using System;
using System.Globalization;

namespace Neo.Afx.ComponentModel
{
    /// <summary>
    /// Contains object extension methods
    /// </summary>
    public static partial class Extensions
    {
        #region IsNull

        /// <summary>
        /// Determines whether the specified object is <code>null</code> or <code>DBNull</code>.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>
        /// 	<code>true</code> if the specified object is <code>null</code> or <code>DBNull</code>; 
        /// 	<code>false</code> otherwise.
        /// </returns>
        public static bool IsNull(this object obj)
        {
            return Convert.IsDBNull(obj) || obj == null;
        }

        #endregion

        #region ToByte

        /// <summary>
        /// Gets the byte value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The byte value of the object; zero if null</returns>
        public static byte? ToByte(this object obj)
        {
            byte result;
            return !obj.IsNull() && byte.TryParse(obj.ToString(), out result) && result != 0 ? (byte?)result : null;
        }

        #endregion

        #region ToByteArray

        /// <summary>
        /// Gets the byte array value of the object; null otherwise.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The byte array value of the object; null otherwise</returns>
        public static byte[] ToByteArray(this object obj)
        {
            return !obj.IsNull() ? obj as byte[] : null;
        }

        #endregion

        #region ToInt16

        /// <summary>
        /// Gets the short value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The short value of the object; zero if null</returns>
        public static short? ToInt16(this object obj)
        {
            short result;
            return !obj.IsNull() && Int16.TryParse(obj.ToString(), out result) && result != 0 ? (short?)result : null;
        }

        #endregion

        #region ToInt32

        /// <summary>
        /// Gets the int value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The int value of the object; zero if null</returns>
        public static int? ToInt32(this object obj)
        {
            int result;
            return !obj.IsNull() && Int32.TryParse(obj.ToString(), out result) && result != 0 ? (int?)result : null;
        }

        #endregion

        #region ToInt64

        /// <summary>
        /// Gets the long value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The long value of the object; zero if null</returns>
        public static long? ToInt64(this object obj)
        {
            long result;
            return !obj.IsNull() && Int64.TryParse(obj.ToString(), out result) && result != 0 ? (long?)result : null;
        }

        #endregion

        #region ToDecimal

        /// <summary>
        /// Gets the decimal value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The decimal value of the object; zero if null</returns>
        public static decimal? ToDecimal(this object obj)
        {
            decimal result;
            return !obj.IsNull() && decimal.TryParse(obj.ToString(), out result) ? (result != 0 ? (decimal?)result : null) : null;
        }

        #endregion

        #region ToDouble

        /// <summary>
        /// Gets the double value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The double value of the object; zero if null</returns>
        public static double? ToDouble(this object obj)
        {
            double result;
            return !obj.IsNull() && double.TryParse(obj.ToString(), out result) && result != 0 ? (double?)result : null;
        }

        #endregion

        #region ToFloat

        /// <summary>
        /// Gets the float value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The float value of the object; zero if null</returns>
        public static float? ToFloat(this object obj)
        {
            float result;
            return !obj.IsNull() && float.TryParse(obj.ToString(), out result) && result != 0 ? (float?)result : null;
        }

        #endregion

        #region ToBoolean

        /// <summary>
        /// Gets the boolean value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The boolean value of the object; zero if null</returns>
        public static bool ToBoolean(this object obj)
        {
            if(obj.IsNull())
            {
                return false;
            }

            if(obj.GetType() == typeof(bool))
            {
                return (bool)obj;
            }

            if(obj.GetType() == typeof(bool?))
            {
                var nullBool = (bool?)obj;
                return nullBool.Value;
            }

            var value = obj.ToString();

            bool bit;
            if(Boolean.TryParse(value, out bit))
            {
                return bit;
            }

            int bitValue;
            return Int32.TryParse(value, out bitValue) && bitValue > 0;
        }

