using AVSCartonShipmentVerifier.DTOs;
using AVSCartonShipmentVerifier.Repositories;

namespace AVSCartonShipmentVerifier.Services;

public sealed class ShipmentVerificationService(
    ICartonVerificationRepository repository,
    IScanHistoryStore historyStore,
    ILogger<ShipmentVerificationService> logger) : IShipmentVerificationService
{
    private readonly ICartonVerificationRepository _repository = repository;
    private readonly IScanHistoryStore _historyStore = historyStore;
    private readonly ILogger<ShipmentVerificationService> _logger = logger;

    public async Task<VerificationResultDto> VerifyQrAsync(string rawQrValue, string? entryMethod, CancellationToken cancellationToken = default)
    {
        var nowUtc = DateTime.UtcNow;
        var raw = (rawQrValue ?? string.Empty).Trim();

        if (IsManualEntry(entryMethod))
        {
            await PersistRejectionAsync(raw, string.Empty, string.Empty, VerificationRejectionReasons.ManualEntryNotAllowed, nowUtc, cancellationToken);
            return Reject(raw, string.Empty, string.Empty, VerificationRejectionReasons.ManualEntryNotAllowed, existsInSystem: false, nowUtc);
        }

        var parseResult = TryParseQr(raw);
        if (!parseResult.IsValid)
        {
            await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.InvalidFormat, nowUtc, cancellationToken);
            return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.InvalidFormat, existsInSystem: false, nowUtc);
        }

        CartonVerificationStatus status;
        try
        {
            status = await _repository.GetCartonStatusByUniqueNumberAsync(parseResult.UniqueNumber, cancellationToken);
        }
        catch (InvalidOperationException exception) when (exception.Message.Contains("Connection string 'VerificationDatabase' is not set", StringComparison.OrdinalIgnoreCase))
        {
            _logger.LogError(exception, "Verification database is not configured.");
            await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, nowUtc, cancellationToken);
            return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, existsInSystem: false, nowUtc);
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Verification lookup failed for unique number {UniqueNumber}.", parseResult.UniqueNumber);
            await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, nowUtc, cancellationToken);
            return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, existsInSystem: false, nowUtc);
        }

        switch (status)
        {
            case CartonVerificationStatus.NotFound:
                await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.CartonDoesNotExist, nowUtc, cancellationToken);
                return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.CartonDoesNotExist, existsInSystem: false, nowUtc);

            case CartonVerificationStatus.AlreadyTransferred:
                await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.AlreadyTransferredDuplicateScan, nowUtc, cancellationToken);
                return Reject(
                    raw,
                    parseResult.ModelNumber,
                    parseResult.UniqueNumber,
                    VerificationRejectionReasons.AlreadyTransferredDuplicateScan,
                    existsInSystem: true,
                    nowUtc);

            case CartonVerificationStatus.PendingTransfer:
                bool marked;
                try
                {
                    marked = await _repository.MarkShipmentVerifiedAsync(parseResult.UniqueNumber, cancellationToken);
                }
                catch (Exception exception)
                {
                    _logger.LogError(exception, "Failed to mark shipment verified for unique number {UniqueNumber}.", parseResult.UniqueNumber);
                    await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, nowUtc, cancellationToken);
                    return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, existsInSystem: true, nowUtc);
                }

                if (!marked)
                {
                    await PersistRejectionAsync(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, nowUtc, cancellationToken);
                    return Reject(raw, parseResult.ModelNumber, parseResult.UniqueNumber, VerificationRejectionReasons.DatabaseOrSystemError, existsInSystem: true, nowUtc);
                }

                var success = new VerificationResultDto
                {
                    ModelNumber = parseResult.ModelNumber,
                    UniqueNumber = parseResult.UniqueNumber,
                    RawQrValue = raw,
                    ExistsInSystem = true,
                    ShipmentMarked = true,
                    Message = "Record found and shipment marked successfully.",
                    RejectionReason = null,
                    ProcessedAtUtc = nowUtc
                };

                await _historyStore.AddSuccessfulScanAsync(ToScannedRecord(success), cancellationToken);
                return success;

            default:
                throw new InvalidOperationException($"Unexpected carton status: {status}.");
        }
    }

    private static bool IsManualEntry(string? entryMethod) =>
        string.Equals(entryMethod?.Trim(), "Manual", StringComparison.OrdinalIgnoreCase);

    private async Task PersistRejectionAsync(
        string rawInput,
        string modelNumber,
        string uniqueNumber,
        string reason,
        DateTime processedAtUtc,
        CancellationToken cancellationToken)
    {
        await _historyStore.AddRejectedScanAsync(new RejectedScanRecordDto
        {
            RawInputValue = rawInput,
            ModelNumber = modelNumber,
            UniqueNumber = uniqueNumber,
            RejectionReason = reason,
            ProcessedAtUtc = processedAtUtc
        }, cancellationToken);
    }

    private static VerificationResultDto Reject(
        string raw,
        string modelNumber,
        string uniqueNumber,
        string reason,
        bool existsInSystem,
        DateTime processedAtUtc) => new()
    {
        RawQrValue = raw,
        ModelNumber = modelNumber,
        UniqueNumber = uniqueNumber,
        ExistsInSystem = existsInSystem,
        ShipmentMarked = false,
        Message = reason,
        RejectionReason = reason,
        ProcessedAtUtc = processedAtUtc
    };

    private static (bool IsValid, string ModelNumber, string UniqueNumber) TryParseQr(string rawQrValue)
    {
        if (string.IsNullOrWhiteSpace(rawQrValue))
        {
            return (false, string.Empty, string.Empty);
        }

        if (!rawQrValue.Contains(';'))
        {
            return (false, string.Empty, string.Empty);
        }

        var parts = rawQrValue.Split(';', StringSplitOptions.TrimEntries);
        if (parts.Length != 2)
        {
            return (false, string.Empty, string.Empty);
        }

        var modelNumber = parts[0];
        var uniqueNumber = parts[1];
        if (string.IsNullOrWhiteSpace(modelNumber) || string.IsNullOrWhiteSpace(uniqueNumber))
        {
            return (false, modelNumber, uniqueNumber);
        }

        return (true, modelNumber, uniqueNumber);
    }

    private static ScannedRecordDto ToScannedRecord(VerificationResultDto result) => new()
    {
        ModelNumber = result.ModelNumber,
        UniqueNumber = result.UniqueNumber,
        ExistsInSystem = result.ExistsInSystem,
        ShipmentMarked = result.ShipmentMarked,
        ProcessedAtUtc = result.ProcessedAtUtc
    };
}