/*
Embedded TinyJSON from https://github.com/pbhogan/TinyJSON (version 71fed96, 2019 May 10) directly here, with
custom namespace wrapped around it so it does not clash with any other embedded TinyJSON. Original license:

The MIT License (MIT)

Copyright (c) 2018 Alex Parker

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text;

namespace GaussianSplatting.Editor.Utils
{
    // Really simple JSON parser in ~300 lines
    // - Attempts to parse JSON files with minimal GC allocation
    // - Nice and simple "[1,2,3]".FromJson<List<int>>() API
    // - Classes and structs can be parsed too!
    //      class Foo { public int Value; }
    //      "{\"Value\":10}".FromJson<Foo>()
    // - Can parse JSON without type information into Dictionary<string,object> and List<object> e.g.
    //      "[1,2,3]".FromJson<object>().GetType() == typeof(List<object>)
    //      "{\"Value\":10}".FromJson<object>().GetType() == typeof(Dictionary<string,object>)
    // - No JIT Emit support to support AOT compilation on iOS
    // - Attempts are made to NOT throw an exception if the JSON is corrupted or invalid: returns null instead.
    // - Only public fields and property setters on classes/structs will be written to
    //
    // Limitations:
    // - No JIT Emit support to parse structures quickly
    // - Limited to parsing <2GB JSON files (due to int.MaxValue)
    // - Parsing of abstract classes or interfaces is NOT supported and will throw an exception.
    public static class JSONParser
    {
        [ThreadStatic] static Stack<List<string>> splitArrayPool;
        [ThreadStatic] static StringBuilder stringBuilder;
        [ThreadStatic] static Dictionary<Type, Dictionary<string, FieldInfo>> fieldInfoCache;
        [ThreadStatic] static Dictionary<Type, Dictionary<string, PropertyInfo>> propertyInfoCache;

        public static T FromJson<T>(this string json)
        {
            // Initialize, if needed, the ThreadStatic variables
            if (propertyInfoCache == null) propertyInfoCache = new Dictionary<Type, Dictionary<string, PropertyInfo>>();
            if (fieldInfoCache == null) fieldInfoCache = new Dictionary<Type, Dictionary<string, FieldInfo>>();
            if (stringBuilder == null) stringBuilder = new StringBuilder();
            if (splitArrayPool == null) splitArrayPool = new Stack<List<string>>();

            //Remove all whitespace not within strings to make parsing simpler
            stringBuilder.Length = 0;
            for (int i = 0; i < json.Length; i++)
            {
                char c = json[i];
                if (c == '"')
                {
                    i = AppendUntilStringEnd(true, i, json);
                    continue;
                }
                if (char.IsWhiteSpace(c))
                    continue;

                stringBuilder.Append(c);
            }

            //Parse the thing!
            return (T)ParseValue(typeof(T), stringBuilder.ToString());
        }

        static int AppendUntilStringEnd(bool appendEscapeCharacter, int startIdx, string json)
        {
            stringBuilder.Append(json[startIdx]);
            for (int i = startIdx + 1; i < json.Length; i++)
            {
                if (json[i] == '\\')
                {
                    if (appendEscapeCharacter)
                        stringBuilder.Append(json[i]);
                    stringBuilder.Append(json[i + 1]);
                    i++;//Skip next character as it is escaped
                }
                else if (json[i] == '"')
                {
                    stringBuilder.Append(json[i]);
                    return i;
                }
                else
                    stringBuilder.Append(json[i]);
            }
            return json.Length - 1;
        }

        //Splits { <value>:<value>, <value>:<value> } and [ <value>, <value> ] into a list of <value> strings
        static List<string> Split(string json)
        {
            List<string> splitArray = splitArrayPool.Count > 0 ? splitArrayPool.Pop() : new List<string>();
            splitArray.Clear();
            if (json.Length == 2)
                return splitArray;
            int parseDepth = 0;
            stringBuilder.Length = 0;
            for (int i = 1; i < json.Length - 1; i++)
            {
                switch (json[i])
                {
                    case '[':
                    case '{':
                        parseDepth++;
                        break;
                    case ']':
                    case '}':
                        parseDepth--;
                        break;
                    case '"':
                        i = AppendUntilStringEnd(true, i, json);
                        continue;
                    case ',':
                    case ':':
                        if (parseDepth == 0)
                        {
                            splitArray.Add(stringBuilder.ToString());
                            stringBuilder.Length = 0;
                            continue;
                        }
                        break;
                }

