LoadResourceFile.cs

using System;
using System.IO;
using System.Threading.Tasks;
using Waher.Content;
using Waher.Runtime.IO;
using Waher.Script;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
 
namespace Waher.IoTGateway.ScriptExtensions.Functions
{
    public class LoadResourceFile : FunctionMultiVariate
    {
        public LoadResourceFile(ScriptNode LocalResource, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { LocalResource }, argumentTypes1Scalar, Start, Length, Expression)
        {
        }
 
        public LoadResourceFile(ScriptNode LocalResource, ScriptNode ContentType, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { LocalResource, ContentType }, argumentTypes2Scalar, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(LoadResourceFile);
 
        public override string[] DefaultArgumentNames => new string[] { "LocalResource", "ContentType" };
 
        public override bool IsAsynchronous => true;
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            return this.EvaluateAsync(Arguments, Variables).Result;
        }
 
        public override async Task<IElement> EvaluateAsync(IElement[] Arguments, Variables Variables)
        {
            string LocalResource = ToString(Arguments[0]);
            string ContentType;
 
            if (!Gateway.HttpServer.TryGetFileName(LocalResource, true, out string FileName))
                throw new ScriptRuntimeException("Unable to convert local resource to file name.", this);
 
            if (Arguments.Length > 1)
                ContentType = ToString(Arguments[1]);
            else
                ContentType = InternetContent.GetContentType(Path.GetExtension(FileName));
 
            byte[] Bin;
 
            try
            {
                using FileStream fs = File.OpenRead(FileName);
                Bin = await fs.ReadAllAsync();
            }
            catch (IOException)
            {
                string TempFileName = Path.GetTempFileName();
                File.Copy(FileName, TempFileName, true);
 
                try
                {
                    using FileStream fs = File.OpenRead(TempFileName);
                    Bin = await fs.ReadAllAsync();
                }
                finally
                {
                    File.Delete(TempFileName);
                }
            }
 
            ContentResponse Content = await InternetContent.DecodeAsync(ContentType, Bin, new Uri(Gateway.GetUrl(LocalResource)));
 
            if (Content.HasError)
                throw new ScriptRuntimeException(Content.Error.Message, this, Content.Error);
 
            return Expression.Encapsulate(Content.Decoded);
        }
    }
}