Add Mint solution

solutions/system_design/mint/mint_mapreduce.py

+# -*- coding: utf-8 -*-
+
+from mrjob.job import MRJob
+
+
+class SpendingByCategory(MRJob):
+
+    def __init__(self, categorizer):
+        self.categorizer = categorizer
+        ...
+
+    def current_year_month(self):
+        """Return the current year and month."""
+        ...
+
+    def extract_year_month(self, timestamp):
+        """Return the year and month portions of the timestamp."""
+        ...
+
+    def handle_budget_notifications(self, key, total):
+        """Call notification API if nearing or exceeded budget."""
+        ...
+
+    def mapper(self, _, line):
+        """Parse each log line, extract and transform relevant lines.
+
+        Emit key value pairs of the form:
+
+        (2016-01, shopping), 25
+        (2016-01, shopping), 100
+        (2016-01, gas), 50
+        """
+        timestamp, seller, amount = line.split('\t')
+        period = self. extract_year_month(timestamp)
+        if period == self.current_year_month():
+            yield (period, category), amount
+
+    def reducer(self, key, value):
+        """Sum values for each key.
+
+        (2016-01, shopping), 125
+        (2016-01, gas), 50
+        """
+        total = sum(values)
+        self.handle_budget_notifications(key, total)
+        yield key, sum(values)
+
+    def steps(self):
+        """Run the map and reduce steps."""
+        return [
+            self.mr(mapper=self.mapper,
+                    reducer=self.reducer)
+        ]
+
+
+if __name__ == '__main__':
+    SpendingByCategory.run()

solutions/system_design/mint/mint_snippets.py

+# -*- coding: utf-8 -*-
+
+class DefaultCategories(Enum):
+
+    HOUSING = 0
+    FOOD = 1
+    GAS = 2
+    SHOPPING = 3
+    ...
+
+seller_category_map = {}
+seller_category_map['Exxon'] = DefaultCategories.GAS
+seller_category_map['Target'] = DefaultCategories.SHOPPING
+
+
+class Categorizer(object):
+
+    def __init__(self, seller_category_map, seller_category_overrides_map):
+        self.seller_category_map = seller_category_map
+        self.seller_category_overrides_map = seller_category_overrides_map
+
+    def categorize(self, transaction):
+        if transaction.seller in self.seller_category_map:
+            return self.seller_category_map[transaction.seller]
+        if transaction.seller in self.seller_category_overrides_map:
+            seller_category_map[transaction.seller] = \
+                self.manual_overrides[transaction.seller].peek_min()
+            return self.seller_category_map[transaction.seller]
+        return None
+
+
+class Transaction(object):
+
+    def __init__(self, timestamp, seller, amount):
+        self.timestamp = timestamp
+        self.seller = seller
+        self.amount = amount
+
+
+class Budget(object):
+
+    def __init__(self, template_categories_to_budget_map):
+        self.categories_to_budget_map = template_categories_to_budget_map
+
+    def override_category_budget(self, category, amount):
+        self.categories_to_budget_map[category] = amount
+