import '../data/bible.dart';
import '../models/tracker.dart';

/// Pure progress calculations over a [Tracker].
///
/// Kept free of Flutter imports so it can be covered by plain unit tests.
class TrackerProgress {
  TrackerProgress(this.tracker);

  final Tracker tracker;

  int chaptersReadIn(Book book) {
    int count = 0;
    for (int chapter = 1; chapter <= book.chapterCount; chapter++) {
      if (tracker.readChapters.contains(
        Bible.chapterKey(book.index, chapter),
      )) {
        count++;
      }
    }
    return count;
  }

  double fractionOf(Book book) {
    if (book.chapterCount == 0) return 0;
    return chaptersReadIn(book) / book.chapterCount;
  }

  bool isBookComplete(Book book) =>
      chaptersReadIn(book) == book.chapterCount && book.chapterCount > 0;

  bool isBookStarted(Book book) => chaptersReadIn(book) > 0;

  int get totalRead => tracker.readChapters.length;

  double get overall =>
      Bible.totalChapters == 0 ? 0 : totalRead / Bible.totalChapters;

  int booksCompleted([Testament? testament]) => Bible.books
      .where(
        (Book book) =>
            (testament == null || book.testament == testament) &&
            isBookComplete(book),
      )
      .length;

  int chaptersReadInTestament(Testament testament) => Bible.books
      .where((Book book) => book.testament == testament)
      .fold<int>(0, (int sum, Book book) => sum + chaptersReadIn(book));

  double testamentFraction(Testament testament) {
    final int total = Bible.totalChaptersIn(testament);
    if (total == 0) return 0;
    return chaptersReadInTestament(testament) / total;
  }
}