Akiba So
3e0b81be92
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For library-wide full-text search (the user's #1 named differentiator): snippetFor() finds the first case-insensitive match of a query in a source string (PDF text page / typed box / OCR'd handwriting) and returns a windowed excerpt centered on it, preserving the match offset + length and truncatedStart/End flags so the results list can render "…ctx **match** ctx…" and jump to the hit. The full match is always included; near-edge matches don't over-truncate. Returns null for empty/absent query. The FTS index + ranking live in the DB (search_indexer, later); this is the pure, storage-free excerpt math, fully unit-tested. flutter analyze lib/editor clean; 164/164 tests (+8). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
74 lines
2.4 KiB
Dart
74 lines
2.4 KiB
Dart
// lib/editor/search/search_snippet.dart
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//
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// Pure snippet extraction for library-wide full-text search (F8 — the user's #1
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// named differentiator). Given a source string (a PDF text page, a typed text
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// box, or OCR'd handwriting) and a query, produce a windowed excerpt centered on
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// the first match with the match offset preserved, so the results list can show
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// "…context **match** context…" and jump to the hit.
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//
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// The FTS index / ranking lives in the DB (search_indexer); THIS is the pure,
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// storage-free excerpt math, fully unit-tested.
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/// A windowed excerpt around a query match.
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class Snippet {
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const Snippet({
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required this.text,
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required this.matchStart,
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required this.matchLength,
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required this.truncatedStart,
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required this.truncatedEnd,
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});
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/// The excerpt (a substring of the source).
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final String text;
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/// Offset of the match WITHIN [text].
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final int matchStart;
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/// Length of the matched run.
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final int matchLength;
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/// True when [text] begins before the source start was reached (show a
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/// leading ellipsis).
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final bool truncatedStart;
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/// True when [text] ends before the source end (show a trailing ellipsis).
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final bool truncatedEnd;
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/// Convenience: the matched substring.
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String get match => text.substring(matchStart, matchStart + matchLength);
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@override
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String toString() =>
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'${truncatedStart ? '…' : ''}$text${truncatedEnd ? '…' : ''}'
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' [match @$matchStart+$matchLength]';
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}
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/// First case-insensitive match of [query] in [source], as a snippet of up to
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/// roughly [window] characters centered on the match. Returns null when [query]
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/// is empty or absent. The full match is always included even if longer than
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/// [window].
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Snippet? snippetFor(String source, String query, {int window = 80}) {
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if (query.isEmpty || source.isEmpty) return null;
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assert(window >= 0);
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final matchIndex = source.toLowerCase().indexOf(query.toLowerCase());
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if (matchIndex < 0) return null;
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final matchLen = query.length;
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final contextEach = ((window - matchLen) ~/ 2).clamp(0, window);
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var start = matchIndex - contextEach;
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if (start < 0) start = 0;
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var end = matchIndex + matchLen + contextEach;
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if (end > source.length) end = source.length;
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return Snippet(
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text: source.substring(start, end),
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matchStart: matchIndex - start,
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matchLength: matchLen,
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truncatedStart: start > 0,
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truncatedEnd: end < source.length,
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);
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}
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