//---------------------------------------------------------------------
// <copyright file="MetadataArtifactLoaderFile.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//
// @owner       Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------

using System.Collections.Generic;
using System.Collections;
using System.Diagnostics;
using System.Globalization;
using System.Reflection;
using System.Text;
using System.Xml;
using System.Data.Mapping;
using System.IO;
using System.Security;
using System.Security.Permissions;
using System.Security.Cryptography;
using System.Data.EntityModel.SchemaObjectModel;
using System.Threading;
using System.Runtime.Versioning;

namespace System.Data.Metadata.Edm
{
    /// <summary>
    /// This class represents one file-based artifact item to be loaded.
    /// </summary>
    internal class MetadataArtifactLoaderFile : MetadataArtifactLoader, IComparable
    {
        /// <summary>
        /// This member indicates whether the file-based artifact has already been loaded.
        /// It is used to prevent other instances of this class from (re)loading the same
        /// artifact. See comment in the MetadataArtifactLoaderFile c'tor below.
        /// </summary>
        private readonly bool _alreadyLoaded = false;
        private readonly string _path;

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="path">The path to the resource to load</param>
        /// <param name="uriRegistry">The global registry of URIs</param>
        [ResourceExposure(ResourceScope.Machine)] //Exposes the file path which is a Machine resource
        public MetadataArtifactLoaderFile(string path, ICollection<string> uriRegistry)
        {
            _path = path;
            _alreadyLoaded = uriRegistry.Contains(_path);
            if (!_alreadyLoaded)
            {
                uriRegistry.Add(_path);

                // '_alreadyLoaded' is not set because while we would like to prevent
                // other instances of MetadataArtifactLoaderFile that wrap the same
                // _path from being added to the list of paths/readers, we do want to
                // include this particular instance.
            }
        }

        public override string Path
        {
            get { return _path; }
        }

        /// <summary>
        /// Implementation of IComparable.CompareTo()
        /// </summary>
        /// <param name="obj">The object to compare to</param>
        /// <returns>0 if the loaders are "equal" (i.e., have the same _path value)</returns>
        public int CompareTo(object obj)
        {
            MetadataArtifactLoaderFile loader = obj as MetadataArtifactLoaderFile;
            if (loader != null)
            {
                return string.Compare(_path, loader._path, StringComparison.OrdinalIgnoreCase);
            }

            Debug.Assert(false, "object is not a MetadataArtifactLoaderFile");
            return -1;
        }

        /// <summary>
        /// Equals() returns true if the objects have the same _path value
        /// </summary>
        /// <param name="obj">The object to compare to</param>
        /// <returns>true if the objects have the same _path value</returns>
        public override bool Equals(object obj)
        {
            return this.CompareTo(obj) == 0;
        }

        /// <summary>
        /// GetHashCode override that defers the result to the _path member variable.
        /// </summary>
        /// <returns></returns>
        public override int GetHashCode()
        {
            return _path.GetHashCode();
        }

        public override void CollectFilePermissionPaths(List<string> paths, DataSpace spaceToGet)
        {
            if (!_alreadyLoaded && MetadataArtifactLoader.IsArtifactOfDataSpace(_path, spaceToGet))
            {
                paths.Add(_path);
            }
        }
        /// <summary>
        /// Get paths to artifacts for a specific DataSpace.
        /// </summary>
        /// <param name="spaceToGet">The DataSpace for the artifacts of interest</param>
        /// <returns>A List of strings identifying paths to all artifacts for a specific DataSpace</returns>
        public override List<string> GetPaths(DataSpace spaceToGet)
        {
            List<string> list = new List<string>();
            if (!_alreadyLoaded && MetadataArtifactLoader.IsArtifactOfDataSpace(_path, spaceToGet))
            {
                list.Add(_path);
            }
            return list;
        }

        /// <summary>
        /// Get paths to all artifacts
        /// </summary>
        /// <returns>A List of strings identifying paths to all resources</returns>
        public override List<string> GetPaths()
        {
            List<string> list = new List<string>();
            if (!_alreadyLoaded)
            {
                list.Add(_path);
            }
            return list;
        }

        /// <summary>
        /// Create and return an XmlReader around the file represented by this instance.
        /// </summary>
        /// <returns>A List of XmlReaders for all resources</returns>
        public override List<XmlReader> GetReaders(Dictionary<MetadataArtifactLoader, XmlReader> sourceDictionary)
        {
            List<XmlReader> list = new List<XmlReader>();
            if (!_alreadyLoaded)
            {
                XmlReader reader = CreateXmlReader();
                list.Add(reader);
                if (sourceDictionary != null)
                {
                    sourceDictionary.Add(this, reader);
                }
            }
            return list;
        }

        /// <summary>
        /// Create and return an XmlReader around the file represented by this instance
        /// if it is of the requested DataSpace type.
        /// </summary>
        /// <param name="spaceToGet">The DataSpace corresponding to the requested artifacts</param>
        /// <returns>A List of XmlReader objects</returns>
        public override List<XmlReader> CreateReaders(DataSpace spaceToGet)
        {
            List<XmlReader> list = new List<XmlReader>();
            if (!_alreadyLoaded && MetadataArtifactLoader.IsArtifactOfDataSpace(_path, spaceToGet))
            {
                XmlReader reader = CreateXmlReader();
                list.Add(reader);
            }
            return list;
        }

        /// <summary>
        /// Create an XmlReader around the artifact file
        /// </summary>
        /// <returns>An XmlReader that wraps a file</returns>
        [ResourceExposure(ResourceScope.None)] //The file path is not passed through to this method so nothing to expose in this method.
        [ResourceConsumption(ResourceScope.Machine, ResourceScope.Machine)] //We are not changing the scope of consumption here
        private XmlReader CreateXmlReader()
        {
            XmlReaderSettings readerSettings = Schema.CreateEdmStandardXmlReaderSettings();
            // we know that we aren't reading a fragment
            readerSettings.ConformanceLevel = ConformanceLevel.Document;
            return XmlReader.Create(_path, readerSettings);
        }

    }
}