From eb2f2ef13c86acf82fbe94df13a70a4857087285 Mon Sep 17 00:00:00 2001
From: Correl Roush <correl@gmail.com>
Date: Thu, 20 Jan 2022 11:57:53 -0500
Subject: [PATCH] Handle invalid material conversions

---
 elite_engineering/trade.py | 12 ++++++++++--
 pyproject.toml             |  1 +
 tests/test_trade.py        | 30 +++++++++++++++---------------
 3 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/elite_engineering/trade.py b/elite_engineering/trade.py
index 5fa3615..f7a3bf4 100644
--- a/elite_engineering/trade.py
+++ b/elite_engineering/trade.py
@@ -1,6 +1,8 @@
 import dataclasses
 import fractions
 
+from returns.maybe import Maybe, Some, Nothing
+
 materials = {
     "raw": {
         "Raw Material Category 1": ["Carbon", "Vanadium", "Niobium", "Yttrium"],
@@ -141,7 +143,9 @@ class Material:
     category: str
     grade: int
 
-    def trade_ratio(self, other: "Material") -> fractions.Fraction:
+    MAX_CAPACITY: int = 300
+
+    def trade_ratio(self, other: "Material") -> Maybe[fractions.Fraction]:
         grade_base = 3 if self.grade <= other.grade else 6
         grade_ratio = fractions.Fraction(
             grade_base ** self.grade, grade_base ** other.grade
@@ -151,4 +155,8 @@ class Material:
             if self.category == other.category
             else fractions.Fraction(6, 1)
         )
-        return grade_ratio * category_ratio
+        ratio = grade_ratio * category_ratio
+        if ratio.numerator > self.MAX_CAPACITY or ratio.denominator > self.MAX_CAPACITY:
+            return Nothing
+        else:
+            return Some(ratio)
diff --git a/pyproject.toml b/pyproject.toml
index 36909da..83a3f41 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,6 +7,7 @@ license = "MIT"
 
 [tool.poetry.dependencies]
 python = "^3.9"
+returns = "^0.18.0"
 
 [tool.poetry.dev-dependencies]
 black = "^21.12b0"
diff --git a/tests/test_trade.py b/tests/test_trade.py
index 115dbb0..4b6112e 100644
--- a/tests/test_trade.py
+++ b/tests/test_trade.py
@@ -1,6 +1,8 @@
 import fractions
 import unittest
 
+from returns.maybe import Maybe
+
 from elite_engineering import trade
 
 
@@ -8,22 +10,21 @@ class TradeCalculationTests(unittest.TestCase):
     def format_ratio(self, ratio: fractions.Fraction) -> str:
         return "{} → {}".format(ratio.numerator, ratio.denominator)
 
-    def test_same_category_exchange(self):
+    def test_same_category_exchange(self) -> None:
         expected = [
             ["1 → 1", "1 → 3", "1 → 9", "1 → 27", "1 → 81"],
             ["6 → 1", "1 → 1", "1 → 3", "1 → 9", "1 → 27"],
             ["36 → 1", "6 → 1", "1 → 1", "1 → 3", "1 → 9"],
             ["216 → 1", "36 → 1", "6 → 1", "1 → 1", "1 → 3"],
-            ["1296 → 1", "216 → 1", "36 → 1", "6 → 1", "1 → 1"],
+            ["-", "216 → 1", "36 → 1", "6 → 1", "1 → 1"],
         ]
 
         actual = [
             [
-                self.format_ratio(
-                    trade.Material("name", "category", grade_in).trade_ratio(
-                        trade.Material("name", "category", grade_out)
-                    )
-                )
+                trade.Material("name", "category", grade_in)
+                .trade_ratio(trade.Material("name", "category", grade_out))
+                .map(self.format_ratio)
+                .value_or("-")
                 for grade_out in [1, 2, 3, 4, 5]
             ]
             for grade_in in [1, 2, 3, 4, 5]
@@ -31,22 +32,21 @@ class TradeCalculationTests(unittest.TestCase):
 
         self.assertEqual(expected, actual)
 
-    def test_different_category_exchange(self):
+    def test_different_category_exchange(self) -> None:
         expected = [
             ["6 → 1", "2 → 1", "2 → 3", "2 → 9", "2 → 27"],
             ["36 → 1", "6 → 1", "2 → 1", "2 → 3", "2 → 9"],
             ["216 → 1", "36 → 1", "6 → 1", "2 → 1", "2 → 3"],
-            ["1296 → 1", "216 → 1", "36 → 1", "6 → 1", "2 → 1"],
-            ["7776 → 1", "1296 → 1", "216 → 1", "36 → 1", "6 → 1"],
+            ["-", "216 → 1", "36 → 1", "6 → 1", "2 → 1"],
+            ["-", "-", "216 → 1", "36 → 1", "6 → 1"],
         ]
 
         actual = [
             [
-                self.format_ratio(
-                    trade.Material("name", "category", grade_in).trade_ratio(
-                        trade.Material("name", "other", grade_out)
-                    )
-                )
+                trade.Material("name", "category", grade_in)
+                .trade_ratio(trade.Material("name", "other", grade_out))
+                .map(self.format_ratio)
+                .value_or("-")
                 for grade_out in [1, 2, 3, 4, 5]
             ]
             for grade_in in [1, 2, 3, 4, 5]