/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 * 
 *  http://aws.amazon.com/apache2.0
 * 
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.IO;

using Amazon.Util;
using System.Linq;

namespace Amazon.Runtime.Internal.Util
{
    /// <summary>
    /// Utilities for converting objects to strings. Used by the marshaller classes.
    /// </summary>
    public static class StringUtils
    {
        private static readonly Encoding UTF_8 = Encoding.UTF8;

        public static string FromString(String value) 
        {
            return value;
        }

        public static string FromStringWithSlashEncoding(String value)
        {
            return AWSSDKUtils.UrlEncodeSlash(FromString(value));
        }

        public static string FromString(ConstantClass value)
        {
            return value == null ? "" : value.Intern().Value;
        }

        public static string FromMemoryStream(MemoryStream value)
        {
            return Convert.ToBase64String(value.ToArray());
        }

        public static string FromInt(int value)
        {
            return value.ToString(CultureInfo.InvariantCulture);
        }
        
        public static string FromInt(int? value)
        {
            if (value != null)
                return value.Value.ToString(CultureInfo.InvariantCulture);

            return null;
        }

        public static string FromLong(long value)
        {
            return value.ToString(CultureInfo.InvariantCulture);
        }

        public static string FromFloat(float value)
        {
            return value.ToString(CultureInfo.InvariantCulture);
        }

        public static string FromBool(bool value)
        {
            return value ? "true" : "false";
        }

        [Obsolete("This method doesn't handle correctly non-UTC DateTimes. Use FromDateTimeToISO8601 instead.", false)]
        public static string FromDateTime(DateTime value)
        {
            return value.ToString(AWSSDKUtils.ISO8601DateFormat, CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Converts a DateTime to ISO8601 formatted string.
        /// </summary>
        public static string FromDateTimeToISO8601(DateTime value)
        {
            return value.ToUniversalTime().ToString(AWSSDKUtils.ISO8601DateFormat, CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Converts a DateTime to RFC822 formatted string.
        /// </summary>
        public static string FromDateTimeToRFC822(DateTime value)
        {
            return value.ToUniversalTime().ToString(
                AWSSDKUtils.RFC822DateFormat, CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Converts a DateTime to Unix epoch time formatted string.
        /// </summary>
        public static string FromDateTimeToUnixTimestamp(DateTime value)
        {
            return AWSSDKUtils.ConvertToUnixEpochSecondsString(value);
        }

        public static string FromDouble(double value)
        {
            return value.ToString(CultureInfo.InvariantCulture);
        }

        public static string FromDecimal(decimal value)
        {
            return value.ToString(CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Combines a list of enums into a comma-separated string to be marshalled as a header
        /// </summary>
        /// <param name="values">List of enums</param>
        /// <returns>Header value representing the list of enums</returns>
        public static string FromList(IEnumerable<Enum> values)
        {
            return FromList(values?.Select(x => x.ToString()));
        }

        /// <summary>
        /// Combines a list of enums into a comma-separated string to be marshalled as a header
        /// </summary>
        /// <param name="values">List of enums</param>
        /// <returns>Header value representing the list of enums</returns>
        public static string FromList(List<Enum> values)
        {
            return FromList(values?.Select(x => x.ToString()));
        }

        /// <summary>
        /// Combines an enumerable of ConstantClass enums into a comma-separated string to be marshalled as a header
        /// </summary>
        /// <param name="values">List of enums</param>
        /// <returns>Header value representing the list of enums</returns>
        public static string FromList<T>(IEnumerable<T> values) where T : ConstantClass
        {
            return FromList(values?.Select(x => x.ToString()));
        }

        /// <summary>
        /// Combines a list of ConstantClass enums into a comma-separated string to be marshalled as a header
        /// </summary>
        /// <param name="values">List of enums</param>
        /// <returns>Header value representing the list of enums</returns>
        public static string FromList<T>(List<T> values) where T : ConstantClass
        {
            return FromList(values?.Select(x => x.ToString()));
        }

        /// <summary>
        /// Combines a list of strings into a comma-separated string to be marshalled as a header
        /// </summary>
        /// <param name="values">List of strings</param>
        /// <returns>Header value representing the list of strings</returns>
        public static string FromList(IEnumerable<string> values)
        {
            if (values == null || values.Count() == 0)
            {
                return "";
            }

            // Comma separate any non-null/non-empty entries with below formatting
            return string.Join(",", values.Where(x => !string.IsNullOrEmpty(x)).Select(x => EscapeHeaderListEntry(x)).ToArray());
        }

        /// <summary>
        /// Wraps an item to be sent in 
        /// </summary>
        /// <param name="headerListEntry">Single item from the header's list</param>
        /// <returns>Item wrapped in double quotes if appropriate</returns>
        private static string EscapeHeaderListEntry(string headerListEntry)
        {
            // If it's already surounded by double quotes, no further formatting needed
            if (headerListEntry.Length >= 2 && headerListEntry[0] == '\"' && headerListEntry[headerListEntry.Length - 1] == '\"')
            {
                return headerListEntry;
            }
            else if (headerListEntry.Contains(",") || headerListEntry.Contains("\""))
            {
                // The string must be double quoted if double quote(s) or comma(s) appear within the string
                return $"\"{headerListEntry}\"";
            }

            return headerListEntry;
        }

        public static long Utf8ByteLength(string value)
        {
            if (value == null)
            {
                return 0;
            }
            return UTF_8.GetByteCount(value);
        }
    }
}