Strategy Patterns

Author: MilovanTomasevic

src/1_patterns/4_BehavioralPatterns/9_Strategy/1_strategy.py

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+from abc import ABC
+from enum import Enum, auto
+
+
+class OutputFormat(Enum):
+    MARKDOWN = auto()
+    HTML = auto()
+
+
+# not required but a good idea
+class ListStrategy(ABC):
+    def start(self, buffer): pass
+
+    def end(self, buffer): pass
+
+    def add_list_item(self, buffer, item): pass
+
+
+class MarkdownListStrategy(ListStrategy):
+
+    def add_list_item(self, buffer, item):
+        buffer.append(f' * {item}\n')
+
+
+class HtmlListStrategy(ListStrategy):
+
+    def start(self, buffer):
+        buffer.append('<ul>\n')
+
+    def end(self, buffer):
+        buffer.append('</ul>\n')
+
+    def add_list_item(self, buffer, item):
+        buffer.append(f'  <li>{item}</li>\n')
+
+
+class TextProcessor:
+    def __init__(self, list_strategy=HtmlListStrategy()):
+        self.buffer = []
+        self.list_strategy = list_strategy
+
+    def append_list(self, items):
+        self.list_strategy.start(self.buffer)
+        for item in items:
+            self.list_strategy.add_list_item(
+                self.buffer, item
+            )
+        self.list_strategy.end(self.buffer)
+
+    def set_output_format(self, format):
+        if format == OutputFormat.MARKDOWN:
+            self.list_strategy = MarkdownListStrategy()
+        elif format == OutputFormat.HTML:
+            self.list_strategy = HtmlListStrategy()
+
+    def clear(self):
+        self.buffer.clear()
+
+    def __str__(self):
+        return ''.join(self.buffer)
+
+
+if __name__ == '__main__':
+    items = ['foo', 'bar', 'baz']
+
+    tp = TextProcessor()
+    tp.set_output_format(OutputFormat.MARKDOWN)
+    tp.append_list(items)
+    print(tp)
+
+    tp.set_output_format(OutputFormat.HTML)
+    tp.clear()
+    tp.append_list(items)
+    print(tp)