using AVSCartonShipmentVerifier.DTOs;
using AVSCartonShipmentVerifier.Repositories;
using AVSCartonShipmentVerifier.ScanHistory;
using Microsoft.EntityFrameworkCore;

namespace AVSCartonShipmentVerifier.Services;

public sealed class MovementAnalyticsService(
    ScanHistoryDbContext dbContext,
    ICartonVerificationRepository cartonVerificationRepository,
    ILogger<MovementAnalyticsService> logger) : IMovementAnalyticsService
{
    private readonly ScanHistoryDbContext _dbContext = dbContext;
    private readonly ICartonVerificationRepository _cartonVerificationRepository = cartonVerificationRepository;
    private readonly ILogger<MovementAnalyticsService> _logger = logger;

    public async Task<MovementAnalyticsDto> GetAnalyticsAsync(DateOnly fromDate, DateOnly toDate, CancellationToken cancellationToken = default)
    {
        if (toDate < fromDate)
        {
            (fromDate, toDate) = (toDate, fromDate);
        }

        var today = DateOnly.FromDateTime(DateTime.Now);
        var (todayStartUtc, todayEndUtc) = GetUtcDayRange(today);
        var (weekStartUtc, weekEndUtc) = GetUtcWeekRange(today);
        var (monthStartUtc, monthEndUtc) = GetUtcMonthRange(today);
        var (rangeStartUtc, rangeEndUtc) = GetUtcDayRange(fromDate, toDate);

        int movedToday;
        int movedThisWeek;
        int movedThisMonth;
        int totalMoved;
        int pending;
        List<ScanHistoryEntry> successfulInRange;
        List<RejectedScanEntry> rejectedInRange;

        try
        {
            movedToday = await CountSuccessfulScansAsync(todayStartUtc, todayEndUtc, cancellationToken);
            movedThisWeek = await CountSuccessfulScansAsync(weekStartUtc, weekEndUtc, cancellationToken);
            movedThisMonth = await CountSuccessfulScansAsync(monthStartUtc, monthEndUtc, cancellationToken);
            totalMoved = await _cartonVerificationRepository.GetTotalMovedCartonCountAsync(cancellationToken);
            pending = await _cartonVerificationRepository.GetAvailableCartonCountAsync(cancellationToken);

            successfulInRange = await _dbContext.ScanHistoryEntries
                .AsNoTracking()
                .Where(x => x.ShipmentMarked && x.ProcessedAtUtc >= rangeStartUtc && x.ProcessedAtUtc <= rangeEndUtc)
                .ToListAsync(cancellationToken);

            rejectedInRange = await _dbContext.RejectedScanEntries
                .AsNoTracking()
                .Where(x => x.ProcessedAtUtc >= rangeStartUtc && x.ProcessedAtUtc <= rangeEndUtc)
                .ToListAsync(cancellationToken);
        }
        catch (OperationCanceledException exception) when (cancellationToken.IsCancellationRequested)
        {
            _logger.LogDebug(exception, "Movement analytics read was cancelled.");
            throw;
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to load movement analytics.");
            throw;
        }

        var successfulByLocalDate = successfulInRange
            .GroupBy(x => ToLocalDateOnly(x.ProcessedAtUtc))
            .ToDictionary(g => g.Key, g => g.ToList());

        var rejectedByLocalDate = rejectedInRange
            .GroupBy(x => ToLocalDateOnly(x.ProcessedAtUtc))
            .ToDictionary(g => g.Key, g => g.ToList());

        var chartByDay = new List<MovementChartDayDto>();
        var dayDetails = new List<MovementDayDetailDto>();

        for (var date = fromDate; date <= toDate; date = date.AddDays(1))
        {
            successfulByLocalDate.TryGetValue(date, out var daySuccessful);
            daySuccessful ??= [];

            rejectedByLocalDate.TryGetValue(date, out var dayRejected);
            dayRejected ??= [];

            var movedCount = daySuccessful.Count;
            var duplicateCount = dayRejected.Count(r =>
                string.Equals(r.RejectionReason, VerificationRejectionReasons.AlreadyTransferredDuplicateScan, StringComparison.Ordinal));
            var manualCount = dayRejected.Count(r =>
                string.Equals(r.RejectionReason, VerificationRejectionReasons.ManualEntryNotAllowed, StringComparison.Ordinal));

