/*
  StarForth — Steady-State Virtual Machine Runtime

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

  Licensed under the StarForth License, Version 1.0
*/

#ifndef __STARKERNEL__
#error "capsule_wirebind.c is kernel-only"
#endif

#include "starkernel/capsule_wirebind.h"
#include "starkernel/capsule_birth.h"
#include "starkernel/capsule_runcap.h"
#include "starkernel/capsule_console.h"
#include "starkernel/vm_identity.h"
#include "starkernel/user_identity_seed.h"
#include "starkernel/console.h"
#include "starkernel/repl.h" /* sk_repl_get/set_active_vm() -- FABRIC-2.md §F.10 EJECT */
#include "blkio.h"
#include "block_subsystem.h" /* compute_crc64() */
#include "word_source/include/block_words.h" /* blk_vm_flush_all() -- §F.10 EJECT */
#include "freestanding/stdio.h"
#include <string.h>
#include <stddef.h>

/* FABRIC-2.md §F.10: "the VM currently attached via the home-blocks USB
 * path" -- WIREBIND's own to track, set at successful birth in
 * capsule_wirebind_try_attach(), read and cleared by both
 * capsule_wirebind_eject() and capsule_wirebind_unclean_detach(). Single-
 * USB-device constraint (§F.8) means there is never more than one
 * candidate, so one tracked id is enough -- no set/list. */
static VMUuid g_wirebind_attached_vm_id;
static int    g_wirebind_attached_valid = 0;
/* Plain username (no "~user" registry-name suffix), tracked separately
 * from g_wirebind_attached_vm_id -- the registry entry's own name is
 * user_vm_name ("<username>~user"), not the bare form the (user) prompt
 * segment wants (FABRIC-2.md §I.1/4.4s). */
static char   g_wirebind_attached_username[USER_IDENTITY_USERNAME_MAX] = {0};
/* FABRIC-2.md §I.2 overflow trigger, 2026-09-05: the attached drive's own
 * blkio_dev pointer, tracked alongside the two fields above so
 * capsule_wirebind_overflow_idle_check() can query its free space later
 * without a new attach-time argument threaded through the idle loop. */
static struct blkio_dev *g_wirebind_attached_dev = (struct blkio_dev *) 0;

/* WIREBIND_CERT_MAX_DEVBLOCKS: a sane upper bound on how much cert
 * content this reads, independent of whatever sig->cert_devblocks
 * claims -- MINT (capsule_mint.c) only ever writes 1 devblock's worth
 * (a real cert is ~150-250 bytes), so 4 devblocks (16KB) is already
 * generous headroom, not a real constraint. */
#define WIREBIND_CERT_MAX_DEVBLOCKS 4u

/* FABRIC-2.md §I.2 overflow trigger, 2026-09-05: fixed constants, "fixed
 * first" per this project's own standing sequencing (MIGRATION_WEAR_
 * THRESHOLD, ZUSE_SESSION_TTL_SECONDS -- adaptive only after a real,
 * measured baseline exists, not from day one). A single DoE-tunable knob
 * apiece, not yet wired to Kconfig -- revisit once real usage data exists.
 * 10% is a conservative first guess (extend well before actually full);
 * 8 devblocks (24 Forth blocks, ~24 KiB) is a modest first extension, not
 * a large land-grab. */
#define WIREBIND_OVERFLOW_FREE_THRESHOLD_PCT 10u
#define WIREBIND_OVERFLOW_CLAIM_DEVBLOCKS    8u

/* Read exactly one devblock (4096 bytes) at devblock offset `devblock`
 * -- same convention capsule_runcap.c/capsule_mint.c already use. */
static int read_devblock(struct blkio_dev *dev, uint32_t devblock, uint8_t *buf4096) {
    uint32_t base = devblock * 4u;
    for (uint32_t i = 0; i < 4u; i++) {
        if (blkio_read((blkio_dev_t *)dev, base + i,
                        buf4096 + (size_t)i * BLKIO_FORTH_BLOCK_SIZE) != BLKIO_OK) {
            return -1;
        }
    }
    return 0;
}

int capsule_wirebind_verify_cert(struct blkio_dev *dev,
                                  const homeblocks_sig_t *sig,
                                  VM *mama_vm, VMIdentity *out) {
    if (!dev || !sig || !mama_vm || !out) return -1;

