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'''
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在书城的业务背景中，组合模式（Composite Pattern）可以用于构建树形结构，比如书籍的分类结构。
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每个分类可以包含子分类，也可以包含具体的书籍。通过这种方式，可以方便地管理和遍历整个书籍分类体系。
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下面是一个简单的实现代码示例，展示如何使用组合模式来构建书城的书籍分类结构
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'''
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from abc import ABC, abstractmethod
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# 组件抽象类
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class BookComponent(ABC):
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@abstractmethod
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def add(self, component):
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pass
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@abstractmethod
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def remove(self, component):
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pass
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@abstractmethod
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def display(self, depth):
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pass
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# 叶子节点：书籍类
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class Book(BookComponent):
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def __init__(self, title, author):
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self.title = title
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self.author = author
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def add(self, component):
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print("Cannot add to a leaf node")
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def remove(self, component):
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print("Cannot remove from a leaf node")
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def display(self, depth):
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print("-" * depth + f" {self.title} by {self.author}")
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# 复合节点：书籍分类类
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class BookCategory(BookComponent):
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def __init__(self, name):
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self.name = name
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self.children = []
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def add(self, component):
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self.children.append(component)
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def remove(self, component):
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self.children.remove(component)
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def display(self, depth):
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print("-" * depth + self.name)
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for child in self.children:
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child.display(depth + 1)
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# 客户端代码
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if __name__ == "__main__":
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# 创建书籍分类和书籍对象
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fiction = BookCategory("Fiction")
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non_fiction = BookCategory("Non-Fiction")
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novel = Book("The Great Gatsby", "F. Scott Fitzgerald")
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biography = Book("Steve Jobs", "Walter Isaacson")
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programming = Book("Clean Code", "Robert C. Martin")
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# 构建书籍分类结构
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fiction.add(novel)
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non_fiction.add(biography)
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non_fiction.add(programming)
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# 创建一个根分类，并将其他分类添加到其中
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root = BookCategory("Root")
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root.add(fiction)
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root.add(non_fiction)
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# 显示整个书籍分类结构
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root.display(0)
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'''
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在这个示例中，BookComponent 是一个抽象类，定义了所有组件（无论是分类还是书籍）都应该有的方法：add、remove 和 display。
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Book 类是叶子节点，代表具体的书籍，它实现了 BookComponent 接口，
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但 add 和 remove 方法对于书籍来说是不适用的，因此它们只是打印一条错误消息。
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BookCategory 类是复合节点，代表书籍的分类，它可以包含其他分类或书籍，因此它实现了 add 和 remove 方法来管理子节点，并且实现了 display 方法来显示分类及其子节点的信息。
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客户端代码创建了一些书籍和分类对象，并构建了一个书籍分类结构。最后，通过调用根分类的 display 方法，可以显示整个书籍分类结构。
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'''
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