                stringBuilder.Append(json[i]);
            }

            splitArray.Add(stringBuilder.ToString());

            return splitArray;
        }

        internal static object ParseValue(Type type, string json)
        {
            if (type == typeof(string))
            {
                if (json.Length <= 2)
                    return string.Empty;
                StringBuilder parseStringBuilder = new StringBuilder(json.Length);
                for (int i = 1; i < json.Length - 1; ++i)
                {
                    if (json[i] == '\\' && i + 1 < json.Length - 1)
                    {
                        int j = "\"\\nrtbf/".IndexOf(json[i + 1]);
                        if (j >= 0)
                        {
                            parseStringBuilder.Append("\"\\\n\r\t\b\f/"[j]);
                            ++i;
                            continue;
                        }
                        if (json[i + 1] == 'u' && i + 5 < json.Length - 1)
                        {
                            UInt32 c = 0;
                            if (UInt32.TryParse(json.Substring(i + 2, 4), System.Globalization.NumberStyles.AllowHexSpecifier, null, out c))
                            {
                                parseStringBuilder.Append((char)c);
                                i += 5;
                                continue;
                            }
                        }
                    }
                    parseStringBuilder.Append(json[i]);
                }
                return parseStringBuilder.ToString();
            }
            if (type.IsPrimitive)
            {
                var result = Convert.ChangeType(json, type, System.Globalization.CultureInfo.InvariantCulture);
                return result;
            }
            if (type == typeof(decimal))
            {
                decimal result;
                decimal.TryParse(json, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out result);
                return result;
            }
            if (type == typeof(DateTime))
            {
                DateTime result;
                DateTime.TryParse(json.Replace("\"",""), System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out result);
                return result;
            }
            if (json == "null")
            {
                return null;
            }
            if (type.IsEnum)
            {
                if (json[0] == '"')
                    json = json.Substring(1, json.Length - 2);
                try
                {
                    return Enum.Parse(type, json, false);
                }
                catch
                {
                    return 0;
                }
            }
            if (type.IsArray)
            {
                Type arrayType = type.GetElementType();
                if (json[0] != '[' || json[json.Length - 1] != ']')
                    return null;

                List<string> elems = Split(json);
                Array newArray = Array.CreateInstance(arrayType, elems.Count);
                for (int i = 0; i < elems.Count; i++)
                    newArray.SetValue(ParseValue(arrayType, elems[i]), i);
                splitArrayPool.Push(elems);
                return newArray;
            }
            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>))
            {
                Type listType = type.GetGenericArguments()[0];
                if (json[0] != '[' || json[json.Length - 1] != ']')
                    return null;

                List<string> elems = Split(json);
                var list = (IList)type.GetConstructor(new Type[] { typeof(int) }).Invoke(new object[] { elems.Count });
                for (int i = 0; i < elems.Count; i++)
                    list.Add(ParseValue(listType, elems[i]));
                splitArrayPool.Push(elems);
                return list;
            }
            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Dictionary<,>))
            {
                Type keyType, valueType;
                {
                    Type[] args = type.GetGenericArguments();
                    keyType = args[0];
                    valueType = args[1];
                }

                //Refuse to parse dictionary keys that aren't of type string
                if (keyType != typeof(string))
                    return null;
                //Must be a valid dictionary element
                if (json[0] != '{' || json[json.Length - 1] != '}')
                    return null;
                //The list is split into key/value pairs only, this means the split must be divisible by 2 to be valid JSON
                List<string> elems = Split(json);
                if (elems.Count % 2 != 0)
                    return null;

                var dictionary = (IDictionary)type.GetConstructor(new Type[] { typeof(int) }).Invoke(new object[] { elems.Count / 2 });
                for (int i = 0; i < elems.Count; i += 2)
                {
                    if (elems[i].Length <= 2)
                        continue;
                    string keyValue = elems[i].Substring(1, elems[i].Length - 2);
                    object val = ParseValue(valueType, elems[i + 1]);
                    dictionary[keyValue] = val;
                }
                return dictionary;
            }
            if (type == typeof(object))
            {
                return ParseAnonymousValue(json);
            }
            if (json[0] == '{' && json[json.Length - 1] == '}')
            {
                return ParseObject(type, json);
            }

