rest-api: implement exercise (exercism#1431)

cmccandless · web-flow · commit 65133219da17 · 2018-08-03T15:32:01.000-04:00
* implement exercise, add to config.json

* add README
diff --git a/config.json b/config.json
@@ -1366,6 +1366,17 @@
         "strings"
       ]
     },
+    {
+      "slug": "rest-api",
+      "uuid": "2abe6eed-c7e4-4ad7-91e3-778bc5176726",
+      "core": true,
+      "unlocked_by": null,
+      "difficulty": 8,
+      "topics": [
+        "parsing",
+        "strings"
+      ]
+    },
     {
       "slug": "accumulate",
       "uuid": "e7351e8e-d3ff-4621-b818-cd55cf05bffd",
diff --git a/exercises/rest-api/README.md b/exercises/rest-api/README.md
@@ -0,0 +1,84 @@
+# 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\>\>} |
+| 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\>\>} |
+
+### 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 the appropriate command below ([why they are different](https://github.com/pytest-dev/pytest/issues/1629#issue-161422224)):
+
+- Python 2.7: `py.test rest_api_test.py`
+- Python 3.4+: `pytest rest_api_test.py`
+
+Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
+`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.
diff --git a/exercises/rest-api/example.py b/exercises/rest-api/example.py
@@ -0,0 +1,85 @@
+import json
+
+
+class RestAPI(object):
+    def __init__(self, database=None):
+        self.database = database or {'users': []}
+
+    def update(self):
+        for user in self.database['users']:
+            owed_by = user['owed_by']
+            owes = user['owes']
+            for debtor in list(owed_by.keys()):
+                if debtor in owes:
+                    diff = 0
+                    if debtor in owes:
+                        diff = owes[debtor]
+                        del owes[debtor]
+                    if debtor in owed_by:
+                        diff -= owed_by[debtor]
+                        del owed_by[debtor]
+                    if diff > 0:
+                        owes[debtor] = diff
+                    elif diff < 0:
+                        owed_by[debtor] = -diff
+            user['balance'] = sum(owed_by.values()) - sum(owes.values())
+
+    def get(self, url, payload=None):
+        if payload is not None:
+            payload = json.loads(payload)
+        if url == '/users':
+            if payload is None:
+                return json.dumps(self.database)
+            else:
+                return json.dumps({
+                    'users': [
+                        u for u in self.database['users']
+                        if u['name'] in payload['users']
+                    ]
+                })
+
+    def post(self, url, payload=None):
+        result = None
+        if payload is not None:
+            payload = json.loads(payload)
+        if url == '/add':
+            if payload is not None:
+                name = payload['user']
+                users = self.database['users']
+                user = None
+                for u in users:
+                    if u['name'] == name:
+                        user = u
+                        break
+                if user is None:
+                    new_user = {
+                        'name': name,
+                        'owes': {},
+                        'owed_by': {},
+                        'balance': 0
+                    }
+                    users.append(new_user)
+                    self.update()
+                    result = json.dumps(new_user)
+        elif url == '/iou':
+            if payload is not None:
+                lender_name = payload['lender']
+                borrower_name = payload['borrower']
+                amount = payload['amount']
+                lender = borrower = None
+                for u in self.database['users']:
+                    if u['name'] == lender_name:
+                        lender = u
+                    elif u['name'] == borrower_name:
+                        borrower = u
+                if lender is not None and borrower is not None:
+                    lender['owed_by'].setdefault(borrower_name, 0)
+                    lender['owed_by'][borrower_name] += amount
+                    borrower['owes'].setdefault(lender_name, 0)
+                    borrower['owes'][lender_name] += amount
+                    self.update()
+                    result = self.get(
+                        '/users',
+                        json.dumps({'users': [lender_name, borrower_name]})
+                    )
+        return result
diff --git a/exercises/rest-api/rest_api.py b/exercises/rest-api/rest_api.py
@@ -0,0 +1,9 @@
+class RestAPI(object):
+    def __init__(self, database=None):
+        pass
+
+    def get(self, url, payload=None):
+        pass
+
+    def post(self, url, payload=None):
+        pass
diff --git a/exercises/rest-api/rest_api_test.py b/exercises/rest-api/rest_api_test.py
