namespace DotNetOpenAuth.ApplicationBlock {
	using System;
	using System.Collections.Generic;
	using System.IO;
	using DotNetOpenAuth.Messaging;

	internal static class Util {
		/// <summary>
		/// Enumerates through the individual set bits in a flag enum.
		/// </summary>
		/// <param name="flags">The flags enum value.</param>
		/// <returns>An enumeration of just the <i>set</i> bits in the flags enum.</returns>
		internal static IEnumerable<long> GetIndividualFlags(Enum flags) {
			long flagsLong = Convert.ToInt64(flags);
			for (int i = 0; i < sizeof(long) * 8; i++) { // long is the type behind the largest enum
				// Select an individual application from the scopes.
				long individualFlagPosition = (long)Math.Pow(2, i);
				long individualFlag = flagsLong & individualFlagPosition;
				if (individualFlag == individualFlagPosition) {
					yield return individualFlag;
				}
			}
		}

		internal static Uri GetCallbackUrlFromContext() {
			Uri callback = MessagingUtilities.GetRequestUrlFromContext().StripQueryArgumentsWithPrefix("oauth_");
			return callback;
		}

		/// <summary>
		/// Copies the contents of one stream to another.
		/// </summary>
		/// <param name="copyFrom">The stream to copy from, at the position where copying should begin.</param>
		/// <param name="copyTo">The stream to copy to, at the position where bytes should be written.</param>
		/// <returns>The total number of bytes copied.</returns>
		/// <remarks>
		/// Copying begins at the streams' current positions.
		/// The positions are NOT reset after copying is complete.
		/// </remarks>
		internal static int CopyTo(this Stream copyFrom, Stream copyTo) {
			return CopyTo(copyFrom, copyTo, int.MaxValue);
		}

		/// <summary>
		/// Copies the contents of one stream to another.
		/// </summary>
		/// <param name="copyFrom">The stream to copy from, at the position where copying should begin.</param>
		/// <param name="copyTo">The stream to copy to, at the position where bytes should be written.</param>
		/// <param name="maximumBytesToCopy">The maximum bytes to copy.</param>
		/// <returns>The total number of bytes copied.</returns>
		/// <remarks>
		/// Copying begins at the streams' current positions.
		/// The positions are NOT reset after copying is complete.
		/// </remarks>
		internal static int CopyTo(this Stream copyFrom, Stream copyTo, int maximumBytesToCopy) {
			if (copyFrom == null) {
				throw new ArgumentNullException("copyFrom");
			}
			if (copyTo == null) {
				throw new ArgumentNullException("copyTo");
			}

			byte[] buffer = new byte[1024];
			int readBytes;
			int totalCopiedBytes = 0;
			while ((readBytes = copyFrom.Read(buffer, 0, Math.Min(1024, maximumBytesToCopy))) > 0) {
				int writeBytes = Math.Min(maximumBytesToCopy, readBytes);
				copyTo.Write(buffer, 0, writeBytes);
				totalCopiedBytes += writeBytes;
				maximumBytesToCopy -= writeBytes;
			}

			return totalCopiedBytes;
		}
	}
}