            DateTime? lastMovedUtc = daySuccessful.Count > 0
                ? daySuccessful.Max(x => x.ProcessedAtUtc)
                : null;

            var daySpan = toDate.DayNumber - fromDate.DayNumber + 1;
            var dayLabel = daySpan <= 7
                ? date.ToString("ddd", System.Globalization.CultureInfo.InvariantCulture)
                : date.ToString("MMM d", System.Globalization.CultureInfo.InvariantCulture);

            chartByDay.Add(new MovementChartDayDto
            {
                DayLabel = dayLabel,
                MovedCartons = movedCount
            });

            dayDetails.Add(new MovementDayDetailDto
            {
                Date = date,
                DateDisplay = $"{date.Day} {date:MMM yyyy} ({date:ddd})",
                MovedCartons = movedCount,
                SuccessfulScans = movedCount,
                DuplicateRejections = duplicateCount,
                ManualEntryRejections = manualCount,
                LastMovedAtUtc = lastMovedUtc
            });
        }

        dayDetails.Reverse();

        return new MovementAnalyticsDto
        {
            Summary = new MovementSummaryDto
            {
                MovedToday = movedToday,
                MovedThisWeek = movedThisWeek,
                MovedThisMonth = movedThisMonth,
                TotalMoved = totalMoved
            },
            StatusShare = new MovementStatusShareDto
            {
                Moved = totalMoved,
                Pending = pending
            },
            ChartByDay = chartByDay,
            DayDetails = dayDetails,
            DateRangeLabel = $"{fromDate:MMM d, yyyy} - {toDate:MMM d, yyyy}"
        };
    }

    private async Task<int> CountSuccessfulScansAsync(DateTime startUtc, DateTime endUtc, CancellationToken cancellationToken) =>
        await _dbContext.ScanHistoryEntries
            .AsNoTracking()
            .CountAsync(x => x.ShipmentMarked && x.ProcessedAtUtc >= startUtc && x.ProcessedAtUtc <= endUtc, cancellationToken);

    private static DateOnly ToLocalDateOnly(DateTime utc) =>
        DateOnly.FromDateTime(DateTime.SpecifyKind(utc, DateTimeKind.Utc).ToLocalTime());

    private static (DateTime StartUtc, DateTime EndUtc) GetUtcDayRange(DateOnly date) =>
        GetUtcDayRange(date, date);

    private static (DateTime StartUtc, DateTime EndUtc) GetUtcDayRange(DateOnly from, DateOnly to)
    {
        var startLocal = from.ToDateTime(TimeOnly.MinValue);
        var endLocal = to.ToDateTime(new TimeOnly(23, 59, 59, 999));
        return (TimeZoneInfo.ConvertTimeToUtc(startLocal), TimeZoneInfo.ConvertTimeToUtc(endLocal));
    }

    private static (DateTime StartUtc, DateTime EndUtc) GetUtcWeekRange(DateOnly anchor)
    {
        var local = anchor.ToDateTime(TimeOnly.MinValue);
        var diff = (7 + (local.DayOfWeek - DayOfWeek.Monday)) % 7;
        var weekStart = local.AddDays(-diff);
        var weekEnd = weekStart.AddDays(6);
        return GetUtcDayRange(DateOnly.FromDateTime(weekStart), DateOnly.FromDateTime(weekEnd));
    }

    private static (DateTime StartUtc, DateTime EndUtc) GetUtcMonthRange(DateOnly anchor)
    {
        var monthStart = new DateOnly(anchor.Year, anchor.Month, 1);
        var monthEnd = monthStart.AddMonths(1).AddDays(-1);
        return GetUtcDayRange(monthStart, monthEnd);
    }
}