import 'package:timezone/timezone.dart' as tz;
import 'package:tasq/models/programmer_task.model.dart';
import 'package:tasq/models/programmer_task_activity_log.model.dart';
import 'app_time.dart';

/// Get the Manila calendar date of an instant as DateTime.utc(y, m, d)
DateTime manilaDay(DateTime instant) {
  final utc = instant.isUtc ? instant : instant.toUtc();
  final manila = tz.TZDateTime.from(utc, tz.local);
  return DateTime.utc(manila.year, manila.month, manila.day);
}

/// Get the Manila midnight of a day key as a TZDateTime
DateTime manilaDayStart(DateTime dayKey) {
  return AppTime.fromComponents(
    year: dayKey.year,
    month: dayKey.month,
    day: dayKey.day,
    hour: 0,
    minute: 0,
  );
}

/// Parse a day key string (e.g., '2026-09-27') to DateTime.utc
DateTime parseDayKey(String yyyyMmDd) {
  final parts = yyyyMmDd.split('-');
  return DateTime.utc(int.parse(parts[0]), int.parse(parts[1]), int.parse(parts[2]));
}

/// Format a day key to string (e.g., DateTime.utc(2026, 9, 27) -> '2026-09-27')
String formatDayKey(DateTime dayKey) {
  final y = dayKey.year.toString();
  final m = dayKey.month.toString().padLeft(2, '0');
  final d = dayKey.day.toString().padLeft(2, '0');
  return '$y-$m-$d';
}

/// Represents a worked interval for an assignee
typedef WorkedInterval = ({String assigneeId, DateTime start, DateTime end});

/// Calculate worked intervals from task and activity logs
List<WorkedInterval> workedIntervals({
  required ProgrammerTask task,
  required List<ProgrammerTaskActivityLog> logs,
  required DateTime now,
}) {
  final sorted = List<ProgrammerTaskActivityLog>.from(logs)
    ..sort((a, b) => a.createdAt.compareTo(b.createdAt));

  final intervals = <WorkedInterval>[];
  DateTime? segmentStart;
  String currentAssignee = _initialAssignee(task, sorted);

  // Check if there's a synthetic started event needed
  if (!sorted.any((l) => l.actionType == 'started') && task.startedAt != null) {
    // Inject synthetic started
    sorted.insert(
      0,
      ProgrammerTaskActivityLog(
        id: 'synthetic-start',
        taskId: task.id,
        actionType: 'started',
        createdAt: task.startedAt!,
      ),
    );
  }

  for (final log in sorted) {
    switch (log.actionType) {
      case 'started':
      case 'resumed':
        if (segmentStart == null) {
          segmentStart = log.createdAt;
        }
        break;

      case 'paused':
      case 'completed':
      case 'cancelled':
        if (segmentStart != null) {
          intervals.add((
            assigneeId: currentAssignee,
            start: segmentStart,
            end: log.createdAt,
          ));
          segmentStart = null;
        }
        break;

      case 'reassigned':
        final wasRunning = segmentStart != null;
        if (segmentStart != null) {
          // Close segment for old assignee
          intervals.add((
            assigneeId: currentAssignee,
            start: segmentStart,
            end: log.createdAt,
          ));
          segmentStart = null;
        }
        // Update assignee and reopen segment only if it was running
        if (log.meta?['assignee_id'] != null) {
          currentAssignee = log.meta!['assignee_id'] as String;
          if (wasRunning) {
            segmentStart = log.createdAt;
          }
        }
        break;
    }
  }

  // Close any remaining open segment
  if (segmentStart != null) {
    final endTime = task.status == ProgrammerTaskStatus.inProgress
        ? now
        : (task.completedAt ?? task.cancelledAt ?? now);
    intervals.add((
      assigneeId: currentAssignee,
      start: segmentStart,
      end: endTime,
    ));
  }

  return intervals;
}

/// Calculate daily seconds by assignee
Map<String, Map<DateTime, int>> dailySecondsByAssignee({
  required ProgrammerTask task,
  required List<ProgrammerTaskActivityLog> logs,
  required DateTime now,
}) {
  final intervals = workedIntervals(task: task, logs: logs, now: now);
  final result = <String, Map<DateTime, int>>{};

  // Process intervals and split at Manila midnights
  for (final interval in intervals) {
    var current = interval.start;
    final end = interval.end;

    while (current.isBefore(end)) {
      final currentDay = manilaDay(current);
      final dayStart = manilaDayStart(currentDay);
      final nextDayStart = dayStart.add(Duration(days: 1));
      final segmentEnd = end.isBefore(nextDayStart) ? end : nextDayStart;

      final seconds = segmentEnd.difference(current).inSeconds;

      if (!result.containsKey(interval.assigneeId)) {
        result[interval.assigneeId] = {};
      }

      result[interval.assigneeId]![currentDay] =
          (result[interval.assigneeId]![currentDay] ?? 0) + seconds;

      current = segmentEnd;
    }
  }

  // Apply adjustments
  for (final log in logs) {
    if (log.actionType == 'adjustment' && log.meta?['seconds'] != null) {
      final adjustSeconds = (log.meta!['seconds'] as num).toInt();
      final adjustDay = manilaDay(log.createdAt);

      // Find the assignee at this time
      final assigneeAtTime = _assigneeAtTime(task, logs, log.createdAt);
      if (assigneeAtTime != null) {
        if (!result.containsKey(assigneeAtTime)) {
          result[assigneeAtTime] = {};
        }
        final current =
            result[assigneeAtTime]![adjustDay] ?? 0;
        result[assigneeAtTime]![adjustDay] =
            (current - adjustSeconds).clamp(0, 999999999);
      }
    }
  }

  return result;
}

/// Find the initial assignee based on task and logs
String _initialAssignee(
  ProgrammerTask task,
  List<ProgrammerTaskActivityLog> logs,
) {
  // First: check for 'assigned' event
  for (final log in logs) {
    if (log.actionType == 'assigned' && log.meta?['assignee_id'] != null) {
      return log.meta!['assignee_id'] as String;
    }
  }

  // Second: if any 'reassigned' event exists, use task.creatorId
  if (logs.any((l) => l.actionType == 'reassigned') && task.creatorId != null) {
    return task.creatorId!;
  }

  // Third: use task.assigneeId
  return task.assigneeId ?? 'unknown';
}

/// Find the assignee at a specific time
String? _assigneeAtTime(
  ProgrammerTask task,
  List<ProgrammerTaskActivityLog> logs,
  DateTime time,
) {
  final sorted = List<ProgrammerTaskActivityLog>.from(logs)
    ..sort((a, b) => a.createdAt.compareTo(b.createdAt));

  var currentAssignee = _initialAssignee(task, sorted);

  for (final log in sorted) {
    if (log.createdAt.isAfter(time)) break;

    if (log.actionType == 'reassigned' &&
        log.meta?['assignee_id'] != null) {
      currentAssignee = log.meta!['assignee_id'] as String;
    }
  }

  return currentAssignee;
}