// Assets/_Project/Scripts/Gameplay/WaveManager.cs
using System.Collections;
using Unity.Netcode;
using UnityEngine;
using TD.Core;
using TD.Levels;
using TD.UI;

namespace TD.Gameplay
{
    /// <summary>
    /// Server-authoritative wave controller. Spawns enemies across all player zones,
    /// tracks wave completion, awards kill gold, and manages the shared lives pool.
    /// </summary>
    /// <remarks>
    /// <b>Wave lifecycle:</b>
    /// <list type="bullet">
    ///   <item>When <see cref="MatchPhase.Playing"/> is entered,
    ///         <see cref="StartNextWave"/> advances <see cref="MatchState.CurrentWave"/>
    ///         immediately (so the HUD shows the wave number during prep), then waits
    ///         <see cref="WaveDefinition.PrepTime"/> before spawning.</item>
    ///   <item>Each <see cref="WaveEntry"/> spawns <c>Count</c> enemies per player zone,
    ///         one zone per frame-group, with <c>SpawnInterval</c> seconds between
    ///         individual enemies in the group.</item>
    ///   <item>After all entries are spawned, the wave is considered complete only when
    ///         every active enemy is either killed or has reached the goal.</item>
    ///   <item>All waves exhausted → <see cref="MatchPhase.Victory"/>.</item>
    ///   <item>Lives drop to 0 → <see cref="MatchPhase.Defeat"/>.</item>
    /// </list>
    ///
    /// <b>Kill gold:</b> When an enemy dies, <see cref="EnemyHealth.LastHitOwner"/> names
    /// the tower's player. <see cref="PlayerMatchState.GetForSlot"/> resolves the
    /// <c>OwnerClientId</c>, and <see cref="PlayerGoldManager.GetForClient"/> awards
    /// the gold.
    ///
    /// <b>Zone leak counts:</b> <see cref="zoneLeakCounts"/> is a <c>NetworkList</c>
    /// indexed by <c>(int)PlayerSlot</c> (indices 0–8). It is incremented when an enemy
    /// crosses from one player zone into another, giving the HUD a per-player leak score.
    /// Index 0 corresponds to <see cref="PlayerSlot.None"/> and is unused.
    ///
    /// <b>Inspector setup:</b>
    /// <list type="bullet">
    ///   <item>Assign <see cref="waveDefinitions"/> in order (Wave 1 at index 0).</item>
    ///   <item>Set <see cref="startingLives"/> to match your level design intent.</item>
    /// </list>
    /// </remarks>
    public class WaveManager : NetworkBehaviour
    {
        // ----- Singleton --------------------------------------------------

        public static WaveManager Instance { get; private set; }

        // ----- Inspector --------------------------------------------------

        [Tooltip("Wave definitions in order. Index 0 = Wave 1.")]
        [SerializeField] private WaveDefinition[] waveDefinitions;

        [Tooltip("Shared lives pool at the start of a match.")]
        [SerializeField] private int startingLives = 20;

        // ----- Networked state --------------------------------------------

        // Per-slot zone-leak counters. Index = (int)PlayerSlot; size = 10 (0-9).
        // Index 0 (PlayerSlot.None) is allocated but never written.
        // Replicated so the HUD can show per-player leak scores on all peers.
        private readonly NetworkList<int> zoneLeakCounts = new NetworkList<int>();

        // ----- Server-local runtime state ---------------------------------

        private int       remainingLives;
        private int       activeEnemyCount;
        private bool      spawningComplete;
        private int       currentWaveIndex = -1;  // -1 = not yet started
        private Coroutine activeWaveCoroutine;

        // ----- NGO lifecycle ----------------------------------------------

        public override void OnNetworkSpawn()
        {
            if (Instance != null && Instance != this)
            {
                Debug.LogError("[WaveManager] Duplicate WaveManager detected. " +
                               "Only one may exist per scene.");
                return;
            }
            Instance = this;

            if (!IsServer) return;

            // Populate the NetworkList with 10 zeros (indices 0-9 for PlayerSlot.None..Player9).
            for (int i = 0; i < 10; i++)
                zoneLeakCounts.Add(0);

            remainingLives = startingLives;

