feat(todo): quick add reads on before a day, durations, every !30m and !1pm

`on` (German `am`) before a day is taken with it, as `at` before a time;
`for 2h`, `for 1h30m`, `for 90 min`, `für 1,5 Std.` set the date's
duration where there is a time, and stay text without one; every `!30m`
counts, each once, sorted, a task without a date due at the latest; and
`!1pm`, `!13:00`, `!tomorrow 9am`, `!Monday 8:30` are reminders at a time
of their own, a time without a day on the task's day, else the next to
come. Todoist's newsletter's four examples parse whole (ADR 0033, D18).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_flutter/lib/src/feature/task/model/quick_add_parser.dart

@@ -9,9 +9,17 @@ enum QuickAddKind() {
   label,
   deadline,
   priority,
+
+  /// `!30m`: so long before the task's time.
   reminder,
+
+  /// `!1pm`, `!tomorrow 9am`: at a time of its own (D18).
+  reminderTime,
   date,
   time,
+
+  /// `for 2h` (D18).
+  duration,
   repeat,
 }
 
@@ -41,6 +49,9 @@ final class const ParsedTask({
 
   /// Reminders, minutes before the task's time, as [TaskContent.reminders].
   final List<int> reminders = const [],
+
+  /// Reminders at times of their own, as [TaskContent.reminderTimes].
+  final List<ReminderTime> reminderTimes = const [],
 });
 
 /// A project's or a label's ID and the name it is typed by.
@@ -50,9 +61,12 @@ typedef NamedId = ({String id, String name});
 /// `@label` by their names (the longest matching, the case aside; an
 /// unknown label to be made, an unknown project left as text), `{deadline}`,
 /// `!!1` and `p1` to `p4`, `!30m` (due that long from now, or reminded that
-/// long before its time), and dates, times and recurrences in [words]. Only
-/// the first of each kind counts. A token whose text, in lower case, is
-/// among [ignored] (tapped off by the person) stays text.
+/// long before its time), `!1pm` and `!tomorrow 9am` (reminded then, D18),
+/// and dates (`on` before one taken with it), times, durations (`for 2h`,
+/// with a time alone) and recurrences in [words]. Only the first of each
+/// kind counts, but for reminders and labels, each of which counts once. A
+/// token whose text, in lower case, is among [ignored] (tapped off by the
+/// person) stays text.
 ParsedTask parseQuickAdd(
   String text, {
   required DateTime now,
@@ -82,21 +96,25 @@ class _Parser(
   Day? _day;
   int? _time;
   Repeat? _repeat;
-  int? _reminder;
-  QuickAddToken? _reminderToken;
+  Duration? _duration;
+  QuickAddToken? _durationToken;
+
+  /// `!30m`'s minutes, each with its token.
+  final _reminders = <(int, QuickAddToken)>[];
+
+  /// `!1pm`'s day where it names one, and time.
+  final _reminderTimes = <(Day?, int)>[];
 
   bool _has(QuickAddKind kind) => _tokens.any((token) => token.kind == kind);
 
   bool _isIgnored(int start, int end) =>
       _ignored.contains(_text.substring(start, end).toLowerCase());
 
-  void _take(QuickAddKind kind, int start, int end) {
+  QuickAddToken _take(QuickAddKind kind, int start, int end) {
     final token = QuickAddToken(kind, start, end);
     _tokens.add(token);
-    if (kind == QuickAddKind.reminder) {
-      _reminderToken = token;
-    }
     _rest = _rest.replaceRange(start, end, ' ' * (end - start));
+    return token;
   }
 
