using Prism.Mvvm;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using UIShare.UIViewModel;

namespace UIShare.GlobalVariable
{
    /// <summary>
    /// 单个 Tab（主程序 / 错误程序）的子程序导航状态。
    /// 主程序和错误程序各自持有一个独立实例，互不干扰。
    /// </summary>
    public class ProgramNavigationState : BindableBase
    {
        /// <summary>是否为错误程序 Tab</summary>
        public bool IsErrorTab { get; set; }

        public Stack<ProgramVM> NavigationStack { get; } = new();

        private ProgramVM _currentProgram;
        public ProgramVM CurrentProgram
        {
            get => _currentProgram;
            set
            {
                if (SetProperty(ref _currentProgram, value))
                    RaisePropertyChanged(nameof(DisplaySteps));
            }
        }

        /// <summary>
        /// DataGrid 实际绑定的步骤集合。
        /// 根程序 + 错误 Tab → ErrorStepCollection；其他情况 → StepCollection。
        /// </summary>
        public ObservableCollection<StepVM> DisplaySteps
        {
            get
            {
                if (CurrentProgram == null)
                    return new ObservableCollection<StepVM>();
                // 在根程序且是错误 Tab → 显示错误步骤集合
                if (NavigationStack.Count == 0 && IsErrorTab)
                    return CurrentProgram.ErrorStepCollection;
                // 其他情况（主 Tab 或已进入子程序）→ 显示正常步骤集合
                return CurrentProgram.StepCollection;
            }
        }

        private string _breadcrumbPath = "主程序";
        public string BreadcrumbPath
        {
            get => _breadcrumbPath;
            set => SetProperty(ref _breadcrumbPath, value);
        }

        private bool _canGoBack;
        public bool CanGoBack
        {
            get => _canGoBack;
            set => SetProperty(ref _canGoBack, value);
        }

        /// <summary>
        /// 用根程序初始化导航状态
        /// </summary>
        public void Initialize(ProgramVM rootProgram, string label)
        {
            NavigationStack.Clear();
            CurrentProgram = rootProgram;
            BreadcrumbPath = label;
            CanGoBack = false;
        }

        /// <summary>
        /// 清空导航栈，回到根程序
        /// </summary>
        public void Reset(ProgramVM rootProgram, string label)
        {
            NavigationStack.Clear();
            CurrentProgram = rootProgram;
            BreadcrumbPath = label;
            CanGoBack = false;
        }

        /// <summary>
        /// 根据栈状态刷新 CanGoBack
        /// </summary>
        public void UpdateCanGoBack() => CanGoBack = NavigationStack.Count > 0;
    }
}