62 lines
2.1 KiB
Python
62 lines
2.1 KiB
Python
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"""唯一允许交给 Android Intent 的商品链接。"""
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from __future__ import annotations
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from dataclasses import dataclass
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from urllib.parse import parse_qsl, urlsplit
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_SCHEME = "https"
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_HOST = "mobile.yangkeduo.com"
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_PATH = "/goods.html"
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class ProductUrlError(ValueError):
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"""输入不是可安全重建的 canonical 商品链接。"""
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@dataclass(frozen=True)
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class ProductUrl:
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"""经验证的商品标识及由它重建的 canonical URL。"""
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goods_id: str
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canonical_url: str
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def parse_product_url(value: str) -> ProductUrl:
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"""只接受一个 ASCII 数字 ``goods_id`` 的拼多多商品直链。
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解析结果绝不原样透传：Intent 使用的 URL 必须从 ``goods_id`` 重新构建，以排除
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短链、额外参数、userinfo、fragment 和 URL 解析器的边缘表示。
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"""
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if not isinstance(value, str):
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raise ProductUrlError("商品链接必须是字符串。")
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try:
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parsed = urlsplit(value)
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port = parsed.port
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query_pairs = parse_qsl(parsed.query, keep_blank_values=True, strict_parsing=True)
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except ValueError as error:
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raise ProductUrlError("商品链接格式无效。") from error
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if (
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parsed.scheme != _SCHEME
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or parsed.hostname != _HOST
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or parsed.username is not None
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or parsed.password is not None
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or port is not None
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or parsed.path != _PATH
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or parsed.fragment
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):
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raise ProductUrlError("商品链接不是允许的拼多多商品直链。")
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if len(query_pairs) != 1 or query_pairs[0][0] != "goods_id":
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raise ProductUrlError("商品链接必须且只能包含一个 goods_id 参数。")
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goods_id = query_pairs[0][1]
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if not goods_id or any(character < "0" or character > "9" for character in goods_id):
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raise ProductUrlError("goods_id 必须是纯数字。")
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canonical_url = f"{_SCHEME}://{_HOST}{_PATH}?goods_id={goods_id}"
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if value != canonical_url:
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raise ProductUrlError("商品链接必须使用唯一 canonical 表示。")
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return ProductUrl(goods_id=goods_id, canonical_url=canonical_url)
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