// SPDX-License-Identifier: BSD-3-Clause OR Apache-2.0
#include "bundle7/parser.h"
#include "bundle7/timestamp.h"

#include "ud3tn/common.h"

#include "compilersupport_p.h" // Private TinyCBOR header, used for endianness

#include <stdint.h>
#include <stdlib.h>

/**
 * Shortcut access to current bundle block
 */
#define BLOCK(state) ((*((state)->current_block_entry))->data)


/**
 * Shortcut to transition into error state
 */
#define FAIL(state) ((state)->basedata->status = PARSER_STATUS_ERROR)


// -----------------------------
// Cyclic Redundancy Check (CRC)
// -----------------------------

static void crc_verify(struct bundle7_parser *state, uint32_t checksum,
	uint32_t expected)
{
	if (checksum != expected)
		state->basedata->flags |= PARSER_FLAG_CRC_INVALID;
}


// --------------------
// Bundle start and end
// --------------------

static CborError bundle_start(struct bundle7_parser *, CborValue *);
static CborError bundle_end(struct bundle7_parser *, CborValue *);


// -------------
// Primary block
// -------------

static CborError primary_block_start(struct bundle7_parser *, CborValue *);
static CborError protocol_version(struct bundle7_parser *, CborValue *);
static CborError primary_proc_flags(struct bundle7_parser *, CborValue *);
static CborError crc_type_field(struct bundle7_parser *, CborValue *);
static CborError destination_eid(struct bundle7_parser *, CborValue *);
static CborError source_eid(struct bundle7_parser *, CborValue *);
static CborError report_to_eid(struct bundle7_parser *, CborValue *);
static CborError creation_timestamp(struct bundle7_parser *, CborValue *);
static CborError lifetime(struct bundle7_parser *, CborValue *);
static CborError fragment_offset(struct bundle7_parser *, CborValue *);
static CborError total_adu_length(struct bundle7_parser *, CborValue *);
static CborError primary_block_crc(struct bundle7_parser *, CborValue *);


// ----------------
// Extension Blocks
// ----------------

static CborError block_start(struct bundle7_parser *, CborValue *);
static CborError block_type(struct bundle7_parser *, CborValue *);
static CborError block_number(struct bundle7_parser *, CborValue *);
static CborError block_proc_flags(struct bundle7_parser *, CborValue *);
static CborError block_crc_type(struct bundle7_parser *, CborValue *);
static CborError block_crc(struct bundle7_parser *, CborValue *);
static CborError block_data(struct bundle7_parser *, CborValue *);
static CborError block_end(struct bundle7_parser *, CborValue *);


// --------------------
// Bundle start and end
// --------------------

CborError bundle_start(struct bundle7_parser *state, CborValue *it)
{
	if (!cbor_value_is_array(it) || cbor_value_is_length_known(it))
		return CborErrorIllegalType;

	state->next = primary_block_start;
	return cbor_value_enter_container(it, it);
}


CborError bundle_end(struct bundle7_parser *state, CborValue *it)
{
	struct bundle *bundle;

	if (*it->source.ptr != 0xff)
		return CborErrorIllegalType;
	it->source.ptr++;

	// Transition into "Done" state
	// NOTE that it is expected that a transition to "DONE" also occurs if
	// the CRC is invalid. In this case, however, the "send" callback
	// is not called. The caller may check for this case by examining the
	// parser flags for `PARSER_FLAG_CRC_INVALID` when the `status` is
	// `PARSER_STATUS_DONE`.
	state->basedata->status = PARSER_STATUS_DONE;

	// Clear bundle reference
	bundle = state->bundle;
	state->bundle = NULL;

	// Call "send" callback if set and all CRCs passed, otherwise discard
	// parsed bundle silently
	if (state->send_callback == NULL ||
	    state->basedata->flags & PARSER_FLAG_CRC_INVALID)
		bundle_free(bundle);
	else
		state->send_callback(bundle, state->send_param);

	return CborNoError;
}


// -------------
// Primary Block
// -------------

CborError primary_block_start(struct bundle7_parser *state, CborValue *it)
{
	if (!cbor_value_is_array(it) || !cbor_value_is_length_known(it))
		return CborErrorIllegalType;

