using System.Data;
using System.Data.Common;
using Microsoft.Extensions.Logging;
using ScadaLink.Commons.Interfaces.Services;

namespace ScadaLink.SiteRuntime.Scripts;

/// <summary>
/// Audit Log #23 — M4 Bundle A: thin decorator over the
/// <see cref="DbConnection"/> returned by
/// <see cref="ScriptRuntimeContext.DatabaseHelper.Connection"/>. The decorator
/// itself does no audit work — it simply intercepts
/// <see cref="CreateDbCommand"/> so the <see cref="DbCommand"/> handed back to
/// the script is wrapped in an <see cref="AuditingDbCommand"/> that emits one
/// <c>DbOutbound</c>/<c>DbWrite</c> audit row per execution.
/// </summary>
/// <remarks>
/// <para>
/// All other <see cref="DbConnection"/> members forward to the inner connection
/// unchanged so the script keeps full ADO.NET semantics (transactions, state
/// transitions, server-version queries, etc.). Disposing the wrapper disposes
/// the inner connection — the caller is still responsible for disposal per
/// the <see cref="IDatabaseGateway"/> contract.
/// </para>
/// <para>
/// The audit-write failure contract (alog.md §7) is honoured at the
/// <see cref="AuditingDbCommand"/> layer — see that class for the 3-layer
/// fail-safe pattern (build, write, observe).
/// </para>
/// </remarks>
internal sealed class AuditingDbConnection : DbConnection
{
    private readonly DbConnection _inner;
    private readonly IAuditWriter _auditWriter;
    private readonly string _connectionName;
    private readonly string _siteId;
    private readonly string _instanceName;
    private readonly string? _sourceScript;
    private readonly ILogger _logger;

    public AuditingDbConnection(
        DbConnection inner,
        IAuditWriter auditWriter,
        string connectionName,
        string siteId,
        string instanceName,
        string? sourceScript,
        ILogger logger)
    {
        _inner = inner ?? throw new ArgumentNullException(nameof(inner));
        _auditWriter = auditWriter ?? throw new ArgumentNullException(nameof(auditWriter));
        _connectionName = connectionName ?? throw new ArgumentNullException(nameof(connectionName));
        _siteId = siteId ?? string.Empty;
        _instanceName = instanceName ?? string.Empty;
        _sourceScript = sourceScript;
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    // ConnectionString is settable on DbConnection — forward both halves.
    public override string ConnectionString
    {
        // Some providers throw on get when the connection hasn't been opened
        // with a string set explicitly. The wrapper has no opinion — forward.
#pragma warning disable CS8765 // nullability of overridden member parameter — base setter accepts null in practice
        get => _inner.ConnectionString;
        set => _inner.ConnectionString = value;
#pragma warning restore CS8765
    }

    public override string Database => _inner.Database;
    public override string DataSource => _inner.DataSource;
    public override string ServerVersion => _inner.ServerVersion;
    public override ConnectionState State => _inner.State;

    public override void ChangeDatabase(string databaseName) => _inner.ChangeDatabase(databaseName);
    public override void Close() => _inner.Close();
    public override void Open() => _inner.Open();
    public override Task OpenAsync(CancellationToken cancellationToken) => _inner.OpenAsync(cancellationToken);

    protected override DbTransaction BeginDbTransaction(IsolationLevel isolationLevel)
        => _inner.BeginTransaction(isolationLevel);

    protected override DbCommand CreateDbCommand()
    {
        var innerCmd = _inner.CreateCommand();
        // Hand the script an auditing wrapper. The wrapper preserves the
        // inner command's identity for parameters / type maps via delegation.
        return new AuditingDbCommand(
            innerCmd,
            _auditWriter,
            _connectionName,
            _siteId,
            _instanceName,
            _sourceScript,
            _logger);
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            _inner.Dispose();
        }
        base.Dispose(disposing);
    }

    public override ValueTask DisposeAsync()
    {
        // DbConnection.DisposeAsync is virtual; calling base would run the
        // synchronous Dispose path. Forward to the inner connection
        // asynchronously and short-circuit the base.
        var task = _inner.DisposeAsync();
        GC.SuppressFinalize(this);
        return task;
    }
}