using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace TeamAAS_VP.Core
{
    public class FileNameTemplate
    {
        private readonly string _template;
        private readonly Dictionary<string, Func<object>> _variables;

        public FileNameTemplate(string template)
        {
            _template = template ?? throw new ArgumentNullException(nameof(template));
            _variables = new Dictionary<string, Func<object>>(StringComparer.OrdinalIgnoreCase);

            // 注册内置变量
            RegisterDefaultVariables();
        }

        // 注册自定义变量
        public void RegisterVariable(string name, Func<object> valueProvider)
        {
            _variables[name] = valueProvider ?? throw new ArgumentNullException(nameof(valueProvider));
        }

        // 生成文件名
        public string Generate()
        {
            string result = _template;

            // 查找所有 {变量名[:格式化字符串]} 格式的占位符
            var matches = Regex.Matches(_template, @"\{([^}:]+)(?::([^}]+))?\}");

            foreach (Match match in matches)
            {
                string fullPlaceholder = match.Value;
                string varName = match.Groups[1].Value;
                string format = match.Groups[2].Success ? match.Groups[2].Value : null;

                if (_variables.TryGetValue(varName, out var valueProvider))
                {
                    object value = valueProvider();
                    string replacement = FormatValue(value, format);
                    result = result.Replace(fullPlaceholder, replacement);
                }
            }

            // 移除文件名中不允许的字符
            result = SanitizeFileName(result);

            return result;
        }

        private string FormatValue(object value, string format)
        {
            if (value == null) return "";

            // 如果是日期时间类型，应用格式
            if (value is DateTime dateTime && !string.IsNullOrEmpty(format))
            {
                return dateTime.ToString(format);
            }

            // 如果是数值类型，应用格式
            if (value is IFormattable formattable && !string.IsNullOrEmpty(format))
            {
                return formattable.ToString(format, null);
            }

            return value.ToString();
        }

        private string SanitizeFileName(string fileName)
        {
            // 移除文件名中不允许的字符
            char[] invalidChars = System.IO.Path.GetInvalidFileNameChars();
            foreach (char c in invalidChars)
            {
                fileName = fileName.Replace(c.ToString(), "");
            }
            return fileName;
        }

        private void RegisterDefaultVariables()
        {
            // 日期时间变量
            RegisterVariable("Now", () => DateTime.Now);
            RegisterVariable("Today", () => DateTime.Today);
            RegisterVariable("Now", () => DateTime.Now);

            // 可以在这里添加更多内置变量
        }
    }
}