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

namespace TD.Gameplay
{
    /// <summary>
    /// Per-player avatar that gates tower placement by proximity. Server-authoritative
    /// position; clients submit move requests via Rpc and the server validates and applies.
    /// </summary>
    /// <remarks>
    /// <para><b>Pure visual avatar.</b> Builders have no collider for gameplay purposes —
    /// they don't block enemies, can't be attacked, and aren't selected as targets. They
    /// are visible to all players but only their owner can move them.</para>
    ///
    /// <para><b>Terrain-aware height.</b> Each frame the server casts a ray straight down
    /// from the builder against the <see cref="terrainLayerMask"/> and sets Y to
    /// <c>hit.point.y + heightOffset</c>. If the ray misses, falls back to the buildable
    /// plane Y. Towers are not on the terrain layer, so they don't influence height.</para>
    ///
    /// <para><b>Range gating.</b> <see cref="IsTileWithinBuildRange"/> is the public query
    /// that <c>TowerPlacementManager</c> uses to validate placement requests. Builder range
    /// is measured center-of-builder to center-of-anchor-tile in world units.</para>
    ///
    /// <para><b>Static registry.</b> Like <see cref="PlayerGoldManager"/>, builders register
    /// themselves in a static dictionary keyed by <c>OwnerClientId</c> on spawn, so server
    /// gameplay code (notably <c>TowerPlacementManager</c>) can find a player's builder without
    /// scene traversal.</para>
    /// </remarks>
    [RequireComponent(typeof(NetworkObject))]
    public class Builder : NetworkBehaviour
    {
        // ----- Static registry --------------------------------------------

        private static readonly Dictionary<ulong, Builder> s_byClientId
            = new Dictionary<ulong, Builder>();

        /// <summary>
        /// Returns the Builder owned by the given client, or null if none is currently spawned.
        /// Safe to call on server or client.
        /// </summary>
        public static Builder GetForClient(ulong clientId)
        {
            s_byClientId.TryGetValue(clientId, out var builder);
            return builder;
        }

        /// <summary>
        /// Convenience: the local client's own builder. Returns null on a dedicated server
        /// or before the local player has spawned.
        /// </summary>
        public static Builder Local
        {
            get
            {
                var nm = NetworkManager.Singleton;
                if (nm == null || !nm.IsClient) return null;
                return GetForClient(nm.LocalClientId);
            }
        }

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

        [Header("Movement")]
        [Tooltip("Speed at which the builder moves toward its target position, in world " +
                 "units per second.")]
        [SerializeField] private float moveSpeed = 8f;

        [Tooltip("Distance below which the builder is considered to have arrived at its " +
                 "target. Smaller = more precise but more jitter; larger = less precise " +
                 "but smoother.")]
        [SerializeField] private float arrivalThreshold = 0.05f;

        [Header("Height tracking")]
        [Tooltip("Vertical offset above the terrain at which the builder hovers. " +
                 "Re-evaluated every server tick by raycasting straight down.")]
        [SerializeField] private float heightOffset = 2f;

        [Tooltip("Maximum distance to cast downward when sampling terrain height. Should " +
                 "exceed your map's vertical range.")]
        [SerializeField] private float terrainRaycastMaxDistance = 100f;

        [Tooltip("Physics layer mask used for terrain height sampling. Towers MUST NOT be " +
                 "on this layer — only ground geometry. Falls back to the buildable plane Y " +
                 "if no terrain hit.")]
        [SerializeField] private LayerMask terrainLayerMask;

        [Header("Build range")]
        [Tooltip("Maximum distance from the builder's center to a tower's anchor tile center " +
                 "for placement to be allowed, measured in world units (== tiles).")]
        [SerializeField] private float buildRange = 6f;

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

        // Server-authoritative target position. The server moves the builder toward this
        // each frame; clients render the builder smoothly via NetworkTransform's interpolation.
        // We replicate the target (not the live position) so the server's intent is visible
        // to clients, but the rendered position is whatever NetworkTransform interpolates to.
        private readonly NetworkVariable<Vector3> targetPosition = new NetworkVariable<Vector3>(
            value: Vector3.zero,
            readPerm: NetworkVariableReadPermission.Everyone,
            writePerm: NetworkVariableWritePermission.Server);

