/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.

  You may obtain a copy of the License at:
      https://github.com/star.4th@proton.me/StarForth/LICENSE.txt

  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
  express or implied, including but not limited to the warranties of
  merchantability, fitness for a particular purpose, and noninfringement.

  See the License for the specific language governing permissions and
  limitations under the License.
*/

/**
 * homeblocks_sig.h - Home-blocks drive signature format (FABRIC-3.md,
 * Milestone 4, Phase 8 kickoff)
 *
 * Identifies and authenticates a physical thumb drive as a legitimate
 * LithosAnanke home-blocks drive, before any write path touches it.
 * Lives at the first 4KiB devblock of the drive's GPT metadata partition
 * (the ~1GB partition decided 2026-08-22) -- this header's own format does
 * not depend on the GPT parser that locates that partition; it is simply
 * what gets written starting at that partition's first devblock, once
 * something can find it.
 *
 * Mirrors two existing precedents exactly, not invented fresh:
 *   - CAPSULE_MAGIC_PACK's bit-packed magic (starkernel/capsule.h)
 *   - blk_volume_meta_t's magic+version+fields+pad-to-4096 structural
 *     convention (block_subsystem.h)
 *
 * Deliberately narrow in scope: this header identifies/authenticates the
 * DRIVE only. It does not invent the on-drive block-map format (Milestone
 * 3, still undesigned) or the credential/cert format (Milestone 6, blocked
 * on a real CA that does not exist yet) -- it only reserves offset/size
 * pointers to where those will attach, so this format does not need to be
 * revisited when those get designed.
 */

#ifndef STARKERNEL_HOMEBLOCKS_SIG_H
#define STARKERNEL_HOMEBLOCKS_SIG_H

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/*===========================================================================
 * Magic Field Packing -- same bit layout convention as CAPSULE_MAGIC_PACK
 *
 * bits  0..31 : 'LAHB' (0x4248414C little-endian) -- LithosAnanke Home Blocks
 * bits 32..39 : version (0 for v0)
 * bits 40..63 : reserved (zero)
 *===========================================================================*/

#define HOMEBLOCKS_SIG_MAGIC     0x4248414CULL /* 'LAHB', same little-endian ASCII
                                                 * packing as CAPSULE_DESC_MAGIC's 'CAPS' */
#define HOMEBLOCKS_SIG_VERSION_0 0

#define HOMEBLOCKS_SIG_PACK(ver) \
    (HOMEBLOCKS_SIG_MAGIC | ((uint64_t)(ver) << 32))

#define HOMEBLOCKS_SIG_GET_MAGIC(m)   ((uint32_t)((m) & 0xFFFFFFFFULL))
#define HOMEBLOCKS_SIG_GET_VERSION(m) ((uint8_t)(((m) >> 32) & 0xFF))

/*===========================================================================
 * homeblocks_sig_t - drive signature header (exactly one 4KiB devblock)
 *===========================================================================*/

typedef struct {
    uint64_t magic;              /* HOMEBLOCKS_SIG_PACK(...) */
    uint8_t  drive_uuid[16];     /* Unique per-mint instance id -- Phase 8 mints multiple
                                  * distinct drives, needs something to tell them apart. */
    uint64_t minted_time_ns;     /* Monotonic timestamp at mint time. */
    uint64_t metadata_devblocks; /* Size of this GPT metadata partition, in 4KiB devblocks --
                                  * sanity/bounds check against the GPT entry once a parser
                                  * exists. */

    uint32_t cert_offset;        /* Devblock offset within this partition where the CA-signed
                                  * cert blob starts; 0 = not yet minted. Format not decided --
                                  * Milestone 6's real CA does not exist yet. */
    uint32_t cert_devblocks;     /* Size reserved for the cert blob, in devblocks. */

    uint32_t blockmap_offset;    /* Devblock offset where the block-map starts; 0 = not yet
                                  * minted. Format not decided -- Milestone 3, still open. */
    uint32_t blockmap_devblocks; /* Size reserved for the block-map, in devblocks. */

    uint64_t hdr_crc;            /* REAL from day one, not a placeholder like
                                  * blk_volume_meta_t's "unused yet" hdr_crc -- this header's
                                  * whole job is gating a warn-and-refuse security check
                                  * against blank/foreign/unrecognized media, so the crc has
                                  * to actually work. Computed over every field above this
                                  * one; callers must fill every other field before computing
                                  * or verifying it. */

    /* Padding to keep the header exactly one 4KiB devblock. */
    uint8_t _pad[4096 - (
                     8 +           /* magic */
                     16 +          /* drive_uuid */
                     8 +           /* minted_time_ns */
                     8 +           /* metadata_devblocks */
                     4 + 4 +       /* cert_offset, cert_devblocks */
                     4 + 4 +       /* blockmap_offset, blockmap_devblocks */
                     8             /* hdr_crc */
                 )];
} homeblocks_sig_t;

/* C99-portable compile-time size assertion (no _Static_assert -- that's C11),
 * same discipline stadium.h's own header-size checks already use. */
typedef char homeblocks_sig_size_check[(sizeof(homeblocks_sig_t) == 4096) ? 1 : -1];

#ifdef __cplusplus
}
#endif

#endif /* STARKERNEL_HOMEBLOCKS_SIG_H */