Add adding grades to a term and enhance grade logic.

app/lib/grades/grades_service/src/grading_system.dart

@@ -0,0 +1,161 @@
+// Copyright (c) 2024 Sharezone UG (haftungsbeschränkt)
+// Licensed under the EUPL-1.2-or-later.
+//
+// You may obtain a copy of the Licence at:
+// https://joinup.ec.europa.eu/software/page/eupl
+//
+// SPDX-License-Identifier: EUPL-1.2
+
+part of '../grades_service.dart';
+
+extension _ToGradingSystem on GradingSystem {
+  _GradingSystem toGradingSystem() {
+    switch (this) {
+      case GradingSystem.oneToFiveteenPoints:
+        return _GradingSystem.oneToFiveteenPoints;
+      case GradingSystem.oneToSixWithPlusAndMinus:
+        return _GradingSystem.oneToSixWithPlusAndMinus;
+    }
+  }
+}
+
+extension _ToGradingSystems on _GradingSystem {
+  GradingSystem toGradingSystems() {
+    if (this is OneToFiveteenPointsGradingSystem) {
+      return GradingSystem.oneToFiveteenPoints;
+    } else if (this is OneToSixWithPlusMinusGradingSystem) {
+      return GradingSystem.oneToSixWithPlusAndMinus;
+    }
+    throw UnimplementedError();
+  }
+}
+
+sealed class _GradingSystem {
+  static final oneToSixWithPlusAndMinus = OneToSixWithPlusMinusGradingSystem();
+  static final oneToFiveteenPoints = OneToFiveteenPointsGradingSystem();
+
+  double toDoubleOrThrow(String grade);
+  IList<String> get possibleValues;
+
+  CalculatedGradeResult toGradeResult(num grade) {
+    final displayableGrade = toDisplayableGrade(grade);
+    return CalculatedGradeResult(
+      asNum: grade,
+      displayableGrade: displayableGrade,
+    );
+  }
+
+  String toDisplayableGrade(num grade) {
+    final res = getDisplayableGradeIfExactMatch(grade);
+    if (res != null) {
+      return res;
+    }
+    return grade.toStringAsFixed(2).replaceAll('.', ',').substring(0, 3);
+  }
+
+  String? getDisplayableGradeIfExactMatch(num grade);
+}
+
+class OneToFiveteenPointsGradingSystem extends _GradingSystem
+    with EquatableMixin {
+  @override
+  IList<String> get possibleValues => const IListConst([
+        '0',
+        '1',
+        '2',
+        '3',
+        '4',
+        '5',
+        '6',
+        '7',
+        '8',
+        '9',
+        '10',
+        '11',
+        '12',
+        '13',
+        '14',
+        '15',
+      ]);
+
+  @override
+  double toDoubleOrThrow(String grade) {
+    return double.parse(grade);
+  }
+
+  @override
+  List<Object?> get props => [];
+
+  @override
+  String? getDisplayableGradeIfExactMatch(num grade) {
+    for (var val in possibleValues) {
+      if (int.parse(val) == grade) {
+        return val;
+      }
+    }
+    return null;
+  }
+}
+
+class OneToSixWithPlusMinusGradingSystem extends _GradingSystem
+    with EquatableMixin {
+  @override
+  IList<String> get possibleValues => const IListConst([
+        '1+',
+        '1',
+        '1-',
+        '2+',
+        '2',
+        '2-',
+        '3+',
+        '3',
+        '3-',
+        '4+',
+        '4',
+        '4-',
+        '5+',
+        '5',
+        '5-',
+        '6',
+      ]);
+
+  @override
+  double toDoubleOrThrow(String grade) {
+    return switch (grade) {
+      '1+' => 0.75,
+      '1' => 1,
+      '1-' => 1.25,
+      '2+' => 1.75,
+      '2' => 2,
+      '2-' => 2.25,
+      '3+' => 2.75,
+      '3' => 3,
+      '3-' => 3.25,
+      '4+' => 3.75,
+      '4' => 4,
+      '4-' => 4.25,
+      '5+' => 4.75,
+      '5' => 5,
+      '5-' => 5.25,
+      '6' => 6,
+      _ => throw ArgumentError.value(
+          grade,
+          'grade',
+          'Invalid grade value',
+        ),
+    };
+  }
+
+  @override
+  List<Object?> get props => [];
+
+  @override
+  String? getDisplayableGradeIfExactMatch(num grade) {
+    for (var val in possibleValues) {
+      if (toDoubleOrThrow(val) == grade) {
+        return val;
+      }
+    }
+    return null;
+  }
+}