using System.Collections;
using System.Xml;
using NewLife.Reflection;

namespace NewLife.Serialization;

/// <summary>列表数据编码</summary>
public class XmlList : XmlHandlerBase
{
    /// <summary>初始化</summary>
    public XmlList()
    {
        // 优先级
        Priority = 20;
    }

    /// <summary>写入</summary>
    /// <param name="value"></param>
    /// <param name="type"></param>
    /// <returns></returns>
    public override Boolean Write(Object value, Type type)
    {
        if (!type.As<IList>() && value is not IList) return false;

        if (value is not IList list || list.Count == 0) return true;

        WriteLog("XmlWrite {0} 元素{1}项", type.Name, list.Count);

        Host.Hosts.Push(value);

        //var xml = Host as Xml;
        //xml.WriteStart(type);
        try
        {
            // 循环写入数据
            foreach (var item in list)
            {
                if (!Host.Write(item)) return false;
            }
        }
        finally
        {
            //xml.WriteEnd();

            Host.Hosts.Pop();
        }

        return true;
    }

    /// <summary>读取</summary>
    /// <param name="type"></param>
    /// <param name="value"></param>
    /// <returns></returns>
    public override Boolean TryRead(Type type, ref Object value)
    {
        if (!type.As<IList>() && !type.As(typeof(IList<>))) return false;

        var reader = Host.GetReader();

        // 读一次开始，移动到内部第一个元素
        if (reader.NodeType == XmlNodeType.Attribute) reader.ReadStartElement();
        if (!reader.IsStartElement()) return true;

        // 子元素类型
        var elmType = type.GetElementTypeEx();

        if (value is not IList list || value is Array) list = typeof(List<>).MakeGenericType(elmType).CreateInstance() as IList;

        // 清空已有数据
        list.Clear();

        while (reader.IsStartElement())
        {
            Object obj = null;
            if (!Host.TryRead(elmType, ref obj)) return false;

            list.Add(obj);
        }

        if (value != list)
        {
            // 数组的创建比较特别
            if (type.As<Array>())
            {
                var arr = Array.CreateInstance(type.GetElementTypeEx(), list.Count);
                list.CopyTo(arr, 0);
                value = arr;
            }
            else
                value = list;
        }

        // 读一次结束
        if (reader.NodeType == XmlNodeType.EndElement) reader.ReadEndElement();

        return true;
    }
}