116 lines
3.2 KiB
Python
116 lines
3.2 KiB
Python
import json
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from collections import defaultdict
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from functools import wraps
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from operator import attrgetter
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VALID_HTTP_METHODS = ['GET', 'POST']
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class User:
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def __init__(self, name):
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self.name = name
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self.owes = defaultdict(float)
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self.owed_by = defaultdict(float)
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self.balance = 0.0
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def lend(self, borrower, amount):
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total_owed = self.owed_by[borrower] - self.owes[borrower] + amount
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if total_owed > 0:
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self.owed_by[borrower] = total_owed
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self.owes.pop(borrower, None)
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elif total_owed < 0:
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self.owes[borrower] = -total_owed
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self.owed_by.pop(borrower, None)
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else:
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self.owed_by.pop(borrower, None)
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self.owes.pop(borrower, None)
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self.balance += amount
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def borrow(self, lender, amount):
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self.lend(lender, -amount)
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@classmethod
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def from_dict(cls, d):
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user = cls(d['name'])
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user.owed_by.update(d['owed_by'])
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user.owes.update(d['owes'])
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user.balance = d['balance']
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return user
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class MethodRegistry:
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def __init__(self):
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self.methods = {k: {} for k in VALID_HTTP_METHODS }
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def register_url(self, url, http_method):
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def actual_decorator(f):
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@wraps(f)
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def _wrapper(f_self, payload):
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if payload:
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payload = json.loads(payload)
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#It would be essential to validate JSON schema here
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f_result = f(f_self, payload)
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return json.dumps(f_result, default=lambda obj: obj.__dict__, sort_keys=True)
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self.methods[http_method][url] = _wrapper
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return actual_decorator
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class RestAPI:
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registry = MethodRegistry()
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def __init__(self, database=None):
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self._users = {user['name'] : User.from_dict(user) for user in database['users']} if database else {}
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def _process_request(self, method, url, payload):
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methods = self.registry.methods[method]
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#It would be natural to handle exceptions here
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if url in methods.keys():
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return methods[url](self, payload)
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def get(self, url, payload=None):
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return self._process_request('GET', url, payload)
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def post(self, url, payload=None):
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return self._process_request('POST', url, payload)
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@registry.register_url('/users', 'GET')
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def users(self, payload=None):
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if payload:
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requested_users = payload['users']
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response = [user for user in self._users.values() if user.name in requested_users]
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else:
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response = [user for user in self._users.values()]
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return {'users': response}
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@registry.register_url('/add', 'POST')
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def add(self, payload=None):
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name = payload['user']
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user = User(name)
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self._users[user.name] = user
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return user
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@registry.register_url('/iou', 'POST')
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def iou(self, payload=None):
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lender = payload['lender']
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borrower = payload['borrower']
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amount = payload['amount']
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self._users[lender].lend(borrower, amount)
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self._users[borrower].borrow(lender, amount)
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return {'users': sorted([self._users[lender], self._users[borrower]], key=attrgetter('name'))}
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