path: root/controller/libs/midi_ci.c

// An implementation of the MIDI Capability Inquiry v1.2 Specification, over a MIDI 1.0 transport,
// with only Property Exchange support.
// Intended to be read alongside the corresponding specs; specifically in the order:
//   - MIDI CI Specification, minimum requirements + Property Exchange chapter,
//   - Common Rules for MIDI CI Property Exchange.

#define DISABLE true
#ifndef DISABLE
#include "base_midi.h"
#include "parson.h"

uint32_t our_muid = rand(); // TODO: think.
uint8_t request_id = 0;

#define MIDI_CI_SUBID 0x0d
#define PROFILE_CONFIGURATION_MASK 0x20
#define PROPERTY_EXCHANGE_MASK 0x30
#define PROCESS_INQUIRY_MASK 0x40
#define MANAGEMENT_MASK 0x70
#define MIDI_CI_VERSION 0x02
#define TO_FUNCTION_BLOCK_ID 0x7f
static void ci(uint8_t source_target, uint8_t message_type, uint32_t destination_miud,
	       uint8_t *contents, size_t contents_len) {
  uint8_t *new = malloc(1 + 4 + 4 + contents_len);
  new[0] = MIDI_CI_VERSION;
  new[1] =  our_muid	       & 0x00'00'00'ff;
  new[2] = (our_muid	>>  8) & 0x00'00'00'ff;
  new[3] = (our_muid	>> 16) & 0x00'00'00'ff;
  new[4] = (our_muid	>> 24) & 0x00'00'00'ff;
  new[8] =  target_muid	       & 0x00'00'00'ff;
  new[7] = (target_muid >>  8) & 0x00'00'00'ff;
  new[6] = (target_muid >> 16) & 0x00'00'00'ff;
  new[5] = (target_muid >> 24) & 0x00'00'00'ff;
  memcpy(new + 9, contents, contents_len);

  universal_nonrealtime(source_target, (MIDI_CI_SUBID << 8) | message_type, contents, 1 + 4 + 4 + contents_len);

  free(new);

}

#define DISCOVERY_SUBID (MANAGEMENT_MASK | 0x00)
#define CI_CATEGORY_SUPPORTED 0b00011100
#define MAX_SYSEX_SIZE 512
#define BROADCAST_MUID 0x7f'7f'7f'7f
#define SINGLE_OUTPUT_PATH 0x00
void discovery() {
  uint8_t *new = malloc(3 + 2 + 2 + 4 + 1 + 4 + 1);
#if (DEVICE_MANUFACTURER <= MAX_DATA_BYTE)
  new[0]  = DEVICE_MANUFACTURER;
  new[1]  = 0;
  new[2]  = 0;
#else
  new[0]  = 0;
  new[1]  = DEVICE_MANUFACTURER >> 8;
  new[2]  = DEVICE_MANUFACTURER	       & 0x00ff;
#endif
  new[3]  = DEVICE_FAMILY	       & 0x00ff;
  new[4]  = DEVICE_FAMILY	>> 8;
  new[5]  = DEVICE_MODEL	       & 0x00ff;
  new[6]  = DEVICE_MODEL	>> 8;
  new[7]  = SOFTWARE_REVISION	       & 0x00'00'00'ff;
  new[8]  = (SOFTWARE_REVISION	>> 8)  & 0x00'00'00'ff;
  new[9]  = (SOFTWARE_REVISION	>> 16) & 0x00'00'00'ff;
  new[10] = (SOFTWARE_REVISION	>> 24) & 0x00'00'00'ff;
  new[11] = CI_CATEGORY_SUPPORTED;
  new[12] = MAX_SYSEX_SIZE	       & 0x00'00'00'ff;
  new[13] = (MAX_SYSEX_SIZE	>> 8)  & 0x00'00'00'ff;
  new[14] = (MAX_SYSEX_SIZE	>> 16) & 0x00'00'00'ff;
  new[15] = (MAX_SYSEX_SIZE	>> 24) & 0x00'00'00'ff;
  new[16] = SINGLE_OUTPUT_PATH;