	// Primary block CRC
	state->flags |= BUNDLE_V7_PARSER_CRC_FEED;

	crc_init(&state->crc16, CRC16_X25);
	crc_init(&state->crc32, CRC32);

	state->next = protocol_version;
	return cbor_value_enter_container(it, it);
}


CborError protocol_version(struct bundle7_parser *state, CborValue *it)
{
	uint64_t version;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &version);

	// Validate that it is indeed BPv7. This parser can only handle RFC9171-conformant bundles.
	if (version != 7)
		return CborErrorImproperValue;

	state->bundle->protocol_version = 7;

	state->next = primary_proc_flags;
	return cbor_value_advance_fixed(it);
}


CborError primary_proc_flags(struct bundle7_parser *state, CborValue *it)
{
	uint64_t flags;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &flags);

	state->bundle->proc_flags = (uint32_t)flags & BP_V7_FLAGS;
	state->next = crc_type_field;
	return cbor_value_advance_fixed(it);
}


CborError crc_type_field(struct bundle7_parser *state, CborValue *it)
{
	uint64_t type;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &type);

	// Validate CRC type
	if (type > BUNDLE_CRC_TYPE_32)
		return CborErrorIllegalType;

	state->bundle->crc_type = type;

	// Deactivate CRC feeding if CRC is not enabled
	if (state->bundle->crc_type == BUNDLE_CRC_TYPE_NONE)
		state->flags &= ~BUNDLE_V7_PARSER_CRC_FEED;

	state->next = destination_eid;
	return cbor_value_advance_fixed(it);
}


CborError parse_eid(struct bundle7_parser *state, CborValue *it, char **eid,
	CborError (*next)(struct bundle7_parser *, CborValue *))
{
	CborError err = bundle7_eid_parse_cbor(it, eid);

	if (err)
		return err;

	state->next = next;
	return CborNoError;
}


CborError destination_eid(struct bundle7_parser *state, CborValue *it)
{
	return parse_eid(state, it, &state->bundle->destination, source_eid);
}


CborError source_eid(struct bundle7_parser *state, CborValue *it)
{
	return parse_eid(state, it, &state->bundle->source, report_to_eid);
}


CborError report_to_eid(struct bundle7_parser *state, CborValue *it)
{
	return parse_eid(state, it, &state->bundle->report_to,
		creation_timestamp);
}


CborError creation_timestamp(struct bundle7_parser *state, CborValue *it)
{
	CborError err;

	err = bundle7_timestamp_parse(it,
		&state->bundle->creation_timestamp_ms,
		&state->bundle->sequence_number);
	if (err)
		return err;

	state->next = lifetime;
	return CborNoError;
}


CborError lifetime(struct bundle7_parser *state, CborValue *it)
{
	uint64_t value;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &value);
	state->bundle->lifetime_ms = value;

	const uint8_t *last_ptr = it->source.ptr;
	CborError err = cbor_value_advance_fixed(it);

	if (bundle_is_fragmented(state->bundle)) {
		state->next = fragment_offset;
	} else if (state->bundle->crc_type != BUNDLE_CRC_TYPE_NONE) {
		state->next = primary_block_crc;
	} else {
		state->next = block_start;

		// -1 Byte infinite array header
		state->bundle->primary_block_length = state->bundle_size - 1 +
			(it->source.ptr - last_ptr);
	}

	return err;
}


CborError fragment_offset(struct bundle7_parser *state, CborValue *it)
{
	uint64_t offset;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &offset);
	state->bundle->fragment_offset = offset;

	state->next = total_adu_length;
	return cbor_value_advance_fixed(it);
}


CborError total_adu_length(struct bundle7_parser *state, CborValue *it)
{
	uint64_t length;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &length);
	state->bundle->total_adu_length = length;

	const uint8_t *last_ptr = it->source.ptr;
	CborError err = cbor_value_advance_fixed(it);

	if (state->bundle->crc_type != BUNDLE_CRC_TYPE_NONE) {
		state->next = primary_block_crc;
	} else {
		state->next = block_start;

