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tiennm99
e5125fcd93
Six public commands let any member of a chat curate two lists of text and ask whether a given text is blocked: /blacklist_add, /blacklist_del, /whitelist_add, /whitelist_del, /blacklist_rules and /blacklist_check. The module is passive. It never reads ordinary chat messages and never deletes, warns or restricts anyone; the lists stay inert until /blacklist_check asks about a specific text. Scope is one forum topic, keyed (Chat.ID, MessageThreadID) and gated on IsTopicMessage so a reply chain in a plain supergroup does not become its own unreachable scope. A plain group, a DM and a forum's General topic all resolve to one chat-wide list. Matching is substring, after NFKC composition, case folding and whitespace collapse. Diacritics stay significant, so ma, má and mà are three entries. A whitelist entry rescues a blacklist match only when it spans that match, which is what keeps "I met an assassin, dumbass" blocked. Entry text is percent-encoded before it becomes a storage key, since keys forbid '/' and cap at 1500 bytes, and is capped at 200 bytes before and after normalization because NFKC can expand as well as contract. /blacklist_rules reads each list with Scan, so listing costs one round trip per list rather than a Get per entry.
64 lines
2.5 KiB
Go
64 lines
2.5 KiB
Go
package blacklist
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import (
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"strconv"
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"strings"
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)
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// The two list tags. They are single letters because they sit inside every
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// storage key, and because the ':' after them is what ends the key prefix.
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const (
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listBlack = "b"
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listWhite = "w"
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)
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// maxEntryBytes caps one entry, measured on the normalized text before key
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// encoding.
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//
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// Storage keys are limited to 1500 bytes (internal/storage/keys.go). Worst-case
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// encoding triples an entry to 600 bytes, which with a prefix well under 30
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// bytes stays far inside that. Two hundred bytes is roughly 65 Vietnamese
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// characters — ample for a phrase, and a deliberate refusal to let a pasted
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// essay become a key.
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const maxEntryBytes = 200
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// scopePrefix is the key prefix for one list of one thread.
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//
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// A thread is (Chat.ID, MessageThreadID), the same pair the lol module uses for
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// subscriptions. A zero thread id means a non-forum group, a forum's General
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// topic, or a DM — a real scope, not a missing value.
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//
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// Both numbers are decimal and the list tag is a single letter, so the third
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// ':' always ends the prefix even though entry text may contain ':' of its own.
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func scopePrefix(chatID int64, threadID int, list string) string {
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return strconv.FormatInt(chatID, 10) + ":" + strconv.Itoa(threadID) + ":" + list + ":"
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}
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// entryKey names one entry. normText must already have been through Normalize.
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func entryKey(chatID int64, threadID int, list, normText string) string {
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return scopePrefix(chatID, threadID, list) + encodeKeyText(normText)
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}
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// encodeKeyText escapes the one character that cannot appear literally in a
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// storage key.
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//
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// '%' is escaped first so the escape marker itself stays unambiguous: reversing
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// the order would make an entry containing the literal text "%2F" decode back
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// as "/". Because every literal '%' becomes "%25", every '%' in the result
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// starts an escape, so decoding can never match one that spans two of them.
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//
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// The other key rules need no work here: "." , ".." and the __namespace__
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// pattern are all unreachable behind the numeric scope prefix.
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func encodeKeyText(s string) string {
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s = strings.ReplaceAll(s, "%", "%25")
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return strings.ReplaceAll(s, "/", "%2F")
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}
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// decodeKeyText reverses encodeKeyText. The order mirrors it: "%2F" can only
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// have come from a real '/', so it is consumed before "%25" reconstitutes the
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// '%' characters that could otherwise form a spurious escape.
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func decodeKeyText(s string) string {
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s = strings.ReplaceAll(s, "%2F", "/")
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return strings.ReplaceAll(s, "%25", "%")
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}
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