            // NGO's scene-object spawn sweep calls all OnNetworkSpawn methods
            // synchronously in a single call stack. Yielding one frame guarantees
            // every sibling NetworkBehaviour (including MatchState) has finished
            // its own OnNetworkSpawn before we try to read MatchState.Instance.
            StartCoroutine(InitAfterSpawn());
        }

        private System.Collections.IEnumerator InitAfterSpawn()
        {
            yield return null; // wait one frame

            var ms = MatchState.Instance;
            if (ms == null)
            {
                Debug.LogWarning("[WaveManager] MatchState not found after spawn. " +
                                 "Waves will not start automatically.");
                yield break;
            }

            ms.SetLives(remainingLives);
            ms.OnPhaseChanged += HandlePhaseChanged;

            if (ms.Phase == MatchPhase.Playing)
                StartNextWave();
        }

        public override void OnNetworkDespawn()
        {
            if (Instance == this) Instance = null;

            if (MatchState.Instance != null)
                MatchState.Instance.OnPhaseChanged -= HandlePhaseChanged;
        }

        // ----- Public accessors -------------------------------------------

        /// <summary>
        /// Total number of waves in this match. Same on every peer because
        /// <see cref="waveDefinitions"/> is a serialized prefab field, identical
        /// on host and clients. Returns 0 if the array is unassigned.
        /// </summary>
        public int TotalWaves => waveDefinitions?.Length ?? 0;

        /// <summary>
        /// Number of times enemies have leaked out of the given player's zone.
        /// Replicated — safe to call on any peer.
        /// </summary>
        public int GetZoneLeakCount(PlayerSlot slot)
        {
            int idx = (int)slot;
            return (idx >= 0 && idx < zoneLeakCounts.Count) ? zoneLeakCounts[idx] : 0;
        }

        // ----- Phase handling ---------------------------------------------

        private void HandlePhaseChanged(MatchPhase previous, MatchPhase next)
        {
            if (!IsServer) return;
            if (next == MatchPhase.Playing && currentWaveIndex < 0)
                StartNextWave();
        }

        // ----- Wave coroutine ---------------------------------------------

        private void StartNextWave(bool skipPrep = false)
        {
            currentWaveIndex++;

            if (waveDefinitions == null || currentWaveIndex >= waveDefinitions.Length)
            {
                Debug.Log("[WaveManager] All waves complete. Victory.");
                MatchState.Instance?.SetPhase(MatchPhase.Victory);
                return;
            }

            // Advance the replicated wave counter at the START of prep so the HUD
            // shows the upcoming wave number during the countdown.
            MatchState.Instance?.SetCurrentWave(currentWaveIndex + 1); // 1-based

            activeEnemyCount = 0;
            spawningComplete = false;

            activeWaveCoroutine = StartCoroutine(
                RunWave(waveDefinitions[currentWaveIndex], skipPrep));
        }

        // ----- Dev / cheats -----------------------------------------------

        /// <summary>
        /// Dev cheat: skip the rest of the current wave (despawn any remaining
        /// enemies, kill the prep timer) and start the next wave immediately.
        /// Server-only — silently no-ops on clients. Safe to call during prep,
        /// mid-spawn, or while enemies are alive.
        /// </summary>
        public void ForceAdvanceToNextWave()
        {
            if (!IsServer) return;

            // Stop the current wave's coroutine (cancels prep timer + remaining spawns).
            if (activeWaveCoroutine != null)
            {
                StopCoroutine(activeWaveCoroutine);
                activeWaveCoroutine = null;
            }

            // Despawn anything still running around. Iterate a snapshot since
            // EnemyHealth.HandleDeath will despawn the NetworkObject, mutating
            // the live collection.
            var spawnManager = NetworkManager.Singleton?.SpawnManager;
            if (spawnManager != null)
            {
                var snapshot = new System.Collections.Generic.List<NetworkObject>(
                    spawnManager.SpawnedObjectsList);
                foreach (var no in snapshot)
                {
                    if (no == null || !no.IsSpawned) continue;
                    var movement = no.GetComponent<EnemyMovement>();
                    if (movement == null) continue;

