#include <mpack.h>
#include <stdio.h>

// MIN() macro
#include <sys/param.h>
// TODO: check if this works on pico as well

#include "puzbusv1.h"

bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz) {
	// remaining bytes to be read to target->data; this is the only variable that
	// needs to persist between buffer blocks, and is therefore static
	static size_t rdata = 0;

	// a new reader is used per buffer block passed to this function
	mpack_reader_t reader;
	mpack_reader_init_data(&reader, buf, buf_sz);

	// at start of message
	if (rdata == 0) {
		// NOTE: This approach will crash and burn when target->addr can be read
		// and target->length is past the end of the current buffer block. This is
		// a highly unlikely scenario, as pb_read is called for each chunk of a TCP
		// frame, and frames (should) include only one puzzle bus message.
		target->addr = mpack_expect_u16(&reader);
		target->length = rdata = mpack_expect_bin(&reader);
		target->data = (char*) malloc(target->length);
	}

	// continue reading chunks of target->data until the amount of bytes
	// specified in target->length
	size_t to_read = MIN(mpack_reader_remaining(&reader, NULL), rdata);
	char* data = target->data + target->length - rdata; // 'ol pointer arithmetic
	mpack_read_bytes(&reader, data, to_read);
	rdata -= to_read;

	// if rdata = 0, the message was completely read
	return rdata == 0;
}

bool pb_write(struct pb_msg* target, char** buf, size_t* buf_sz) {
	mpack_writer_t writer;
	mpack_writer_init_growable(&writer, buf, buf_sz);

	mpack_write_u16(&writer, target->addr);
	mpack_write_bin(&writer, target->data, target->length);

	// finish writing
	return mpack_writer_destroy(&writer) == mpack_ok;
}