BrotliContentEncoding.cs

using System;
using System.IO;
using Waher.Events;
using Waher.Networking.HTTP.ContentEncodings;
using Waher.Runtime.Inventory;
using Waher.Runtime.Timing;
 
namespace Waher.Networking.HTTP.Brotli
{
    public class BrotliContentEncoding : IContentEncoding
    {
        private static readonly Random rnd = new Random();
        private static Scheduler? scheduler = null;
        private static string? appDataFolder = null;
        private static string? brotliFolder = null;
        private static bool compressDynamic = false;
        private static bool compressStatic = true;
 
        public string Label => "br";
 
        public bool SupportsDynamicEncoding => compressDynamic;
 
        public bool SupportsStaticEncoding => compressStatic;
 
        public void ConfigureSupport(bool Dynamic, bool Static)
        {
            compressDynamic = Dynamic;
            compressStatic = Static;
        }
 
        public Grade Supports(string Label) => Label == this.Label ? Grade.Ok : Grade.NotAtAll;
 
        public TransferEncoding GetEncoder(TransferEncoding Output, long? ExpectedContentLength, string ETag)
        {
            string? CompressedFileName;
 
            if (!string.IsNullOrEmpty(brotliFolder))
                CompressedFileName = Path.Combine(brotliFolder, ETag + ".br");
            else
                CompressedFileName = null;
 
            BrotliEncoder Encoder = new BrotliEncoder(CompressedFileName, Output, ExpectedContentLength);
            Encoder.PrepareForCompression();
            return Encoder;
        }
 
        public FileInfo? TryGetPrecompressedFile(string ETag)
        {
            if (string.IsNullOrEmpty(ETag) || string.IsNullOrEmpty(brotliFolder))
                return null;
 
            string CompressedFileName = Path.Combine(brotliFolder, ETag + ".br");
 
            return new FileInfo(CompressedFileName);
        }
 
        public static void Init(string AppDataFolder)
        {
            try
            {
                appDataFolder = AppDataFolder;
                brotliFolder = Path.Combine(appDataFolder, "Brotli");
 
                if (!Directory.Exists(brotliFolder))
                    Directory.CreateDirectory(brotliFolder);
 
                if (scheduler is null)
                {
                    if (Types.TryGetModuleParameter("Scheduler", out object Obj) && Obj is Scheduler Scheduler)
                        scheduler = Scheduler;
                    else
                    {
                        scheduler = new Scheduler();
 
                        Log.Terminating += (Sender, e) =>
                        {
                            scheduler?.Dispose();
                            scheduler = null;
                        };
                    }
                }
 
                DeleteOldFiles(TimeSpan.FromDays(7));
            }
            catch (Exception ex)
            {
                Log.Exception(ex);
            }
        }
 
        private static void DeleteOldFiles(object P)
        {
            if (P is TimeSpan MaxAge)
                DeleteOldFiles(MaxAge, true);
        }
 
        public static void DeleteOldFiles(TimeSpan MaxAge, bool Reschedule)
        {
            DateTime Limit = DateTime.Now - MaxAge;
            int Count = 0;
 
            DirectoryInfo BrotliFolder = new DirectoryInfo(brotliFolder);
            FileInfo[] Files = BrotliFolder.GetFiles("*.*");
 
            foreach (FileInfo FileInfo in Files)
            {
                if (FileInfo.LastAccessTime < Limit)
                {
                    try
                    {
                        File.Delete(FileInfo.FullName);
                        Count++;
                    }
                    catch (Exception ex)
                    {
                        Log.Error("Unable to delete old file: " + ex.Message, FileInfo.FullName);
                    }
                }
            }
 
            if (Count > 0)
                Log.Informational(Count.ToString() + " old file(s) deleted.", brotliFolder);
 
            if (Reschedule)
            {
                lock (rnd)
                {
                    scheduler?.Add(DateTime.Now.AddDays(rnd.NextDouble() * 2), DeleteOldFiles, MaxAge);
                }
            }
        }
 
    }
}