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

        /// <summary>The builder's current world position (its actual transform position,
        /// not the target).</summary>
        public Vector3 CurrentPosition => transform.position;

        /// <summary>The builder's target position. Server moves toward this each frame.</summary>
        public Vector3 TargetPosition => targetPosition.Value;

        /// <summary>True if the builder has arrived at its target (within
        /// <see cref="arrivalThreshold"/>).</summary>
        public bool IsAtTarget =>
            Vector3.SqrMagnitude(transform.position - targetPosition.Value)
            < arrivalThreshold * arrivalThreshold;

        /// <summary>Build range in world units.</summary>
        public float BuildRange => buildRange;

        // ----- Lifecycle --------------------------------------------------

        public override void OnNetworkSpawn()
        {
            s_byClientId[OwnerClientId] = this;

            if (IsServer)
            {
                // Set initial target = current position so the builder doesn't drift on spawn.
                // The spawner is responsible for placing this builder at a sensible position
                // BEFORE Spawn() — see PlayerSpawnHelper / Player.OnNetworkSpawn.
                targetPosition.Value = transform.position;
                Debug.Log($"[Builder] Spawned for client {OwnerClientId} at " +
                          $"{transform.position}.");
            }

            ApplyOwnerColor();
        }

        // ----- Owner color tinting ----------------------------------------

        // Lazily allocated; reused across renderers. Construction in a field initializer
        // would throw on this MonoBehaviour at scene load.
        private MaterialPropertyBlock colorPropertyBlock;
        // Both _Color (legacy Standard) and _BaseColor (URP Lit) — writing both lets the
        // tint apply regardless of which shader the prefab uses. Unknown property writes
        // are silently ignored by the shader.
        private static readonly int ColorPropertyId = Shader.PropertyToID("_Color");
        private static readonly int BaseColorPropertyId = Shader.PropertyToID("_BaseColor");

        private void ApplyOwnerColor()
        {
            // Owner color comes from the slot mapping. Same stub mapping as elsewhere —
            // replaced when MatchState lands.
            byte slotByte = (byte)(OwnerClientId + 1);
            PlayerSlot slot = (slotByte >= 1 && slotByte <= 9) ? (PlayerSlot)slotByte : PlayerSlot.None;

            Color c = PlayerColors.Get(slot);
            c.a = 1f;

            colorPropertyBlock ??= new MaterialPropertyBlock();
            colorPropertyBlock.SetColor(ColorPropertyId, c);
            colorPropertyBlock.SetColor(BaseColorPropertyId, c);

            foreach (var rend in GetComponentsInChildren<MeshRenderer>())
                rend.SetPropertyBlock(colorPropertyBlock);
        }

        public override void OnNetworkDespawn()
        {
            if (s_byClientId.TryGetValue(OwnerClientId, out var registered) && registered == this)
                s_byClientId.Remove(OwnerClientId);
        }

        // ----- Per-frame movement (server only) ---------------------------

        private void Update()
        {
            if (!IsServer) return;

            // Move toward target on the XZ plane.
            Vector3 current = transform.position;
            Vector3 target = targetPosition.Value;

            // Flatten to XZ for distance/movement calculations; Y is driven by terrain raycast.
            Vector3 currentXZ = new Vector3(current.x, 0f, current.z);
            Vector3 targetXZ = new Vector3(target.x, 0f, target.z);

            Vector3 newXZ;
            if (Vector3.SqrMagnitude(currentXZ - targetXZ) <= arrivalThreshold * arrivalThreshold)
            {
                newXZ = targetXZ;
            }
            else
            {
                newXZ = Vector3.MoveTowards(currentXZ, targetXZ, moveSpeed * Time.deltaTime);
            }

            // Resolve Y from terrain.
            float groundY = SampleTerrainY(new Vector3(newXZ.x, 0f, newXZ.z));
            transform.position = new Vector3(newXZ.x, groundY + heightOffset, newXZ.z);
        }

