Fix mime type headers

src/HyperSharp/Protocol/HyperSerializers/JsonAsync.cs

@@ -9,7 +9,7 @@ namespace HyperSharp.Protocol
 {
     public static partial class HyperSerializers
     {
-        private static readonly byte[] _jsonEncodingHeader = "Content-Type: application/json; charset=utf-8\r\nContent-Length: "u8.ToArray();
+        private static readonly byte[] _contentTypeJsonEncodingHeader = "Content-Type: application/json; charset=utf-8\r\nContent-Length: "u8.ToArray();
 
         /// <summary>
         /// Serializes the body to the client as JSON using the <see cref="JsonSerializer.SerializeToUtf8Bytes{TValue}(TValue, JsonSerializerOptions?)"/> method with the <see cref="HyperConfiguration.JsonSerializerOptions"/> options.
@@ -24,11 +24,11 @@ public static ValueTask<bool> JsonAsync(HyperContext context, HyperStatus status
             ArgumentNullException.ThrowIfNull(status);
 
             // Write Content-Type header and beginning of Content-Length header
-            context.Connection.StreamWriter.Write<byte>(_jsonEncodingHeader);
+            context.Connection.StreamWriter.Write<byte>(_contentTypeJsonEncodingHeader);
             byte[] body = JsonSerializer.SerializeToUtf8Bytes(status.Body, context.Connection.Server.Configuration.JsonSerializerOptions);
 
             // Finish the Content-Length header
-            context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes(body.Length.ToString())); // TODO: This could probably be done without allocating a string
+            context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes(body.Length.ToString()));
             context.Connection.StreamWriter.Write<byte>(_newLine);
 
