// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry and contributors
//
// 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.Globalization;
using System.Text.RegularExpressions;
using YamlDotNet.Core;
using YamlDotNet.Core.Events;
using YamlDotNet.Core.ObjectPool;
using YamlDotNet.Helpers;
using YamlDotNet.Serialization.NamingConventions;
using YamlDotNet.Serialization.Utilities;

namespace YamlDotNet.Serialization.NodeDeserializers
{
    public sealed class ScalarNodeDeserializer : INodeDeserializer
    {
        private const string BooleanTruePattern = "^(true|y|yes|on)$";
        private const string BooleanFalsePattern = "^(false|n|no|off)$";
        private readonly bool attemptUnknownTypeDeserialization;
        private readonly ITypeConverter typeConverter;
        private readonly ITypeInspector typeInspector;
        private readonly YamlFormatter formatter;
        private readonly INamingConvention enumNamingConvention;

        public ScalarNodeDeserializer(bool attemptUnknownTypeDeserialization,
            ITypeConverter typeConverter,
            ITypeInspector typeInspector,
            YamlFormatter formatter,
            INamingConvention enumNamingConvention)
        {
            this.attemptUnknownTypeDeserialization = attemptUnknownTypeDeserialization;
            this.typeConverter = typeConverter ?? throw new ArgumentNullException(nameof(typeConverter));
            this.typeInspector = typeInspector;
            this.formatter = formatter;
            this.enumNamingConvention = enumNamingConvention;
        }

        public bool Deserialize(IParser parser, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, out object? value, ObjectDeserializer rootDeserializer)
        {
            if (!parser.TryConsume<Scalar>(out var scalar))
            {
                value = null;
                return false;
            }

            // Strip off the nullable & fsharp option type, if present
            var underlyingType = Nullable.GetUnderlyingType(expectedType)
                ?? FsharpHelper.GetOptionUnderlyingType(expectedType)
                ?? expectedType;

            if (underlyingType.IsEnum())
            {
                var enumName = enumNamingConvention.Reverse(scalar.Value);

                enumName = typeInspector.GetEnumName(underlyingType, enumName);

                value = Enum.Parse(underlyingType, enumName, true);
                return true;
            }

            var typeCode = underlyingType.GetTypeCode();
            switch (typeCode)
            {
                case TypeCode.Boolean:
                    value = DeserializeBooleanHelper(scalar.Value);
                    break;

                case TypeCode.Byte:
                case TypeCode.Int16:
                case TypeCode.Int32:
                case TypeCode.Int64:
                case TypeCode.SByte:
                case TypeCode.UInt16:
                case TypeCode.UInt32:
                case TypeCode.UInt64:
                    value = DeserializeIntegerHelper(typeCode, scalar.Value);
                    break;

                case TypeCode.Single:
                    value = float.Parse(scalar.Value, formatter.NumberFormat);
                    break;

                case TypeCode.Double:
                    value = double.Parse(scalar.Value, formatter.NumberFormat);
                    break;

                case TypeCode.Decimal:
                    value = decimal.Parse(scalar.Value, formatter.NumberFormat);
                    break;

                case TypeCode.String:
                    value = scalar.Value;
                    break;

                case TypeCode.Char:
                    value = scalar.Value[0];
                    break;

                case TypeCode.DateTime:
                    // TODO: This is probably incorrect. Use the correct regular expression.
                    value = DateTime.Parse(scalar.Value, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind);
                    break;

                default:
                    if (expectedType == typeof(object))
                    {
                        if (!scalar.IsKey && attemptUnknownTypeDeserialization)
                        {
                            value = AttemptUnknownTypeDeserialization(scalar);
                        }
                        else
                        {
                            // Default to string
                            value = scalar.Value;
                        }
                    }
                    else
                    {
                        value = typeConverter.ChangeType(scalar.Value, expectedType, enumNamingConvention, typeInspector);
                    }
                    break;
            }
            return true;
        }

        private static bool DeserializeBooleanHelper(string value)
        {
            bool result;

            if (Regex.IsMatch(value, BooleanTruePattern, RegexOptions.IgnoreCase))
            {
                result = true;
            }
            else if (Regex.IsMatch(value, BooleanFalsePattern, RegexOptions.IgnoreCase))
            {
                result = false;
            }
            else
            {
                throw new FormatException($"The value \"{value}\" is not a valid YAML Boolean");
            }

            return result;
        }

        private object DeserializeIntegerHelper(TypeCode typeCode, string value)
        {
            using var numberBuilderStringBuilder = StringBuilderPool.Rent();
            var numberBuilder = numberBuilderStringBuilder.Builder;
            var currentIndex = 0;
            var isNegative = false;
            int numberBase;
            ulong result = 0;

            if (value[0] == '-')
            {
                currentIndex++;
                isNegative = true;
            }

            else if (value[0] == '+')
            {
                currentIndex++;
            }

            if (value[currentIndex] == '0')
            {
                // Could be binary, octal, hex, decimal (0)

                // If there are no characters remaining, it's a decimal zero
                if (currentIndex == value.Length - 1)
                {
                    numberBase = 10;
                    result = 0;
                }

                else
                {
                    // Check the next character
                    currentIndex++;

                    if (value[currentIndex] == 'b')
                    {
                        // Binary
                        numberBase = 2;

                        currentIndex++;
                    }

                    else if (value[currentIndex] == 'x')
                    {
                        // Hex
                        numberBase = 16;

                        currentIndex++;
                    }

                    else
                    {
                        // Octal
                        numberBase = 8;
                    }
                }

