using KronaStaffTerminal.Models;

namespace KronaStaffTerminal.Services;

public sealed record AttendanceRecordResult(
    bool Success,
    AttendanceRecord? Record,
    string Message,
    bool IsDuplicateSuppressed,
    int RemainingSeconds = 0);

public sealed record ScanRecognitionResult(
    bool Success,
    AttendanceRecordResult AttendanceResult,
    bool ShouldUnlock,
    string? LockScreenMessage,
    string StatusMessage);

public sealed class AttendanceTracker
{
    private readonly SemaphoreSlim _gate = new(1, 1);

    public async Task<AttendanceRecordResult> TryRecordAttendanceAsync(
        TerminalState state,
        EmployeeRecord employee,
        int readerIndex,
        DateTimeOffset nowUtc,
        Func<TerminalState, Task> saveStateCallback)
    {
        await _gate.WaitAsync();
        try
        {
            var last = state.Attendance
                .Where(item => item.EmployeeId == employee.Id)
                .OrderByDescending(item => item.OccurredAtUtc)
                .FirstOrDefault();

            var guardSeconds = Math.Clamp(state.Settings.DuplicateScanGuardSeconds, 10, 3600);
            var guard = TimeSpan.FromSeconds(guardSeconds);

            if (last is not null && nowUtc - last.OccurredAtUtc < guard)
            {
                var remaining = Math.Max(1, (int)Math.Ceiling((guard - (nowUtc - last.OccurredAtUtc)).TotalSeconds));
                return new AttendanceRecordResult(
                    Success: false,
                    Record: null,
                    Message: $"Повторный скан отклонён. Повторите через {remaining} сек.",
                    IsDuplicateSuppressed: true,
                    RemainingSeconds: remaining);
            }

            var maximumShift = TimeSpan.FromHours(Math.Clamp(state.Settings.MaximumShiftHours, 1, 48));
            var isCheckIn = last is null || last.EventType != "Приход" || (nowUtc - last.OccurredAtUtc > maximumShift);
            var eventType = isCheckIn ? "Приход" : "Уход";

            var record = new AttendanceRecord
            {
                Id = UlidGenerator.New(),
                EmployeeId = employee.Id,
                EmployeeName = employee.DisplayName,
                OccurredAtUtc = nowUtc,
                ReaderIndex = readerIndex,
                EventType = eventType,
                IsAutomatic = false
            };

            state.Attendance.Insert(0, record);
            if (state.Attendance.Count > 100_000)
            {
                state.Attendance.RemoveRange(100_000, state.Attendance.Count - 100_000);
            }

            await saveStateCallback(state);

            return new AttendanceRecordResult(
                Success: true,
                Record: record,
                Message: $"{eventType} отмечен в {nowUtc.ToLocalTime():HH:mm}",
                IsDuplicateSuppressed: false);
        }
        finally
        {
            _gate.Release();
        }
    }

    public async Task<ScanRecognitionResult> ProcessScanAsync(
        TerminalState state,
        EmployeeRecord employee,
        int readerIndex,
        DateTimeOffset nowUtc,
        bool isApplicationLocked,
        Func<TerminalState, Task> saveStateCallback)
    {
        if (employee.IsBlocked)
        {
            return new ScanRecognitionResult(
                Success: false,
                AttendanceResult: new AttendanceRecordResult(
                    Success: false,
                    Record: null,
                    Message: "Сотрудник заблокирован. Отметка не создана.",
                    IsDuplicateSuppressed: false),
                ShouldUnlock: false,
                LockScreenMessage: isApplicationLocked ? "Этот сотрудник заблокирован." : null,
                StatusMessage: "Сотрудник заблокирован. Отметка не создана.");
        }

        var attendanceResult = await TryRecordAttendanceAsync(
            state,
            employee,
            readerIndex,
            nowUtc,
            saveStateCallback);

        if (isApplicationLocked)
        {
            if (!employee.IsAdministrator)
            {
                var lockMessage = attendanceResult.Success
                    ? "Отметка прихода или ухода зафиксирована. Интерфейс остаётся заблокированным."
                    : attendanceResult.IsDuplicateSuppressed
                        ? $"Повторный скан отклонён. Повторите через {attendanceResult.RemainingSeconds} сек."
                        : "Отметка не создана. Интерфейс остаётся заблокированным.";

                return new ScanRecognitionResult(
                    Success: attendanceResult.Success,
                    AttendanceResult: attendanceResult,
                    ShouldUnlock: false,
                    LockScreenMessage: lockMessage,
                    StatusMessage: attendanceResult.Message);
            }

