/*
 * 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.Linq;
using System.Xml;
using Amazon.S3.Model.Internal.MarshallTransformations;

namespace Amazon.S3.Model
{
    /// <summary>
    /// This class contains the meta data for an S3 object.
    /// </summary>
    public sealed class MetadataCollection
    {
        internal const string MetaDataHeaderPrefix = "x-amz-meta-";
            
        IDictionary<string, string> values = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

        /// <summary>
        /// Gets and sets meta data for the object. Meta data names must start with "x-amz-meta-". If the name passeed in as the indexer 
        /// doesn't start with "x-amz-meta-" then it will be prepended.
        /// </summary>
        /// <param name="name">The name of the meta data.</param>
        /// <returns>The value for the meta data</returns>
        public string this[string name]
        {
            get
            {
                if (!name.StartsWith(MetaDataHeaderPrefix, StringComparison.OrdinalIgnoreCase))
                    name = MetaDataHeaderPrefix + name;

                string value;
                if (values.TryGetValue(name, out value))
                    return value;

                return null;
            }
            set
            {
                if (!name.StartsWith(MetaDataHeaderPrefix, StringComparison.OrdinalIgnoreCase))
                    name = MetaDataHeaderPrefix + name;

                values[name] = value;
            }
        }

        /// <summary>
        /// Adds the metadata to the collection, if the name already exists it will be overwritten.
        /// </summary>
        /// <param name="name">The name of the metadata element</param>
        /// <param name="value">The value for the metadata</param>
        public void Add(string name, string value)
        {
            this[name] = value;
        }

        /// <summary>
        /// Clears user defined metadata from the collection.
        /// </summary>
        public void Clear()
        {
            foreach (var key in values.Keys.ToList())
            {
                if (key.StartsWith(MetaDataHeaderPrefix, StringComparison.OrdinalIgnoreCase))
                {
                    values.Remove(key);
                }
            }
        }

        /// <summary>
        /// Gets the count of headers.
        /// </summary>
        public int Count
        {
            get { return this.values.Count; }
        }

        /// <summary>
        /// Gets the names of the meta data elements.
        /// </summary>
        public ICollection<string> Keys
        {
            get { return values.Keys; }
        }

        internal void Marshall(string memberName, XmlWriter xmlWriter)
        {
            xmlWriter.WriteStartElement(memberName);
            {
                foreach(var t in values)
                {
                    xmlWriter.WriteStartElement("MetadataEntry");
                    {
                        // since this is not being marshalled into header, 
                        // normalize it by stripping it of "x-amz-meta" prefix.
                        var name = t.Key.Replace(MetaDataHeaderPrefix, "");

                        xmlWriter.WriteElementString("Name", S3Transforms.ToXmlStringValue(name));
                        xmlWriter.WriteElementString("Value", S3Transforms.ToXmlStringValue(t.Value));
                    }
                    xmlWriter.WriteEndElement();
                }
            }
            xmlWriter.WriteEndElement();
        }
    }
}