                // Copy remaining digits to the number buffer (skip underscores)
                while (currentIndex < value.Length)
                {
                    if (value[currentIndex] != '_')
                    {
                        numberBuilder.Append(value[currentIndex]);
                    }
                    currentIndex++;
                }

                // Parse the magnitude of the number
                switch (numberBase)
                {
                    case 2:
                    case 8:
                        // TODO: how to incorporate the numberFormat?
                        result = Convert.ToUInt64(numberBuilder.ToString(), numberBase);
                        break;

                    case 16:
                        result = ulong.Parse(numberBuilder.ToString(), NumberStyles.HexNumber, formatter.NumberFormat);
                        break;

                    case 10:
                        // Result is already zero
                        break;
                }
            }

            else
            {
                // Could be decimal or base 60
                var chunks = value.Substring(currentIndex).Split(':');
                result = 0;

                for (var chunkIndex = 0; chunkIndex < chunks.Length; chunkIndex++)
                {
                    result *= 60;

                    // TODO: verify that chunks after the first are non-negative and less than 60
                    result += ulong.Parse(chunks[chunkIndex].Replace("_", ""), CultureInfo.InvariantCulture);
                }
            }

            if (isNegative)
            {
                long toCast;

                // we do this because abs(long.minvalue) is 1 more than long.maxvalue.
                if (result == 9223372036854775808) // abs(long.minvalue) => ulong
                {
                    toCast = long.MinValue;
                }
                else
                {
                    // this will throw if it's too big.
                    toCast = checked(-(long)result);
                }

                return CastInteger(toCast, typeCode);
            }
            else
            {
                return CastInteger(result, typeCode);
            }
        }

        private static object CastInteger(long number, TypeCode typeCode)
        {
            checked
            {
                return typeCode switch
                {
                    TypeCode.Byte => (byte)number,
                    TypeCode.Int16 => (short)number,
                    TypeCode.Int32 => (int)number,
                    TypeCode.Int64 => number,
                    TypeCode.SByte => (sbyte)number,
                    TypeCode.UInt16 => (ushort)number,
                    TypeCode.UInt32 => (uint)number,
                    TypeCode.UInt64 => (ulong)number,
                    _ => number,
                };
            }
        }

        private static object CastInteger(ulong number, TypeCode typeCode)
        {
            checked
            {
                return typeCode switch
                {
                    TypeCode.Byte => (byte)number,
                    TypeCode.Int16 => (short)number,
                    TypeCode.Int32 => (int)number,
                    TypeCode.Int64 => (long)number,
                    TypeCode.SByte => (sbyte)number,
                    TypeCode.UInt16 => (ushort)number,
                    TypeCode.UInt32 => (uint)number,
                    TypeCode.UInt64 => number,
                    _ => number,
                };
            }
        }

        private object? AttemptUnknownTypeDeserialization(Scalar value)
        {
            if (value.Style == ScalarStyle.SingleQuoted ||
                value.Style == ScalarStyle.DoubleQuoted ||
                value.Style == ScalarStyle.Folded)
            {
                return value.Value;
            }
            var v = value.Value;
            object? result;

            switch (v)
            {
                case "":
                case "~":
                case "null":
                case "Null":
                case "NULL":
                    return null;
                case "true":
                case "True":
                case "TRUE":
                    return true;
                case "false":
                case "False":
                case "FALSE":
                    return false;
                default:
                    if (Regex.IsMatch(v, "0x[0-9a-fA-F]+")) //base16 number
                    {
                        if (TryAndSwallow(() => Convert.ToByte(v, 16), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt16(v, 16), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt32(v, 16), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt64(v, 16), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToUInt64(v, 16), out result)) { }
                        else
                        {
                            //we couldn't parse it, default to a string. It's probably to big.
                            result = v;
                        }
                    }
                    else if (Regex.IsMatch(v, "0o[0-9a-fA-F]+")) //base8 number
                    {
                        if (TryAndSwallow(() => Convert.ToByte(v, 8), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt16(v, 8), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt32(v, 8), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToInt64(v, 8), out result)) { }
                        else if (TryAndSwallow(() => Convert.ToUInt64(v, 8), out result)) { }
                        else
                        {
                            //we couldn't parse it, default to a string. It's probably to big.
                            result = v;
                        }
                    }
                    else if (Regex.IsMatch(v, @"[-+]?(\.[0-9]+|[0-9]+(\.[0-9]*)?)([eE][-+]?[0-9]+)?")) //regular number
                    {
                        if (TryAndSwallow(() => byte.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => short.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => int.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => long.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => ulong.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => float.Parse(v, formatter.NumberFormat), out result)) { }
                        else if (TryAndSwallow(() => double.Parse(v, formatter.NumberFormat), out result)) { }
                        else
                        {
                            //we couldn't parse it, default to string, It's probably too big
                            result = v;
                        }
                    }
                    else if (Regex.IsMatch(v, @"^[-+]?(\.inf|\.Inf|\.INF)$")) //infinities
                    {
                        if (v.StartsWith('-'))
                        {
                            result = float.NegativeInfinity;
                        }
                        else
                        {
                            result = float.PositiveInfinity;
                        }
                    }
                    else if (Regex.IsMatch(v, @"^(\.nan|\.NaN|\.NAN)$")) //not a number
                    {
                        result = float.NaN;
                    }
                    else
                    {
                        // not a known type, so make it a string.
                        result = v;
                    }
                    break;
            }

            return result;
        }

        private static bool TryAndSwallow(Func<object> attempt, out object? value)
        {
            try
            {
                value = attempt();
                return true;
            }
            catch
            {
                value = null;
                return false;
            }
        }
    }
}