using FishNet.Connection;
using FishNet.Object;
using UnityEngine;

namespace Ashwild.Building
{
    /// <summary>
    /// The networked side of building: it commits placements and owns the live ghost preview.
    ///
    /// Every committed structure — a wall as much as a chest or a campfire — is spawned as a real
    /// NetworkObject owned by the server. That is the whole design: FishNet already replicates spawns,
    /// catches late joiners up, and tears objects down on despawn, so there is no build list to keep,
    /// no index to align, and no rebuild path to write. Each build carries its own state on its own
    /// <see cref="BuiltStructure"/>, which is what lets a stateful structure (chest, cooking station)
    /// be placed by exactly the same code as a plain wall instead of needing a parallel mechanism.
    ///
    /// This replaced an earlier data-driven registry (a SyncList of pose records that every client
    /// instantiated locally). That saved FishNet's per-object bookkeeping but not the GameObjects —
    /// they were instantiated locally anyway — while forcing a second, incompatible path for anything
    /// with real state. One mechanism is worth the bookkeeping.
    ///
    /// The ghost is likewise a NetworkObject, but owned by the placer so FishNet's NetworkTransform
    /// replicates its motion smoothly; it is transient and one per player.
    ///
    /// BuildManager (the local build UX) drives the owned ghost; on confirm this registry spawns the
    /// structure and despawns the ghost. One instance per scene, a scene NetworkObject like the others.
    /// </summary>
    [RequireComponent(typeof(NetworkObject))]
    public class BuildRegistry : NetworkBehaviour
    {
        #region State

        /// <summary>
        /// The single scene instance, so BuildManager can request ghost spawns/despawns and build commits.
        /// </summary>
        public static BuildRegistry Instance { get; private set; }

        #endregion

        #region Network Lifecycle

        /// <summary>
        /// Claims the singleton on every machine.
        /// </summary>
        public override void OnStartNetwork()
        {
            base.OnStartNetwork();
            Instance = this;
        }

        /// <summary>
        /// Releases the singleton when the session ends. Committed structures are NetworkObjects, so
        /// FishNet despawns them itself — there is nothing to tear down here.
        /// </summary>
        public override void OnStopNetwork()
        {
            base.OnStopNetwork();
            if (Instance == this) Instance = null;
        }

        #endregion

        #region Commit Build

        /// <summary>
        /// Called by BuildManager when the local player confirms a placement: commit this buildable at
        /// this pose so the real structure appears for every player.
        /// </summary>
        public void RequestBuild(ushort buildableId, Vector3 position, Quaternion rotation)
            => RequestBuildServerRpc(buildableId, position, rotation);

        /// <summary>
        /// Server-side: validates the id, instantiates the built prefab, seeds its identity and health,
        /// then spawns it for everyone. The appear pop is sent separately to current observers only, so a
        /// late joiner streaming in an existing base does not watch all of it pop at once.
        ///
        /// The structure is spawned server-owned (no connection passed): builds are shared world state
        /// and several players interact with the same chest or fire, so handing ownership to whoever
        /// placed it would tie everyone's access to that player's connection.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void RequestBuildServerRpc(ushort buildableId, Vector3 position, Quaternion rotation, NetworkConnection conn = null)
        {
            BuildableData data = BuildableDatabase.Instance != null ? BuildableDatabase.Instance.GetBuildable(buildableId) : null;
            if (data == null || data.BuiltPrefab == null)
            {
                Debug.LogWarning($"[BuildRegistry] Buildable id {buildableId} is unknown or has no BuiltPrefab — nothing spawned.", this);
                return;
            }

            // TODO: validate + consume the requester's resources (conn → PlayerInventory) before committing.
            GameObject go = Instantiate(data.BuiltPrefab, position, rotation);

            BuiltStructure structure = go.GetComponent<BuiltStructure>();
            if (structure == null)
            {
                Debug.LogError($"[BuildRegistry] BuiltPrefab '{data.BuiltPrefab.name}' has no BuiltStructure — add one (it carries the build's identity, health and demolition).", this);
                Destroy(go);
                return;
            }

            structure.InitialiseOnServer(buildableId, data.MaxHealth);
            base.ServerManager.Spawn(go);
            structure.PlaySpawnBumpForObservers();
        }