            // Administrator scan in locked state:
            // Attendance is recorded AND the interface should be unlocked
            return new ScanRecognitionResult(
                Success: attendanceResult.Success,
                AttendanceResult: attendanceResult,
                ShouldUnlock: true,
                LockScreenMessage: null,
                StatusMessage: $"Вход выполнен по отпечатку администратора {employee.DisplayName}.");
        }

        return new ScanRecognitionResult(
            Success: attendanceResult.Success,
            AttendanceResult: attendanceResult,
            ShouldUnlock: false,
            LockScreenMessage: null,
            StatusMessage: attendanceResult.Message);
    }

    public async Task<List<AttendanceRecord>> RunScheduledCheckoutAsync(
        TerminalState state,
        DateTimeOffset nowUtc,
        Func<TerminalState, Task> saveStateCallback)
    {
        await _gate.WaitAsync();
        try
        {
            if (!state.Settings.AutomaticCheckoutEnabled)
            {
                return [];
            }

            var hour = Math.Clamp(state.Settings.AutomaticCheckoutHour, 0, 23);
            var minute = Math.Clamp(state.Settings.AutomaticCheckoutMinute, 0, 59);
            var latestScheduleUtc = LatestAutomaticCheckoutScheduleUtc(nowUtc, hour, minute);

            if (state.Settings.LastAutomaticCheckoutUtc >= latestScheduleUtc)
            {
                return [];
            }

            var createdRecords = new List<AttendanceRecord>();
            foreach (var employee in state.Employees)
            {
                if (employee.IsBlocked) continue;

                var last = state.Attendance
                    .Where(item => item.EmployeeId == employee.Id)
                    .OrderByDescending(item => item.OccurredAtUtc)
                    .FirstOrDefault();

                if (last is null || last.EventType != "Приход") continue;

                var checkoutUtc = NextAutomaticCheckoutAfter(last.OccurredAtUtc, hour, minute);
                if (checkoutUtc > nowUtc) continue;

                var record = new AttendanceRecord
                {
                    Id = UlidGenerator.New(),
                    EmployeeId = employee.Id,
                    EmployeeName = employee.DisplayName,
                    OccurredAtUtc = checkoutUtc,
                    ReaderIndex = -1,
                    EventType = "Уход автоматически",
                    IsAutomatic = true
                };

                createdRecords.Add(record);
            }

            if (createdRecords.Count > 0)
            {
                state.Attendance.InsertRange(0, createdRecords);
                if (state.Attendance.Count > 100_000)
                {
                    state.Attendance.RemoveRange(100_000, state.Attendance.Count - 100_000);
                }
            }

            state.Settings.LastAutomaticCheckoutUtc = latestScheduleUtc;
            await saveStateCallback(state);

            return createdRecords;
        }
        finally
        {
            _gate.Release();
        }
    }

    public static DateTimeOffset LatestAutomaticCheckoutScheduleUtc(DateTimeOffset nowUtc, int hour, int minute)
    {
        var localNow = nowUtc.ToLocalTime();
        var scheduledToday = new DateTimeOffset(
            localNow.Year, localNow.Month, localNow.Day,
            hour, minute, 0,
            localNow.Offset);

        var targetLocal = localNow >= scheduledToday ? scheduledToday : scheduledToday.AddDays(-1);
        return targetLocal.ToUniversalTime();
    }

    public static DateTimeOffset NextAutomaticCheckoutAfter(DateTimeOffset startUtc, int hour, int minute)
    {
        var localStart = startUtc.ToLocalTime();
        var scheduledSameDay = new DateTimeOffset(
            localStart.Year, localStart.Month, localStart.Day,
            hour, minute, 0,
            localStart.Offset);

        var targetLocal = scheduledSameDay > localStart ? scheduledSameDay : scheduledSameDay.AddDays(1);
        return targetLocal.ToUniversalTime();
    }
}