Implement Crawler and DummyCrawler

PFERD/crawlers/__init__.py

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+from .dummy import DummyCrawler
+
+CRAWLERS = {
+    "dummy": DummyCrawler,
+}

PFERD/crawlers/dummy.py

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+import asyncio
+import random
+from pathlib import Path
+from typing import Any
+
+from rich.markup import escape
+
+from ..crawler import Crawler
+
+DUMMY_TREE = {
+    "Blätter": {
+        "Blatt_01.pdf": (),
+        "Blatt_02.pdf": (),
+        "Blatt_03.pdf": (),
+        "Blatt_04.pdf": (),
+        "Blatt_05.pdf": (),
+        "Blatt_01_Lösung.pdf": (),
+        "Blatt_02_Lösung.pdf": (),
+        "Blatt_03_Lösung.pdf": (),
+        "Blatt_04_Lösung.pdf": (),
+        "Blatt_05_Lösung.pdf": (),
+    },
+    "Vorlesungsfolien": {
+        "VL_01.pdf": (),
+        "VL_02.pdf": (),
+        "VL_03.pdf": (),
+        "VL_04.pdf": (),
+        "VL_05.pdf": (),
+    },
+    "noch_mehr.txt": (),
+    "dateien.jar": (),
+}
+
+
+class DummyCrawler(Crawler):
+    async def crawl(self) -> None:
+        await self._crawl_entry(Path(), DUMMY_TREE)
+
+    async def _crawl_entry(self, path: Path, value: Any) -> None:
+        if value == ():
+            n = random.randint(5, 20)
+            async with self.progress_bar(path, n) as bar:
+                await asyncio.sleep(random.random() / 2)
+                for i in range(n):
+                    await asyncio.sleep(0.5)
+                    bar.advance()
+            self.print(f"[green]Downloaded {escape(str(path))}")
+        else:
+            t = random.random() * 2 + 1
+            async with self.progress_bar(path) as bar:
+                await asyncio.sleep(t)
+            tasks = [self._crawl_entry(path / k, v) for k, v in value.items()]
+            await asyncio.gather(*tasks)