		// -1 Byte infinite array header
		state->bundle->primary_block_length = state->bundle_size - 1 +
			(it->source.ptr - last_ptr);
	}

	return err;
}


CborError primary_block_crc(struct bundle7_parser *state, CborValue *it)
{
	union crc crc;
	size_t len = sizeof(crc);
	CborError err;

	if (!cbor_value_is_byte_string(it))
		return CborErrorIllegalType;

	err = cbor_value_copy_byte_string(it, crc.bytes, &len, it);
	if (err)
		return err;

	// Deactivate CRC feeding for the CRC field itself
	state->flags &= ~BUNDLE_V7_PARSER_CRC_FEED;

	if (state->bundle->crc_type == BUNDLE_CRC_TYPE_16) {
		// Ensure correct CRC 16 length
		if (len != 2)
			return CborErrorIllegalType;

		// CRC field is populated with zero
		state->crc16.feed(&state->crc16, 0x42); // CBOR 2-b array header
		state->crc16.feed(&state->crc16, 0x00);
		state->crc16.feed(&state->crc16, 0x00);
		state->crc16.feed_eof(&state->crc16);

		// Swap from network byte order to native order and clear all
		// higher bits
		state->bundle->crc.checksum = cbor_ntohs(crc.checksum & 0xffff);

		crc_verify(state,
			state->crc16.checksum,
			state->bundle->crc.checksum);

		// -1 Byte infinite array header + 3 Bytes CRC field
		state->bundle->primary_block_length = state->bundle_size - 1 + 3;
	} else {
		// Ensure correct CRC 32 length
		if (len != 4)
			return CborErrorIllegalType;

		// CRC field is populated with zero
		state->crc32.feed(&state->crc32, 0x44); // CBOR 4-b array header
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed_eof(&state->crc32);

		// Swap from network byte order to native order
		state->bundle->crc.checksum = cbor_ntohl(crc.checksum);

		crc_verify(state,
			state->crc32.checksum,
			state->bundle->crc.checksum);

		// -1 Byte infinite array header + 5 Bytes CRC field
		state->bundle->primary_block_length = state->bundle_size - 1 + 5;
	}

	state->next = block_start;

	return CborNoError;
}


// ----------------
// Extension Blocks
// ----------------

CborError block_start(struct bundle7_parser *state, CborValue *it)
{
	if (!cbor_value_is_array(it))
		return CborErrorIllegalType;

	// Reset CRC streams
	crc_init(&state->crc16, CRC16_X25);
	crc_init(&state->crc32, CRC32);

	// Enable CRC feeding again
	state->flags |= BUNDLE_V7_PARSER_CRC_FEED;

	state->next = block_type;
	return cbor_value_enter_container(it, it);
}


CborError block_type(struct bundle7_parser *state, CborValue *it)
{
	uint64_t type;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &type);

	// Invalid block type
	if (type > (uint64_t)BUNDLE_BLOCK_TYPE_MAX)
		return CborErrorImproperValue;

	if (*state->current_block_entry == NULL) {
		// Create bundle block
		struct bundle_block *block = bundle_block_create(type);

		if (block == NULL)
			return CborErrorOutOfMemory;

		// Create bundle block list entry
		*state->current_block_entry = bundle_block_entry_create(block);

		if (*state->current_block_entry == NULL) {
			bundle_block_free(block);
			return CborErrorOutOfMemory;
		}
	} else {
		// Was already created but the last operation failed with a
		// too-short chunk (CborErrorUnexpectedEOF).
		ASSERT(
			(*state->current_block_entry)->data->type ==
			(enum bundle_block_type)type
		);
	}

	state->next = block_number;
	return cbor_value_advance_fixed(it);
}


CborError block_number(struct bundle7_parser *state, CborValue *it)
{
	uint64_t number;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &number);
	BLOCK(state)->number = number;

	state->next = block_proc_flags;
	return cbor_value_advance_fixed(it);
}


CborError block_proc_flags(struct bundle7_parser *state, CborValue *it)
{
	uint64_t flags;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &flags);