  ci(TO_FUNCTION_BLOCK_ID, DISCOVERY_SUBID, BROADCAST_MUID, new, 17);

  free(new);
}

#define REPLY_TO_DISCOVERY_SUBID 0x71
#define NO_FUNCTION_BLOCK 0x7f
void discovery_reply(uint8_t initiator_muid, uint8_t initiator_output_path_id) {
  uint8_t *new = malloc(3 + 2 + 2 + 4 + 1 + 4 + 1 + 1);
#if (DEVICE_MANUFACTURER <= MAX_DATA_BYTE)
  new[0]  = DEVICE_MANUFACTURER;
  new[1]  = 0;
  new[2]  = 0;
#else
  new[0]  = 0;
  new[1]  = DEVICE_MANUFACTURER >> 8;
  new[2]  = DEVICE_MANUFACTURER	       & 0x00ff;
#endif
  new[3]  = DEVICE_FAMILY	       & 0x00ff;
  new[4]  = DEVICE_FAMILY	>> 8;
  new[5]  = DEVICE_MODEL	       & 0x00ff;
  new[6]  = DEVICE_MODEL	>> 8;
  new[7]  = SOFTWARE_REVISION	       & 0x00'00'00'ff;
  new[8]  = (SOFTWARE_REVISION	>> 8)  & 0x00'00'00'ff;
  new[9]  = (SOFTWARE_REVISION	>> 16) & 0x00'00'00'ff;
  new[10] = (SOFTWARE_REVISION	>> 24) & 0x00'00'00'ff;
  new[11] = CI_CATEGORY_SUPPORTED;
  new[12] = MAX_SYSEX_SIZE	       & 0x00'00'00'ff;
  new[13] = (MAX_SYSEX_SIZE	>> 8)  & 0x00'00'00'ff;
  new[14] = (MAX_SYSEX_SIZE	>> 16) & 0x00'00'00'ff;
  new[15] = (MAX_SYSEX_SIZE	>> 24) & 0x00'00'00'ff;
  new[16] = initiator_output_path_id;
  new[17] = NO_FUNCTION_BLOCK;

  ci(TO_FUNCTION_BLOCK_ID, REPLY_TO_DISCOVERY_SUBID, initiator_muid, new, 18);

  free(new);

}

// TODO: should we set a new MUID inside this function?
#define INVALIDATE_MUID_SUBID 0x7e
void invalidate_muid(uint8_t muid) {
  uint8_t *new = malloc(4);
  new[0] = muid	    & 0x00'00'00'ff;
  new[1] = (muid >> 8)  & 0x00'00'00'ff;
  new[2] = (muid >> 16) & 0x00'00'00'ff;
  new[3] = (muid >> 24) & 0x00'00'00'ff;

  ci(TO_FUNCTION_BLOCK_ID, BROADCAST_MUID, new, 4);

  free(new);

}

static inline void invalidate_our_muid() {
  invalidate_muid(our_muid);
}

// TODO: consider structifying?
#define ACK_SUBID 0x7d
void ci_ack(uint8_t acking_device_id, uint8_t acking_muid, uint8_t original_classification, uint8_t status_code,
	    uint8_t status_data,
	    uint8_t details1, uint8_t details2, uint8_t details3, uint8_t details4, uint8_t details5,
	    uint16_t length, uint8_t *text) {
  uint8_t *new = malloc(1 + 1 + 1 + 5 + 2 + length);
  new[0] = original_classification;
  new[1] = status_code;
  new[2] = status_data;
  new[3] = details1;
  new[4] = details2;
  new[5] = details3;
  new[6] = details4;
  new[7] = details5;
  new[8] = length & 0x00ff;
  new[9] = length >> 8;
  memcpy(new + 10, text, length);

  ci(acking_device_id, ACK_SUBID, acking_muid, new, 1 + 1 + 1 + 5 + 2 + length);

  free(new);

