From 4ebe8fe29a1bd23f3cd7d04f40ea18b373c57ece Mon Sep 17 00:00:00 2001
From: Joakim Soderlund <joakim.soderlund@gmail.com>
Date: Sun, 29 Jan 2017 00:06:15 +0100
Subject: [PATCH] Add merge method to Story

---
 fimfarchive/stories.py  | 15 +++++++++++++++
 tests/test_mappers.py   | 20 ++++++++++----------
 tests/test_selectors.py | 16 +++-------------
 tests/test_stories.py   | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 23 deletions(-)

diff --git a/fimfarchive/stories.py b/fimfarchive/stories.py
index 7bd4f02..85749c1 100644
--- a/fimfarchive/stories.py
+++ b/fimfarchive/stories.py
@@ -94,3 +94,18 @@ class Story:
             self._data = self.fetcher.fetch_data(self.key)
 
         return self._data
+
+    def merge(self, **params):
+        """
+        Returns a shallow copy, optionally replacing attributes.
+
+        Args:
+            **params: Overrides parameters from the current instance.
+
+        Raises:
+            TypeError: If passed an unexpected parameter.
+        """
+        kwargs = {k.lstrip('_'): v for k, v in vars(self).items()}
+        kwargs.update(params)
+
+        return type(self)(**kwargs)
diff --git a/tests/test_mappers.py b/tests/test_mappers.py
index 5c77c5d..eb63dd3 100644
--- a/tests/test_mappers.py
+++ b/tests/test_mappers.py
@@ -121,7 +121,7 @@ class TestStoryDateMapper:
         """
         Tests `None` is returned when meta is empty.
         """
-        story = self.merge(story, dict())
+        story = story.merge(meta=dict())
 
         assert mapper(story) is None
 
@@ -137,7 +137,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) is None
 
@@ -149,7 +149,7 @@ class TestStoryDateMapper:
             MODIFIED: 5,
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -162,7 +162,7 @@ class TestStoryDateMapper:
             CHAPTERS: None,
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -175,7 +175,7 @@ class TestStoryDateMapper:
             CHAPTERS: [],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -191,7 +191,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -208,7 +208,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -225,7 +225,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -242,7 +242,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
@@ -259,7 +259,7 @@ class TestStoryDateMapper:
             ],
         }
 
-        story = self.merge(story, meta)
+        story = story.merge(meta=meta)
 
         assert mapper(story) == 5
 
diff --git a/tests/test_selectors.py b/tests/test_selectors.py
index 8244e86..26b926d 100644
--- a/tests/test_selectors.py
+++ b/tests/test_selectors.py
@@ -46,16 +46,6 @@ class TestUpdateSelector:
         """
         return UpdateSelector()
 
-    def merge(self, story, **params):
-        """
-        Returns a cloned story, optionally overriding parameters.
-        """
-        data = vars(story)
-        data = {k.lstrip('_'): v for k, v in data.items()}
-        data.update(params)
-
-        return Story(**data)
-
     def populate(self, story, date=0):
         """
         Returns a cloned story populated with chapter meta.
@@ -70,7 +60,7 @@ class TestUpdateSelector:
             ],
         }
 
-        return self.merge(story, meta=meta)
+        return story.merge(meta=meta)
 
     def test_filter_empty_with_chapters(self, selector, story):
         """
@@ -98,7 +88,7 @@ class TestUpdateSelector:
             'chapters': []
         }
 
-        story = self.merge(story, meta=meta)
+        story = story.merge(meta=meta)
         selected = selector.filter_empty(story)
 
         assert selected is None
@@ -268,7 +258,7 @@ class TestUpdateSelector:
 
         fetcher = Mock(spec=Fetcher)
         fetcher.fetch_data.side_effect = InvalidStoryError
-        new = self.merge(story, fetcher=fetcher, data=None)
+        new = story.merge(fetcher=fetcher, data=None)
 
         selected = selector(old, new)
 
diff --git a/tests/test_stories.py b/tests/test_stories.py
index 865a120..78af850 100644
--- a/tests/test_stories.py
+++ b/tests/test_stories.py
@@ -211,3 +211,40 @@ class TestStory:
         assert story.flavors is not flavors
         assert story.flavors == {flavor.A}
         assert type(story.flavors) == set
+
+    def test_merge_without_parameters(self, story):
+        """
+        Tests `merge` returns new story containing current attributes.
+        """
+        merge = story.merge()
+
+        assert merge is not story
+        assert merge.data is story.data
+        assert merge.meta is story.meta
+
+        for k, v in vars(story).items():
+            assert getattr(merge, k) == v
+
+    def test_merge_with_parameters(self, story):
+        """
+        Tests `merge` can override attributes.
+        """
+        meta = dict(story.meta)
+        merge = story.merge(meta=meta)
+
+        assert meta is not story.meta
+        assert meta is merge.meta
+
+    def test_merge_with_invalid_state(self, story):
+        """
+        Tests `merge` is affected by validation in `__init__`.
+        """
+        with pytest.raises(ValueError):
+            story.merge(fetcher=None, meta=None)
+
+    def test_merge_with_invalid_arguments(self, story):
+        """
+        Tests `merge` cannot create story using invalid arguments.
+        """
+        with pytest.raises(TypeError):
+            story.merge(alpaca=True)