   static bool _boundary(String text, int at) =>
@@ -104,6 +122,8 @@ class _Parser(
 
   ParsedTask parse(List<NamedId> projects, List<NamedId> labels) {
     _symbols(projects, labels);
+    _reminderTimesIn();
+    _durationIn();
     _phrases();
     return _result();
   }
@@ -183,10 +203,97 @@ class _Parser(
     for (final match in RegExp(
       r'(?<=^|\s)!(\d{1,4})(m|min|h)(?=\s|$)',
     ).allMatches(_text)) {
-      if (_reminder == null && !_isIgnored(match.start, match.end)) {
+      if (!_isIgnored(match.start, match.end)) {
         final amount = int.parse(match.group(1)!);
-        _reminder = match.group(2) == 'h' ? amount * 60 : amount;
-        _take(QuickAddKind.reminder, match.start, match.end);
+        _reminders.add((
+          match.group(2) == 'h' ? amount * 60 : amount,
+          _take(QuickAddKind.reminder, match.start, match.end),
+        ));
+      }
+    }
+  }
+
+  /// Every `!` before a time, or before a day and a time (D18): `!1pm`,
+  /// `!13:00`, `!tomorrow 9am`, `!Monday at 8:30`.
+  void _reminderTimesIn() {
+    final words = _wordsIn(_rest);
+    for (var i = 0; i < words.length; i++) {
+      final word = words[i];
+      if (!word.text.startsWith('!') || word.text.length < 2) {
+        continue;
+      }
+      final stripped = [
+        ...words.take(i),
+        _Word(word.text.substring(1), word.start + 1, word.end),
+        ...words.skip(i + 1),
+      ];
+      (Day?, int, int)? found;
+      if (_timeAt(stripped, i) case (final time, final length)) {
+        found = (null, time, length);
+      } else if (_dateAt(stripped, i) case (final day, final length)
+          when i + length < words.length) {
+        if (_timeAt(stripped, i + length) case (final time, final more)) {
+          found = (day, time, length + more);
+        }
+      }
+      if (found case (final day, final time, final length)) {
+        final end = words[i + length - 1].end;
+        if (!_isIgnored(word.start, end)) {
+          _reminderTimes.add((day, time));
+          _take(QuickAddKind.reminderTime, word.start, end);
+          i += length - 1;
+        }
+      }
+    }
+  }
+
+  /// The first duration (D18): `for 2h`, `for 1h30m`, `for 90 min`, `für
+  /// 1,5 Std.`, a day at most; a decimal comma or point taken, which the
+  /// words alone would split.
+  void _durationIn() {
+    final leads = {for (final words in _words) ...words.forWords};
+    final units = <String, int>{
+      for (final words in _words.reversed) ...words.durationUnits,
+    };
+    if (leads.isEmpty || units.isEmpty) {
+      return;
+    }
+    String either(Iterable<String> options) =>
+        (options.toList()..sort((a, b) => b.length.compareTo(a.length)))
+            .map(RegExp.escape)
+            .join('|');
+    final unit =
+        '(${either(units.keys)})'
+        r'\.?';
+    final pattern = RegExp(
+      r'(?<=^|\s)(?:'
+      '${either(leads)}'
+      r')\s+(\d+(?:[.,]\d+)?)\s*'
+      '$unit'
+      r'(?:\s*(\d+)\s*'
+      '$unit'
+      r')?(?=$|[\s,;!?])',
+      caseSensitive: false,
+      unicode: true,
+    );
+    for (final match in pattern.allMatches(_rest)) {
+      if (_isIgnored(match.start, match.end)) {
+        continue;
+      }
+      double minutesOf(String amount, String name) =>
+          double.parse(amount.replaceAll(',', '.')) *
+          units[name.toLowerCase()]!;
+      final minutes =
+          (minutesOf(match.group(1)!, match.group(2)!) +
+                  switch ((match.group(3), match.group(4))) {
+                    (final amount?, final name?) => minutesOf(amount, name),
+                    _ => 0,
+                  })
+              .round();
+      if (minutes > 0 && minutes <= 24 * 60) {
+        _duration = Duration(minutes: minutes);
+        _durationToken = _take(QuickAddKind.duration, match.start, match.end);
+        return;
       }
     }
   }
@@ -387,9 +494,15 @@ class _Parser(
 
   /// A day at [i]: today, tomorrow, a weekday, `next` one, the weekend, `in`
   /// a span, a month's day (either way round, with or without its year),
-  /// `2026-12-24` or `24.12.` (`24.12.2026`).
+  /// `2026-12-24` or `24.12.` (`24.12.2026`); maybe after `on` (D18).
   (Day, int)? _dateAt(List<_Word> words, int i) {
     final word = words[i].text;
+    if (_in((words) => words.on, word) && i + 1 < words.length) {
+      return switch (_dateAt(words, i + 1)) {
+        (final day, final length) => (day, length + 1),
+        null => null,
+      };
+    }
     String? after(int n) => i + n < words.length ? words[i + n].text : null;
     if (_in((words) => words.today, word)) {
       return (_today, 1);
@@ -546,26 +659,42 @@ class _Parser(
     var day = _day;
     var time = _time;
     var reminders = const <int>[];
-    if (_reminder case final reminder?) {
+    final before = {for (final (minutes, _) in _reminders) minutes};
+    if (before.isNotEmpty) {
       if (time != null) {
-        reminders = [reminder];
+        reminders = before.toList()..sort();
       } else if (day == null) {
-        final due = _now.add(Duration(minutes: reminder));
+        // Due at the latest, each reminding that long from now.
+        final latest = before.reduce((a, b) => a > b ? a : b);
+        final due = _now.add(Duration(minutes: latest));
         day = Day.of(due);
         time = due.hour * 60 + due.minute;
-        reminders = [0];
+        reminders = [for (final minutes in before) latest - minutes]..sort();
       } else {
         // A day without a time has nothing to be reminded before.
-        _tokens.remove(_reminderToken);
+        for (final (_, token) in _reminders) {
+          _tokens.remove(token);
+        }
       }
     }
+    if (time == null && _durationToken != null) {
+      // A duration lasts from a time; without one it is text (D18).
+      _tokens.remove(_durationToken);
+    }
+    final nowMinutes = _now.hour * 60 + _now.minute;
+    Day next(int time) => time > nowMinutes ? _today : _today.plus(1);
     if (day == null && time != null) {
-      final nowMinutes = _now.hour * 60 + _now.minute;
-      day = time > nowMinutes ? _today : _today.plus(1);
+      day = next(time);
     }
     if (_repeat case final repeat?) {
       day = repeat.firstFrom(day ?? _today);
     }
+    // A reminder's time without its day: the task's day, else the next to
+    // come (D18).
+    final reminderTimes = {
+      for (final (named, at) in _reminderTimes)
+        ReminderTime(named ?? day ?? next(at), at),
+    }.toList()..sort();
     _tokens.sort((a, b) => a.start.compareTo(b.start));
     final title = StringBuffer();
     var from = 0;
@@ -582,8 +711,16 @@ class _Parser(
       newLabels: List.unmodifiable(_newLabels),
       priority: _priority,
       deadline: _deadline,
-      date: day == null ? null : TaskDate(day, time: time, repeat: _repeat),
+      date: day == null
+          ? null
+          : TaskDate(
+              day,
+              time: time,
+              duration: time == null ? null : _duration,
+              repeat: _repeat,
+            ),
       reminders: reminders,
+      reminderTimes: reminderTimes,
     );
   }
 }

