[WIP] Python: rest_api

python/rest-api/.exercism/metadata.json

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+{"track":"python","exercise":"rest-api","id":"f59934ec5ea24dcfa20ccaabf4dc5f4c","url":"https://exercism.io/my/solutions/f59934ec5ea24dcfa20ccaabf4dc5f4c","handle":"DmitryKokorin","is_requester":true,"auto_approve":false}

python/rest-api/README.md

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+# Rest Api
+
+Implement a RESTful API for tracking IOUs.
+
+Four roommates have a habit of borrowing money from each other frequently, and have trouble remembering who owes whom, and how much.
+
+Your task is to implement a simple [RESTful API](https://en.wikipedia.org/wiki/Representational_state_transfer) that receives [IOU](https://en.wikipedia.org/wiki/IOU)s as POST requests, and can deliver specified summary information via GET requests.
+
+### API Specification
+
+#### User object
+```json
+{
+  "name": "Adam",
+  "owes": {
+    "Bob": 12.0,
+    "Chuck": 4.0,
+    "Dan": 9.5
+  },
+  "owed_by": {
+    "Bob": 6.5,
+    "Dan": 2.75,
+  },
+  "balance": "<(total owed by other users) - (total owed to other users)>"
+}
+```
+
+#### Methods
+
+| Description | HTTP Method | URL | Payload Format | Response w/o Payload | Response w/ Payload |
+| --- | --- | --- | --- | --- | --- |
+| List of user information | GET | /users | `{"users":["Adam","Bob"]}` | `{"users":<List of all User objects>}` | `{"users":<List of User objects for <users> (sorted by name)}` |
+| Create user | POST | /add | `{"user":<name of new user (unique)>}` | N/A | `<User object for new user>` |
+| Create IOU | POST | /iou | `{"lender":<name of lender>,"borrower":<name of borrower>,"amount":5.25}` | N/A | `{"users":<updated User objects for <lender> and <borrower> (sorted by name)>}` |
+
+### Other Resources:
+- https://restfulapi.net/
+- Example RESTful APIs
+  - [GitHub](https://developer.github.com/v3/)
+  - [Reddit](https://www.reddit.com/dev/api/)
+
+## Exception messages
+
+Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
+indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
+every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
+a message.
+
+To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
+`raise Exception`, you should write:
+
+```python
+raise Exception("Meaningful message indicating the source of the error")
+```
+
+## Running the tests
+
+To run the tests, run `pytest rest_api_test.py`
+
+Alternatively, you can tell Python to run the pytest module:
+`python -m pytest rest_api_test.py`
+
+### Common `pytest` options
+
+- `-v` : enable verbose output
+- `-x` : stop running tests on first failure
+- `--ff` : run failures from previous test before running other test cases
+
+For other options, see `python -m pytest -h`
+
+## Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the solution is in the `$EXERCISM_WORKSPACE/python/rest-api` directory.
+
+You can find your Exercism workspace by running `exercism debug` and looking for the line that starts with `Workspace`.
+
+For more detailed information about running tests, code style and linting,
+please see [Running the Tests](http://exercism.io/tracks/python/tests).
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

python/rest-api/rest_api.py

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+import json
+from enum import Enum
+from functools import wraps
+
+VALID_HTTP_METHODS = ['GET', 'POST']
+
+def register_url(url, http_method):
+    def actual_decorator(f):
+        @wraps(f)
+        def _impl(self, *f_args, **f_kwargs):
+            RestAPI._register_url(self, f, url, http_method)
+            return f(self, *f_args, **f_kwargs)
+    return actual_decorator
+
+class RestAPI:
+    def __init__(self, database=None):
+        self._rest_methods = {}
+        self._database = database if database else {}
+
+    def get(self, url, payload=None):
+        methods = self._rest_methods['GET']
+        if url in methods.keys():
+            return methods[url](payload)
+        else:
+            raise Exception('Error 404')
+
+    def post(self, url, payload=None):
+        methods = self._rest_methods['POST']
+        if url in methods.keys():
+            return methods[url](payload)
+        else:
+            raise Exception('Error 404')
+
+    def _register_url(self, f, url, http_method):
+
+        if http_method not in VALID_HTTP_METHODS:
+            raise Exception('Invalid Http method')
+
+        self._rest_methods[http_method][url] = f
+
+    @register_url('/users', 'GET')
+    def users(self, payload=None):
+        pass
+
+    @register_url('/add', 'POST')
+    def add(self, payload=None):
+        pass
+
+    @register_url('/iou', 'POST')
+    def iou(self, payload=None):
+        pass

