using System.Collections;
using System.Linq;
using NUnit.Framework;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.TestTools;

namespace NightclubArcadia.PlayMode.Tests
{
    /// <summary>
    /// The level must survive being loaded BEFORE the systems it depends on.
    ///
    /// BootstrapTests only covers the happy order — Bootstrap loads Systems, then the
    /// level, so by the time an NPC awakes the dialogue runner is already there. The
    /// Editor does not guarantee that. Open the level on its own, or open scenes in a
    /// different order, press Play, and NPCStandIn.Awake runs with no Systems scene in
    /// sight. That produced:
    ///
    ///   [SceneServices] Bartender: could not resolve dialogueRunner
    ///
    /// Resolving a cross-scene dependency in Awake is a race by construction. The fix
    /// is to resolve at the point of use instead, so any load order works — and this is
    /// the test that holds that property.
    /// </summary>
    public class SceneOrderTests
    {
        const string Systems = "Systems";
        const string Level = "SC101_ConferenceHall";

        [UnityTearDown]
        public IEnumerator TearDown()
        {
            yield return SceneManager.LoadSceneAsync("Bootstrap", LoadSceneMode.Single);
        }

        [UnityTest]
        public IEnumerator LevelLoadedBeforeSystems_NpcsStillResolveTheirRunner()
        {
            // deliberately the wrong way round
            yield return SceneManager.LoadSceneAsync(Level, LoadSceneMode.Single);
            yield return SceneManager.LoadSceneAsync(Systems, LoadSceneMode.Additive);
            for (var i = 0; i < 3; i++)
            {
                yield return null;
            }

            var npcs = Object.FindObjectsByType<NPCStandIn>(
                FindObjectsInactive.Include, FindObjectsSortMode.None);
            Assert.IsNotEmpty(npcs, "Expected NPCs in the level scene");

            // Read the serialized field BEFORE touching the lazy property, which caches
            // into it. If this is null, Awake really did run with no Systems scene — i.e.
            // the race this test exists for is genuinely reproduced here, and the
            // assertion below is not passing for free.
            var eager = npcs.Count(n => n.dialogueRunner == null);
            Debug.Log($"[Order] NPCs whose Awake-time resolution failed: {eager}/{npcs.Length}");
            Assert.Greater(eager, 0,
                "Awake-time resolution succeeded, so this test is not reproducing the race " +
                "it was written for. Rewrite it before trusting it.");

            foreach (var npc in npcs)
            {
                Assert.IsNotNull(npc.ResolvedDialogueRunner,
                    $"'{npc.name}' could not reach the DialogueRunner when the level loaded " +
                    "before Systems. Cross-scene resolution must not depend on load order.");
            }
        }
    }
}