107 lines
3.8 KiB
Dart
107 lines
3.8 KiB
Dart
import '../../data/ducet_order.dart';
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import '../../media/library_first_character.dart';
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/// Shared letter-index mapping logic used by both [AlphaJumpBar] (desktop/tablet/TV)
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/// and [AlphaScrollHandle] (phone).
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///
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/// Builds a dynamic letter list and cumulative index map from [LibraryFirstCharacter]
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/// data returned by the server's first-character endpoint. Only letters that
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/// have items are included, supporting non-Latin scripts (Korean, Japanese,
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/// Cyrillic, etc.).
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///
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/// Plex's `/firstCharacter` endpoint returns characters in Unicode codepoint
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/// order, which doesn't match the content endpoint's ICU locale-aware sort.
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/// We re-sort using ICU collation so cumulative indices are correct.
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class AlphaJumpHelper {
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/// Dynamic letter list derived from the API's firstCharacter data,
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/// re-sorted to match ICU collation order.
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final List<String> letters;
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/// Maps each letter to its cumulative start index in the full item list.
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final Map<String, int> letterToIndex;
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/// Maps each letter to its item count.
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final Map<String, int> letterSizes;
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/// Total number of items across all letters.
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final int totalItemCount;
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AlphaJumpHelper._(this.letters, this.letterToIndex, this.letterSizes, this.totalItemCount);
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factory AlphaJumpHelper(List<LibraryFirstCharacter> firstCharacters, {bool descending = false}) {
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final entries = <({String letter, int size})>[];
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final letterSizes = <String, int>{};
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for (final fc in firstCharacters) {
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final letter = fc.title.toUpperCase();
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if (fc.size > 0) {
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entries.add((letter: letter, size: fc.size));
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letterSizes[letter] = fc.size;
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}
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}
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entries.sort((a, b) => ducetCompare(a.letter, b.letter));
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if (descending) {
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entries.setAll(0, entries.reversed.toList());
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}
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final letters = <String>[];
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final letterToIndex = <String, int>{};
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int cumulative = 0;
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for (final e in entries) {
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letters.add(e.letter);
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letterToIndex[e.letter] = cumulative;
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cumulative += e.size;
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}
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return AlphaJumpHelper._(letters, letterToIndex, letterSizes, cumulative);
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}
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/// Returns at most [maxCount] letters, prioritizing those with the most
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/// items. The returned letters maintain their original order.
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List<String> displayLetters(int maxCount) {
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if (maxCount >= letters.length) return letters;
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if (maxCount <= 0) return const [];
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final indices = List.generate(letters.length, (i) => i);
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indices.sort((a, b) => (letterSizes[letters[b]] ?? 0).compareTo(letterSizes[letters[a]] ?? 0));
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final kept = indices.take(maxCount).toList()..sort();
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return [for (final i in kept) letters[i]];
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}
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/// Returns the letter that the given item index falls within.
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String currentLetter(int itemIndex) {
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if (letters.isEmpty) return '#';
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String current = letters.first;
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for (final letter in letters) {
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final startIndex = letterToIndex[letter];
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if (startIndex != null && startIndex <= itemIndex) {
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current = letter;
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}
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}
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return current;
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}
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/// Returns the cumulative start index for a letter, or null if not present.
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int? indexForLetter(String letter) => letterToIndex[letter];
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/// Returns the fractional position (0.0–1.0) for a letter, proportional to
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/// item count. Letters with more items occupy a larger segment.
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double fractionForLetter(String letter) {
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if (totalItemCount == 0) return 0.0;
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final index = letterToIndex[letter];
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if (index == null) return 0.0;
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return index / totalItemCount;
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}
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/// Returns the letter at a given fractional position (0.0–1.0), proportional
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/// to item count.
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String letterAtFraction(double fraction) {
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if (letters.isEmpty) return '#';
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if (totalItemCount == 0) return letters.first;
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final targetIndex = (fraction * totalItemCount).round().clamp(0, totalItemCount - 1);
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return currentLetter(targetIndex);
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}
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}
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