using System.Collections.Generic;
using AfterHours.Core;
using AfterHours.Data;
using AfterHours.Interaction;
using Unity.Netcode;
using UnityEngine;

namespace AfterHours.Shop
{
    /// <summary>
    /// Kasse. Kunden reihen sich ein; ein Spieler scannt Position für Position
    /// und schließt ab. Sämtliche Geldbewegung passiert hier auf dem Server.
    /// </summary>
    public sealed class CashRegister : NetworkBehaviour, IInteractable
    {
        [SerializeField] private ProductCatalog _catalog;
        [SerializeField] private Transform _queueStart;
        [SerializeField] private float _queueSpacing = 0.8f;

        /// <summary>Server-only. Clients sehen die Schlange über die NPC-Positionen.</summary>
        private readonly List<Customers.CustomerAgent> _queue = new();

        private readonly NetworkVariable<float> _pendingTotal = new(0f);
        private readonly NetworkVariable<int> _scannedItems = new(0);

        public float PendingTotal => _pendingTotal.Value;
        public int QueueLength => _queue.Count;

        public string GetPrompt(ulong clientId)
        {
            if (_queue.Count == 0) return "Kasse (frei)";
            return _scannedItems.Value > 0
                ? $"Kassieren — {_pendingTotal.Value:0.00} €"
                : "Artikel scannen";
        }

        /// <summary>Server: ein Klick = ein Artikel scannen, oder abschließen wenn fertig.</summary>
        public void Interact(NetworkObject actor)
        {
            if (!IsServer || _queue.Count == 0) return;

            var customer = _queue[0];
            if (customer == null) { _queue.RemoveAt(0); return; }

            if (_scannedItems.Value < customer.BasketCount)
            {
                ScanNext(customer);
                return;
            }

            Finalize(customer);
        }

        private void ScanNext(Customers.CustomerAgent customer)
        {
            var line = customer.BasketAt(_scannedItems.Value);
            _pendingTotal.Value += line.Price;
            _scannedItems.Value++;
        }

        private void Finalize(Customers.CustomerAgent customer)
        {
            ShopEconomy.Instance.Earn(_pendingTotal.Value);
            ShopEconomy.Instance.RegisterSale(customer.Comfort);

            customer.OnPaid();
            _queue.RemoveAt(0);

            _pendingTotal.Value = 0f;
            _scannedItems.Value = 0;

            ReflowQueue();
        }

        /// <summary>Server: Kunde stellt sich an. Gibt die Zielposition zurück.</summary>
        public Vector3 Enqueue(Customers.CustomerAgent customer)
        {
            if (!IsServer) return _queueStart.position;

            if (!_queue.Contains(customer)) _queue.Add(customer);
            return SlotPosition(_queue.IndexOf(customer));
        }

        /// <summary>Server: Kunde verlässt die Schlange (z. B. weil er aufgibt).</summary>
        public void Remove(Customers.CustomerAgent customer)
        {
            if (!IsServer) return;
            if (_queue.Remove(customer)) ReflowQueue();
        }

        private void ReflowQueue()
        {
            for (int i = 0; i < _queue.Count; i++)
                if (_queue[i] != null) _queue[i].MoveTo(SlotPosition(i));
        }

        private Vector3 SlotPosition(int index)
        {
            return _queueStart.position + _queueStart.forward * (-_queueSpacing * index);
        }
    }
}