apps/todo/halkyon_todo_flutter/lib/src/feature/task/model/quick_add_words.dart

@@ -3,7 +3,8 @@ import 'package:halkyon_todo_flutter/src/feature/task/model/repeat.dart';
 /// The words quick add reads dates, times and recurrences in, one table a
 /// language (ADR 0033, D15): a new app language adds a table here, not a
 /// parser. Quick add reads the app's language and English together; the
-/// symbols (`#`, `@`, `{}`, `!!`, `p1`, `!30m`) hold in every one. Every
+/// symbols (`#`, `@`, `{}`, `!!`, `p1`, `!30m`, `!` before a time) hold
+/// in every one. Every
 /// word is lower case, as the text is compared folded to it.
 final class const QuickAddWords({
   /// Today, and the words for it.
@@ -49,6 +50,15 @@ final class const QuickAddWords({
   /// What may stand before a time: `at 7pm`.
   required final Set<String> at,
 
+  /// What may stand before a day: `on Monday`, `on 1st March`.
+  final Set<String> on = const {},
+
+  /// What starts a duration: `for 2h`.
+  final Set<String> forWords = const {},
+
+  /// A duration's units, each to its minutes: `h` to 60, `min` to 1.
+  final Map<String, int> durationUnits = const {},
+
   /// What joins weekdays: `mon and fri`.
   required final Set<String> and,
 
@@ -154,6 +164,20 @@ final class const QuickAddWords({
     next: {'next'},
     inWords: {'in'},
     at: {'at'},
+    on: {'on'},
+    forWords: {'for'},
+    durationUnits: {
+      'h': 60,
+      'hr': 60,
+      'hrs': 60,
+      'hour': 60,
+      'hours': 60,
+      'm': 1,
+      'min': 1,
+      'mins': 1,
+      'minute': 1,
+      'minutes': 1,
+    },
     and: {'and', '&'},
     meridiem: {'am': 0, 'pm': 12},
     daySuffixes: {'st', 'nd', 'rd', 'th'},
@@ -235,6 +259,17 @@ final class const QuickAddWords({
     next: {'nächsten', 'nächste', 'nächster', 'kommenden', 'kommende'},
     inWords: {'in'},
     at: {'um'},
+    on: {'am'},
+    forWords: {'für'},
+    durationUnits: {
+      'h': 60,
+      'std': 60,
+      'stunde': 60,
+      'stunden': 60,
+      'min': 1,
+      'minute': 1,
+      'minuten': 1,
+    },
     and: {'und'},
     oClock: {'uhr'},
     daySuffixes: {'.'},

apps/todo/halkyon_todo_flutter/lib/src/feature/task/widget/quick_add_sheet.dart

@@ -32,8 +32,9 @@ import 'package:material_ui/material_ui.dart';
 /// It shows the title alone at first, its chips once typing starts, and its
 /// description from its + or the down arrow (the developer's, 1 Nov, D15).
 /// What the title says is read as it is typed (`parseQuickAdd`): `#project`,
-/// `@label`, `{deadline}`, `!!1`, `p1`, `!30m`, dates, times and
-/// recurrences in the app's language and English, each highlighted and
+/// `@label`, `{deadline}`, `!!1`, `p1`, `!30m` (as many as typed), `!1pm`,
+/// dates, times, durations and recurrences in the app's language and
+/// English, each highlighted and
 /// shown on its chip; a tap on one keeps it as text, and a chip picked
 /// takes its token out of the title. As `#` or `@` is typed, the projects
 /// or labels it may mean are offered below the title, one tapped
@@ -320,6 +321,7 @@ class _QuickAddState() extends State<_QuickAdd> {
           priority: parsed.priority ?? _priority,
           labelIds: {..._labelIds, ...parsed.labelIds, ...made}.toList(),
           reminders: parsed.reminders,
+          reminderTimes: parsed.reminderTimes,
         ),
       );
     } on KeysMissing {
@@ -473,6 +475,7 @@ class _QuickAddState() extends State<_QuickAdd> {
                                 QuickAddKind.date,
                                 QuickAddKind.time,
                                 QuickAddKind.repeat,
+                                QuickAddKind.duration,
                                 QuickAddKind.reminder,
                               });
                               setState(() => _date = date);