}


#define NAK_SUBID 0x7f
void ci_nack(uint8_t naking_device_id, uint8_t naking_muid, uint8_t original_classification, uint8_t status_code,
	     uint8_t status_data,
	     uint8_t details1, uint8_t details2, uint8_t details3, uint8_t details4, uint8_t details5,
	     uint16_t length, uint8_t *text) {
  uint8_t *new = malloc(1 + 1 + 1 + 5 + 2 + length);
  new[0] = original_classification;
  new[1] = status_code;
  new[2] = status_data;
  new[3] = details1;
  new[4] = details2;
  new[5] = details3;
  new[6] = details4;
  new[7] = details5;
  new[8] = length & 0x00ff;
  new[9] = length >> 8;
  memcpy(new + 10, text, length);

  ci(naking_device_id, NAK_SUBID, naking_muid, new, 1 + 1 + 1 + 5 + 2 + length);

  free(new);

}

#define WHOLE_FUNCTION_BLOCK_ID 0x0f
#define PROPERTY_EXCHANGE_MAJOR_VERSION 0x00
#define PROPERTY_EXCHANGE_MINOR_VERSION 0x00
#define SIMULTANEOUS_REQUESTS 0x01
#define INQUIRE_EXCHANGE_CAPABILITIES_SUBID 0x30
void inquire_property_exchange_capabilities(uint8_t destination_muid) {
  uint8_t *new = malloc(3);
  new[0] = SIMULTANEOUS_REQUESTS;
  new[1] = PROPERTY_EXCHANGE_MAJOR_VERSION;
  new[2] = PROPERTY_EXCHANGE_MINOR_VERSION;

  ci(WHOLE_FUNCTION_BLOCK_ID, INQUIRE_EXCHANGE_CAPABILITIES_SUBID, destination_muid, new, 3);

  free(new);

}

#define REPLY_EXCHANGE_CAPABILITIES_SUBID 0x31
void reply_proprty_exchange_capabilities (uint8_t initiator_muid) {
  uint8_t *new = malloc(3);
  new[0] = SIMULTANEOUS_REQUESTS;
  new[1] = PROPERTY_EXCHANGE_MAJOR_VERSION;
  new[2] = PROPERTY_EXCHANGE_MINOR_VERSION;

  ci(WHOLE_FUNCTION_BLOCK_ID, REPLY_EXCHANGE_CAPABILITIES_SUBID, initiator_muid, new, 3);

  free(new);

}

// TODO: complain; standard doesn't specify what goes into the "Max SysEx size." E.g. do I include the EOX?
#define CI_MESSAGE_NONVARIABLE_SIZE (1 + 1 + 1 + 1 + 1 + 1 + 4 + 4 + 1 + 2  +  2 + 2 + 2  +  1)
#define min(X, Y)  ((X) < (Y) ? (X) : (Y))
static void chunked_property_exchange_send(uint32_t receiver_max_sysex, uint8_t message_subid, uint32_t destination_muid,
					   uint8_t request_id, uint8_t *header_data, uint16_t header_len,
					   uint8_t *property_data, uint16_t property_len) {
  uint32_t total_len = CI_MESSAGE_NONVARIABLE_SIZE + header_len + property_len;
  uint32_t leftover_bytes = total_len % receiver_max_sysex;
  uint32_t chunk_count =  total_len / receiver_max_sysex + (leftover_bytes == 0 ? 0 : 1);
  uint32_t leftover_property_bytes = leftover_bytes - CI_MESSAGE_NONVARIABLE_SIZE;
  uint32_t max_per_message_property_bytes = receiver_max_sysex - CI_MESSAGE_NONVARIABLE_SIZE;

