using System.Collections.Concurrent;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Server.History;

/// <summary>
///     Default <see cref="IHistoryRouter"/> implementation.
/// </summary>
public sealed class HistoryRouter : IHistoryRouter
{
    private readonly ConcurrentDictionary<string, IHistorianDataSource> _registry =
        new(StringComparer.OrdinalIgnoreCase);

    private bool _disposed;

    /// <inheritdoc />
    public void Register(string fullReferencePrefix, IHistorianDataSource source)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        ArgumentNullException.ThrowIfNull(fullReferencePrefix);
        ArgumentNullException.ThrowIfNull(source);

        if (!_registry.TryAdd(fullReferencePrefix, source))
        {
            throw new InvalidOperationException(
                $"A historian data source is already registered for prefix '{fullReferencePrefix}'.");
        }
    }

    /// <inheritdoc />
    public IHistorianDataSource? Resolve(string fullReference)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        ArgumentNullException.ThrowIfNull(fullReference);

        // Longest-prefix match. Sources are typically a handful per server, so a linear
        // scan is fine and avoids building a trie for a low-cardinality registry.
        IHistorianDataSource? best = null;
        var bestPrefixLength = -1;

        foreach (var (prefix, source) in _registry)
        {
            if (fullReference.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)
                && prefix.Length > bestPrefixLength)
            {
                best = source;
                bestPrefixLength = prefix.Length;
            }
        }

        return best;
    }

    /// <summary>
    ///     Disposes every registered source and prevents further registrations or
    ///     resolutions. Sources may not all be disposable — null-safe disposal pattern.
    /// </summary>
    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;

        foreach (var source in _registry.Values)
        {
            try { source.Dispose(); }
            catch { /* best-effort — server shutdown should not throw on a misbehaving source */ }
        }

        _registry.Clear();
    }
}