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https://github.com/emilybache/GildedRose-Refactoring-Kata.git
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1891347585
- add characterization tests covering all existing item rules - replace nested conditionals with per-item updater classes - add Conjured items that degrade twice as fast as normal
116 lines
3.2 KiB
Python
Executable File
116 lines
3.2 KiB
Python
Executable File
# -*- coding: utf-8 -*-
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"""Gilded Rose inventory system.
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The quality-update rules differ per item category. Rather than branch on the
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item name inside one giant method, each category is modelled as an updater that
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knows how to age a single item by one day. ``GildedRose`` simply dispatches each
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item to the matching updater.
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NOTE: The ``Item`` class and its attributes are owned by the "goblin in the
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corner" and must not be modified, so all behaviour lives in the updaters.
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"""
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MIN_QUALITY = 0
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MAX_QUALITY = 50
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AGED_BRIE = "Aged Brie"
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BACKSTAGE_PASS = "Backstage passes to a TAFKAL80ETC concert"
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SULFURAS = "Sulfuras, Hand of Ragnaros"
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CONJURED_PREFIX = "Conjured"
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def _clamp(quality):
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"""Keep quality within the legal [0, 50] range."""
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return max(MIN_QUALITY, min(MAX_QUALITY, quality))
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class ItemUpdater(object):
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"""Base updater: a normal item degrades by 1, then by 2 once expired."""
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daily_degradation = 1
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def __init__(self, item):
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self.item = item
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def update(self):
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self._update_sell_in()
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self._update_quality()
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def _update_sell_in(self):
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self.item.sell_in -= 1
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def _update_quality(self):
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amount = self.daily_degradation
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if self.item.sell_in < 0:
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amount *= 2 # degrades twice as fast after the sell-by date
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self.item.quality = _clamp(self.item.quality - amount)
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class AgedBrieUpdater(ItemUpdater):
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"""Aged Brie increases in quality the older it gets, faster once expired."""
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def _update_quality(self):
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amount = 1
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if self.item.sell_in < 0:
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amount *= 2
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self.item.quality = _clamp(self.item.quality + amount)
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class BackstagePassUpdater(ItemUpdater):
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"""Backstage passes gain value as the concert approaches, then drop to zero
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once the concert has passed."""
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def _update_quality(self):
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if self.item.sell_in < 0:
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self.item.quality = 0
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return
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amount = 1
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if self.item.sell_in < 5:
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amount = 3
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elif self.item.sell_in < 10:
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amount = 2
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self.item.quality = _clamp(self.item.quality + amount)
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class SulfurasUpdater(ItemUpdater):
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"""Sulfuras is legendary: it never has to be sold and never changes."""
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def update(self):
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pass
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class ConjuredUpdater(ItemUpdater):
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"""Conjured items degrade twice as fast as normal items."""
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daily_degradation = 2
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def updater_for(item):
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"""Pick the right updater for an item based on its name."""
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if item.name == AGED_BRIE:
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return AgedBrieUpdater(item)
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if item.name == BACKSTAGE_PASS:
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return BackstagePassUpdater(item)
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if item.name == SULFURAS:
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return SulfurasUpdater(item)
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if item.name.startswith(CONJURED_PREFIX):
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return ConjuredUpdater(item)
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return ItemUpdater(item)
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class GildedRose(object):
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def __init__(self, items):
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self.items = items
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def update_quality(self):
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for item in self.items:
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updater_for(item).update()
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class Item:
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def __init__(self, name, sell_in, quality):
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self.name = name
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self.sell_in = sell_in
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self.quality = quality
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def __repr__(self):
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return "%s, %s, %s" % (self.name, self.sell_in, self.quality) |