  uint8_t *new = malloc(3 + header_len + 6 + max_per_message_property_bytes);
  new[0] = request_id;
  new[1] = header_len & 0x00ff;
  new[2] = header_len >> 8;
  memcpy(new + 3, header_data, header_len);

  for (uint32_t chunk = 1; chunk < chunk_count, i++) {
    new[3 + header_len]	    = chunk_count		     & 0x00ff;
    new[3 + header_len + 1] = chunk_count		     >> 8;
    new[3 + header_len + 2] = chunk			     & 0x00ff;
    new[3 + header_len + 3] = chunk			     >> 8;
    new[3 + header_len + 4] = max_per_message_property_bytes & 0x00ff;
    new[3 + header_len + 5] = max_per_message_property_bytes >> 8;

    memcpy(3 + header_len + 6, property_data + (chunk - 1) * max_per_message_property_bytes, max_per_message_property_bytes);

    ci(WHOLE_FUNCTION_BLOCK_ID, message_subid, destination_muid, new, 3 + header_len + 6 + max_per_message_property_bytes);

  }

  if (leftover_property_bytes != 0) {
    new[3 + header_len]	    = chunk_count	      & 0x00ff;
    new[3 + header_len + 1] = chunk_count	      >> 8;
    new[3 + header_len + 2] = chunk		      & 0x00ff;
    new[3 + header_len + 3] = chunk		      >> 8;
    new[3 + header_len + 4] = leftover_property_bytes & 0x00ff;
    new[3 + header_len + 5] = leftover_property_bytes >> 8;

    memcpy(3 + header_len + 6, property_data + (chunk_count - 1) * max_per_message_property_bytes, leftover_property_bytes);

    ci(WHOLE_FUNCTION_BLOCK_ID, message_subid, destination_muid, new, 3 + header_len + 6 + leftover_property_bytes);

  }


  free(new);

}

#define INQUIRE_GET_SUBID 0x34
void inquiry_get_property(uint32_t destination_muid, uint8_t request_id, uint8_t *header_data, uint16_t header_len) {
  uint8_t *new = malloc(3 + header_len + 3);
  new[0] = request_id;
  new[1] = header_len & 0x00ff;
  new[2] = header_len >> 8;

  memcpy(new + 3, header_data, header_len);

  // Chunk count.
  new[3 + header_len]	  = 0x01;
  new[3 + header_len + 1] = 0x00;
  // Current chunk number.
  new[3 + header_len + 2] = 0x01;
  new[3 + header_len + 3] = 0x00;
  // Property length.
  new[3 + header_len + 4] = 0x00;
  new[3 + header_len + 5] = 0x00;

  ci(WHOLE_FUNCTION_BLOCK_ID, INQUIRE_GET_SUBID, destination_muid, new, 3 + header_len + 6);

  free(new);
}

#define REPLY_GET_SUBID 0x35
void reply_get_property(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
			uint16_t header_len, uint8_t *property_data, uint16_t property_len) {


  chunked_property_exchange_send(receiver_max_sysex, REPLY_GET_SUBID, destination_muid, request_id, header_data,
				 header_len, property_data, property_len);

}

#define INQURIE_SET_SUBID 0x36
void inquiry_set_property(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
			  uint16_t header_len, uint8_t *property_data, uint16_t property_len) {

  chunked_property_exchange_send(receiver_max_sysex, INQUIRE_GET_SUBID, destination_muid, request_id,
				 header_data, header_len, property_data, property_len)

}

#define REPLY_SET_SUBID 0x37
void reply_set_property(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
			uint16_t header_len, uint8_t *property_data, uint16_t property_len) {


  chunked_property_exchange_send(receiver_max_sysex, REPLY_SET_SUBID, destination_muid, request_id,
				 header_data, header_len, property_data, property_len);

}

#define SUBSCRIPTION_SUBID 0x38
void subscription(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
		  uint16_t header_len, uint8_t *property_data, uint16_t property_len) {

  chunked_property_exchange_send(receiver_max_sysex, SUBSCRIPTION_SUBID, destination_muid, request_id,
				 header_data, header_len, property_data, property_len);

