Adds detached support. Closes #1511

DevProxy/ApiControllers/ProxyController.cs

@@ -2,12 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.AspNetCore.Mvc;
+using DevProxy.Abstractions.Proxy;
+using DevProxy.Commands;
 using DevProxy.Jwt;
-using System.Security.Cryptography.X509Certificates;
-using System.ComponentModel.DataAnnotations;
 using DevProxy.Proxy;
-using DevProxy.Abstractions.Proxy;
+using Microsoft.AspNetCore.Mvc;
+using System.ComponentModel.DataAnnotations;
+using System.Security.Cryptography.X509Certificates;
 
 namespace DevProxy.ApiControllers;
 
@@ -137,4 +138,265 @@ public IActionResult GetRootCertificate([FromQuery][Required] string format)
 
         return File(pemBytes, "application/x-x509-ca-cert", "devProxy.pem");
     }
-}
+
+    [HttpGet("logs")]
+    public async Task GetLogsAsync(
+        [FromQuery] int? lines,
+        [FromQuery] bool follow = false,
+        [FromQuery] string? since = null,
+        CancellationToken cancellationToken = default)
+    {
+        // Only available in detached/daemon mode
+        if (!DevProxyCommand.IsInternalDaemon)
+        {
+            Response.StatusCode = StatusCodes.Status404NotFound;
+            await Response.WriteAsync("Logs endpoint is only available in detached mode.", cancellationToken);
+            return;
+        }
+
+        var logFile = DevProxyCommand.DetachedLogFilePath;
+        if (string.IsNullOrEmpty(logFile) || !System.IO.File.Exists(logFile))
+        {
+            Response.StatusCode = StatusCodes.Status404NotFound;
+            await Response.WriteAsync("Log file not found.", cancellationToken);
+            return;
+        }
+
+        var acceptHeader = Request.Headers.Accept.ToString();
+        var useJson = acceptHeader.Contains("application/json", StringComparison.OrdinalIgnoreCase);
+        var useSse = acceptHeader.Contains("text/event-stream", StringComparison.OrdinalIgnoreCase) || follow;
+
+        if (useSse)
+        {
+            Response.ContentType = "text/event-stream";
+            Response.Headers.CacheControl = "no-cache";
+            Response.Headers.Connection = "keep-alive";
+
+            await StreamLogsAsync(logFile, lines ?? 50, since, useJson, cancellationToken);
+        }
+        else
+        {
+            Response.ContentType = useJson ? "application/json" : "text/plain";
+            await WriteLogsAsync(logFile, lines ?? 50, since, useJson, cancellationToken);
+        }
+    }
+
+    private async Task WriteLogsAsync(string logFile, int lineCount, string? since, bool useJson, CancellationToken cancellationToken)
+    {
+        var allLines = await ReadAllLinesAsync(logFile, cancellationToken);
+        var filteredLines = FilterLines(allLines, since).TakeLast(lineCount).ToList();
+
+        if (useJson)
+        {
+            var logEntries = filteredLines.Select(ParseLogLine).ToList();
+            var json = System.Text.Json.JsonSerializer.Serialize(logEntries);
+            await Response.WriteAsync(json, cancellationToken);
+        }
+        else
+        {
+            foreach (var line in filteredLines)
+            {
+                await Response.WriteAsync(line + Environment.NewLine, cancellationToken);
+            }
+        }
+    }
+
+    private async Task StreamLogsAsync(string logFile, int initialLines, string? since, bool useJson, CancellationToken cancellationToken)
+    {
+        // Write initial lines
+        var allLines = await ReadAllLinesAsync(logFile, cancellationToken);
+        var filteredLines = FilterLines(allLines, since).TakeLast(initialLines).ToList();
+
+        foreach (var line in filteredLines)
+        {
+            await WriteSseEventAsync(line, useJson, cancellationToken);
+        }
+
+        // Follow new lines
+        var lastPosition = new FileInfo(logFile).Length;
+
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            await Task.Delay(500, cancellationToken);
+
+            try
+            {
+                using var fs = new FileStream(logFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+                if (fs.Length > lastPosition)
+                {
+                    _ = fs.Seek(lastPosition, SeekOrigin.Begin);
+                    using var reader = new StreamReader(fs);
+
+                    string? line;
+                    while ((line = await reader.ReadLineAsync(cancellationToken)) != null)
+                    {
+                        await WriteSseEventAsync(line, useJson, cancellationToken);
+                    }
+
+                    lastPosition = fs.Length;
+                }
+            }
+            catch (IOException)
+            {
+                // File might be temporarily locked
