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ff27c568c5
Similar to the frontend `web/src/topic_link_util.ts`, we introduce a backend module to avoid generating broken channe/topic links. Fixes part of #34608
82 lines
2.5 KiB
Python
82 lines
2.5 KiB
Python
# Keep this synchronized with web/src/topic_link_util.ts
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import re
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import urllib.parse
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invalid_stream_topic_regex = re.compile(r"[`>*&\[\]]|(\$\$)")
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def will_produce_broken_stream_topic_link(word: str) -> bool:
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return bool(invalid_stream_topic_regex.search(word))
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escape_mapping = {
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"`": "`",
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">": ">",
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"*": "*",
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"&": "&",
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"$$": "$$",
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"[": "[",
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"]": "]",
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}
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def escape_invalid_stream_topic_characters(text: str) -> str:
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return re.sub(
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invalid_stream_topic_regex,
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lambda match: escape_mapping.get(match.group(0), match.group(0)),
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text,
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)
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hash_replacements = {
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"%": ".",
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"(": ".28",
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")": ".29",
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".": ".2E",
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}
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def encode_hash_component(s: str) -> str:
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encoded = urllib.parse.quote(s, safe="*")
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return "".join(hash_replacements.get(c, c) for c in encoded)
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def channel_topic_url(stream_id: int, stream_name: str, topic_name: str | None = None) -> str:
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link = f"#narrow/channel/{stream_id}-{encode_hash_component(stream_name.replace(' ', '-'))}"
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if topic_name:
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link += f"/topic/{encode_hash_component(topic_name)}"
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return link
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def get_fallback_markdown_link(
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stream_id: int, stream_name: str, topic_name: str | None = None
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) -> str:
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"""
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Generates the markdown link syntax for a stream or topic link.
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"""
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escape = escape_invalid_stream_topic_characters
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url = channel_topic_url(stream_id, stream_name, topic_name)
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if topic_name:
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return f"[#{escape(stream_name)} > {escape(topic_name)}]({url})"
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return f"[#{escape(stream_name)}]({url})"
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def get_stream_topic_link_syntax(stream_id: int, stream_name: str, topic_name: str) -> str:
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# If the topic name is such that it will generate an invalid #**stream>topic** syntax,
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# we revert to generating the normal markdown syntax for a link.
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if will_produce_broken_stream_topic_link(topic_name) or will_produce_broken_stream_topic_link(
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stream_name
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):
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return get_fallback_markdown_link(stream_id, stream_name, topic_name)
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return f"#**{stream_name}>{topic_name}**"
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def get_stream_link_syntax(stream_id: int, stream_name: str) -> str:
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# If the topic name is such that it will generate an invalid #**stream>topic** syntax,
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# we revert to generating the normal markdown syntax for a link.
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if will_produce_broken_stream_topic_link(stream_name):
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return get_fallback_markdown_link(stream_id, stream_name)
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return f"#**{stream_name}**"
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