mirror of
https://github.com/Garmelon/PFERD.git
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122 lines
3.9 KiB
Python
122 lines
3.9 KiB
Python
import configparser
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from abc import ABC, abstractmethod
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from contextlib import asynccontextmanager
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from pathlib import PurePath
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# TODO In Python 3.9 and above, AsyncContextManager is deprecated
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from typing import AsyncContextManager, AsyncIterator, Optional
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from rich.markup import escape
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from .conductor import ProgressBar, TerminalConductor
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from .config import Config
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from .limiter import Limiter
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from .output_dir import OnConflict, OutputDirectory, Redownload
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from .transformer import RuleParseException, Transformer
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class CrawlerLoadException(Exception):
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pass
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class Crawler(ABC):
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def __init__(
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self,
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name: str,
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config: Config,
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section: configparser.SectionProxy,
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) -> None:
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"""
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Initialize a crawler from its name and its section in the config file.
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If you are writing your own constructor for your own crawler, make sure
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to call this constructor first (via super().__init__).
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May throw a CrawlerLoadException.
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"""
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self.name = name
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self._conductor = TerminalConductor()
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self._limiter = Limiter()
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try:
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self._transformer = Transformer(section.get("transform", ""))
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except RuleParseException as e:
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e.pretty_print()
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raise CrawlerLoadException()
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output_dir = config.working_dir / section.get("output_dir", name)
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redownload = Redownload.NEVER_SMART
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on_conflict = OnConflict.PROMPT
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self._output_dir = OutputDirectory(
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output_dir, redownload, on_conflict, self._conductor)
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def print(self, text: str) -> None:
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"""
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Print rich markup to the terminal. Crawlers *must* use this function to
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print things unless they are holding an exclusive output context
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manager! Be careful to escape all user-supplied strings.
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"""
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self._conductor.print(text)
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def exclusive_output(self) -> AsyncContextManager[None]:
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"""
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Acquire exclusive rights™ to the terminal output. While this context
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manager is held, output such as printing and progress bars from other
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threads is suspended and the current thread may do whatever it wants
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with the terminal. However, it must return the terminal to its original
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state before exiting the context manager.
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No two threads can hold this context manager at the same time.
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Useful for password or confirmation prompts as well as running other
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programs while crawling (e. g. to get certain credentials).
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"""
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return self._conductor.exclusive_output()
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@asynccontextmanager
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async def progress_bar(
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self,
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desc: str,
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total: Optional[int] = None,
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) -> AsyncIterator[ProgressBar]:
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async with self._limiter.limit():
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with self._conductor.progress_bar(desc, total=total) as bar:
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yield bar
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def crawl_bar(self, path: PurePath) -> AsyncContextManager[ProgressBar]:
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pathstr = escape(str(path))
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desc = f"[bold magenta]Crawling[/bold magenta] {pathstr}"
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return self.progress_bar(desc)
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def download_bar(
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self,
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path: PurePath,
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size: int,
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) -> AsyncContextManager[ProgressBar]:
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pathstr = escape(str(path))
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desc = f"[bold green]Downloading[/bold green] {pathstr}"
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return self.progress_bar(desc, total=size)
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async def run(self) -> None:
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"""
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Start the crawling process. Call this function if you want to use a
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crawler.
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"""
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async with self._conductor:
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await self.crawl()
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@abstractmethod
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async def crawl(self) -> None:
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"""
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Overwrite this function if you are writing a crawler.
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This function must not return before all crawling is complete. To crawl
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multiple things concurrently, asyncio.gather can be used.
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"""
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pass
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