}

#define REPLY_SUBSCRIPTION_SUBID 0x39
void reply_subscription(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
			uint16_t header_len, uint8_t *property_data, uint16_t property_len) {

  chunked_property_exchange_send(receiver_max_sysex, REPLY_SUBSCRIPTION_SUBID, destination_muid, request_id,
				 header_data, header_len, property_data, property_len);

}

#define NOTIFY_SUBID 0x3f
void notify(uint32_t receiver_max_sysex, uint32_t destination_muid, uint8_t request_id, uint8_t *header_data,
	    uint16_t header_len, uint8_t *property_data, uint16_t property_len) {

  chunked_property_exchange_send(receiver_max_sysex, NOTIFY_SUBID, destination_muid, request_id,
				 header_data, header_len, property_data, property_len);

}


// Parsing.

typedef enum {
  DEVICE_ID,
  SUBID,
  VERSION,
  SOURCE,
  DESTINATION,
  // Discovery.
  MANUFACTURER,
  FAMILY,
  MODEL,
  REVISION,
  CI_CATEGORY,
  MAX_SYSEX,
  INITIATOR_OUTPUT_PATH,
  // Invalidate.
  TARGET_MUID,
  // Ack.
  ACK_ORIG_SUBID,
  ACK_CODE,
  ACK_DATA,
  ACK_DETAILS,
  ACK_TEXT_LENGTH,
  ACK_TEXT,
  // Nak.
  NAK_ORIG_SUBID,
  NAK_CODE,
  NAK_DATA,
  NAK_DETAILS,
  NAK_LENGTH,
  NAK_TEXT,
  // Property Exchange Capabilites.
  MAX_SIMUL_EXCHANGE,
  EXCHANGE_MAJOR_VER,
  EXCHANGE_MINOR_VER,
  // Property Exchange messages.
  REQUEST_ID,
  HEADER_LEN,
  HEADER_DATA,
  CHUNK_COUNT,
  THIS_CHUNK,
  PROPERTY_LEN,
  PROPERTY_DATA

} ParseState;


const JSON_String supported_resources[] = {
  {"ResourceList"},
  {"DeviceInfo"},
  {"ChannelList"},
  {"X-KeyLayout"},
  /* {"X-"} */
};

typedef struct {
  uint8_t *stack;
  size_t top;
  size_t size;
  size_t field_position;
  ParseState state;
} CIParser;

extern CIParser ci_memory;

static inline void next_in_field() {
  ++ci_memory.field_position;
}

static inline void new_field(ParseState to) {
  ci_memory.field_position = 0;
  ci_memory.state = to;
}

static inline void push_fn(uint8_t val) {
  if (ci_memory.top == ci_memory.size - 1) {
    ci_memory.stack = realloc(ci_memory.stack, ci_memory.size + 128);
  }

  ci_memory.stack[ci_memory.top + 1] = val;
  ++ci_memory.top;
}

#define push() do {				\
    push_fn(byte);				\
  } while(0)


static inline void reset() {
  ci_memory.stack = realloc(ci_memory.stack, 128);
  ci_memory.size = 128;
  ci_memory.top = 0;
  ci_memory.status = WAITING_FOR_STATUS;
}

static inline uint8_t device_id() {
  return ci_memory.stack[0];
}

static inline uint8_t command_id() {
  return ci_memory.stack[1];
}

static inline uint32_t lsb_32bit_from(size_t start_index) {
  return (ci_memory.stack[start_index + 3] << 24) | (ci_memory.stack[start_index + 2] << 16) \
    | (ci_memory.stack[start_index + 1] << 8) | (ci_memory.stack[start_index]);
}
static inline uint32_t source_muid() {
  return lsb_32bit_from(2);
}

static inline uint32_t dest_muid() {
  return lsb_32bit_from(6);
}

#define STACK_FIRST_NONCOMMON_IDX 10

#define push_until(val, then_block) do {	\
    switch(ci_memory.field_position) {		\
    case 0 ... (val - 1):			\
      push();					\
      next_in_field();				\
      return true;				\
    case val:					\
      then_block				\
    }						\
  } while(0)