                    // Unsubscribe so the despawn doesn't deduct lives or fire side effects.
                    var h = no.GetComponent<EnemyHealth>();
                    UnsubscribeEnemy(h);
                    no.Despawn();
                }
            }

            // Reset bookkeeping and start the next wave's RunWave coroutine,
            // skipping the prep timer so spawning starts immediately.
            activeEnemyCount = 0;
            spawningComplete = false;
            StartNextWave(skipPrep: true);
        }

        private IEnumerator RunWave(WaveDefinition def, bool skipPrep = false)
        {
            // Prep phase — players build while the countdown ticks. Skipped when
            // a dev cheat forces the wave to start immediately.
            if (!skipPrep)
                yield return new WaitForSeconds(def.PrepTime);

            // Spawn phase.
            if (def.Entries != null)
            {
                foreach (var entry in def.Entries)
                {
                    if (entry.EnemyType == null || entry.Count <= 0) continue;

                    for (int i = 0; i < entry.Count; i++)
                    {
                        SpawnEnemyInAllZones(entry.EnemyType);

                        if (entry.SpawnInterval > 0f)
                            yield return new WaitForSeconds(entry.SpawnInterval);
                    }
                }
            }

            spawningComplete = true;

            // If every spawned enemy was already resolved before this coroutine finished
            // (edge case: SpawnInterval = 0 and enemies die instantly), complete the wave now.
            CheckWaveComplete();
        }

        // ----- Spawn helpers ----------------------------------------------

        private void SpawnEnemyInAllZones(EnemyDefinition def)
        {
            var loader = LevelLoader.Instance;
            if (loader?.LevelData?.PlayerZones == null) return;

            foreach (var zone in loader.LevelData.PlayerZones)
            {
                if (zone.Spawners == null || zone.Spawners.Length == 0) continue;

                // Skip zones whose owning slot is empty. Until a lobby exists,
                // this means a 1-player test session only spawns enemies in
                // Player 1's zone; Player 2/3/... zones stay quiet until those
                // slots are actually filled. PlayerMatchState.GetForSlot returns
                // null for unoccupied slots (and for PlayerSlot.None).
                if (PlayerMatchState.GetForSlot(zone.Owner) == null) continue;

                // Use the first spawner in the zone. Future: round-robin through Spawners.
                SpawnEnemy(def, zone.Spawners[0].TilePosition);
            }
        }

        private void SpawnEnemy(EnemyDefinition def, Vector2Int spawnerTile)
        {
            if (def.EnemyPrefab == null)
            {
                Debug.LogWarning($"[WaveManager] EnemyDefinition '{def.name}' has no EnemyPrefab assigned.");
                return;
            }

            var go = Instantiate(
                def.EnemyPrefab,
                GridCoordinates.GridToWorld(spawnerTile),
                Quaternion.identity);

            var health   = go.GetComponent<EnemyHealth>();
            var movement = go.GetComponent<EnemyMovement>();

            if (health == null || movement == null)
            {
                Debug.LogError($"[WaveManager] Enemy prefab '{def.EnemyPrefab.name}' is missing " +
                               $"EnemyHealth or EnemyMovement. Enemy will not be spawned.");
                Destroy(go);
                return;
            }

            health.InitializeServer(def.MaxHp, def.GoldReward, def.LivesCost, def.IsFlying);
            movement.InitializeServer(def.MoveSpeed, spawnerTile);

            health.OnDied         += HandleEnemyKilled;
            movement.OnZoneLeaked += HandleZoneLeak;
            movement.OnReachedGoal += HandleEnemyReachedGoal;

            activeEnemyCount++;

            go.GetComponent<NetworkObject>().Spawn();
        }

        // ----- Enemy event handlers (server-only) -------------------------

        private void HandleEnemyKilled(EnemyHealth health)
        {
            // Award kill gold to the tower owner that landed the killing blow.
            PlayerSlot killerSlot = health.LastHitOwner;
            if (killerSlot != PlayerSlot.None)
            {
                var pms = PlayerMatchState.GetForSlot(killerSlot);
                if (pms != null)
                    PlayerGoldManager.GetForClient(pms.OwnerClientId)
                                     ?.AwardGold(health.GoldReward);
            }

