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77 lines
2.4 KiB
77 lines
2.4 KiB
// GoToSocial |
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// Copyright (C) GoToSocial Authors admin@gotosocial.org |
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// SPDX-License-Identifier: AGPL-3.0-or-later |
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// |
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// This program is free software: you can redistribute it and/or modify |
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// it under the terms of the GNU Affero General Public License as published by |
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// the Free Software Foundation, either version 3 of the License, or |
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// (at your option) any later version. |
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// |
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// This program is distributed in the hope that it will be useful, |
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// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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// GNU Affero General Public License for more details. |
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// |
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// You should have received a copy of the GNU Affero General Public License |
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// along with this program. If not, see <http://www.gnu.org/licenses/>. |
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package text |
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import ( |
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"strings" |
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"golang.org/x/text/unicode/norm" |
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) |
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const ( |
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maximumHashtagLength = 100 |
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) |
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// NormalizeHashtag normalizes the given hashtag text by |
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// removing the initial '#' symbol, and then decomposing |
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// and canonically recomposing chars + combining diacritics |
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// in the text to single unicode characters, following |
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// Normalization Form C (https://unicode.org/reports/tr15/). |
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// |
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// Finally, it will do a check on the normalized string to |
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// ensure that it's below maximumHashtagLength chars, and |
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// contains only letters, numbers, and underscores (and not |
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// *JUST* underscores). |
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// |
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// If all this passes, returned bool will be true. |
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func NormalizeHashtag(text string) (string, bool) { |
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// This normalization is specifically to avoid cases |
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// where visually-identical hashtags are stored with |
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// different unicode representations (e.g. with combining |
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// diacritics). It allows a tasteful number of combining |
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// diacritics to be used, as long as they can be combined |
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// with parent characters to form regular letter symbols. |
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normalized := norm.NFC.String(strings.TrimPrefix(text, "#")) |
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// Validate normalized result. |
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var ( |
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atLeastOneRequiredChar = false |
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onlyPermittedChars = true |
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lengthOK = true |
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) |
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for i, r := range normalized { |
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if !isPermittedIfNotEntireHashtag(r) { |
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// This isn't an underscore, mark, etc, |
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// so the hashtag contains at least one |
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atLeastOneRequiredChar = true |
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} |
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if i >= maximumHashtagLength { |
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lengthOK = false |
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break |
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} |
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if !isPermittedInHashtag(r) { |
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onlyPermittedChars = false |
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break |
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} |
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} |
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return normalized, lengthOK && onlyPermittedChars && atLeastOneRequiredChar |
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}
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