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

namespace NewLife.Serialization
{
    /// <summary>Json序列化接口</summary>
    public interface IJsonHost
    {
        /// <summary>写入对象，得到Json字符串</summary>
        /// <param name="value"></param>
        /// <param name="indented">是否缩进。默认false</param>
        /// <param name="nullValue">是否写空值。默认true</param>
        /// <param name="camelCase">是否驼峰命名。默认false</param>
        /// <returns></returns>
        String Write(Object value, Boolean indented = false, Boolean nullValue = true, Boolean camelCase = false);

        /// <summary>从Json字符串中读取对象</summary>
        /// <param name="json"></param>
        /// <param name="type"></param>
        /// <returns></returns>
        Object Read(String json, Type type);

        /// <summary>类型转换</summary>
        /// <param name="obj"></param>
        /// <param name="targetType"></param>
        /// <returns></returns>
        Object Convert(Object obj, Type targetType);
    }

    /// <summary>Json助手</summary>
    public static class JsonHelper
    {
        /// <summary>默认实现</summary>
        public static IJsonHost Default { get; set; } = new FastJson();

        static JsonHelper()
        {
            //Default = new FastJson();

            //if (JsonNet.Support())
            //    Default = new JsonNet();
            //else
            //    Default = new JsonDefault();
        }

        /// <summary>写入对象，得到Json字符串</summary>
        /// <param name="value"></param>
        /// <param name="indented">是否缩进</param>
        /// <returns></returns>
        public static String ToJson(this Object value, Boolean indented = false) => Default.Write(value, indented);

        /// <summary>写入对象，得到Json字符串</summary>
        /// <param name="value"></param>
        /// <param name="indented">是否换行缩进。默认false</param>
        /// <param name="nullValue">是否写空值。默认true</param>
        /// <param name="camelCase">是否驼峰命名。默认false</param>
        /// <returns></returns>
        public static String ToJson(this Object value, Boolean indented, Boolean nullValue, Boolean camelCase) => Default.Write(value, indented, nullValue, camelCase);

        /// <summary>从Json字符串中读取对象</summary>
        /// <param name="json"></param>
        /// <param name="type"></param>
        /// <returns></returns>
        public static Object ToJsonEntity(this String json, Type type)
        {
            if (json.IsNullOrEmpty()) return null;

            return Default.Read(json, type);
        }

        /// <summary>从Json字符串中读取对象</summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="json"></param>
        /// <returns></returns>
        public static T ToJsonEntity<T>(this String json)
        {
            if (json.IsNullOrEmpty()) return default;

            return (T)Default.Read(json, typeof(T));
        }

        /// <summary>格式化Json文本</summary>
        /// <param name="json"></param>
        /// <returns></returns>
        public static String Format(String json)
        {
            var sb = Pool.StringBuilder.Get();

            var escaping = false;
            var inQuotes = false;
            var indentation = 0;

            foreach (var ch in json)
            {
                if (escaping)
                {
                    escaping = false;
                    sb.Append(ch);
                }
                else
                {
                    if (ch == '\\')
                    {
                        escaping = true;
                        sb.Append(ch);
                    }
                    else if (ch == '\"')
                    {
                        inQuotes = !inQuotes;
                        sb.Append(ch);
                    }
                    else if (!inQuotes)
                    {
                        if (ch == ',')
                        {
                            sb.Append(ch);
                            sb.Append("\r\n");
                            sb.Append(' ', indentation * 2);
                        }
                        else if (ch == '[' || ch == '{')
                        {
                            sb.Append(ch);
                            sb.Append("\r\n");
                            sb.Append(' ', ++indentation * 2);
                        }
                        else if (ch == ']' || ch == '}')
                        {
                            sb.Append("\r\n");
                            sb.Append(' ', --indentation * 2);
                            sb.Append(ch);
                        }
                        else if (ch == ':')
                        {
                            sb.Append(ch);
                            sb.Append(' ', 2);
                        }
                        else
                        {
                            sb.Append(ch);
                        }
                    }
                    else
                    {
                        sb.Append(ch);
                    }
                }
            }

            return sb.Put(true);
        }

        /// <summary>Json类型对象转换实体类</summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static T Convert<T>(Object obj)
        {
            if (obj == null) return default;
            if (obj is T) return (T)obj;
            if (obj.GetType().As<T>()) return (T)obj;

            return (T)Default.Convert(obj, typeof(T));
        }
    }

    class FastJson : IJsonHost
    {
        #region IJsonHost 成员
        public String Write(Object value, Boolean indented, Boolean nullValue, Boolean camelCase) => JsonWriter.ToJson(value, indented, nullValue, camelCase);

        public Object Read(String json, Type type) => new JsonReader().Read(json, type);

        public Object Convert(Object obj, Type targetType) => new JsonReader().ToObject(obj, targetType, null);
        #endregion
    }
}