using System;
using Prism.Mvvm;
using XP.Common.Localization;

namespace XP.Common.GeneralForm.ViewModels
{
    /// <summary>
    /// 输入对话框 ViewModel | Input dialog ViewModel
    /// </summary>
    public class InputDialogViewModel : BindableBase
    {
        private readonly Func<string, string?>? _validate;
        private string _inputText;
        private string? _validationError;

        /// <summary>
        /// 窗口标题 | Window title
        /// </summary>
        public string Title { get; }

        /// <summary>
        /// 提示文本 | Prompt text
        /// </summary>
        public string Prompt { get; }

        /// <summary>
        /// 确定按钮文本（多语言）| OK button text (localized)
        /// </summary>
        public string OkText { get; }

        /// <summary>
        /// 取消按钮文本（多语言）| Cancel button text (localized)
        /// </summary>
        public string CancelText { get; }

        /// <summary>
        /// 用户输入的文本 | User input text
        /// </summary>
        public string InputText
        {
            get => _inputText;
            set
            {
                if (SetProperty(ref _inputText, value))
                {
                    // 输入变化时清除验证错误 | Clear validation error on input change
                    ValidationError = null;
                }
            }
        }

        /// <summary>
        /// 验证错误信息，null 表示无错误 | Validation error message, null means no error
        /// </summary>
        public string? ValidationError
        {
            get => _validationError;
            set
            {
                if (SetProperty(ref _validationError, value))
                {
                    RaisePropertyChanged(nameof(HasValidationError));
                }
            }
        }

        /// <summary>
        /// 是否存在验证错误 | Whether there is a validation error
        /// </summary>
        public bool HasValidationError => !string.IsNullOrEmpty(ValidationError);

        /// <summary>
        /// 构造函数 | Constructor
        /// </summary>
        /// <param name="prompt">提示文本 | Prompt text</param>
        /// <param name="title">窗口标题 | Window title</param>
        /// <param name="defaultValue">默认值 | Default value</param>
        /// <param name="validate">验证委托，返回 null 表示通过，返回错误信息则显示 | Validation delegate</param>
        public InputDialogViewModel(
            string prompt,
            string title,
            string defaultValue = "",
            Func<string, string?>? validate = null)
        {
            Prompt = prompt;
            Title = title;
            _inputText = defaultValue;
            _validate = validate;

            // 按钮文本使用多语言 | Button text uses localization
            OkText = LocalizationHelper.Get("Button_OK");
            CancelText = LocalizationHelper.Get("Button_Cancel");
        }

        /// <summary>
        /// 执行验证，返回是否通过 | Run validation, returns whether it passed
        /// </summary>
        /// <returns>true 表示验证通过 | true means validation passed</returns>
        public bool Validate()
        {
            if (_validate == null)
                return true;

            var error = _validate(InputText);
            ValidationError = error;
            return error == null;
        }
    }
}