	BLOCK(state)->flags = (((uint8_t)flags) & (
		BUNDLE_BLOCK_FLAG_MUST_BE_REPLICATED |
		BUNDLE_BLOCK_FLAG_DISCARD_IF_UNPROC |
		BUNDLE_BLOCK_FLAG_REPORT_IF_UNPROC |
		BUNDLE_BLOCK_FLAG_DELETE_BUNDLE_IF_UNPROC
	));

	state->next = block_crc_type;
	return cbor_value_advance_fixed(it);
}


CborError block_crc_type(struct bundle7_parser *state, CborValue *it)
{
	uint64_t crc_type;

	if (!cbor_value_is_unsigned_integer(it))
		return CborErrorIllegalType;

	cbor_value_get_uint64(it, &crc_type);
	BLOCK(state)->crc_type = crc_type;

	state->next = block_data;

	// Deactivate CRC feeding
	if (crc_type == BUNDLE_CRC_TYPE_NONE)
		state->flags &= ~BUNDLE_V7_PARSER_CRC_FEED;

	return cbor_value_advance_fixed(it);
}


CborError block_crc(struct bundle7_parser *state, CborValue *it)
{
	union crc crc;
	size_t len = sizeof(crc);
	CborError err;

	if (!cbor_value_is_byte_string(it))
		return CborErrorIllegalType;

	// Deactivate CRC feeding for the CRC field itself
	state->flags &= ~BUNDLE_V7_PARSER_CRC_FEED;

	err = cbor_value_copy_byte_string(it, crc.bytes, &len, it);
	if (err)
		return err;

	// Feed CRC with raw CBOR block data
	if (BLOCK(state)->crc_type == BUNDLE_CRC_TYPE_16) {
		// Ensure correct CRC 16 checksum length
		if (len != 2)
			return CborErrorIllegalType;

		crc_feed_bytes(&state->crc16,
			BLOCK(state)->data,
			BLOCK(state)->length);

		// CRC field is populated with zero
		state->crc16.feed(&state->crc16, 0x42); // CBOR byte string(2)
		state->crc16.feed(&state->crc16, 0x00);
		state->crc16.feed(&state->crc16, 0x00);
		state->crc16.feed_eof(&state->crc16);

		// Swap from network byte order to native order and clear all
		// higher bits
		BLOCK(state)->crc.checksum = cbor_ntohs(crc.checksum & 0xffff);

		crc_verify(state,
			state->crc16.checksum,
			BLOCK(state)->crc.checksum);
	} else {
		// Ensure correct CRC 32 checksum length
		if (len != 4)
			return CborErrorIllegalType;

		crc_feed_bytes(&state->crc32,
			BLOCK(state)->data,
			BLOCK(state)->length);

		// CRC field is populated with zero
		state->crc32.feed(&state->crc32, 0x44); // CBOR byte string(4)
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed(&state->crc32, 0x00);
		state->crc32.feed_eof(&state->crc32);

		// Swap from network byte order to native order
		BLOCK(state)->crc.checksum = cbor_ntohl(crc.checksum);

		crc_verify(state,
			state->crc32.checksum,
			BLOCK(state)->crc.checksum);
	}
	block_end(state, it);

	return CborNoError;
}


CborError block_data(struct bundle7_parser *state, CborValue *it)
{
	size_t length;
	CborError err;

	if (!cbor_value_is_byte_string(it))
		return CborErrorIllegalType;

	err = cbor_value_get_string_length(it, &length);
	// CBOR length may be unknown (which is not allowed by the BPbis spec)
	if (err)
		return err;

