room_price_calc/app.py

import json
import os
from flask import Flask, request, jsonify
from flask_cors import CORS

_url_prefix = os.environ.get("URL_PREFIX", "room").strip("/")
_port = os.environ.get("FLASK_PORT", "5000").strip()
_debug = os.environ.get("FLASK_DEBUG", "").strip()
_here = os.path.dirname(__file__)
DEBUG = True if _debug else False
URL_PREFIX = f"/{_url_prefix}" if _url_prefix else ""
PORT = int(_port)

app = Flask(__name__)
CORS(app)

# Config
with open(os.path.join(_here, "config.json")) as f:
  CONFIG = json.load(f)
if not CONFIG or 'services' not in CONFIG or 'global' not in CONFIG:
  raise ValueError('CONFIG: Missing services or global')
SERVICES = CONFIG['services']
GLOBAL = CONFIG['global']
if not GLOBAL or 'taxes' not in GLOBAL or 'sales' not in GLOBAL['taxes']:
  raise ValueError('GLOBAL: Missing sales tax')
SALES_TAX = GLOBAL['taxes']['sales']

# Formatters
def dollar_fmt(value: float) -> str:
    return "{:.2f}".format(round(value, 2))
def title_fmt(value: str) -> str:
    return value.replace('_', ' ').title()
def details_fmt(details: dict) -> dict:
  fmt = {}
  for k, v in details.items():
    fmt[title_fmt(k)] = dollar_fmt(v)
  return fmt

# Request handlers
def _request(request) -> dict:
  _req = request.get_json(silent=True) or request.args
  _data = { 'service_key': None }
  if 'service' in _req:
    _data['service_key'] = str(_req['service']).lower().strip()
  if 'amount' in _req:
    _data['amount'] = float(_req['amount'])
  for k in [ 'service_key', 'amount' ]:
    if k not in _data or not _data[k]:
      raise ValueError(k)
  _data['service'] = SERVICES.get(_data['service_key'])
  if _data['service'] is None:
    raise ValueError('service')
  _data['details'] = {}
  return _data

def _response(**data) -> str:
  _dict = { 'service_key' : data['service_key'] }
  for k in [ 'list', 'retail', 'net' ]:
    if data.get(k) is not None:
      _dict[k] = dollar_fmt(data.get(k))
  if data.get('details') is not None:
    _dict['details'] = details_fmt(data.get('details'))
  return jsonify(_dict)

def make_handler(*transforms):
  def handler():
    try:
      data = _request(request)
    except (TypeError, ValueError):
      return jsonify({'error': 'Invalid or missing parameters'}), 400
    for transform in transforms:
      transform(data)
    return _response(**data)
  return handler

# Actual math
def _n2l(data: dict) -> None:
  svc = data['service']
  det = data['details']
  net = data['net'] if data.get('net') else data['amount']

  comm_rate = svc.get('fees', {}).get('commission', 0)
  wrong_rate = svc.get('taxes', {}).get('wrong', SALES_TAX)
  list_ = (net / (1 - comm_rate - SALES_TAX + wrong_rate))
  if 'fees' in svc and 'commission' in svc['fees']:
    det['commission'] = list_ * comm_rate
  if 'taxes' in svc and 'wrong' in svc['taxes']:
    det['wrong_tax'] = list_ * wrong_rate
    det['sales_tax'] = list_ * SALES_TAX
    det['wrong_tax_loss'] = det['sales_tax'] - det['wrong_tax']
  data['list'] = round(list_, 2)
def _l2n(data: dict) -> None:
  svc = data['service']
  det = data['details']
  net = data['list'] if data.get('list') else data['amount']
  if 'fees' in svc and 'commission' in svc['fees']:
    det['commission'] = net * svc['fees']['commission']
  if 'taxes' in svc and 'wrong' in svc['taxes']:
    det['sales_tax'] = net * SALES_TAX
    det['wrong_tax'] = net * svc['taxes']['wrong']
    det['wrong_tax_loss'] = det['sales_tax'] - det['wrong_tax']
  for k in [ 'commission', 'wrong_tax_loss' ]:
    if k in det:
      net -= det[k]
  data['net'] = round(net,2)

def _l2r(data: dict) -> None:
  svc = data['service']
  det = data['details']
  retail = data['list'] if data.get('list') else data['amount']
  if 'fees' in svc and 'client_fee' in svc['fees']:
    det['client_fee'] = retail * svc['fees']['client_fee']
    retail += det['client_fee']
  if 'taxes' in svc and 'wrong' in svc['taxes']:
    det['wrong_tax'] = retail * svc['taxes']['wrong']
    retail += det['wrong_tax']
  else:
    det['sales_tax'] = retail * SALES_TAX
    retail += det['sales_tax']
  if 'taxes' in svc and 'flat_tax' in svc['taxes']:
    det['service_tax'] = svc['taxes']['flat_tax']
    retail += det['service_tax']
  data['retail'] = round(retail, 2)
def _r2l(data: dict) -> None:
  svc = data['service']
  det = data['details']
  list_ = data['retail'] if data.get('retail') else data['amount']
  if 'taxes' in svc and 'flat_tax' in svc['taxes']:
    det['service_tax'] = svc['taxes']['flat_tax']
    list_ -= det['service_tax']
  if 'taxes' in svc and 'wrong' in svc['taxes']:
    det['wrong_tax'] = list_ - (list_ / (1 + svc['taxes']['wrong']))
    list_ -= det['wrong_tax']
  else:
    det['sales_tax'] = list_ - (list_ / (1 + SALES_TAX))
    list_ -= det['sales_tax']
  if 'fees' in svc and 'client_fee' in svc['fees']:
    det['client_fee'] = list_ - (list_ / (1 + svc['fees']['client_fee']))
    list_ -= det['client_fee']
  data['list'] = round(list_, 2)

# Routing
routes = [
  ('net_to_list',    _n2l),
  ('list_to_net',    _l2n),
  ('list_to_retail', _l2r),
  ('retail_to_list', _r2l),
  ('net_to_retail',  _n2l, _l2r),
  ('retail_to_net',  _r2l, _l2n),
]
for route_def in routes:
  endpoint, *transforms = route_def
  handler = make_handler(*transforms)
  # Flask requires unique function names
  handler.__name__ = endpoint
  app.add_url_rule(
    f"{URL_PREFIX}/{endpoint}",
    endpoint=endpoint,
    view_func=handler,
    methods=['GET', 'POST']
  )
@app.route(f"{URL_PREFIX}/services", methods=['GET'])
def list_services():
  return jsonify([
    {'key': key, 'name': cfg['name']}
    for key, cfg in SERVICES.items()
  ])

# Main app
if __name__ == '__main__':
    app.run(debug=DEBUG, port=PORT)