using System.Security.Cryptography;
using SVSim.BattleNode.Sessions;

namespace SVSim.BattleNode.Bridge;

/// <summary>
/// In-process implementation of <see cref="IMatchingBridge"/>. The HTTP-side
/// <c>do_matching</c> controller calls <see cref="RegisterPendingBattle"/>, which mints a
/// 12-digit decimal battle id, stashes a <see cref="PendingBattle"/> entry in the
/// <see cref="IBattleSessionStore"/>, and returns the node URL the client should connect to.
/// The WebSocket handler resolves the same battle id back to the viewer on connect.
/// </summary>
public sealed class MatchingBridge : IMatchingBridge
{
    private readonly IBattleSessionStore _store;
    private readonly BattleNodeOptions _options;

    public MatchingBridge(IBattleSessionStore store, BattleNodeOptions options)
    {
        _store = store;
        _options = options;
    }

    public PendingMatch RegisterPendingBattle(long viewerId, MatchContext context)
    {
        // 12-digit decimal battle id mirrors the captures (e.g. "975695075012").
        // Two unbiased 6-digit draws concatenated — RandomNumberGenerator.GetInt32 uses
        // rejection sampling so the result is uniform on [0, 10^6). The previous
        // implementation (Guid.GetHashCode + mod) collapsed 128 bits into ~32 of entropy
        // and tripped Math.Abs(int.MinValue) UB on the unlucky hash.
        var hi = RandomNumberGenerator.GetInt32(0, 1_000_000);
        var lo = RandomNumberGenerator.GetInt32(0, 1_000_000);
        var battleId = $"{hi:D6}{lo:D6}";
        _store.RegisterPending(new PendingBattle(battleId, viewerId, context));
        return new PendingMatch(battleId, _options.NodeServerUrl);
    }
}