using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Kean.Domain.Order.Models
{
    /// <summary>
    /// 单号格式
    /// </summary>
    public class Format
    {
        private readonly IEnumerable<string> _span; // 片段

        /// <summary>
        /// 初始化  Kean.Domain.Order.Models.Format 类的新实例
        /// </summary>
        /// <param name="span">片段</param>
        public Format(IEnumerable<string> span) => _span = span;

        /// <summary>
        /// 隐式转换为字符串
        /// </summary>
        /// <param name="format">格式</param>
        public static implicit operator string(Format format) => format.ToString();

        /*
         * 重写 System.ToString 方法，实现片段到字符串的转换
         */
        public override string ToString() => string.Join(string.Empty, _span.Select(i =>
        {
            var parts = i.Split(':', 2);
            return parts[0] switch
            {
                "const" => parts[1],
                "date" or "serial" => $"{{{parts[0]}:{parts[1]}}}",
                _ => null,
            };
        }));

        /// <summary>
        /// 解释片段
        /// </summary>
        /// <param name="format">格式</param>
        /// <returns>片段</returns>
        public static IEnumerable<(string Type, string Value)> Interpret(string format)
        {
            var span = new Stack<StringBuilder[]>();
            bool? flag = null;
            foreach (var @char in format)
            {
                switch (@char)
                {
                    case '{':
                        span.Push(new StringBuilder[2] { new(), new() });
                        flag = false;
                        break;
                    case ':':
                        flag = true;
                        break;
                    case '}':
                        flag = null;
                        break;
                    default:
                        switch (flag)
                        {
                            case false:
                                span.Peek()[0].Append(@char);
                                break;
                            case true:
                                span.Peek()[1].Append(@char);
                                break;
                            case null:
                                span.Push(new StringBuilder[2] { new("const"), new(@char.ToString()) });
                                flag = true;
                                break;
                        }
                        break;
                }
            }
            return span
                .Reverse()
                .Select(a => (a[0].ToString(), a[1].ToString()))
                .ToArray();
        }
    }
}