Remotely/Server/Services/LogsManager.cs

using Microsoft.Extensions.Logging;
using Remotely.Shared.Extensions;
using Serilog;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Remotely.Server.Services
{
    public interface ILogsManager
    {
        string GetLogsDirectory();
        Task<FileInfo> ZipAllLogs();
        Task DeleteLogs();
        IAsyncEnumerable<string> GetLogs(
            DateTimeOffset startDate, 
            DateTimeOffset endDate,
            string messageFilter,
            LogLevel? logLevelFilter);
    }

    public class LogsManager : ILogsManager
    {
        public static LogsManager Default { get; } = new();

        public string GetLogsDirectory()
        {
            var logsDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "logs");
            if (Directory.Exists("/remotely-data"))
            {
                logsDir = "/remotely-data/logs";
            }
            return Directory.CreateDirectory(logsDir).FullName;
        }

        public async Task<FileInfo> ZipAllLogs()
        {
            var logsDir = GetLogsDirectory();
            var baseDir = AppDomain.CurrentDomain.BaseDirectory;
            var tempDir = Directory.CreateDirectory(Path.Combine(baseDir, "temp", Guid.NewGuid().ToString())).FullName;
            var zipFilePath = Path.Combine(
                tempDir, 
                $"Remotely_Logs-{DateTimeOffset.Now:yyyy-MM-dd-HH-mm-ss}.zip");

            using var zipArchive = ZipFile.Open(zipFilePath, ZipArchiveMode.Update);

            var files = Directory.GetFiles(logsDir);

            foreach (var file in files)
            {
                var entry = zipArchive.CreateEntry(Path.GetFileName(file));
                using var entryStream = entry.Open();
                using var fs = File.Open(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                await fs.CopyToAsync(entryStream);
            }

            return new FileInfo(zipFilePath);
        }

        public async Task DeleteLogs()
        {
            var logsDir = GetLogsDirectory();

            var files = Directory.GetFiles(logsDir);
            
            if (!files.Any())
            {
                return;
            }

            await foreach (var file in files.ToAsyncEnumerable())
            {
                try
                {
                    File.Delete(file);
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"Failed to delete log file: {file}.  Message: {ex.Message}");
                    try
                    {
                        Console.WriteLine("Attempting to zero out log contents.");
                        using var fs = File.Open(file, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
                        fs.SetLength(0);
                    }
                    catch (Exception ex2)
                    {
                        Console.WriteLine($"Failed to clear log contents: {file}.  Message: {ex2.Message}");
                    }
                }
            }
        }

        public async IAsyncEnumerable<string> GetLogs(
            DateTimeOffset startDate, 
            DateTimeOffset endDate,
            string messageFilter,
            LogLevel? logLevelFilter)
        {
            var fromDate = startDate.UtcDateTime.Date;
            var toDate = endDate.UtcDateTime.Date.AddDays(1);

            var result = new StringBuilder();
            var logsDir = GetLogsDirectory();

            var files = Directory
                .GetFiles(logsDir)
                .Select(x => new FileInfo(x))
                .Where(x =>
                    x.LastWriteTimeUtc >= fromDate &&
                    x.LastWriteTimeUtc <= toDate);

            foreach (var file in files)
            {
                var linesAsync = GetLines(file, messageFilter, logLevelFilter);
                await foreach (var line in linesAsync)
                {
                    yield return line;
                }
              
            }
        }

        private async IAsyncEnumerable<string> GetLines(
            FileInfo file,
            string messageFilter,
            LogLevel? logLevelFilter)
        {
            LogLevel? currentLogLevel = null;

            using var fs = File.Open(file.FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            using var sr = new StreamReader(fs);

            while (true)
            {
                var currentLine = await sr.ReadLineAsync();

                if (currentLine is null)
                {
                    break;
                }

                if (logLevelFilter is not null)
                {
                    if (TryGetLogLevel(currentLine, out var parsedLevel))
                    {
                        currentLogLevel = parsedLevel;
                    }

                    if (currentLogLevel != logLevelFilter)
                    {
                        continue;
                    }
                }

                if (!string.IsNullOrWhiteSpace(messageFilter) && 
                    !currentLine.Contains(messageFilter, StringComparison.OrdinalIgnoreCase))
                {
                    continue;
                }

                yield return currentLine;
            }
        }

        private bool TryGetLogLevel(
            string lineContent,
            [NotNullWhen(true)] out LogLevel? logLevel)
        {
            try
            {
                var logLevelTag = lineContent[31..36];
                if (_logLevelMap.TryGetValue(logLevelTag, out var result))
                {
                    logLevel = result;
                    return true;
                }
            }
            catch
            {
                // Ignored.
            }

            logLevel = default;
            return false;
        }

        private static readonly ReadOnlyDictionary<string, LogLevel> _logLevelMap = new(new Dictionary<string, LogLevel>()
        {
            ["[VRB]"] = LogLevel.Trace,
            ["[DBG]"] = LogLevel.Debug,
            ["[INF]"] = LogLevel.Information,
            ["[WRN]"] = LogLevel.Warning,
            ["[ERR]"] = LogLevel.Error,
            ["[FTL]"] = LogLevel.Critical
        });
    }
}