        #endregion

        #region Networked Ghost Preview

        /// <summary>
        /// Client → asks the server to spawn a ghost of this buildable, owned by us. The spawned
        /// object is handed back to BuildManager through <see cref="TargetAttachGhost"/>, carrying
        /// the request token so a superseded spawn can be discarded.
        /// </summary>
        public void RequestSpawnGhost(ushort buildableId, int token) => RequestSpawnGhostServerRpc(buildableId, token);

        /// <summary>
        /// Client → asks the server to despawn a ghost we own (on confirm, cancel or switch).
        /// </summary>
        public void RequestDespawnGhost(NetworkObject ghost)
        {
            if (ghost != null) RequestDespawnGhostServerRpc(ghost);
        }

        /// <summary>
        /// Server-side: spawns the buildable's ghost prefab owned by the requester, then tells that
        /// client which object to drive. The prefab must be a NetworkObject registered in
        /// DefaultPrefabObjects with a client-authoritative NetworkTransform.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void RequestSpawnGhostServerRpc(ushort buildableId, int token, NetworkConnection conn = null)
        {
            if (conn == null) return;

            BuildableData data = BuildableDatabase.Instance != null ? BuildableDatabase.Instance.GetBuildable(buildableId) : null;
            if (data == null || data.GhostPrefab == null) return;

            GameObject go = Instantiate(data.GhostPrefab);
            base.ServerManager.Spawn(go, conn);
            TargetAttachGhost(conn, go.GetComponent<NetworkObject>(), token);
        }

        /// <summary>
        /// Owner-side: hands the freshly spawned ghost (and its request token) to BuildManager to drive.
        /// </summary>
        [TargetRpc]
        private void TargetAttachGhost(NetworkConnection conn, NetworkObject ghost, int token)
        {
            if (ghost == null || BuildManager.Instance == null) return;
            BuildManager.Instance.AttachGhost(ghost.gameObject, token);
        }

        /// <summary>
        /// Server-side: destroys a ghost (never pools it — a ghost is single-use). Ownership guards
        /// that a client only despawns its own.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void RequestDespawnGhostServerRpc(NetworkObject ghost, NetworkConnection conn = null)
        {
            if (ghost == null) return;
            if (ghost.Owner != conn) return;
            base.ServerManager.Despawn(ghost, DespawnType.Destroy);
        }

        /// <summary>
        /// Owner → replicates the ghost's current spot validity to every other client so teammates see
        /// the same green (clear) / red (blocked) preview. Only the owner drives the evaluation locally,
        /// so without this a remote ghost stays on its default look; BuildManager calls this only when the
        /// value actually changes, so the traffic is a rare per-ghost blip, not a per-frame stream.
        /// </summary>
        public void SetGhostValidity(NetworkObject ghost, bool valid)
        {
            if (ghost != null) SetGhostValidityServerRpc(ghost, valid);
        }

        /// <summary>
        /// Server-side relay: forwards the placer's validity to all observers.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void SetGhostValidityServerRpc(NetworkObject ghost, bool valid, NetworkConnection conn = null)
        {
            if (ghost == null) return;
            ObserversSetGhostValidity(ghost, valid);
        }

        /// <summary>
        /// Applies the replicated validity on every client except the placer, whose own local evaluation
        /// already drives the richer verdict (and knows about affordability, which is never sent). A
        /// missing ghost is ignored — it may have been despawned mid-flight.
        /// </summary>
        [ObserversRpc]
        private void ObserversSetGhostValidity(NetworkObject ghost, bool valid)
        {
            if (ghost == null || ghost.IsOwner) return;
            BuildGhost bg = ghost.GetComponent<BuildGhost>();
            if (bg != null) bg.SetRemoteValidity(valid);
        }

        #endregion
    }
}