/* merkle.h — BitTorrent v2 (BEP-52) SHA-256 Merkle trees.
 *
 * In v2 each file is split into 16 KiB leaf blocks; the leaf hashes form a
 * binary Merkle tree whose interior nodes are SHA-256(left || right). When the
 * leaf count is not a power of two, the tree is padded with *zero hashes* (a
 * block of 32 zero bytes at the leaf level, then SHA-256 of two children up the
 * tree) so the shape is a perfect binary tree. The root at the "piece layer"
 * boundary gives per-piece verifiability; the whole-file root goes in the
 * metainfo file tree.
 *
 * This module provides the tree primitive; metainfo/storage wire it to files.
 */
#ifndef NAUT_MERKLE_H
#define NAUT_MERKLE_H

#include "naut/common.h"
#include "naut/hash.h"

#define NAUT_MERKLE_LEAF (16u * 1024u)   /* BEP-52 block size */

/* Compute the Merkle root of `nleaves` 32-byte leaf hashes, padding up to the
 * next power of two with zero hashes. nleaves==0 yields the all-zero hash.
 * `leaves` is nleaves*32 bytes; out is 32 bytes. Scratch is allocated
 * internally. Returns NAUT_OK or NAUT_ERR_NOMEM. */
naut_err naut_merkle_root(const uint8_t *leaves, size_t nleaves,
                          uint8_t out[NAUT_SHA256_LEN]);

/* As above but pad to a fixed `block_count` (>= nleaves, power of two) rather
 * than the next power of two — used to compute a piece-layer root where the
 * tree height is fixed by the piece size. */
naut_err naut_merkle_root_padded(const uint8_t *leaves, size_t nleaves,
                                 size_t block_count,
                                 uint8_t out[NAUT_SHA256_LEN]);

/* Hash a contiguous data buffer into leaf hashes (one SHA-256 per 16 KiB, last
 * leaf may be short). out must hold ceil(len/16KiB)*32 bytes. Returns the leaf
 * count. */
size_t naut_merkle_leaves(const uint8_t *data, size_t len, uint8_t *out);

#endif /* NAUT_MERKLE_H */