mirror of
https://github.com/Garmelon/PFERD.git
synced 2023-12-21 10:23:01 +01:00
347 lines
11 KiB
Python
347 lines
11 KiB
Python
from abc import ABC, abstractmethod
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from contextlib import asynccontextmanager
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from datetime import datetime
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from pathlib import Path, PurePath
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# TODO In Python 3.9 and above, AsyncContextManager is deprecated
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from typing import Any, AsyncContextManager, AsyncIterator, Awaitable, Callable, Dict, Optional, TypeVar
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import aiohttp
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from rich.markup import escape
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from .authenticator import Authenticator
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from .conductor import ProgressBar, TerminalConductor
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from .config import Config, Section
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from .limiter import Limiter
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from .output_dir import FileSink, OnConflict, OutputDirectory, Redownload
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from .transformer import RuleParseException, Transformer
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from .version import __version__
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class CrawlerLoadException(Exception):
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pass
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Wrapped = TypeVar("Wrapped", bound=Callable[..., None])
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def noncritical(f: Wrapped) -> Wrapped:
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"""
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Warning: Must only be applied to member functions of the Crawler class!
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Catches all exceptions occuring during the function call. If an exception
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occurs, the crawler's error_free variable is set to False.
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"""
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def wrapper(self: "Crawler", *args: Any, **kwargs: Any) -> None:
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try:
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f(self, *args, **kwargs)
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except Exception as e:
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self.print(f"[red]Something went wrong: {escape(str(e))}")
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self.error_free = False
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return wrapper # type: ignore
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def repeat(attempts: int) -> Callable[[Wrapped], Wrapped]:
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"""
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Warning: Must only be applied to member functions of the Crawler class!
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If an exception occurs during the function call, retries the function call
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a set amount of times. Exceptions that occur during the last attempt are
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not caught and instead passed on upwards.
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"""
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def decorator(f: Wrapped) -> Wrapped:
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def wrapper(self: "Crawler", *args: Any, **kwargs: Any) -> None:
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for _ in range(attempts - 1):
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try:
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f(self, *args, **kwargs)
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return
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except Exception:
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pass
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f(self, *args, **kwargs)
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return wrapper # type: ignore
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return decorator
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AWrapped = TypeVar("AWrapped", bound=Callable[..., Awaitable[None]])
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def anoncritical(f: AWrapped) -> AWrapped:
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"""
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An async version of @noncritical.
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Warning: Must only be applied to member functions of the Crawler class!
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Catches all exceptions occuring during the function call. If an exception
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occurs, the crawler's error_free variable is set to False.
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"""
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async def wrapper(self: "Crawler", *args: Any, **kwargs: Any) -> None:
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try:
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await f(self, *args, **kwargs)
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except Exception as e:
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self.print(f"[red]Something went wrong: {escape(str(e))}")
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self.error_free = False
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return wrapper # type: ignore
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def arepeat(attempts: int) -> Callable[[AWrapped], AWrapped]:
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"""
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An async version of @noncritical.
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Warning: Must only be applied to member functions of the Crawler class!
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If an exception occurs during the function call, retries the function call
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a set amount of times. Exceptions that occur during the last attempt are
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not caught and instead passed on upwards.