#define push_whole_field(val, new) do {		\
    switch(ci_memory.field_position) {		\
    case 0 ... (val - 1):			\
      push();					\
      next_in_field();				\
      return true;				\
    case val:					\
      push();					\
      new_field(new);				\
      return true;				\
    }						\
  } while(0)


typedef struct {
  void (*ack_handler)(uint8_t, uint8_t, uint8_t, uint32_t, uint8_t, uint16_t, char*);
  void (*nak_handler)(uint8_t, uint8_t, uint8_t, uint32_t, uint8_t, uint16_t, char*);
} CIConsumerBehavior;

extern CIConsumerBehavior ci_pfns;

// The user's `universal_system_exclusive_handler` should feed everything into this, device-ID down,
// once it recognizes a MIDI-CI message.
bool midi_ci_parse(uint8_t byte) {
  switch (ci_memory.state) {
  case DEVICE_ID:
    push();
    new_field(SUBID);
    return true;
  case SUBID:
    switch (ci_memory.field_position) {
    case 0:
#ifdef DEBUG
      if (byte != 0x0d) {
	while(true); // Non-MIDI-CI Universal SysEx Sub ID 1.
      }
#endif
      next_in_field();
      return true;
    case 1:
      push()
      new_field(VERSION);
      return true;
    }
  case VERSION:
#ifdef DEBUGp
    if (byte > 0x01) {
      while(true); // Unsupported future MIDI-CI Message Version/Format.
    }
#endif
    new_field(SOURCE);
    return true;
  case SOURCE:
    push_whole_field(4, DESTINATION);
  case DESTINATION:
    push_until(4, {
      push();
      switch (command_id()) {
      case DISCOVERY_SUBID:
	new_field(MANUFACTURER);
	return true;
      case REPLY_TO_DISCOVERY_SUBID:
	new_field(MANUFACTURER);
	return true;
      case INVALIDATE_MUID_SUBID:
	new_field(TARGET_MUID);
	return true;
      case ACK_SUBID:
	new_field(ACK_ORIG_SUBID);
	return true;
      case NAK_SUBID:
	new_field(NAK_ORIG_SUBID);
	return true;
      case INQUIRE_EXCHANGE_CAPABILITIES_SUBID:
	new_field(MAX_SIMUL_EXCHANGE);
	return true;
      case REPLY_EXCHANGE_CAPABILITIES_SUBID:
	new_field(MAX_SIMUL_EXCHANGE);
	return true;
      case INQUIRE_GET_SUBID:
      case REPLY_GET_SUBID:
      case INQUIRE_SET_SUBID:
      case REPLY_SET_SUBID:
      case SUBSCRIPTION_SUBID:
      case REPLY_SUBSCRIPTION_SUBID:
      case NOTIFY_SUBID:
	new_field(REQUEST_ID);
	return true;
      default:
#ifdef DEBUG
      while(true); //  Unsupported MIDI-CI command.
#endif
      return false;
      }});