            return null;
        }

        static object ParseAnonymousValue(string json)
        {
            if (json.Length == 0)
                return null;
            if (json[0] == '{' && json[json.Length - 1] == '}')
            {
                List<string> elems = Split(json);
                if (elems.Count % 2 != 0)
                    return null;
                var dict = new Dictionary<string, object>(elems.Count / 2);
                for (int i = 0; i < elems.Count; i += 2)
                    dict[elems[i].Substring(1, elems[i].Length - 2)] = ParseAnonymousValue(elems[i + 1]);
                return dict;
            }
            if (json[0] == '[' && json[json.Length - 1] == ']')
            {
                List<string> items = Split(json);
                var finalList = new List<object>(items.Count);
                for (int i = 0; i < items.Count; i++)
                    finalList.Add(ParseAnonymousValue(items[i]));
                return finalList;
            }
            if (json[0] == '"' && json[json.Length - 1] == '"')
            {
                string str = json.Substring(1, json.Length - 2);
                return str.Replace("\\", string.Empty);
            }
            if (char.IsDigit(json[0]) || json[0] == '-')
            {
                if (json.Contains("."))
                {
                    double result;
                    double.TryParse(json, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out result);
                    return result;
                }
                else
                {
                    int result;
                    int.TryParse(json, out result);
                    return result;
                }
            }
            if (json == "true")
                return true;
            if (json == "false")
                return false;
            // handles json == "null" as well as invalid JSON
            return null;
        }

        static Dictionary<string, T> CreateMemberNameDictionary<T>(T[] members) where T : MemberInfo
        {
            Dictionary<string, T> nameToMember = new Dictionary<string, T>(StringComparer.OrdinalIgnoreCase);
            for (int i = 0; i < members.Length; i++)
            {
                T member = members[i];
                if (member.IsDefined(typeof(IgnoreDataMemberAttribute), true))
                    continue;

                string name = member.Name;
                if (member.IsDefined(typeof(DataMemberAttribute), true))
                {
                    DataMemberAttribute dataMemberAttribute = (DataMemberAttribute)Attribute.GetCustomAttribute(member, typeof(DataMemberAttribute), true);
                    if (!string.IsNullOrEmpty(dataMemberAttribute.Name))
                        name = dataMemberAttribute.Name;
                }

                nameToMember.Add(name, member);
            }

            return nameToMember;
        }

        static object ParseObject(Type type, string json)
        {
            object instance = FormatterServices.GetUninitializedObject(type);

            //The list is split into key/value pairs only, this means the split must be divisible by 2 to be valid JSON
            List<string> elems = Split(json);
            if (elems.Count % 2 != 0)
                return instance;

            Dictionary<string, FieldInfo> nameToField;
            Dictionary<string, PropertyInfo> nameToProperty;
            if (!fieldInfoCache.TryGetValue(type, out nameToField))
            {
                nameToField = CreateMemberNameDictionary(type.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.FlattenHierarchy));
                fieldInfoCache.Add(type, nameToField);
            }
            if (!propertyInfoCache.TryGetValue(type, out nameToProperty))
            {
                nameToProperty = CreateMemberNameDictionary(type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.FlattenHierarchy));
                propertyInfoCache.Add(type, nameToProperty);
            }

            for (int i = 0; i < elems.Count; i += 2)
            {
                if (elems[i].Length <= 2)
                    continue;
                string key = elems[i].Substring(1, elems[i].Length - 2);
                string value = elems[i + 1];

                FieldInfo fieldInfo;
                PropertyInfo propertyInfo;
                if (nameToField.TryGetValue(key, out fieldInfo))
                    fieldInfo.SetValue(instance, ParseValue(fieldInfo.FieldType, value));
                else if (nameToProperty.TryGetValue(key, out propertyInfo))
                    propertyInfo.SetValue(instance, ParseValue(propertyInfo.PropertyType, value), null);
            }

            return instance;
        }
    }
}