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"""
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def decorator(f: AWrapped) -> AWrapped:
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async def wrapper(self: "Crawler", *args: Any, **kwargs: Any) -> None:
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for _ in range(attempts - 1):
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try:
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await f(self, *args, **kwargs)
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return
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except Exception:
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pass
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await f(self, *args, **kwargs)
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return wrapper # type: ignore
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return decorator
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class CrawlerSection(Section):
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def output_dir(self, name: str) -> Path:
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# TODO Use removeprefix() after switching to 3.9
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if name.startswith("crawl:"):
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name = name[len("crawl:"):]
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return Path(self.s.get("output_dir", name)).expanduser()
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def redownload(self) -> Redownload:
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value = self.s.get("redownload", "never-smart")
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try:
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return Redownload.from_string(value)
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except ValueError as e:
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self.invalid_value(
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"redownload",
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value,
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str(e).capitalize(),
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)
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def on_conflict(self) -> OnConflict:
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value = self.s.get("on_conflict", "prompt")
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try:
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return OnConflict.from_string(value)
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except ValueError as e:
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self.invalid_value(
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"on_conflict",
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value,
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str(e).capitalize(),
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)
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def transform(self) -> str:
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return self.s.get("transform", "")
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def max_concurrent_tasks(self) -> int:
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value = self.s.getint("max_concurrent_tasks", fallback=1)
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if value <= 0:
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self.invalid_value("max_concurrent_tasks", value,
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"Must be greater than 0")
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return value
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def max_concurrent_downloads(self) -> int:
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tasks = self.max_concurrent_tasks()
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value = self.s.getint("max_concurrent_downloads", fallback=None)
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if value is None:
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return tasks
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if value <= 0:
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self.invalid_value("max_concurrent_downloads", value,
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"Must be greater than 0")
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if value > tasks:
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self.invalid_value("max_concurrent_downloads", value,
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"Must not be greater than max_concurrent_tasks")
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return value
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def delay_between_tasks(self) -> float:
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value = self.s.getfloat("delay_between_tasks", fallback=0.0)
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if value < 0:
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self.invalid_value("delay_between_tasks", value,
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"Must not be negative")
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return value
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def auth(self, authenticators: Dict[str, Authenticator]) -> Authenticator:
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value = self.s.get("auth")
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if value is None:
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self.missing_value("auth")
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auth = authenticators.get(value)
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if auth is None:
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self.invalid_value("auth", value, "No such auth section exists")
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return auth
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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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section: CrawlerSection,
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config: Config,
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conductor: TerminalConductor,
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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 = conductor
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self.error_free = True
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self._limiter = Limiter(
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task_limit=section.max_concurrent_tasks(),
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download_limit=section.max_concurrent_downloads(),
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task_delay=section.delay_between_tasks(),
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)
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try:
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self._transformer = Transformer(section.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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self._output_dir = OutputDirectory(
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config.working_dir / section.output_dir(name),
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section.redownload(),
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section.on_conflict(),
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self._conductor,
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)
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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 crawl_bar(
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self,
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path: PurePath,
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total: Optional[int] = None,
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) -> AsyncIterator[ProgressBar]:
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desc = f"[bold bright_cyan]Crawling[/] {escape(str(path))}"
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async with self._limiter.limit_crawl():
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with self._conductor.progress_bar(desc, total=total) as bar:
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yield bar
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@asynccontextmanager
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async def download_bar(
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self,
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path: PurePath,
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total: Optional[int] = None,
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) -> AsyncIterator[ProgressBar]:
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desc = f"[bold bright_cyan]Downloading[/] {escape(str(path))}"
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async with self._limiter.limit_download():
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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 should_crawl(self, path: PurePath) -> bool:
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return self._transformer.transform(path) is not None
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async def download(
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self,
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path: PurePath,
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mtime: Optional[datetime] = None,
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redownload: Optional[Redownload] = None,
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on_conflict: Optional[OnConflict] = None,
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) -> Optional[AsyncContextManager[FileSink]]:
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transformed_path = self._transformer.transform(path)
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if transformed_path is None:
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return None
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return await self._output_dir.download(
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transformed_path, mtime, redownload, on_conflict)
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async def cleanup(self) -> None:
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await self._output_dir.cleanup()
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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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class HttpCrawler(Crawler):
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COOKIE_FILE = PurePath(".cookies")
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def __init__(
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self,
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name: str,
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section: CrawlerSection,
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config: Config,
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conductor: TerminalConductor,
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) -> None:
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super().__init__(name, section, config, conductor)
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self._cookie_jar_path = self._output_dir.resolve(self.COOKIE_FILE)
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self._output_dir.register_reserved(self.COOKIE_FILE)
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async def run(self) -> None:
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cookie_jar = aiohttp.CookieJar()
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try:
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cookie_jar.load(self._cookie_jar_path)
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except Exception:
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pass
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async with aiohttp.ClientSession(
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headers={"User-Agent": f"pferd/{__version__}"},
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cookie_jar=cookie_jar,
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) as session:
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self.session = session
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try:
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await super().run()
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finally:
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del self.session
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try:
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cookie_jar.save(self._cookie_jar_path)
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except Exception:
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self.print(
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"[bold red]Warning:[/] Failed to save cookies to "
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+ escape(str(self.COOKIE_FILE))
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)
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