| // An `@` starts a mention only when preceded by start-of-string or one of | |
| // these; identifier chars are not delimiters, so a mid-word `@` does not. | |
| const TOKEN_BOUNDARY_CHARS = new Set([ | |
| ' ', | |
| '\t', | |
| '\n', | |
| '\r', | |
| '(', | |
| ')', | |
| '[', | |
| ']', | |
| ',', | |
| ';', | |
| ':', | |
| '"', | |
| "'" | |
| ]); | |
| /** | |
| * Find the most-recent `@`-mention token whose extent includes `cursor`; | |
| * the query covers the whole `@...` token regardless of caret position. | |
| */ | |
| export function findMentionToken( | |
| value: string, | |
| cursor: number | |
| ): { start: number; end: number; query: string } | null { | |
| if (cursor <= 0 || cursor > value.length) return null; | |
| let atIndex = -1; | |
| for (let i = cursor - 1; i >= 0; i--) { | |
| const ch = value[i]; | |
| if (ch === '@') { | |
| const prev = i > 0 ? value[i - 1] : ''; | |
| if (i === 0 || TOKEN_BOUNDARY_CHARS.has(prev)) { | |
| atIndex = i; | |
| } | |
| break; | |
| } | |
| if (TOKEN_BOUNDARY_CHARS.has(ch)) break; | |
| } | |
| if (atIndex === -1) return null; | |
| let end = atIndex + 1; | |
| while (end < value.length && !TOKEN_BOUNDARY_CHARS.has(value[end])) { | |
| end++; | |
| } | |
| return { | |
| end, | |
| query: value.slice(atIndex + 1, end), | |
| start: atIndex | |
| }; | |
| } | |
| /** | |
| * Stable signature of a mention token for use as a "dismissed" marker: | |
| * while the picker is closed and this exact token is still intact, the | |
| * picker does not silently re-open on in-token edits. | |
| */ | |
| export interface MentionDismissSnapshot { | |
| start: number; | |
| query: string; | |
| } | |
| export function takeMentionDismissSnapshot( | |
| value: string, | |
| cursor: number | |
| ): MentionDismissSnapshot | null { | |
| const token = findMentionToken(value, cursor); | |
| if (!token) return null; | |
| return { query: token.query, start: token.start }; | |
| } | |