using System.Data;
using System.Data.Common;
using System.Diagnostics.CodeAnalysis;
using Microsoft.Data.SqlClient;
using Microsoft.EntityFrameworkCore;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Repositories;

namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests.Repositories;

public class AuditPurgeBudgetTests
{
    /// <summary>Verifies that a backlogged channel purge stops at the row budget, including a partial final batch.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task BackloggedChannel_StopsAtBudgetIncludingPartialFinalBatch()
    {
        using var connection = new BackloggedConnection();
        await using var context = new ScadaBridgeDbContext(new DbContextOptionsBuilder<ScadaBridgeDbContext>()
            .UseSqlServer(connection).Options);
        var deleted = await new AuditLogRepository(context).PurgeChannelOlderThanAsync(
            "ScriptTrace", DateTime.UtcNow, batchSize: 3, maxRows: 5);
        Assert.Equal(5, deleted);
        Assert.Equal(new[] { 3, 2 }, connection.RequestedBatches);
        Assert.Equal(ConnectionState.Closed, connection.State);
    }

    private sealed class BackloggedConnection : DbConnection
    {
        /// <summary>Gets the batch sizes requested by the purge, in order.</summary>
        public List<int> RequestedBatches { get; } = new();
        private ConnectionState _state;
        /// <inheritdoc />
        [AllowNull] public override string ConnectionString { get; set; } = "Server=localhost;Database=test";
        /// <inheritdoc />
        public override string Database => "test";
        /// <inheritdoc />
        public override string DataSource => "localhost";
        /// <inheritdoc />
        public override string ServerVersion => "16.0";
        /// <inheritdoc />
        public override ConnectionState State => _state;
        /// <inheritdoc />
        public override void Open() => _state = ConnectionState.Open;
        /// <inheritdoc />
        public override void Close() => _state = ConnectionState.Closed;
        /// <inheritdoc />
        public override void ChangeDatabase(string databaseName) => throw new NotSupportedException();
        /// <inheritdoc />
        protected override DbTransaction BeginDbTransaction(IsolationLevel isolationLevel) => throw new NotSupportedException();
        /// <inheritdoc />
        protected override DbCommand CreateDbCommand() => new BackloggedCommand(this);
    }

    private sealed class BackloggedCommand(BackloggedConnection owner) : DbCommand
    {
        private readonly SqlCommand _parameters = new();
        /// <inheritdoc />
        [AllowNull] public override string CommandText { get; set; } = "";
        /// <inheritdoc />
        public override int CommandTimeout { get; set; }
        /// <inheritdoc />
        public override CommandType CommandType { get; set; }
        /// <inheritdoc />
        public override bool DesignTimeVisible { get; set; }
        /// <inheritdoc />
        public override UpdateRowSource UpdatedRowSource { get; set; }
        /// <inheritdoc />
        protected override DbConnection? DbConnection { get; set; }
        /// <inheritdoc />
        protected override DbTransaction? DbTransaction { get; set; }
        /// <inheritdoc />
        protected override DbParameterCollection DbParameterCollection => _parameters.Parameters;
        /// <inheritdoc />
        protected override DbParameter CreateDbParameter() => new SqlParameter();
        /// <inheritdoc />
        public override int ExecuteNonQuery()
        {
            // A server with more eligible rows than any tick is allowed to delete.
            // Fail rapidly if the repository loops indefinitely, without a timer-based test.
            if (owner.RequestedBatches.Count >= 10)
                throw new InvalidOperationException("Purge did not yield despite exhausting its row budget.");
            var requested = (int)_parameters.Parameters["@batch"].Value;
            owner.RequestedBatches.Add(requested);
            return requested;
        }
        /// <inheritdoc />
        public override object? ExecuteScalar() => throw new NotSupportedException();
        /// <inheritdoc />
        protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) => throw new NotSupportedException();
        /// <inheritdoc />
        public override void Cancel() { }
        /// <inheritdoc />
        public override void Prepare() { }
        /// <inheritdoc />
        protected override void Dispose(bool disposing)
        {
            if (disposing) _parameters.Dispose();
            base.Dispose(disposing);
        }
    }
}