        /// <summary>
        /// Casts a ray straight down at <paramref name="xzPos"/> and returns the hit Y, or
        /// <see cref="GridCoordinates.BUILDABLE_PLANE_Y"/> if nothing was hit on the
        /// terrain layer.
        /// </summary>
        private float SampleTerrainY(Vector3 xzPos)
        {
            // Ray origin: high above the map. terrainRaycastMaxDistance defines how far to cast.
            Vector3 origin = new Vector3(xzPos.x, terrainRaycastMaxDistance, xzPos.z);
            if (Physics.Raycast(origin, Vector3.down, out RaycastHit hit,
                                terrainRaycastMaxDistance * 2f, terrainLayerMask))
            {
                return hit.point.y;
            }

            // Fallback: builder hovers above the buildable plane.
            return GridCoordinates.BUILDABLE_PLANE_Y;
        }

        // ----- Server move API --------------------------------------------

        /// <summary>
        /// Server-side entry point: directly sets the move target. Called by the input
        /// controller's Rpc handler after validation. Out-of-map positions are clamped
        /// to the current position (no-op).
        /// </summary>
        public void ServerSetMoveTarget(Vector3 worldPos)
        {
            if (!IsServer)
            {
                Debug.LogError("[Builder] ServerSetMoveTarget called on a client.");
                return;
            }

            // Clamp to map area: convert XZ to a tile and check IsInMap.
            var loader = LevelLoader.Instance;
            if (loader != null && loader.IsLoaded)
            {
                Vector2Int tile = GridCoordinates.WorldToGrid(worldPos);
                if (!loader.IsInMap(tile))
                {
                    // Out-of-map move requests are rejected silently. Could log if useful for
                    // debugging client/server mismatch, but otherwise this is normal.
                    return;
                }
            }

            // Y is overwritten by terrain raycast each Update; we only honor X and Z here.
            targetPosition.Value = new Vector3(worldPos.x, 0f, worldPos.z);
        }

        // ----- Owner-only move RPC ----------------------------------------

        /// <summary>
        /// Owner-only Rpc: a client requests their builder move to a world position.
        /// Server validates (in-map check) and applies via <see cref="ServerSetMoveTarget"/>.
        /// </summary>
        [Rpc(SendTo.Server, InvokePermission = RpcInvokePermission.Owner)]
        public void RequestMoveRpc(Vector3 worldPos)
        {
            ServerSetMoveTarget(worldPos);
        }

        // ----- Range query (used by TowerPlacementManager) ----------------

        /// <summary>
        /// True if the tower with the given anchor and footprint size is within build range
        /// of this builder's CURRENT position. Range is measured from builder center to the
        /// nearest point of the tower footprint, in world units.
        /// </summary>
        /// <remarks>
        /// "Nearest point of the footprint" rather than "footprint center" so that a tower
        /// is reachable when ANY of its tiles is within range, even if the center is
        /// slightly outside. Aligns with player intuition that "I can reach this tile."
        /// </remarks>
        public bool IsTileWithinBuildRange(Vector2Int anchor, Vector2Int footprintSize)
        {
            Vector3 builderXZ = new Vector3(transform.position.x, 0f, transform.position.z);

            // Find the point on the footprint rectangle nearest to the builder.
            float minX = anchor.x * GridCoordinates.TILE_SIZE - GridCoordinates.TILE_SIZE * 0.5f;
            float maxX = (anchor.x + footprintSize.x - 1) * GridCoordinates.TILE_SIZE
                         + GridCoordinates.TILE_SIZE * 0.5f;
            float minZ = anchor.y * GridCoordinates.TILE_SIZE - GridCoordinates.TILE_SIZE * 0.5f;
            float maxZ = (anchor.y + footprintSize.y - 1) * GridCoordinates.TILE_SIZE
                         + GridCoordinates.TILE_SIZE * 0.5f;

            float nearestX = Mathf.Clamp(builderXZ.x, minX, maxX);
            float nearestZ = Mathf.Clamp(builderXZ.z, minZ, maxZ);
            Vector3 nearestPoint = new Vector3(nearestX, 0f, nearestZ);

            return Vector3.SqrMagnitude(builderXZ - nearestPoint)
                   <= buildRange * buildRange;
        }
    }
}