ConversionState.cs

using System;
using System.IO;
using Waher.Events;
using Waher.Script;

namespace Waher.Content
{
	/// <summary>
	/// Delegate to callback functions that resolve local file names for local resources.
	/// </summary>
	/// <param name="Resource">Resource</param>
	/// <param name="Host">Optional host, if available.</param>
	/// <param name="FileName">Local file name, if found.</param>
	/// <returns>If resource corresponds to a local file resource.</returns>
	public delegate bool TryGetLocalResourceFileName(string Resource, string Host, out string FileName);

	/// <summary>
	/// Contains the state of a content conversion process.
	/// </summary>
	public class ConversionState
	{
		private readonly TryGetLocalResourceFileName tryGetLocalResourceFileName;

		/// <summary>
		/// Contains the state of a content conversion process.
		/// </summary>
		/// <param name="FromContentType">Content type of the content to convert from.</param>
		/// <param name="From">Stream pointing to binary representation of content.</param>
		/// <param name="FromFileName">If the content is coming from a file, this parameter contains the name of that file. 
		/// Otherwise, the parameter is the empty string.</param>
		/// <param name="LocalResourceName">Local resource name of file, if accessed from a web server.</param>
		/// <param name="URL">URL of resource, if accessed from a web server.</param>
		/// <param name="ToContentType">Content type of the content to convert to. This value might be changed, in case
		/// the converter finds a better option.</param>
		/// <param name="To">Stream pointing to where binary representation of content is to be sent.</param>
		/// <param name="Session">Session states.</param>
		/// <param name="Progress">Optional interface for reporting progress during conversion.</param>
		/// <param name="ResourceMap">Optional resource map.</param>
		/// <param name="TryGetLocalResourceFileName">Callback function to get a local file name from a resource.</param>
		/// <param name="PossibleContentTypes">Possible content types the converter is allowed to convert to. 
		/// Can be null if there are no alternatives.</param>
		public ConversionState(string FromContentType, Stream From, string FromFileName, string LocalResourceName, string URL,
			string ToContentType, Stream To, Variables Session, ICodecProgress Progress, IResourceMap ResourceMap,
			TryGetLocalResourceFileName TryGetLocalResourceFileName, params string[] PossibleContentTypes)
		{
			this.FromContentType = FromContentType;
			this.From = From;
			this.FromFileName = FromFileName;
			this.LocalResourceName = LocalResourceName;
			this.URL = URL;
			this.ToContentType = ToContentType;
			this.To = To;
			this.Session = Session;
			this.Progress = Progress;
			this.PossibleContentTypes = PossibleContentTypes;
			this.ResourceMap = ResourceMap;
			this.tryGetLocalResourceFileName = TryGetLocalResourceFileName;
		}

		/// <summary>
		/// Content type of the content to convert from.
		/// </summary>
		public string FromContentType { get; }

		/// <summary>
		/// Stream pointing to binary representation of content.
		/// </summary>
		public Stream From { get; }

		/// <summary>
		/// If the content is coming from a file, this parameter contains the name of that file. 
		/// Otherwise, the parameter is the empty string.
		/// </summary>
		public string FromFileName { get; set; }

		/// <summary>
		/// Local resource name of file, if accessed from a web server.
		/// </summary>
		public string LocalResourceName { get; set; }

		/// <summary>
		/// URL of resource, if accessed from a web server.
		/// </summary>
		public string URL { get; }

		/// <summary>
		/// Content type of the content to convert to. This value might be changed, in case
		/// the converter finds a better option. May get updated during the conversion process.
		/// </summary>
		public string ToContentType { get; set; }

		/// <summary>
		/// Stream pointing to where binary representation of content is to be sent.
		/// </summary>
		public Stream To { get; }

		/// <summary>
		/// Session states.
		/// </summary>
		public Variables Session { get; }

		/// <summary>
		/// Optional interface for reporting progress during conversion.
		/// </summary>
		public ICodecProgress Progress { get; }

		/// <summary>
		/// Optional resource map.
		/// </summary>
		public IResourceMap ResourceMap { get; }

		/// <summary>
		/// Possible content types the converter is allowed to convert to. 
		/// Can be null if there are no alternatives.
		/// </summary>
		public string[] PossibleContentTypes { get; }

		/// <summary>
		/// Error response, in case conversion should return an error.
		/// </summary>
		public Exception Error { get; set; }

		/// <summary>
		/// If an error should be returned.
		/// </summary>
		public bool HasError => !(this.Error is null);

		/// <summary>
		/// Tries to get a file name for a resource, if local.
		/// </summary>
		/// <param name="Resource">Resource</param>
		/// <param name="Host">Optional host, if available.</param>
		/// <param name="FileName">File name, if resource identified as a local resource.</param>
		/// <returns>If successful in identifying a local file name for the resource.</returns>
		public bool TryGetLocalResourceFileName(string Resource, string Host, out string FileName)
		{
			if (!(this.tryGetLocalResourceFileName is null))
			{
				try
				{
					return this.tryGetLocalResourceFileName(Resource, Host, out FileName);
				}
				catch (Exception ex)
				{
					Log.Exception(ex);
				}
			}

			FileName = null;
			return false;
		}
	}
}