-time integral.
"""
from pathlib import Path
from decimal import Decimal, getcontext
import hashlib,json,math,sys
getcontext().prec=40
path=Path(sys.argv[1]) if len(sys.argv)>1 else Path(__file__).with_name('scales.json')
raw=path.read_bytes();d=json.loads(raw,parse_float=Decimal)
c=Decimal('299792.458');year=Decimal('31557600');au=Decimal('149597870.7')
# pi is the platform double approximation; errors are below displayed precision.
pc=au*Decimal(648000)/Decimal(str(math.pi));ly=c*year
factors={'km':Decimal(1),'au':au,'ly':ly,'pc':pc,'Mpc':pc*1000000}
print('source_sha256='+hashlib.sha256(raw).hexdigest())
print('station_id,quantity_kind,length_km,static_light_interval_s,earth_diameter_ratio')
for station in d['stations']:
 length=Decimal(str(station['sourceValue']))*factors[station['sourceUnit']]
 expected=Decimal(str(station['lengthKm']))
 assert abs(length-expected)<=length*Decimal('1e-14')
 interval='' if station['lightTimeMode']=='none' else format(length/c,'.12g')
 print(','.join([station['id'],station['kind'],format(length,'.12g'),interval,format(length/Decimal(12742),'.12g')]))