    /* Genesis-mode Zuse drives have no cert region -- capsule_zuse_boot_
     * try_attach() owns that case, not this one. */
    if (sig->cert_offset == 0 || sig->cert_devblocks == 0) return -1;

    /* Nothing to verify a regular cert against until Zuse herself has
     * authenticated this boot. */
    if (!mama_vm->zuse_cert_installed) return -1;

    /* Read the cert region into a local buffer. */
    uint32_t n_devblocks = sig->cert_devblocks;
    if (n_devblocks > WIREBIND_CERT_MAX_DEVBLOCKS) n_devblocks = WIREBIND_CERT_MAX_DEVBLOCKS;
    uint8_t cert_der[WIREBIND_CERT_MAX_DEVBLOCKS * 4096];
    for (uint32_t d = 0; d < n_devblocks; d++) {
        if (read_devblock(dev, sig->cert_offset + d, cert_der + (size_t)d * 4096) != 0) {
            return -1;
        }
    }
    size_t cert_len = (size_t)n_devblocks * 4096;

    memset(out, 0, sizeof(*out));
    return vm_identity_from_cert(out, cert_der, cert_len,
                                  mama_vm->zuse_cert_pubkey, sig->drive_uuid,
                                  0 /* acl_caps: no bits assigned yet, §F.2 */);
}

void capsule_wirebind_try_attach(struct blkio_dev *dev,
                                  const homeblocks_sig_t *sig,
                                  VM *mama_vm) {
    if (!dev || !sig || !mama_vm) return;

    /* Genesis-mode Zuse drives have no cert region -- capsule_zuse_boot_
     * try_attach() already owns that case. Check here too so the right
     * "not applicable" case stays silent (matches capsule_wirebind_
     * verify_cert()'s own -1, but avoids a misleading refusal message
     * for a drive this function was never going to act on anyway). */
    if (sig->cert_offset == 0 || sig->cert_devblocks == 0) return;
    if (!mama_vm->zuse_cert_installed) return;

    VMIdentity identity;
    if (capsule_wirebind_verify_cert(dev, sig, mama_vm, &identity) != 0) {
        console_println("WIREBIND: cert verification FAILED -- drive refused");
        return;
    }

    /* Verified. Read the drive's own profile for its username. */
    if (sig->identity_src_offset == 0 || sig->identity_src_devblocks < 1) {
        console_println("WIREBIND: verified cert but no identity_src region -- refusing");
        return;
    }
    user_identity_seed_t idrec;
    if (read_devblock(dev, sig->identity_src_offset, (uint8_t *)&idrec) != 0) {
        console_println("WIREBIND: verified cert but identity record unreadable -- refusing");
        return;
    }
    /* Same magic -> version -> CRC-64 discipline as capsule_zuse_boot.c:
     * the identity record is the same on-disk format, so a corrupt or
     * format-mismatched record must be refused rather than trusted. */
    if (idrec.magic != USER_IDENTITY_SEED_MAGIC ||
        idrec.version != USER_IDENTITY_SEED_VERSION) {
        console_println("WIREBIND: verified cert but identity record unreadable -- refusing");
        return;
    }
    uint64_t want_crc = compute_crc64((const uint8_t *)&idrec,
                                      offsetof(user_identity_seed_t, crc));
    if (want_crc != idrec.crc) {
        console_println("WIREBIND: verified cert but identity record corrupt -- refusing");
        return;
    }

    char username[USER_IDENTITY_USERNAME_MAX];
    memcpy(username, idrec.username, sizeof(username));
    username[sizeof(username) - 1] = '\0'; /* defensive; MINT already NUL-terminates */

    char user_vm_name[USER_IDENTITY_USERNAME_MAX + 8];
    size_t ulen = strlen(username);
    if (ulen == 0 || ulen + 6 > sizeof(user_vm_name)) {
        console_println("WIREBIND: empty or oversized username -- refusing");
        return;
    }
    memcpy(user_vm_name, username, ulen);
    memcpy(user_vm_name + ulen, "~user", 6);

    /* Idempotent: already bound this session (console VM already live
     * under this username) -- nothing to do. Matches BIRTH's own
     * idempotent convention. */
    {
        VMRegistryEntry existing;
        if (capsule_vm_find_by_name(username, &existing) == 0 &&
            existing.state == VM_STATE_LIVE) {
            return;
        }
    }

