// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.IO;
using Microsoft.ML.Data;
using Microsoft.ML.Data.IO;
using Microsoft.ML.Runtime;
 
namespace Microsoft.ML
{
    /// <summary>
    /// Collection of extension methods for the <see cref="DataOperationsCatalog"/> to create instances of
    /// components to save and read <see cref="IDataView"/> objects to and from a high-performance binary format.
    /// </summary>
    public static class BinaryLoaderSaverCatalog
    {
        /// <summary>
        /// Load a <see cref="IDataView"/> from an <see cref="IMultiStreamSource"/> on a binary file.
        /// Note that <see cref="IDataView"/>'s are lazy, so no actual loading happens here, just schema validation.
        /// </summary>
        /// <param name="catalog">The catalog.</param>
        /// <param name="fileSource">The file source to load from. This can be a <see cref="MultiFileSource"/>, for example.</param>
        public static IDataView LoadFromBinary(this DataOperationsCatalog catalog, IMultiStreamSource fileSource)
        {
            Contracts.CheckValue(fileSource, nameof(fileSource));
 
            var env = catalog.GetEnvironment();
 
            var loader = new BinaryLoader(env, new BinaryLoader.Arguments(), fileSource);
            return loader;
        }
 
        /// <summary>
        /// Load a <see cref="IDataView"/> from a binary file.
        /// Note that <see cref="IDataView"/>'s are lazy, so no actual loading happens here, just schema validation.
        /// </summary>
        /// <param name="catalog">The catalog.</param>
        /// <param name="path">The path to the file to load from.</param>
        /// <example>
        /// <format type="text/markdown">
        /// <![CDATA[
        /// [!code-csharp[LoadFromBinary](~/../docs/samples/docs/samples/Microsoft.ML.Samples/Dynamic/DataOperations/SaveAndLoadFromBinary.cs)]
        /// ]]>
        /// </format>
        /// </example>
        public static IDataView LoadFromBinary(this DataOperationsCatalog catalog, string path)
        {
            Contracts.CheckNonEmpty(path, nameof(path));
            if (!File.Exists(path))
            {
                throw Contracts.ExceptParam(nameof(path), "File does not exist at path: {0}", path);
            }
 
            var env = catalog.GetEnvironment();
 
            var loader = new BinaryLoader(env, new BinaryLoader.Arguments(), path);
            return loader;
        }
 
        /// <summary>
        /// Save the <see cref="IDataView"/> into a binary stream.
        /// </summary>
        /// <param name="catalog">The catalog.</param>
        /// <param name="data">The data view to save.</param>
        /// <param name="stream">The stream to write to.</param>
        /// <param name="keepHidden">Whether to keep hidden columns in the dataset.</param>
        /// <example>
        /// <format type="text/markdown">
        /// <![CDATA[
        /// [!code-csharp[SaveAsBinary](~/../docs/samples/docs/samples/Microsoft.ML.Samples/Dynamic/DataOperations/SaveAndLoadFromBinary.cs)]
        /// ]]>
        /// </format>
        /// </example>
        public static void SaveAsBinary(this DataOperationsCatalog catalog, IDataView data, Stream stream,
            bool keepHidden = false)
        {
            Contracts.CheckValue(catalog, nameof(catalog));
            Contracts.CheckValue(data, nameof(data));
            Contracts.CheckValue(stream, nameof(stream));
 
            var env = catalog.GetEnvironment();
            var saver = new BinarySaver(env, new BinarySaver.Arguments());
 
            using (var ch = env.Start("Saving data"))
                DataSaverUtils.SaveDataView(ch, saver, data, stream, keepHidden);
        }
    }
}