using System.Collections.Generic;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Historian;

/// <summary>
///     Binds the <c>ServerHistorian</c> configuration section that gates the server-side
///     HistoryRead backend. When <see cref="Enabled"/> is <c>true</c>, <c>AddServerHistorian</c>
///     registers a read-only <c>WonderwareHistorianClient</c> (supplied by the Host) as the
///     <c>IHistorianDataSource</c> in place of the <c>NullHistorianDataSource</c> default;
///     otherwise the Null default survives and HistoryRead returns <c>GoodNoData</c>-empty.
///     <para>
///         This is the READ path only — there are no DatabasePath / drain / capacity / retention
///         knobs (those belong to the write-side <c>AlarmHistorian</c> store-and-forward sink). The
///         client's own <c>CallTimeout</c> bounds each read; the node manager adds no extra timeout.
///     </para>
/// </summary>
public sealed class ServerHistorianOptions
{
    /// <summary>The configuration section name this options class binds.</summary>
    public const string SectionName = "ServerHistorian";

    /// <summary>
    ///     When <c>true</c>, the Wonderware read client is registered as the
    ///     <c>IHistorianDataSource</c>; when <c>false</c> (the default) the no-op
    ///     <c>NullHistorianDataSource</c> stays in place and HistoryRead returns empty.
    /// </summary>
    public bool Enabled { get; init; }

    /// <summary>TCP hostname or IP address the Wonderware historian sidecar listens on.</summary>
    public string Host { get; init; } = "localhost";

    /// <summary>TCP port the Wonderware historian sidecar listens on.</summary>
    public int Port { get; init; } = 32569;

    /// <summary>When <c>true</c>, the client connects over TLS.</summary>
    public bool UseTls { get; init; }

    /// <summary>Expected TLS server certificate thumbprint (hex, no spaces). Null or empty disables pinning.</summary>
    public string? ServerCertThumbprint { get; init; }

    /// <summary>Per-process shared secret the sidecar verifies in the Hello frame.</summary>
    public string SharedSecret { get; init; } = "";

    /// <summary>Returns operator-facing misconfiguration warnings for an <c>Enabled</c> historian
    /// (empty when disabled or correctly configured). Pure — the registration logs each entry.</summary>
    /// <returns>Zero or more human-readable warning messages.</returns>
    public IReadOnlyList<string> Validate()
    {
        var warnings = new List<string>();
        if (!Enabled) return warnings;
        if (string.IsNullOrWhiteSpace(SharedSecret))
            warnings.Add("ServerHistorian:SharedSecret is empty while the historian is enabled — the Wonderware sidecar Hello frame will carry an empty secret.");
        if (Port <= 0)
            warnings.Add($"ServerHistorian:Port is {Port} — must be > 0; the read client cannot dial the sidecar.");
        return warnings;
    }
}