             // Write body

src/HyperSharp/Protocol/HyperSerializers/MimeTypeMapper.cs

@@ -0,0 +1,149 @@
+using System;
+using System.Collections.Generic;
+#if NET8_0_OR_GREATER
+using System.Collections.Frozen;
+#else
+using System.Collections.Immutable;
+#endif
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.Toolkit.HighPerformance;
+
+namespace HyperSharp.Protocol
+{
+    /// <summary>
+    /// Holds a collection of static methods implementing <see cref="HyperSerializerDelegate"/> for the most common of Content-Types.
+    /// </summary>
+    public static partial class HyperSerializers
+    {
+        private static readonly IReadOnlyDictionary<string, IReadOnlyList<string>> _mimeTypes;
+        private static readonly IReadOnlyDictionary<string, Lazy<HyperSerializerDelegate>> _mimeTypeSerializers;
+        private static readonly IReadOnlyDictionary<string, Lazy<HyperSerializerDelegate>> _fileExtensionSerializers;
+
+        static HyperSerializers()
+        {
+            string? mimeFile = null;
+            if (Path.Exists("/etc/mime.types"))
+            {
+                mimeFile = "/etc/mime.types";
+            }
+            else
+            {
+                string? home = Environment.GetEnvironmentVariable(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "HOMEPATH" : "HOME");
+                if (!string.IsNullOrWhiteSpace(home) && Path.Exists(Path.Combine(home, ".mime.types")))
+                {
+                    mimeFile = Path.Combine(home, ".mime.types");
+                }
+            }
+
+            Dictionary<string, List<string>> mimeTypes = new(StringComparer.OrdinalIgnoreCase)
+            {
+                { "application/json", new List<string>() { "json" } },
+                { "text/plain", new List<string>() { "txt" } },
+            };
+
+            Dictionary<string, Lazy<HyperSerializerDelegate>> mimeTypeSerializers = new(StringComparer.OrdinalIgnoreCase)
+            {
+                { "application/json", new Lazy<HyperSerializerDelegate>(JsonAsync) },
+                { "text/plain", new Lazy<HyperSerializerDelegate>(PlainTextAsync) },
+            };
+
+            Dictionary<string, Lazy<HyperSerializerDelegate>> fileExtensionSerializers = new(StringComparer.OrdinalIgnoreCase)
+            {
+                { "json", new Lazy<HyperSerializerDelegate>(JsonAsync) },
+                { "txt", new Lazy<HyperSerializerDelegate>(PlainTextAsync) },
+            };
+
+            if (!string.IsNullOrWhiteSpace(mimeFile))
+            {
+                FileStream fileStream = File.OpenRead(mimeFile);
+                StreamReader streamReader = new(fileStream);
+
+                string? line;
+                while ((line = streamReader.ReadLine()) is not null)
+                {
+                    if (line.StartsWith('#') || string.IsNullOrWhiteSpace(line))
+                    {
+                        continue;
+                    }
+
+                    string[] parts = line.Replace('\t', ' ').Split(' ', StringSplitOptions.RemoveEmptyEntries);
+                    string mimeType = parts[0];
+                    Lazy<HyperSerializerDelegate> serializer = new(() => (context, status, cancellationToken) =>
+                    {
+                        ArgumentNullException.ThrowIfNull(context);
+                        ArgumentNullException.ThrowIfNull(status);
+
+                        // Write Content-Type header and beginning of Content-Length header
+                        context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes($"Content-Type: {mimeType}\r\nContent-Length: "));
+
+                        byte[] body = Encoding.UTF8.GetBytes(status.Body?.ToString() ?? "");
+
+                        // Write Content-Length header
+                        context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes(body.Length.ToString()));
+                        context.Connection.StreamWriter.Write<byte>(_newLine);
+
+                        // Write body
+                        context.Connection.StreamWriter.Write<byte>(_newLine);
+                        context.Connection.StreamWriter.Write<byte>(body);
+
+                        return ValueTask.FromResult(true);
+                    });
+
+                    mimeTypeSerializers[mimeType] = serializer;
+
+                    List<string> fileExtensions = mimeTypes.TryGetValue(mimeType, out List<string>? extensions) ? extensions : new List<string>();
+                    foreach (string fileExtension in parts[1..])
+                    {
+                        fileExtensionSerializers[fileExtension] = serializer;
+                        fileExtensions.Add(fileExtension);
+                    }
+                }
+            }
+
+#if NET8_0_OR_GREATER
+            _fileExtensionSerializers = fileExtensionSerializers.ToFrozenDictionary();
+            _mimeTypeSerializers = mimeTypeSerializers.ToFrozenDictionary();
+#else
+            _fileExtensionSerializers = fileExtensionSerializers.ToImmutableDictionary();
+            _mimeTypeSerializers = mimeTypeSerializers.ToImmutableDictionary();
+#endif
+        }
+
+        /// <summary>
+        /// Gets the <see cref="HyperSerializerDelegate"/> for the specified MIME type.
+        /// </summary>
+        /// <param name="mimeType">The MIME type to get the <see cref="HyperSerializerDelegate"/> for.</param>
+        /// <param name="context">The <see cref="HyperContext"/> to get the <see cref="HyperSerializerDelegate"/> for.</param>
+        /// <returns>The <see cref="HyperSerializerDelegate"/> for the specified MIME type. Defaults to <see cref="PlainTextAsync"/> if the MIME type is not found.</returns>
+        public static HyperSerializerDelegate GetSerializerFromMimeType(string mimeType, HyperContext? context = null)
+        {
+            if (context is not null && context.Headers.TryGetValues("Accept", out List<string>? accept) && !accept.Contains(mimeType) && mimeType.StartsWith("text", StringComparison.OrdinalIgnoreCase))
+            {
+                mimeType = "text/html";
+            }
+
+            return _mimeTypeSerializers.TryGetValue(mimeType, out Lazy<HyperSerializerDelegate>? serializer) ? serializer.Value : PlainTextAsync;
+        }
+
+        /// <summary>
+        /// Gets the <see cref="HyperSerializerDelegate"/> associated with the specified file extension.
+        /// </summary>
+        /// <param name="fileExtension">The file extension to get the <see cref="HyperSerializerDelegate"/> for.</param>
+        /// <returns>The <see cref="HyperSerializerDelegate"/> for the specified file extension. Defaults to <see cref="PlainTextAsync"/> if the file extension is not found.</returns>
+        public static HyperSerializerDelegate GetSerializerFromFileExtension(string fileExtension) => _fileExtensionSerializers.TryGetValue(fileExtension, out Lazy<HyperSerializerDelegate>? serializer)
+            ? serializer.Value
+            : PlainTextAsync;
+
+        public static string GetMimeTypeFromFileExtension(string fileExtension) => _fileExtensionSerializers.TryGetValue(fileExtension, out Lazy<HyperSerializerDelegate>? serializer)
+            ? serializer.Value.Method.Name switch
+            {
+                nameof(JsonAsync) => "application/json",
+                nameof(PlainTextAsync) => "text/plain",
+                _ => "text/html",
+            }
+            : "text/html";
+    }
+}

src/HyperSharp/Protocol/HyperSerializers/PlainTextAsync.cs

@@ -12,7 +12,7 @@ namespace HyperSharp.Protocol
     public static partial class HyperSerializers
     {
         private static readonly byte[] _newLine = "\r\n"u8.ToArray();
-        private static readonly byte[] _contentTypeJsonEncodingHeader = "Content-Type: application/json; charset=utf-8\r\nContent-Length: "u8.ToArray();
+        private static readonly byte[] _contentTypeTextEncodingHeader = "Content-Type: text/plain; charset=utf-8\r\nContent-Length: "u8.ToArray();
 
         /// <summary>
         /// Serializes the body to the client as plain text using the <see cref="object.ToString"/> method with the <see cref="Encoding.UTF8"/> encoding.
@@ -24,12 +24,12 @@ public static ValueTask<bool> PlainTextAsync(HyperContext context, HyperStatus s
             ArgumentNullException.ThrowIfNull(status);
 
             // Write Content-Type header and beginning of Content-Length header
-            context.Connection.StreamWriter.Write<byte>(_contentTypeJsonEncodingHeader);
+            context.Connection.StreamWriter.Write<byte>(_contentTypeTextEncodingHeader);
 
             byte[] body = Encoding.UTF8.GetBytes(status.Body?.ToString() ?? "");
 
             // Write Content-Length header
-            context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes(body.Length.ToString())); // TODO: This could probably be done without allocating a string
+            context.Connection.StreamWriter.Write<byte>(Encoding.ASCII.GetBytes(body.Length.ToString()));
             context.Connection.StreamWriter.Write<byte>(_newLine);
 
             // Write body