+            }
+        }
+    }
+
+    private async Task WriteSseEventAsync(string line, bool useJson, CancellationToken cancellationToken)
+    {
+        if (useJson)
+        {
+            var logEntry = ParseLogLine(line);
+            var json = System.Text.Json.JsonSerializer.Serialize(logEntry);
+            await Response.WriteAsync($"event: log\ndata: {json}\n\n", cancellationToken);
+        }
+        else
+        {
+            await Response.WriteAsync($"data: {line}\n\n", cancellationToken);
+        }
+
+        await Response.Body.FlushAsync(cancellationToken);
+    }
+
+    private static IEnumerable<string> FilterLines(IList<string> lines, string? since)
+    {
+        if (string.IsNullOrEmpty(since))
+        {
+            return lines;
+        }
+
+        var sinceTime = ParseSinceOption(since);
+        if (sinceTime == null)
+        {
+            return lines;
+        }
+
+        return lines.Where(line => LineMatchesSince(line, sinceTime.Value));
+    }
+
+    private static DateTime? ParseSinceOption(string? since)
+    {
+        if (string.IsNullOrEmpty(since))
+        {
+            return null;
+        }
+
+        // Try parsing as a duration (e.g., "5m", "1h", "30s")
+        if (since.Length >= 2)
+        {
+            var unit = since[^1];
+            if (int.TryParse(since[..^1], out var value))
+            {
+                return unit switch
+                {
+                    's' => DateTime.Now.AddSeconds(-value),
+                    'm' => DateTime.Now.AddMinutes(-value),
+                    'h' => DateTime.Now.AddHours(-value),
+                    'd' => DateTime.Now.AddDays(-value),
+                    _ => null
+                };
+            }
+        }
+
+        // Try parsing as a datetime
+        if (DateTime.TryParse(since, System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out var dateTime))
+        {
+            return dateTime;
+        }
+
+        return null;
+    }
+
+    private static bool LineMatchesSince(string line, DateTime sinceTime)
+    {
+        // Parse timestamp from line format: [HH:mm:ss.fff] ...
+        if (line.Length < 14 || line[0] != '[' || line[13] != ']')
+        {
+            return true;
+        }
+
+        var timestampStr = line[1..13];
+        if (TimeSpan.TryParseExact(timestampStr, "hh\\:mm\\:ss\\.fff", System.Globalization.CultureInfo.InvariantCulture, out var timeOfDay))
+        {
+            var lineTime = DateTime.Today.Add(timeOfDay);
+            if (lineTime > DateTime.Now)
+            {
+                lineTime = lineTime.AddDays(-1);
+            }
+
+            return lineTime >= sinceTime;
+        }
+
+        return true;
+    }
+
+    private static LogEntryDto ParseLogLine(string line)
+    {
+        // Parse: [HH:mm:ss.fff] level: category: message
+        var entry = new LogEntryDto { Raw = line };
+
+        if (line.Length < 14 || line[0] != '[' || line[13] != ']')
+        {
+            entry.Message = line;
+            return entry;
+        }
+
+        entry.Time = line[1..13];
+
+        if (line.Length < 16)
+        {
+            entry.Message = line;
+            return entry;
+        }
+
+        var rest = line[15..]; // Skip "] "
+        var colonIndex = rest.IndexOf(':', StringComparison.Ordinal);
+        if (colonIndex > 0)
+        {
+            entry.Level = rest[..colonIndex].Trim();
+            rest = rest[(colonIndex + 1)..].TrimStart();
+
+            colonIndex = rest.IndexOf(':', StringComparison.Ordinal);
+            if (colonIndex > 0)
+            {
+                entry.Category = rest[..colonIndex].Trim();
+                entry.Message = rest[(colonIndex + 1)..].TrimStart();
+            }
+            else
+            {
+                entry.Message = rest;
+            }
+        }
+        else
+        {
+            entry.Message = rest;
+        }
+
+        return entry;
+    }
+
+    private sealed class LogEntryDto
+    {
+        public string? Time { get; set; }
+        public string? Level { get; set; }
+        public string? Category { get; set; }
+        public string? Message { get; set; }
+        public string? Raw { get; set; }
+    }
+
+    private static async Task<List<string>> ReadAllLinesAsync(string filePath, CancellationToken cancellationToken)
+    {
+        var lines = new List<string>();
+        using var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+        using var reader = new StreamReader(fs);
+
+        string? line;
+        while ((line = await reader.ReadLineAsync(cancellationToken)) != null)
+        {
+            lines.Add(line);
+        }
+
+        return lines;
+    }
+}