[api] Split frame helper implementation into protocol-specific files (#9746)

esphome/components/api/api_frame_helper_noise.h

@@ -0,0 +1,70 @@
+#pragma once
+#include "api_frame_helper.h"
+#ifdef USE_API
+#ifdef USE_API_NOISE
+#include "noise/protocol.h"
+#include "api_noise_context.h"
+
+namespace esphome {
+namespace api {
+
+class APINoiseFrameHelper : public APIFrameHelper {
+ public:
+  APINoiseFrameHelper(std::unique_ptr<socket::Socket> socket, std::shared_ptr<APINoiseContext> ctx,
+                      const ClientInfo *client_info)
+      : APIFrameHelper(std::move(socket), client_info), ctx_(std::move(ctx)) {
+    // Noise header structure:
+    // Pos 0: indicator (0x01)
+    // Pos 1-2: encrypted payload size (16-bit big-endian)
+    // Pos 3-6: encrypted type (16-bit) + data_len (16-bit)
+    // Pos 7+: actual payload data
+    frame_header_padding_ = 7;
+  }
+  ~APINoiseFrameHelper() override;
+  APIError init() override;
+  APIError loop() override;
+  APIError read_packet(ReadPacketBuffer *buffer) override;
+  APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) override;
+  APIError write_protobuf_packets(ProtoWriteBuffer buffer, std::span<const PacketInfo> packets) override;
+  // Get the frame header padding required by this protocol
+  uint8_t frame_header_padding() override { return frame_header_padding_; }
+  // Get the frame footer size required by this protocol
+  uint8_t frame_footer_size() override { return frame_footer_size_; }
+
+ protected:
+  APIError state_action_();
+  APIError try_read_frame_(std::vector<uint8_t> *frame);
+  APIError write_frame_(const uint8_t *data, uint16_t len);
+  APIError init_handshake_();
+  APIError check_handshake_finished_();
+  void send_explicit_handshake_reject_(const std::string &reason);
+  APIError handle_handshake_frame_error_(APIError aerr);
+  APIError handle_noise_error_(int err, const char *func_name, APIError api_err);
+
+  // Pointers first (4 bytes each)
+  NoiseHandshakeState *handshake_{nullptr};
+  NoiseCipherState *send_cipher_{nullptr};
+  NoiseCipherState *recv_cipher_{nullptr};
+
+  // Shared pointer (8 bytes on 32-bit = 4 bytes control block pointer + 4 bytes object pointer)
+  std::shared_ptr<APINoiseContext> ctx_;
+
+  // Vector (12 bytes on 32-bit)
+  std::vector<uint8_t> prologue_;
+
+  // NoiseProtocolId (size depends on implementation)
+  NoiseProtocolId nid_;
+
+  // Group small types together
+  // Fixed-size header buffer for noise protocol:
+  // 1 byte for indicator + 2 bytes for message size (16-bit value, not varint)
+  // Note: Maximum message size is UINT16_MAX (65535), with a limit of 128 bytes during handshake phase
+  uint8_t rx_header_buf_[3];
+  uint8_t rx_header_buf_len_ = 0;
+  // 4 bytes total, no padding
+};
+
+}  // namespace api
+}  // namespace esphome
+#endif  // USE_API_NOISE
+#endif  // USE_API