	// Activate CRC feeding again
	state->flags |= BUNDLE_V7_PARSER_CRC_FEED;

	BLOCK(state)->length = length;

	// Block-specific data
	// -------------------
	//
	BLOCK(state)->data = malloc(length);
	if (BLOCK(state)->data == NULL)
		return CborErrorOutOfMemory;

	// Enable "bulk read" mode
	state->basedata->next_buffer = BLOCK(state)->data;
	state->basedata->next_bytes = length;
	state->basedata->flags |= PARSER_FLAG_BULK_READ;
	state->bundle_size += length;

	if (BLOCK(state)->crc_type != BUNDLE_CRC_TYPE_NONE)
		state->next = block_crc;
	else
		state->next = block_end;

	// The CBOR byte string length is represented in the same manner as a
	// CBOR uint. We thus change the type to uint to allow cleanly
	// advancing the iterator to just the start of the block payload.
	it->type = CborIntegerType;
	// NOTE: This may return an error depending on the following data
	// which it tries to preparse. It is already ensured that the header
	// and length can safely be read and advanced over by the result of
	// cbor_value_get_string_length. As we have requested a BULK_READ,
	// control will be handed over to the bulk_read handler and afterwards
	// we re-initialize the parser.
	cbor_value_advance_fixed(it);
	return CborNoError;
}


/**
 * Bulk read operation handler
 *
 * This function gets called with an null-pointer instead of an iterator after
 * the "bulk read" operation was performed and the bulk buffer was filled.
 *
 * @return This function never fails and always returns CborNoError
 */
CborError block_end(struct bundle7_parser *state, CborValue *it)
{
	(void)it;

	// Update parsing callback directly because there is no transition for
	// this callback as it gets called after the bulk read operation with
	// a null pointer instead an CBOR iterator.
	//
	// Set the "next" callback to the same function to prevent undesirable
	// transitions to an old callback of a previous stage
	if (BLOCK(state)->type == BUNDLE_BLOCK_TYPE_PAYLOAD) {
		state->bundle->payload_block = BLOCK(state);
		state->parse = bundle_end;
		state->next = bundle_end;
	} else {
		state->parse = block_start;
		state->next = block_start;
	}

	// Iterate to next block entry element
	state->current_block_entry = &(*state->current_block_entry)->next;

	return CborNoError;
}


// -----------
// Parser Core
// -----------

struct parser *bundle7_parser_init(struct bundle7_parser *state,
	void (*send_callback)(struct bundle *, void *), void *param)
{
	state->basedata = malloc(sizeof(struct parser));
	if (state->basedata == NULL)
		return NULL;

	state->bundle_quota = BUNDLE7_DEFAULT_BUNDLE_QUOTA;
	state->send_callback = send_callback;
	state->send_param = param;
	state->bundle = NULL;
	state->next = NULL;  // force reset to do its job

	// Set to error that the reset handler does not abort
	state->basedata->status = PARSER_STATUS_ERROR;

	if (bundle7_parser_reset(state) != UD3TN_OK) {
		free(state->basedata);
		return NULL;
	}

	return state->basedata;
}


enum ud3tn_result bundle7_parser_reset(struct bundle7_parser *state)
{
	if (state->basedata->status == PARSER_STATUS_GOOD &&
	    state->next == bundle_start)
		return UD3TN_OK;

	state->basedata->status = PARSER_STATUS_GOOD;
	state->basedata->flags = PARSER_FLAG_NONE;

	state->parse = bundle_start;
	state->flags = 0;
	state->bundle_size = 0;

	if (state->bundle != NULL)
		bundle_reset(state->bundle);
	else
		state->bundle = bundle_init();

	if (state->bundle == NULL)
		return UD3TN_FAIL;

	state->current_block_entry = &state->bundle->blocks;

	return UD3TN_OK;
}

enum ud3tn_result bundle7_parser_deinit(struct bundle7_parser *state)
{
	free(state->basedata);
	if (state->bundle != NULL)
		bundle_free(state->bundle);

	return UD3TN_OK;
}


size_t bundle7_parser_read(struct bundle7_parser *state,
	const uint8_t *buffer, size_t length)
{
	CborParser parser;
	CborValue it;
	CborError err;
	size_t parsed = 0;
	bool initialize_parser = true;

