using AVSCartonShipmentVerifier.DTOs;
using AVSCartonShipmentVerifier.Configuration;
using AVSCartonShipmentVerifier.ScanHistory;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;

namespace AVSCartonShipmentVerifier.Services;

public sealed class SqliteScanHistoryStore(
    ScanHistoryDbContext dbContext,
    IOptions<ScanHistoryOptions> options,
    ILogger<SqliteScanHistoryStore> logger) : IScanHistoryStore
{
    private readonly ScanHistoryDbContext _dbContext = dbContext;
    private readonly ScanHistoryOptions _options = options.Value;
    private readonly ILogger<SqliteScanHistoryStore> _logger = logger;

    public async Task AddSuccessfulScanAsync(ScannedRecordDto record, CancellationToken cancellationToken = default)
    {
        try
        {
            _dbContext.ScanHistoryEntries.Add(new ScanHistoryEntry
            {
                ModelNumber = record.ModelNumber,
                UniqueNumber = record.UniqueNumber,
                ExistsInSystem = record.ExistsInSystem,
                ShipmentMarked = record.ShipmentMarked,
                ProcessedAtUtc = record.ProcessedAtUtc
            });

            await _dbContext.SaveChangesAsync(cancellationToken);
            await TrimSuccessfulAsync(cancellationToken);
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to persist successful scan history entry.");
        }
    }

    public async Task AddRejectedScanAsync(RejectedScanRecordDto record, CancellationToken cancellationToken = default)
    {
        try
        {
            _dbContext.RejectedScanEntries.Add(new RejectedScanEntry
            {
                RawInputValue = record.RawInputValue,
                ModelNumber = record.ModelNumber,
                UniqueNumber = record.UniqueNumber,
                RejectionReason = record.RejectionReason,
                ProcessedAtUtc = record.ProcessedAtUtc
            });

            await _dbContext.SaveChangesAsync(cancellationToken);
            await TrimRejectedAsync(cancellationToken);
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to persist rejected scan history entry.");
        }
    }

    public async Task<IReadOnlyCollection<ScannedRecordDto>> GetLastFiveSuccessfulScansAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var entries = await _dbContext.ScanHistoryEntries
                .AsNoTracking()
                .Where(x => x.ShipmentMarked)
                .OrderByDescending(x => x.ProcessedAtUtc)
                .Take(5)
                .ToArrayAsync(cancellationToken);

            return MapSuccessful(entries);
        }
        catch (Exception exception) when (TryHandleReadCancellation(exception, cancellationToken, "Successful scan history (last five)"))
        {
            return Array.Empty<ScannedRecordDto>();
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to read successful scan history.");
            return Array.Empty<ScannedRecordDto>();
        }
    }

    public async Task<IReadOnlyCollection<RejectedScanRecordDto>> GetLastFiveRejectedScansAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var entries = await _dbContext.RejectedScanEntries
                .AsNoTracking()
                .OrderByDescending(x => x.ProcessedAtUtc)
                .Take(5)
                .ToArrayAsync(cancellationToken);

            return MapRejected(entries);
        }
        catch (Exception exception) when (TryHandleReadCancellation(exception, cancellationToken, "Rejected scan history (last five)"))
        {
            return Array.Empty<RejectedScanRecordDto>();
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to read rejected scan history.");
            return Array.Empty<RejectedScanRecordDto>();
        }
    }

    public async Task<IReadOnlyCollection<ScannedRecordDto>> GetAllSuccessfulScansAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var entries = await _dbContext.ScanHistoryEntries
                .AsNoTracking()
                .Where(x => x.ShipmentMarked)
                .OrderByDescending(x => x.ProcessedAtUtc)
                .ToArrayAsync(cancellationToken);

            return MapSuccessful(entries);
        }
        catch (Exception exception) when (TryHandleReadCancellation(exception, cancellationToken, "Successful scan history (all)"))
        {
            return Array.Empty<ScannedRecordDto>();
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to read full successful scan history.");
            return Array.Empty<ScannedRecordDto>();
        }
    }

    public async Task<IReadOnlyCollection<RejectedScanRecordDto>> GetAllRejectedScansAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var entries = await _dbContext.RejectedScanEntries
                .AsNoTracking()
                .OrderByDescending(x => x.ProcessedAtUtc)
                .ToArrayAsync(cancellationToken);

            return MapRejected(entries);
        }
        catch (Exception exception) when (TryHandleReadCancellation(exception, cancellationToken, "Rejected scan history (all)"))
        {
            return Array.Empty<RejectedScanRecordDto>();
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Failed to read full rejected scan history.");
            return Array.Empty<RejectedScanRecordDto>();
        }
    }

    private bool TryHandleReadCancellation(Exception exception, CancellationToken cancellationToken, string operation)
    {
        if (exception is not OperationCanceledException || !cancellationToken.IsCancellationRequested)
        {
            return false;
        }

        _logger.LogDebug(exception, "{Operation} read was cancelled.", operation);
        return true;
    }

    private static ScannedRecordDto[] MapSuccessful(IEnumerable<ScanHistoryEntry> entries) =>
        entries
            .Select(x => new ScannedRecordDto
            {
                ModelNumber = x.ModelNumber,
                UniqueNumber = x.UniqueNumber,
                ExistsInSystem = x.ExistsInSystem,
                ShipmentMarked = x.ShipmentMarked,
                ProcessedAtUtc = DateTime.SpecifyKind(x.ProcessedAtUtc, DateTimeKind.Utc)
            })
            .ToArray();

    private static RejectedScanRecordDto[] MapRejected(IEnumerable<RejectedScanEntry> entries) =>
        entries
            .Select(x => new RejectedScanRecordDto
            {
                RawInputValue = x.RawInputValue,
                ModelNumber = x.ModelNumber,
                UniqueNumber = x.UniqueNumber,
                RejectionReason = x.RejectionReason,
                ProcessedAtUtc = DateTime.SpecifyKind(x.ProcessedAtUtc, DateTimeKind.Utc)
            })
            .ToArray();

    private async Task TrimSuccessfulAsync(CancellationToken cancellationToken)
    {
        var max = _options.MaxRecordsToKeep;
        if (max <= 0)
        {
            return;
        }

        var toDelete = await _dbContext.ScanHistoryEntries
            .OrderByDescending(x => x.ProcessedAtUtc)
            .Skip(max)
            .Select(x => x.Id)
            .ToArrayAsync(cancellationToken);

        if (toDelete.Length == 0)
        {
            return;
        }

        _dbContext.ScanHistoryEntries.RemoveRange(toDelete.Select(id => new ScanHistoryEntry { Id = id }));
        await _dbContext.SaveChangesAsync(cancellationToken);
    }

    private async Task TrimRejectedAsync(CancellationToken cancellationToken)
    {
        var max = _options.MaxRecordsToKeep;
        if (max <= 0)
        {
            return;
        }

        var toDelete = await _dbContext.RejectedScanEntries
            .OrderByDescending(x => x.ProcessedAtUtc)
            .Skip(max)
            .Select(x => x.Id)
            .ToArrayAsync(cancellationToken);

        if (toDelete.Length == 0)
        {
            return;
        }

        _dbContext.RejectedScanEntries.RemoveRange(toDelete.Select(id => new RejectedScanEntry { Id = id }));
        await _dbContext.SaveChangesAsync(cancellationToken);
    }
}