chameleon/Assets/Scripts/StartMatchTrigger.cs

using Unity.Netcode;
using UnityEngine;

/// <summary>
/// Sits on the Lobby's "Start Match" trigger volume (a BoxCollider with isTrigger on). When the match
/// AUTHORITY's avatar stands inside it, it asks the <see cref="MatchManager"/> to start the match.
///
/// Detection POLLS a server-side physics overlap every frame instead of relying on OnTriggerEnter.
/// Why: the authority can be a REMOTE client (a dedicated server with no host player hands authority to
/// the first client). On the server that client's avatar is a NetworkTransform-driven replica - its
/// CharacterController is disabled (<see cref="NetworkPlayerSetup"/>) and it carries no Rigidbody, so it
/// is moved by direct transform writes. Unity only sends OnTriggerEnter when one of the two colliders has
/// a Rigidbody (or is a CharacterController moving via Move()); a transform-moved non-Rigidbody collider
/// against a static trigger fires nothing. That is exactly why a host's own (Move()-driven) avatar tripped
/// the trigger but a remote authority never did. An explicit overlap query finds the avatar's (baked)
/// collider regardless of HOW it is moved, so start works for a host and a dedicated server alike.
///
/// Server-gated: pure clients query nothing. Only the authority avatar starts the match; a passing
/// non-authority avatar is ignored. Runs only while in the lobby phase and stops once it has started a
/// match. The trigger lives in the additively-loaded Lobby and is destroyed when the lobby unloads, so a
/// re-match (back in the lobby) gets a fresh instance with its guard reset.
/// </summary>
[RequireComponent(typeof(Collider))]
[DisallowMultipleComponent]
public class StartMatchTrigger : MonoBehaviour
{
    private Collider _collider;
    private readonly Collider[] _overlap = new Collider[32];
    private bool _started;
    private bool _overlapSaturated; // log-once: a full buffer could silently drop the authority's avatar

    private void Awake() => _collider = GetComponent<Collider>();

    private void Update()
    {
        if (_started) return;

        var nm = NetworkManager.Singleton;
        if (!nm || !nm.IsServer) return; // detection + start are server-side
        var match = MatchManager.Instance;
        if (!match || match.Phase != MatchManager.MatchPhase.Lobby) return;

        int count = OverlapTrigger();
        if (count == _overlap.Length && !_overlapSaturated)
        {
            _overlapSaturated = true;
            Debug.LogWarning($"StartMatchTrigger: overlap buffer saturated ({count}); the authority avatar may be missed.", this);
        }
        for (int i = 0; i < count; i++)
        {
            var netObj = _overlap[i].GetComponentInParent<NetworkObject>();
            if (!netObj || !netObj.IsPlayerObject) continue;            // must be a player avatar
            if (!match.IsMatchAuthority(netObj.OwnerClientId)) continue; // ...the authority's

            _started = true;
            match.StartMatch();
            return;
        }
    }

    // Overlaps the trigger's own volume. Uses the oriented box for a BoxCollider (the authored shape);
    // falls back to the collider's world AABB for any other collider type. Triggers are ignored so the
    // query skips this volume itself and reports only solid avatar colliders (e.g. the baked mesh).
    private int OverlapTrigger()
    {
        if (_collider is BoxCollider box)
        {
            Vector3 center = transform.TransformPoint(box.center);
            Vector3 scale = transform.lossyScale;
            Vector3 half = new Vector3(
                Mathf.Abs(box.size.x * scale.x),
                Mathf.Abs(box.size.y * scale.y),
                Mathf.Abs(box.size.z * scale.z)) * 0.5f;
            return Physics.OverlapBoxNonAlloc(
                center, half, _overlap, transform.rotation, ~0, QueryTriggerInteraction.Ignore);
        }

        Bounds b = _collider.bounds;
        return Physics.OverlapBoxNonAlloc(
            b.center, b.extents, _overlap, Quaternion.identity, ~0, QueryTriggerInteraction.Ignore);
    }
}