	// Special case:
	//     Bulk read operation was performed and this function gets called
	//     with an empty buffer to continue processing
	if (buffer == NULL) {
		// If no CRC is to be read, block_end needs to be called now.
		// "block_end" never fails - therefore no error handling
		if (state->parse == block_end) {
			state->parse(state, NULL);
			state->parse = state->next;
		}
		return 0;
	}

	while (parsed < length && state->basedata->status == PARSER_STATUS_GOOD) {
		// For arbitrarily-long data such as block payload data, a
		// "BULK_READ" operation is requested, normally to be handled
		// by the RX task. Though, sometimes we can handle this on our
		// own (if we have enough data in the current buffer). Thus, we
		// first check whether, given the bytes in the buffer, we can
		// perform the bulk read operation on our own.
		// NOTE: At this point the CBOR parser may be in an invalid
		// state because we have to interrupt it before it starts
		// trying to read the bytes from the array by itself. This is
		// not possible as the array might be too short and we want to
		// be able to "stream" the data.
		if (state->basedata->flags & PARSER_FLAG_BULK_READ) {
			if (parsed + state->basedata->next_bytes > length) {
				// Bulk read operation was requested but cannot
				// be performed by us. -> RX task will do it.
				break;
			}

			memcpy(
				state->basedata->next_buffer,
				buffer + parsed,
				state->basedata->next_bytes
			);

			parsed += state->basedata->next_bytes;

			// Disables bulk read mode again
			state->basedata->flags &= ~PARSER_FLAG_BULK_READ;

			// Process copied data and proceed to next block if
			// there is not CRC to be read.
			// This call to "block_end" is always successful.
			if (state->parse == block_end) {
				state->parse(state, NULL);
				state->parse = state->next;
			}

			// Re-initialize after the "bulk read".
			initialize_parser = true;

			// Force checking the loop condition again.
			continue;
		}

		if (initialize_parser) {
			err = cbor_parser_init(
				buffer + parsed,
				length - parsed,
				0, &parser, &it
			);

			// CBOR decoding error when preparsing first byte
			if (err) {
				// Insufficient data
				if (err == CborErrorUnexpectedEOF)
					break;

				// We allow "unexpected" breaks
				//
				// The bundle is an indefinite array and its end
				// is marked by the "break" symbol.
				// Therefore, the buffer could contain a single
				// "break". This happens because we cut the
				// indefinite array by the chunked reading
				// operation.
				if (err != CborErrorUnexpectedBreak) {
					FAIL(state);
					break;
				}
			}

			initialize_parser = false;
		}

		// Parsing step
		err = state->parse(state, &it);

		// Parsing error
		if (err) {
			if (err != CborErrorUnexpectedEOF)
				FAIL(state);
			break;
		}

		// Transition to next stage
		size_t new_parsed = (cbor_value_get_next_byte(&it) - buffer);

		state->bundle_size += new_parsed - parsed;

		// Bundle is larger than allowed
		if (state->bundle_size > state->bundle_quota) {
			FAIL(state);
			break;
		}

		if (state->flags & BUNDLE_V7_PARSER_CRC_FEED) {
			crc_feed_bytes(&state->crc16,
				buffer + parsed, new_parsed - parsed);
			crc_feed_bytes(&state->crc32,
				buffer + parsed, new_parsed - parsed);
		}

		state->parse = state->next;
		parsed = new_parsed;

		// If we have reached the end of the current item/container,
		// we re-initialize the parser as we might want to read more
		// than that. The parser is not fully aware of the bundle
		// CBOR structure because we interrupt the process due to
		// the chunked and bulk read mechanics.
		if (cbor_value_at_end(&it))
			initialize_parser = true;
	}

	return parsed;
}