using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Input;
using leak_test_project.Models;
using leak_test_project.Services;
using leak_test_project.ViewModels.Core;

namespace leak_test_project.ViewModels
{
    /// <summary>
    /// In/Out Monitor 화면의 데이터 페이징 로직을 담당하는 ViewModel.
    /// </summary>
    public class InOutViewModel : ObservableObject
    {
        private readonly List<InOutItem> _allInputs;
        private readonly List<InOutItem> _allOutputs;
        private const int PageSize = 30;

        private int _inputCurrentPage = 0;
        private int _outputCurrentPage = 0;

        private List<InOutItem> _currentInputs = new List<InOutItem>();
        public List<InOutItem> CurrentInputs { get => _currentInputs; set => SetProperty(ref _currentInputs, value); }

        private List<InOutItem> _currentOutputs = new List<InOutItem>();
        public List<InOutItem> CurrentOutputs { get => _currentOutputs; set => SetProperty(ref _currentOutputs, value); }

        // Input 페이징 커맨드
        public ICommand InputFirstCommand { get; }
        public ICommand InputPrevCommand { get; }
        public ICommand InputNextCommand { get; }
        public ICommand InputLastCommand { get; }

        // Output 페이징 커맨드
        public ICommand OutputFirstCommand { get; }
        public ICommand OutputPrevCommand { get; }
        public ICommand OutputNextCommand { get; }
        public ICommand OutputLastCommand { get; }

        /// <summary> Close 버튼 시 홈으로 돌아가는 커맨드 </summary>
        public ICommand CloseCommand { get; }

        public InOutViewModel(Action navigateHome, IoBoardService ioService)
        {
            _allInputs = ioService.Inputs;
            _allOutputs = ioService.Outputs;

            InputFirstCommand = new RelayCommand(o => { _inputCurrentPage = 0; UpdateInputs(); });
            InputPrevCommand = new RelayCommand(o => { if (_inputCurrentPage > 0) { _inputCurrentPage--; UpdateInputs(); } });
            InputNextCommand = new RelayCommand(o => { if ((_inputCurrentPage + 1) * PageSize < _allInputs.Count) { _inputCurrentPage++; UpdateInputs(); } });
            InputLastCommand = new RelayCommand(o => { _inputCurrentPage = Math.Max(0, (_allInputs.Count - 1) / PageSize); UpdateInputs(); });

            OutputFirstCommand = new RelayCommand(o => { _outputCurrentPage = 0; UpdateOutputs(); });
            OutputPrevCommand = new RelayCommand(o => { if (_outputCurrentPage > 0) { _outputCurrentPage--; UpdateOutputs(); } });
            OutputNextCommand = new RelayCommand(o => { if ((_outputCurrentPage + 1) * PageSize < _allOutputs.Count) { _outputCurrentPage++; UpdateOutputs(); } });
            OutputLastCommand = new RelayCommand(o => { _outputCurrentPage = Math.Max(0, (_allOutputs.Count - 1) / PageSize); UpdateOutputs(); });

            CloseCommand = new RelayCommand(o => navigateHome?.Invoke());

            UpdateInputs();
            UpdateOutputs();
        }

        private void UpdateInputs()
        {
            CurrentInputs = _allInputs.Skip(_inputCurrentPage * PageSize).Take(PageSize).ToList();
        }

        private void UpdateOutputs()
        {
            CurrentOutputs = _allOutputs.Skip(_outputCurrentPage * PageSize).Take(PageSize).ToList();
        }
    }
}