/* sbc_harness/uf2.h - Universal Flashing Format
 *
 * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

#include <string.h> /* for memcpy(), memcmp() */

#include <libmisc/endian.h>

#define IMPLEMENTATION_FOR_UF2_H YES
#include "uf2.h"

#define MIN(a, b) (((a) < (b)) ? (a) : (b))

#define UF2_FLAG_NOTMAIN   0x00000001
#define UF2_FLAG_CONTAINER 0x00001000
#define UF2_FLAG_FAMILYID  0x00002000
#define UF2_FLAG_MD5SUM    0x00004000
#define UF2_FLAG_EXTENSION 0x00008000

static const uint8_t uf2_magic_beg[8] = { 'U', 'F', '2', '\n', 0x57, 0x51, 0x5D, 0x9E };
static const uint8_t uf2_magic_end[4] = { 0x30, 0x6F, 0xB1, '\n' };

static size_t_and_error uf2_decoder_write(struct uf2_decoder *self, const char *dat, size_t len_in) {
	assert(self);
	assert(ctx);
	if (!len_in)
		return ERROR_AND(size_t, 0, ERROR_NULL);
	assert(dat);

	if (self->seen_err)
		return ERROR_AND(size_t, 0, error_new(E_POSIX_ESPIPE, "write after error"));

	size_t len_consumed = 0;

	while (len_consumed < len_in) {
		size_t n = MIN(512 - self->len_dat, /* how much we're willing to take */
		               len_in - len_consumed); /* how much we're being offered */
		memcpy(&self->dat[self->dat_len], &dat[len_consumed], n);
		self->dat_len += n;
		len_consumed += n;

		if (self->dat_len != 512)
			continue;

		if (memcmp(&self->dat[0], uf2_magic_beg, 8)) {
			self->seen_err = true;
			return ERROR_AND(size_t, len_consumed, error_new(E_POSIX_EPROTO, "block does not begin with magic"));
		}
		if (memcmp(&self->dat[512-4], uf2_magic_end, 4)) {
			self->seen_err = true;
			return ERROR_AND(size_t, len_consumed, error_new(E_POSIX_EPROTO, "block does not end with magic"));
		}
		uint32_t flag = uint32le_decode(&self->dat[8]);
		uint32_t addr = uint32le_decode(&self->dat[12]);
		uint32_t size = uint32le_decode(&self->dat[16]);
		uint32_t bnum = uint32le_decode(&self->dat[20]);
		uint32_t bcnt = uint32le_decode(&self->dat[24]);
		uint32_t famid = uint32le_decode(&self->dat[28]);
		uint8_t *data = &self->dat[32];
		// TODO
	}

	assert(len_consumed == len_in);
	return ERROR_AND(size_t, len_in, ERROR_NULL);
}

size_t_and_error uf2_decoder_writev(struct uf2_decoder *self, const struct iovec *iov, int iovcnt) {
	assert(self);
	assert(iov);
	assert(iovcnt);

	size_t total = 0;
	for (int i = 0; i < iovcnt; i++) {
		size_t_and_error r = uf2_decoder_write(self, iov[i].iov_base, iov[i].iov_len);
		total += r.size_t;
		if (!ERROR_IS_NULL(r.err))
			return ERROR_AND(size_t, total, r.err);
	}
	return ERROR_AND(size_t, total, ERROR_NULL);
}