python/rest-api/rest_api_test.py

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+import unittest
+
+from rest_api import RestAPI
+
+# Tests adapted from `problem-specifications//canonical-data.json`
+import json
+
+
+class RestApiTest(unittest.TestCase):
+    def test_no_users(self):
+        database = {"users": []}
+        api = RestAPI(database)
+
+        response = api.get("/users")
+        expected = {"users": []}
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_add_user(self):
+        database = {"users": []}
+        api = RestAPI(database)
+        payload = json.dumps({"user": "Adam"})
+        response = api.post("/add", payload)
+        expected = {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0}
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_get_single_user(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0},
+                {"name": "Bob", "owes": {}, "owed_by": {}, "balance": 0.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"users": ["Bob"]})
+        response = api.get("/users", payload)
+        expected = {
+            "users": [{"name": "Bob", "owes": {}, "owed_by": {}, "balance": 0.0}]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_both_users_have_0_balance(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0},
+                {"name": "Bob", "owes": {}, "owed_by": {}, "balance": 0.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 3.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {"Bob": 3.0}, "balance": 3.0},
+                {"name": "Bob", "owes": {"Adam": 3.0}, "owed_by": {}, "balance": -3.0},
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_borrower_has_negative_balance(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0},
+                {"name": "Bob", "owes": {"Chuck": 3.0}, "owed_by": {}, "balance": -3.0},
+                {"name": "Chuck", "owes": {}, "owed_by": {"Bob": 3.0}, "balance": 3.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 3.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {"Bob": 3.0}, "balance": 3.0},
+                {
+                    "name": "Bob",
+                    "owes": {"Adam": 3.0, "Chuck": 3.0},
+                    "owed_by": {},
+                    "balance": -6.0,
+                },
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_lender_has_negative_balance(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0},
+                {"name": "Bob", "owes": {"Chuck": 3.0}, "owed_by": {}, "balance": -3.0},
+                {"name": "Chuck", "owes": {}, "owed_by": {"Bob": 3.0}, "balance": 3.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Bob", "borrower": "Adam", "amount": 3.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {"Bob": 3.0}, "owed_by": {}, "balance": -3.0},
+                {
+                    "name": "Bob",
+                    "owes": {"Chuck": 3.0},
+                    "owed_by": {"Adam": 3.0},
+                    "balance": 0.0,
+                },
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_lender_owes_borrower(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {"Bob": 3.0}, "owed_by": {}, "balance": -3.0},
+                {"name": "Bob", "owes": {}, "owed_by": {"Adam": 3.0}, "balance": 3.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 2.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {"Bob": 1.0}, "owed_by": {}, "balance": -1.0},
+                {"name": "Bob", "owes": {}, "owed_by": {"Adam": 1.0}, "balance": 1.0},
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_lender_owes_borrower_less_than_new_loan(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {"Bob": 3.0}, "owed_by": {}, "balance": -3.0},
+                {"name": "Bob", "owes": {}, "owed_by": {"Adam": 3.0}, "balance": 3.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 4.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {"Bob": 1.0}, "balance": 1.0},
+                {"name": "Bob", "owes": {"Adam": 1.0}, "owed_by": {}, "balance": -1.0},
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+    def test_lender_owes_borrower_same_as_new_loan(self):
+        database = {
+            "users": [
+                {"name": "Adam", "owes": {"Bob": 3.0}, "owed_by": {}, "balance": -3.0},
+                {"name": "Bob", "owes": {}, "owed_by": {"Adam": 3.0}, "balance": 3.0},
+            ]
+        }
+        api = RestAPI(database)
+        payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 3.0})
+        response = api.post("/iou", payload)
+        expected = {
+            "users": [
+                {"name": "Adam", "owes": {}, "owed_by": {}, "balance": 0.0},
+                {"name": "Bob", "owes": {}, "owed_by": {}, "balance": 0.0},
+            ]
+        }
+        self.assertDictEqual(json.loads(response), expected)
+
+
+if __name__ == "__main__":
+    unittest.main()