Handle basic HTTP errors

src/http/server.zig

@@ -54,7 +54,7 @@ fn handleConnection(conn: Connection) void {
     var request_buf: [request_buf_size]u8 = undefined;
     var fba = std.heap.FixedBufferAllocator.init(&request_buf);
 
-    const request = try parseRequest(fba.allocator(), conn.stream.reader());
+    const request = parseRequest(fba.allocator(), conn.stream.reader()) catch |err| handleError(conn.stream.writer(), err);
     _ = request;
 }
 
@@ -195,6 +195,21 @@ fn parseEncoding(encoding: ?[]const u8) !Encoding {
     return error.UnsupportedMediaType;
 }
 
+fn handleError(writer: anytype, err: anyerror) !void {
+    const status: http.Status = switch (err) {
+        error.BadRequest => .bad_request,
+        error.MethodNotImplemented => .method_not_implemented,
+        error.UnknownProtocol => .unknown_protocol,
+        error.UnsupportedMediaType => .unsupported_media_type,
+        error.RequestEntityTooLarge => .request_entity_too_large,
+        error.HttpVersionNotSupported => .http_version_not_supported,
+
+        else => err,
+    };
+
+    try writer.print("HTTP/1.1 {} {}\r\n\r\n", .{ @enumToInt(status), status.phrase() });
+}
+
 const _test = struct {
     const expectEqual = std.testing.expectEqual;
     const expectEqualStrings = std.testing.expectEqualStrings;