using System;
using System.IO;
using System.Text;
using System.Xml;
using NewLife.Log;

namespace NewLife.Configuration
{
    /// <summary>Xml文件配置提供者</summary>
    /// <remarks>
    /// 支持从不同配置文件加载到不同配置模型
    /// </remarks>
    public class XmlConfigProvider : FileConfigProvider
    {
        /// <summary>根元素名称</summary>
        public String RootName { get; set; } = "Root";

        /// <summary>初始化</summary>
        /// <param name="value"></param>
        public override void Init(String value)
        {
            if ((RootName.IsNullOrEmpty() || RootName == "Root") && !value.IsNullOrEmpty()) RootName = Path.GetFileNameWithoutExtension(value);

            // 加上默认后缀
            if (!value.IsNullOrEmpty() && Path.GetExtension(value).IsNullOrEmpty()) value += ".config";

            base.Init(value);
        }

        /// <summary>读取配置文件</summary>
        /// <param name="fileName">文件名</param>
        /// <param name="section">配置段</param>
        protected override void OnRead(String fileName, IConfigSection section)
        {
            using var fs = File.OpenRead(fileName);
            using var reader = XmlReader.Create(fs);

            // 移动到第一个元素
            while (reader.NodeType != XmlNodeType.Element) reader.Read();

            if (!reader.Name.IsNullOrEmpty()) RootName = reader.Name;

            reader.ReadStartElement();
            while (reader.NodeType == XmlNodeType.Whitespace) reader.Skip();

            ReadNode(reader, section);

            if (reader.NodeType == XmlNodeType.EndElement) reader.ReadEndElement();
        }

        private void ReadNode(XmlReader reader, IConfigSection section)
        {
            while (true)
            {
                var remark = "";
                if (reader.NodeType == XmlNodeType.Comment) remark = reader.Value;
                while (reader.NodeType == XmlNodeType.Comment || reader.NodeType == XmlNodeType.Whitespace) reader.Skip();
                if (reader.NodeType != XmlNodeType.Element) break;

                var name = reader.Name;
                var cfg = section.GetOrAddChild(name);
                // 前一行是注释
                if (!remark.IsNullOrEmpty()) cfg.Comment = remark;

                reader.ReadStartElement();
                while (reader.NodeType == XmlNodeType.Whitespace) reader.Skip();

                // 遇到下一层节点
                if (reader.NodeType == XmlNodeType.Element || reader.NodeType == XmlNodeType.Comment)
                    ReadNode(reader, cfg);
                else if (reader.NodeType == XmlNodeType.Text)
                    cfg.Value = reader.ReadContentAsString();

                if (reader.NodeType == XmlNodeType.Attribute) reader.Read();
                if (reader.NodeType == XmlNodeType.EndElement) reader.ReadEndElement();
                while (reader.NodeType == XmlNodeType.Whitespace) reader.Skip();
            }
        }

        /// <summary>写入配置文件</summary>
        /// <param name="fileName">文件名</param>
        /// <param name="section">配置段</param>
        protected override void OnWrite(String fileName, IConfigSection section)
        {
            var str = GetString(section);
            var old = "";
            if (File.Exists(fileName)) old = File.ReadAllText(fileName);

            if (str != old)
            {
                XTrace.WriteLine("保存配置 {0}", fileName);

                File.WriteAllText(fileName, str);
            }
        }

        /// <summary>获取字符串形式</summary>
        /// <param name="section">配置段</param>
        /// <returns></returns>
        public override String GetString(IConfigSection section = null)
        {
            if (section == null) section = Root;

            var set = new XmlWriterSettings
            {
                Encoding = Encoding.UTF8,
                Indent = true,
                CloseOutput = true,
            };

            using var ms = new MemoryStream();
            using var writer = XmlWriter.Create(ms, set);

            writer.WriteStartDocument();
            WriteNode(writer, RootName, section);
            writer.WriteEndDocument();

            writer.Flush();
            ms.Position = 0;

            return ms.ToStr();
        }

        private void WriteNode(XmlWriter writer, String name, IConfigSection section)
        {
            writer.WriteStartElement(name);

            foreach (var item in section.Childs)
            {
                // 写注释
                if (!item.Comment.IsNullOrEmpty()) writer.WriteComment(item.Comment);

                if (item.Childs != null)
                    WriteNode(writer, item.Key, item);
                else
                {
                    // 避免写null时导致xml元素未闭合
                    writer.WriteStartElement(item.Key);
                    writer.WriteValue(item.Value + "");
                    writer.WriteEndElement();
                }
            }

            writer.WriteEndElement();
        }
    }
}