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web2_projects/maze-puzzle/README.md

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+# Follower Maze Code Challenge Instructions
+
+Follower-Maze is a **client-server application** built for social networking. 
+Users follow other users, post messages, send private messages, unfollow users, and so on. 
+* Each of these actions is an _event_, created by an _event-source_ and sent to the _server_.
+* Each event is processed by the _server_.
+* The processing of the event may have follow-on effects on other _user-clients_.
+
+The **server** listens for two kinds of **clients**:
+* **1 event source**, which emits events.
+* **N user-clients** that connect to the server.
+
+
+#### Client/Server Protocol
+
+* The protocol is line-based i.e. a LF control character terminates each message. 
+All strings are encoded in UTF-8.
+* Data is transmitted over TCP sockets.
+* The _event source_ connects on port 9090 and will start sending events as soon as the connection is accepted.
+* The _user clients_ connect on port 9099 and identify themselves with their user ID. 
+For example, once connected a _user client_ may send down `2932\r\n`, 
+indicating that it is representing user 2932.
+* After the identification is sent, 
+the user client starts waiting for events to be sent to them by the server.
+
+#### Events
+
+There are five possible events. 
+The table below describes payloads sent by the event source and what each represents:
+
+```
+| Payload       | Sequence # | Type          | From User Id | To User Id |
+|---------------|------------|---------------|--------------|------------|
+| 666|F|60|50   | 666        | Follow        | 60           | 50         |
+| 1|U|12|9      | 1          | Unfollow      | 12           | 9          |
+| 542532|B      | 542532     | Broadcast     | -            | -          |
+| 43|P|32|56    | 43         | Private Msg   | 32           | 56         |
+| 634|S|32      | 634        | Status Update | 32           | -          |
+```
+
+#### Event Rules
+
+* Each message begins with a sequence number.
+* However, the event source _does not send events in any given order_. 
+In particular, sequence number has no effect on the order in which events are sent.
+* Events _may_ generate notifications for _user clients_. 
+If there is a respective target _user client_ connected, 
+the notification is routed according to the following rules:
+  * Follow: Only the `To User Id` is notified
+    * A follow event from user A to user B means that user A now follows user B.
+  * Unfollow: No clients are notified
+    * An unfollow event from user A to user B means that user A stopped following user B.
+  * Broadcast: All connected _user clients_ are notified
+  * Private Message: Only the `To User Id` is notified
+  * Status Update: All current followers of the `From User ID` are notified
+* If there are no _user clients_ connected for a user, 
+any notifications for them are currently ignored. 
+_User clients_ are notified of events _in the correct sequence-number order_, 
+regardless of the order in which the _event source_ sent them.
+
+
+

web2_projects/maze-puzzle/src/clients/product_detail_client.py

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+"""
+Interview note:
+    This is a client "stub", here for demonstration and documentation
+    purposes only.
+
+    In a real production environment, this client would send requests over
+    the network to a product detail backend service.
+
+The product detail backend service is responsible for retrieving product
+detail records from its datastore (e.g., a mysql database), and
+returning them to callers.
+"""
+class ProductDetailClient:
+
+    def lookup(product_token):
+        """
+        Given a product token, makes a blocking call to the lookup endpoint of
+        the product detail backend service,
+        and returns a corresponding product detail record, if found.
+        If no record is found, returns None.
+
+        Example result:
+
+        {"token": "AAA",
+         "description": "Red Bike",
+         "price_cents": 45000}
+        """
+        pass
+
+    def batch_lookup(product_tokens):
+        """
+        Given a list of product tokens, makes a blocking call to the
+        batch lookup endpoint of the product detail backend service,
+        and returns a map of product token to product detail record, for all
+        that are found.
+        Any records that cannot be found are ommitted from the result.
+
+        Example result:
+
+        {"AAA": {
+            "token": "AAA",
+            "description": "Red Bike",
+            "price_cents": 45000},
+         "BBB": {
+            "token": "BBB",
+            "description": "Blue Bike",
+            "price_cents": 37500}}
+        """
+        pass

web2_projects/maze-puzzle/src/clients/product_search_client.py

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+"""
+Interview note:
+    This is a client "stub", here for demonstration and documentation
+    purposes only.
+
+    In a real production environment, this client would send requests over
+    the network to a product search backend service.
+
+The product search backend service is responsible for performing lookups
+against a product search index (e.g., elasticsearch) and returning product
+tokens that are search result "hits".
+"""
+class ProductSearchClient:
+
+    def search_for_all_in_price_range(lower_cents, upper_cents, start_record, num_records):
+        """
+        Given a price range plus pagination information,
+        returns a list of product tokens of products
+        whose price falls in the range.
+
+        The price range is inclusive - that is,
+        a given price "p" matches if:
+
+        upper_cents >= p >= lower_cents
+
+        If no products have prices in the price range,
+        returns an empty list.
+
+        Product tokens are ordered by price, from lowest to highest.
+
+        Out of the total list of possible product tokens,
+        only the "page" of product tokens starting at the list position
+        start_record, and ending at start_record+num_records, are returned.
+
+        If start_record+num_records is greater than the number of actual
+        result records, the resulting list size will be (accordingly)
+        smaller than num_records.
+
+        Example result:
+
+        ["AAA",
+         "BBB"]
+        """
+        pass