            // Show a "+N" gold popup above the corpse on every peer. Capture the
            // position here on the server — by the time the RPC fires on clients
            // the death sequence will be moving the corpse, but the spawn point
            // is good enough and we want the popup to anchor where the kill happened.
            if (health.GoldReward > 0)
                ShowGoldRewardClientRpc(health.transform.position, health.GoldReward);

            UnsubscribeEnemy(health);
            DecrementAndCheckComplete();
        }

        private void HandleZoneLeak(PlayerSlot leavingZone)
        {
            // Increment the per-slot leak counter for the zone the enemy is leaving.
            int idx = (int)leavingZone;
            if (idx >= 0 && idx < zoneLeakCounts.Count)
                zoneLeakCounts[idx]++;
        }

        private void HandleEnemyReachedGoal(EnemyMovement movement, int livesCost)
        {
            // Capture the leak position BEFORE the enemy NetworkObject despawns
            // (HandleGoalReached on the enemy calls Despawn right after firing the
            // event we're handling here). Show the "-N" popup on every peer.
            Vector3 leakPos = movement.transform.position;
            if (livesCost > 0)
                ShowLifeLossClientRpc(leakPos, livesCost);

            UnsubscribeEnemy(movement.GetComponent<EnemyHealth>());

            remainingLives = Mathf.Max(0, remainingLives - livesCost);
            MatchState.Instance?.SetLives(remainingLives);

            if (remainingLives <= 0)
            {
                Debug.Log("[WaveManager] Lives depleted. Defeat.");
                MatchState.Instance?.SetPhase(MatchPhase.Defeat);
                return;
            }

            DecrementAndCheckComplete();
        }

        // ----- Floating-text ClientRpcs -----------------------------------

        // Fired on every peer (server + clients) so each one spawns its own local
        // FloatingText. The spawned GameObjects are not networked — purely visual.
        [ClientRpc]
        private void ShowGoldRewardClientRpc(Vector3 worldPos, int amount)
        {
            FloatingTextSpawner.Instance?.SpawnGoldReward(worldPos, amount);
        }

        [ClientRpc]
        private void ShowLifeLossClientRpc(Vector3 worldPos, int amount)
        {
            FloatingTextSpawner.Instance?.SpawnLifeLoss(worldPos, amount);
            OnLifeLost?.Invoke(amount);
        }

        // ----- Local-only notification events -----------------------------

        /// <summary>
        /// Fired on every peer immediately after a life-loss popup spawns.
        /// HUD subscribes to flash a centered banner; gameplay code can also
        /// hook this for audio cues, screen-shake, etc. Argument is the number
        /// of lives lost (usually 1, but boss enemies with LivesCost &gt; 1
        /// fire a single event carrying the larger value).
        /// </summary>
        public static event System.Action<int> OnLifeLost;

        // ----- Helpers ----------------------------------------------------

        private void UnsubscribeEnemy(EnemyHealth health)
        {
            if (health == null) return;
            health.OnDied -= HandleEnemyKilled;

            var movement = health.GetComponent<EnemyMovement>();
            if (movement != null)
            {
                movement.OnZoneLeaked  -= HandleZoneLeak;
                movement.OnReachedGoal -= HandleEnemyReachedGoal;
            }
        }

        private void DecrementAndCheckComplete()
        {
            activeEnemyCount--;
            CheckWaveComplete();
        }

        private void CheckWaveComplete()
        {
            if (!spawningComplete) return;
            if (activeEnemyCount > 0) return;

            // Guard: don't start the next wave if the match is already decided.
            var ms = MatchState.Instance;
            if (ms == null || ms.Phase == MatchPhase.Defeat || ms.Phase == MatchPhase.Victory)
                return;

            Debug.Log($"[WaveManager] Wave {currentWaveIndex + 1} complete. Starting next wave.");
            StartNextWave();
        }
    }
}