using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer;
using ZB.MOM.WW.OtOpcUa.Runtime.Historian;

namespace ZB.MOM.WW.OtOpcUa.Host.Configuration;

/// <summary>
///     Maps <c>ServerHistorian:Backend</c> to an <see cref="IHistorianBackendProvider"/>. Names are
///     case-insensitive. To add a backend, add one entry to <see cref="Factories"/>.
///     <see cref="Resolve"/> only constructs the provider; option validation belongs to
///     <see cref="ServerHistorianOptionsValidator"/>.
/// </summary>
public static class HistorianBackendRegistry
{
    /// <summary>Backend name for the SQL Server historian.</summary>
    public const string SqlServerBackendName = "SqlServer";

    /// <summary>Binds the <c>ServerHistorian:SqlServer</c> section (shared by the registry and the validator).</summary>
    public static SqlServerHistorianOptions BindSqlServer(IConfiguration configuration)
    {
        var o = new SqlServerHistorianOptions();
        configuration.GetSection($"{ServerHistorianOptions.SectionName}:SqlServer").Bind(o);
        return o;
    }

    /// <summary>Backend name for the QuestDB historian.</summary>
    public const string QuestDbBackendName = "QuestDb";

    /// <summary>Binds the <c>ServerHistorian:QuestDb</c> section (shared by the registry and the validator).</summary>
    public static QuestDbHistorianOptions BindQuestDb(IConfiguration configuration)
    {
        var o = new QuestDbHistorianOptions();
        configuration.GetSection($"{ServerHistorianOptions.SectionName}:QuestDb").Bind(o);
        return o;
    }

    private static readonly IReadOnlyDictionary<string, Func<ServerHistorianOptions, IConfiguration, IHistorianBackendProvider>> Factories =
        new Dictionary<string, Func<ServerHistorianOptions, IConfiguration, IHistorianBackendProvider>>(StringComparer.OrdinalIgnoreCase)
        {
            [ServerHistorianOptions.GatewayBackendName] = (o, _) => new GatewayHistorianProvider(o),
            [SqlServerBackendName] = (o, c) => new SqlServerHistorianProvider(BindSqlServer(c), o.MaxTimeWeightedRawRows),
            [QuestDbBackendName] = (o, c) => new QuestDbHistorianProvider(BindQuestDb(c), o.MaxTimeWeightedRawRows),
        };

    /// <summary>The registered backend names, for validation messages.</summary>
    public static IReadOnlyCollection<string> KnownBackends { get; } = Factories.Keys.ToArray();

    /// <summary>True when <paramref name="backend"/> names a registered backend.</summary>
    public static bool IsKnown(string? backend) =>
        !string.IsNullOrWhiteSpace(backend) && Factories.ContainsKey(backend.Trim());

    /// <summary>Builds the provider for <c>options.Backend</c>; throws <see cref="OptionsValidationException"/> if unknown.</summary>
    public static IHistorianBackendProvider Resolve(ServerHistorianOptions options, IConfiguration configuration)
    {
        ArgumentNullException.ThrowIfNull(options);
        ArgumentNullException.ThrowIfNull(configuration);
        if (!IsKnown(options.Backend))
            throw new OptionsValidationException(
                ServerHistorianOptions.SectionName, typeof(ServerHistorianOptions),
                [$"ServerHistorian:Backend '{options.Backend}' is not a known historian backend. Allowed values: {string.Join(", ", KnownBackends)}."]);
        return Factories[options.Backend.Trim()](options, configuration);
    }
}