web2_projects/maze-puzzle/src/service.py

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+import re
+
+TOKEN_REGEX = re.compile("^[0-9A-F-]+$")
+
+class Service:
+    def __init__(self, product_detail_client, product_search_client):
+        self.product_detail_client = product_detail_client
+        self.product_search_client = product_search_client
+
+    def lookup(self, product_token):
+        """
+        Given a valid product token,
+        lookup product detail information from the product detail backend service.
+
+        - Results in Bad Request if the token is invalid
+        - Results in Not Found if the product is unknown to the backend service
+        """
+        if not TOKEN_REGEX.match(product_token):
+            return {"status": 400}
+
+        lookup_result = self.product_detail_client.lookup(product_token)
+        if lookup_result:
+            return {"status": 200, "product": lookup_result}
+        else:
+            return {"status": 404}
+
+    def search_by_price_range(self, lower_cents, upper_cents, start_record, num_records):
+        page_of_product_tokens = \
+            self.product_search_client.search_for_all_in_price_range(
+                lower_cents,
+                upper_cents,
+                start_record,
+                num_records)
+
+        product_detail_results = []
+        for product_token in page_of_product_tokens:
+            product_detail_results.append(self.lookup(product_token)["product"])
+
+        return {"status": 200, "products": product_detail_results}
+
+if __name__ == "__main__":
+    a = Service()
+    print(a.lookup('aaa'))

web2_projects/maze-puzzle/tests/service_test.py

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+import os
+import sys
+import unittest
+
+sys.path.append(os.path.join(os.path.dirname(os.path.realpath(__file__)), "../src"))
+
+from service import Service
+
+
+class ProductDetailClientTestDouble:
+    def __init__(self):
+        self.contents = {}
+
+    def lookup(self, product_token):
+        if product_token in self.contents:
+            return self.contents[product_token]
+        else:
+            return None
+
+class ProductSearchClientTestDouble:
+    def __init__(self):
+        self.search_to_results = {}
+
+    def search_for_all_in_price_range(self, lower_cents, upper_cents, start_record, num_records):
+        return self.search_to_results[(lower_cents, upper_cents, start_record, num_records)]
+
+class ServiceTest(unittest.TestCase):
+    def setUp(self):
+        self.detail_client = ProductDetailClientTestDouble()
+        self.search_client = ProductSearchClientTestDouble()
+        self.service = Service(self.detail_client, self.search_client)
+
+    def test_lookup_success(self):
+        expected_product = {
+            "token": "AAA",
+            "description": "Red Bike",
+            "price_cents": 45000
+        }
+
+        self.detail_client.contents["AAA"] = expected_product
+
+        self.assertEqual(
+            self.service.lookup("AAA"),
+            {"status": 200,
+             "product": expected_product})
+
+    def test_lookup_not_found(self):
+        self.assertEqual(
+            self.service.lookup("AAA"),
+            {"status": 404})
+
+    def test_lookup_bad_input(self):
+        self.assertEqual(
+            self.service.lookup("this-is-not-a-uuid"),
+            {"status": 400})
+
+    def test_search_price_range(self):
+        brown_bike = {
+            "token": "AAA",
+            "description": "Brown Bike",
+            "price_cents": 10000
+        }
+
+        blue_bike = {
+            "token": "BBB",
+            "description": "Blue Bike",
+            "price_cents": 37500
+        }
+
+        red_bike = {
+            "token": "CCC",
+             "description": "Red Bike",
+             "price_cents": 45000
+        }
+
+        gray_bike = {
+            "token": "DDD",
+             "description": "Gray Bike",
+             "price_cents": 99900
+        }
+
+        self.detail_client.contents["AAA"] = brown_bike
+        self.detail_client.contents["BBB"] = blue_bike
+        self.detail_client.contents["CCC"] = red_bike
+        self.detail_client.contents["DDD"] = gray_bike
+
+        self.search_client.search_to_results[(30000, 50000, 0, 10)] = ["BBB", "CCC"]
+
+        self.assertEqual(
+            self.service.search_by_price_range(30000, 50000, 0, 10),
+            {"status": 200,
+             "products": [blue_bike, red_bike]})
+
+if __name__ == '__main__':
+    unittest.main()