        #endregion

        #region ToDateTime

        /// <summary>
        /// Gets the DateTime value of the object; zero if null.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The DateTime value of the object; DateTime.MinValue if null</returns>
        public static DateTime? ToDateTime(this object obj)
        {
            DateTime result;
            if(!obj.IsNull() && DateTime.TryParse(obj.ToString(), out result))
            {
                if(result != DateTime.MinValue)
                {
                    return result;
                }
            }
            return null;
        }

        #endregion

        #region ToDDMMYYYY

        /// <summary>
        /// Gets the date in "dd-MM-yyyy" format.
        /// </summary>
        /// <param name="dateObj">The <see cref="DateTime"/> object to be formatted.</param>
        /// <returns>A string representation of the date.</returns>
        public static string ToDDMMYYYY(this object dateObj)
        {
            DateTime date;
            if(!dateObj.IsNull() && DateTime.TryParse(dateObj.ToString(), out date))
            {
                return date.ToString("dd-MM-yyyy");
            }
            return String.Empty;
        }

        #endregion

        #region ToYYYYMMDD

        /// <summary>
        /// Gets the date in "yyyy-MM-dd" format.
        /// </summary>
        /// <param name="dateObj">The <see cref="DateTime"/> object to be formatted.</param>
        /// <returns>A string representation of the date.</returns>
        public static string ToYYYYMMDD(this object dateObj)
        {
            DateTime date;
            if(!dateObj.IsNull() && DateTime.TryParse(dateObj.ToString(), out date))
            {
                return date.ToString("yyyy-MM-dd");
            }
            return String.Empty;
        }

        #endregion

        #region ToHHMM

        /// <summary>
        /// Gets the time in "HH:mm" format.
        /// </summary>
        /// <param name="dateObj">The <see cref="DateTime"/> object to be formatted.</param>
        /// <returns>A string representation of the date.</returns>
        public static string ToHHMM(this object dateObj)
        {
            DateTime date;
            if(!dateObj.IsNull() && DateTime.TryParse(dateObj.ToString(), out date))
            {
                return date.ToString("HH:mm");
            }
            return String.Empty;
        }

        #endregion

        #region ToHHMMSS

        /// <summary>
        /// Gets the time in "HH:mm:ss" format.
        /// </summary>
        /// <param name="dateObj">The <see cref="DateTime"/> object to be formatted.</param>
        /// <returns>A string representation of the date.</returns>
        public static string ToHHMMSS(this object dateObj)
        {
            DateTime date;
            if(!dateObj.IsNull() && DateTime.TryParse(dateObj.ToString(), out date))
            {
                return date.ToString("HH:mm:ss");
            }
            return String.Empty;
        }

        #endregion

        #region ToClr

        /// <summary>
        /// Converts the object to it's CLR representation (e.g. DBNull to null).
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>The CLR representation of the object.</returns>
        public static object ToClr(this object obj)
        {
            return obj.IsNull() ? null : obj;
        }

        #endregion

        #region ToStringSafe

        /// <summary>
        /// Converts the object to its string representation;
        /// returns <code>String.Empty</code> if it is a <code>DBNull</code> 
        /// or a <code>null</code> value.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns>A string representation of the object.</returns>
        public static string ToStringSafe(this object obj)
        {
            return obj.IsNull() ? String.Empty : obj.ToString();
        }

        #endregion

        #region ToDbValue

        /// <summary>
        /// Converts the object to <code>Convert.DBNull</code> if it is <code>null</code>.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns><code>Convert.DBNull</code> if the object is <code>null</code>.</returns>
        public static object ToDbValue(this object obj)
        {
            return obj ?? Convert.DBNull;
        }

        /// <summary>
        /// Converts the object to <code>Convert.DBNull</code> if it is <code>null</code>.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns><code>Convert.DBNull</code> if the object is <code>null</code>.</returns>
        public static object ToDbValue<T>(this T? obj)
            where T : struct
        {
            return obj.HasValue ? obj.Value : Convert.DBNull;
        }

