Added more folders and restructured classes inside them.
This commit is contained in:
212
src/ptlinux/download.py
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212
src/ptlinux/download.py
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"""Secure, conditional download of the official PristonTale EU launcher."""
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from __future__ import annotations
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from dataclasses import asdict, dataclass
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from datetime import datetime
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import hashlib
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import json
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import os
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from pathlib import Path
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import struct
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from typing import Callable
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from urllib.error import HTTPError
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from urllib.request import Request, urlopen
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from . import __version__
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OFFICIAL_LAUNCHER_URL = (
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"https://pristontale.eu/storage/uploads/Pristontale%20EU%20Launcher.exe"
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)
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MAX_LAUNCHER_BYTES = 64 * 1024 * 1024
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READ_SIZE = 256 * 1024
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USER_AGENT = f"PT-Linux/{__version__} (+https://pristontale.eu/)"
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class DownloadError(RuntimeError):
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"""Raised when the official launcher cannot be safely downloaded."""
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@dataclass(frozen=True)
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class LauncherDownload:
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path: str
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url: str
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sha256: str
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size: int
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etag: str | None
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last_modified: str | None
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fetched_at: str
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changed: bool
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def fetch_official_launcher(
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destination: Path,
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metadata_path: Path,
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*,
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url: str = OFFICIAL_LAUNCHER_URL,
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timeout_seconds: float = 60.0,
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progress: Callable[[int, int | None], None] | None = None,
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) -> LauncherDownload:
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"""Download the current official launcher and atomically replace the cache."""
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metadata = _read_metadata(metadata_path)
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headers = {"User-Agent": USER_AGENT}
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if destination.is_file() and _looks_like_pe(destination):
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etag = metadata.get("etag")
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last_modified = metadata.get("last_modified")
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if isinstance(etag, str) and etag:
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headers["If-None-Match"] = etag
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if isinstance(last_modified, str) and last_modified:
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headers["If-Modified-Since"] = last_modified
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request = Request(url, headers=headers, method="GET")
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try:
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response = urlopen(request, timeout=timeout_seconds)
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except HTTPError as exc:
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status = exc.code
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exc.close()
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if status == 304 and destination.is_file():
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return _existing_download(destination, metadata, url)
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raise DownloadError(f"official launcher request failed: HTTP {status}") from exc
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except OSError as exc:
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raise DownloadError(f"official launcher request failed: {exc}") from exc
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with response:
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length = _content_length(response.headers.get("Content-Length"))
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if length is not None and length > MAX_LAUNCHER_BYTES:
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raise DownloadError(
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f"launcher response is unexpectedly large: {length} bytes"
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)
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destination.parent.mkdir(parents=True, exist_ok=True)
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temporary = destination.with_name(f".{destination.name}.{os.getpid()}.part")
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digest = hashlib.sha256()
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written = 0
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try:
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with temporary.open("wb") as handle:
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while True:
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chunk = response.read(READ_SIZE)
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if not chunk:
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break
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written += len(chunk)
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if written > MAX_LAUNCHER_BYTES:
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raise DownloadError(
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"launcher response exceeded the 64 MiB safety limit"
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)
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digest.update(chunk)
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handle.write(chunk)
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if progress is not None:
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progress(written, length)
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handle.flush()
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os.fsync(handle.fileno())
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if length is not None and written != length:
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raise DownloadError(
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f"incomplete launcher response: {written}/{length} bytes"
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)
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validate_pe_launcher(temporary)
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temporary.replace(destination)
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except BaseException:
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temporary.unlink(missing_ok=True)
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raise
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result = LauncherDownload(
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path=str(destination),
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url=url,
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sha256=digest.hexdigest(),
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size=written,
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etag=response.headers.get("ETag"),
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last_modified=response.headers.get("Last-Modified"),
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fetched_at=datetime.now().astimezone().isoformat(),
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changed=True,
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)
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_write_json(metadata_path, asdict(result))
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return result
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def validate_pe_launcher(path: Path) -> None:
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"""Validate the minimum PE structure and require a 64-bit GUI executable."""
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try:
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with path.open("rb") as handle:
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dos = handle.read(64)
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if len(dos) < 64 or dos[:2] != b"MZ":
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raise DownloadError("download is not a DOS/PE executable")
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pe_offset = struct.unpack_from("<I", dos, 0x3C)[0]
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if pe_offset < 64 or pe_offset > 8 * 1024 * 1024:
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raise DownloadError("launcher has an invalid PE header offset")
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handle.seek(pe_offset)
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pe_header = handle.read(24)
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if len(pe_header) != 24 or pe_header[:4] != b"PE\x00\x00":
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raise DownloadError("launcher has no valid PE signature")
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machine = struct.unpack_from("<H", pe_header, 4)[0]
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if machine != 0x8664:
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raise DownloadError(
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f"launcher has unexpected PE machine type 0x{machine:04x}"
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)
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except OSError as exc:
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raise DownloadError(f"cannot validate launcher: {exc}") from exc
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def _looks_like_pe(path: Path) -> bool:
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try:
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validate_pe_launcher(path)
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except DownloadError:
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return False
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return True
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def _existing_download(
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path: Path,
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metadata: dict[str, object],
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url: str,
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) -> LauncherDownload:
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validate_pe_launcher(path)
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return LauncherDownload(
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path=str(path),
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url=url,
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sha256=_sha256(path),
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size=path.stat().st_size,
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etag=_optional_string(metadata.get("etag")),
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last_modified=_optional_string(metadata.get("last_modified")),
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fetched_at=datetime.now().astimezone().isoformat(),
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changed=False,
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)
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def _read_metadata(path: Path) -> dict[str, object]:
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try:
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value = json.loads(path.read_text(encoding="utf-8"))
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except (OSError, json.JSONDecodeError):
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return {}
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return value if isinstance(value, dict) else {}
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def _write_json(path: Path, value: object) -> None:
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path.parent.mkdir(parents=True, exist_ok=True)
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temporary = path.with_name(f".{path.name}.{os.getpid()}.tmp")
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temporary.write_text(json.dumps(value, indent=2, sort_keys=True) + "\n", encoding="utf-8")
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temporary.replace(path)
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def _sha256(path: Path) -> str:
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digest = hashlib.sha256()
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with path.open("rb") as handle:
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for chunk in iter(lambda: handle.read(READ_SIZE), b""):
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digest.update(chunk)
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return digest.hexdigest()
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def _content_length(value: str | None) -> int | None:
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if value is None:
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return None
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try:
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length = int(value)
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except ValueError as exc:
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raise DownloadError(f"invalid Content-Length: {value!r}") from exc
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if length < 0:
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raise DownloadError(f"invalid Content-Length: {value!r}")
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return length
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def _optional_string(value: object) -> str | None:
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return value if isinstance(value, str) else None
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