  // Discovery messages.
  case MANUFACTURER:
    push_whole_field(3, FAMILY);
  case FAMILY:
    push_whole_field(2, MODEL);
  case REVISION:
    push_whole_field(4, CI_SUPPORTED);
  case CI_SUPPORTED:
    push_whole_field(1, MAX_SYSEX);
  case MAX_SYSEX:
    push_whole_field(4, INITIATOR_OUTPUT_PATH);
  case INITIATOR_OUTPUT_PATH:
    switch (command_id()) {
    case DISCOVERY_SUBID:
      if (source_muid() == our_muid) {
	invalidate_our_muid();
	our_muid = rand(); // TODO: user function for new MUID?
	discovery();
	reset();
	return false;
      }
      discovery_reply(source_muid(), byte);
      reset();
      return false;
    case DISCOVERY_REPLY_SUBID:
      if (already_seen(source_muid())) { // TODO: already_seen and associated logging.
	invalidate_muid(source_muid());
	discovery();
	reset();
	return false;
      }
    default:
#ifdef DEBUG
      while(true); // Unexpected non-Discovery command id.
#endif
      reset();
      return false;
    }
 // Invalidate.
  case TARGET_MUID:
    push_until(4, {
	uint32_t to_invalidate = lsb_32bit_from(STACK_FIRST_NONCOMMON_IDX);
	if (to_invalidate == our_muid) {
	  our_muid = rand();
	  discovery();
	} else if (already_seen(to_invalidate)) {
	  invalidate_stored_data(to_invalidate); // TODO: to_invalidate; see above.

	}
	reset();
	return false;
      });
  // ACK.
  case ACK_ORIG_SUBID:
    push_whole_field(1, ACK_CODE);
  case ACK_CODE:
    push_whole_field(1, ACK_DATA);
  case ACK_DATA:
    push_whole_field(1, ACK_DETAILS);
  case ACK_DETAILS:
    push_whole_field(5, ACK_TEXT_LENGTH);
  case ACK_TEXT_LENGTH:
    push_whole_field(2, ACK_TEXT);
  case ACK_TEXT:
    push_until((ci_memory.stack[ci_memory.top - 1] << 8) | ci_memory.stack[ci_memory.top], {
	// TODO:
      });
    reset();
    return false;
  // NAK.
  case NAK_ORIG_SUBID:
    push_whole_field(1, ACK_CODE);
  case NAK_CODE:
    push_whole_field(1, ACK_DATA);
  case NAK_DATA:
    push_whole_field(1, ACK_DETAILS);
  case NAK_DETAILS:
    push_whole_field(5, ACK_TEXT_LENGTH);
  case NAK_LENGTH:
    push_whole_field(2, ACK_TEXT);
  case NAK_TEXT:
    push_until((ci_memory.stack[ci_memory.top - 1] << 8) | ci_memory.stack[ci_memory.top], {
	// TODO:
      });
    reset();
    return false;

  // TODO: Property Exchange Capabilites
  // Property Exchange.
  case REQUEST_ID:
    push_whole_field(1, HEADER_LEN);
  case HEADER_LEN:
    push_whole_field(2, HEADER_DATA);
  case HEADER_DATA:
    push_until((ci_memory.stack[ci_memory.top - 1] << 8) | ci_memory.stack[ci_memory.top], {
	// TODO:
      });
  case CHUNK_COUNT:
    push_whole_field(2, THIS_CHUNK);
  case THIS_CHUNK:
    push_whole_field(2, PROPERTY_LEN);
  case PROPERTY_LEN:
    push_whole_field(2, PROPERTY_DATA);
  case PROPERTY_DATA:
    push_until((ci_memory.stack[ci_memory.top - 1] << 8) | ci_memory.stack[ci_memory.top], {
	JSON_Value *header = json_parse_string(ci_memory.stack + \
					       (ci_memory.stack[ci_memory.top - 1] << 8) | ci_memory.stack[ci_memory.top]);
	switch (command_id()) {
	case INQUIRE_GET_SUBID:
#ifdef DEBUG
	  if (header->type != JSONObject) {
	    while(true); // Non-object JSON Value.
	  }
#endif

	  // TODO: the spec kinda sucks, ngl. I'll get MIDI 1.0, and then return here.
	case REPLY_GET_SUBID:
	case INQUIRE_SET_SUBID:
	case REPLY_SET_SUBID:
	case SUBSCRIPTION_SUBID:
	case REPLY_SUBSCRIPTION_SUBID:
	case NOTIFY_SUBID:
	}
      });
  }
}
#endif