        /// <summary>
        /// Converts the object to <code>Convert.DBNull</code> if it is <code>DateTime.MinValue</code>.
        /// </summary>
        /// <param name="obj">The object to be queried.</param>
        /// <returns><code>Convert.DBNull</code> if the object is <code>null</code>.</returns>
        public static object ToDbValue(this DateTime obj)
        {
            return obj == DateTime.MinValue ? Convert.DBNull : obj;
        }

        #endregion

        #region Value

        /// <summary>
        /// Gets the value at the given index.
        /// </summary>
        /// <param name="values">The array to be queried.</param>
        /// <param name="index">The index of the value to be retrieved.</param>
        /// <returns>
        /// The value at the given index if found; <code>null</code> otherwise.
        /// </returns>
        public static object Value(this object[] values, int index)
        {
            if(values != null && values.Length > index)
            {
                return values[index];
            }
            return null;
        }

        #endregion

        #region ChangeType

        /// <summary>
        /// Converts the given <paramref name="obj"/> to an object of the given <see cref="Type"/>.
        /// </summary>
        /// <param name="obj">The object to be converted.</param>
        /// <param name="type">The type of the result.</param>
        /// <returns>An object of the requested type.</returns>
        public static object ChangeType(this object obj, Type type)
        {
            if(type.IsSubclassOf(typeof(Enum)))
            {
                var s = obj.ToStringSafe();
                return s.ToEnum(type);
            }

            if(type == typeof(bool))
            {
                return obj.ToBoolean();
            }

            if(type == typeof(DateTime?))
            {
                return obj.ToDateTime();
            }
            if(type == typeof(DateTime))
            {
                return obj.ToDateTime() ?? DateTime.MinValue;
            }

            if(type == typeof(byte?))
            {
                return obj.ToByte();
            }
            if(type == typeof(byte))
            {
                return obj.ToByte() ?? 0;
            }

            if(type == typeof(short?))
            {
                return obj.ToInt16();
            }
            if(type == typeof(short))
            {
                return obj.ToInt16() ?? 0;
            }

            if(type == typeof(int?))
            {
                return obj.ToInt32();
            }
            if(type == typeof(int))
            {
                return obj.ToInt32() ?? 0;
            }

            if(type == typeof(long?))
            {
                return obj.ToInt64();
            }
            if(type == typeof(long))
            {
                return obj.ToInt64() ?? 0;
            }

            if(type == typeof(float?))
            {
                return obj.ToFloat();
            }
            if(type == typeof(float))
            {
                return obj.ToFloat() ?? 0;
            }

            if(type == typeof(double?))
            {
                return obj.ToDouble();
            }
            if(type == typeof(double))
            {
                return obj.ToDouble() ?? 0;
            }

            if(type == typeof(decimal?))
            {
                return obj.ToDecimal();
            }
            if(type == typeof(decimal))
            {
                return obj.ToDecimal() ?? 0;
            }

            return Convert.ChangeType(obj, type, CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Converts the given <paramref name="obj"/> to an object of the given <see cref="TypeCode"/>.
        /// </summary>
        /// <param name="obj">The object to be converted.</param>
        /// <param name="typeCode">The type code of the result.</param>
        /// <returns>An object of the requested type.</returns>
        public static object ChangeType(this object obj, string typeCode)
        {
            return obj.ChangeType((TypeCode)typeCode.ToEnum(typeof(TypeCode)));
        }

        /// <summary>
        /// Converts the given <paramref name="obj"/> to an object of the given <see cref="TypeCode"/>.
        /// </summary>
        /// <param name="obj">The object to be converted.</param>
        /// <param name="typeCode">The <see cref="TypeCode"/> of the result.</param>
        /// <returns>An object of the requested type.</returns>
        public static object ChangeType(this object obj, TypeCode typeCode)
        {
            if(typeCode == TypeCode.Boolean)
            {
                return obj.ToBoolean();
            }
            return typeCode == TypeCode.DateTime ? obj.ToDateTime() : Convert.ChangeType(obj, typeCode, CultureInfo.InvariantCulture);
        }

        #endregion
    }
}