    VMUuid console_id, user_id;
    void  *console_ctx = (void *)0;
    void  *user_ctx    = (void *)0;
    if (capsule_console_birth(username, mama_vm->stadium_vm_id, &console_id, &console_ctx)
        != CAPSULE_RUN_OK) {
        console_println("WIREBIND: console VM birth FAILED");
        return;
    }
    if (capsule_runcap_birth(dev, sig, user_vm_name, mama_vm->stadium_vm_id, &user_id,
                              &user_ctx) != CAPSULE_RUN_OK) {
        console_println("WIREBIND: user VM birth FAILED");
        /* The console VM above already succeeded and is live/registered
         * under `username` -- without this, it's an orphan: nothing ever
         * points a real user at it (WIREBIND only ever hands the caller
         * the user VM's id), so it just sits there permanently holding
         * its own kernel-heap arena allocation. Confirmed live 2026-09-07
         * (identity-heap-capacity testing): this is exactly what turns a
         * single failed identity attach into a permanent net loss of
         * heap, compounding every subsequent attempt's odds of failing
         * too, rather than a neutral retry. capsule_vm_kill() is the same
         * teardown capsule_wirebind_eject()/capsule_wirebind_unclean_
         * detach() already use elsewhere in this file -- vm_cleanup() +
         * sf_free(), verified to actually reclaim per-word dictionary
         * allocations (FABRIC-3.md §IX.2/§IX.3, 2026-09-06). */
        capsule_vm_kill(username);
        return;
    }

    /* Install the verified identity onto the user VM -- the one BINDSTEP
     * (§F.9) will later re-verify against on every USE. */
    if (user_ctx) {
        ((VM *)user_ctx)->identity = identity;
    }

    /* FABRIC-2.md §F.10: this is the successful-birth point EJECT/UNCLEAN
     * need a tracked VMUuid from -- the user VM, not the console VM
     * (blk_vm_flush_all()/capsule_vm_kill() below both act on the VM that
     * actually owns block-subsystem state). */
    g_wirebind_attached_vm_id = user_id;
    g_wirebind_attached_valid = 1;
    g_wirebind_attached_dev   = dev;
    memcpy(g_wirebind_attached_username, username, sizeof(g_wirebind_attached_username));

    /* Decided 2026-09-05: no console for the running system unless a
     * thumbdrive is present. Revised 2026-09-06: this used to call
     * sk_console_mark_login() here (a one-way sticky flag) -- the gate is
     * now a live check (sk_console_identity_present(), repl.c) driven
     * directly by g_wirebind_attached_username being set above, re-checked
     * continuously by sk_repl_run()'s own main loop rather than a one-shot
     * signal at login time. Nothing to call here anymore. */

    /* Register the pairing in the console's own routing table, index 3
     * -- the fixed convention sk_repl_dispatch_line() (repl.c) uses. */
    {
        char reg_cmd[sizeof(user_vm_name) + 32];
        int  n = snprintf(reg_cmd, sizeof(reg_cmd), "S\" %s\" 3 VM-NAME-REG", user_vm_name);
        if (n > 0 && (size_t)n < sizeof(reg_cmd)) {
            vm_interpret((VM *)console_ctx, reg_cmd);
        }
    }

    console_puts("WIREBIND: ");
    console_puts(username);
    console_println(" attached and ready -- USE it to begin");
}

/* Shared by capsule_wirebind_eject() and capsule_wirebind_unclean_detach():
 * resolve the tracked attached-VM id to a live entry, or clear the tracked
 * state and report "nothing attached" if it's already gone (idempotent --
 * matches capsule_vm_kill()'s own convention). */
static int wirebind_resolve_attached(VMRegistryEntry *out) {
    if (!g_wirebind_attached_valid) return -1;
    if (capsule_vm_registry_get(g_wirebind_attached_vm_id, out) != 0 ||
        out->state != VM_STATE_LIVE) {
        g_wirebind_attached_valid       = 0;
        g_wirebind_attached_username[0] = '\0';
        return -1;
    }
    return 0;
}

int capsule_wirebind_eject(void) {
    VMRegistryEntry entry;
    if (wirebind_resolve_attached(&entry) != 0) {
        console_println("EJECT: nothing attached via WIREBIND");
        return -1;
    }

    /* Drive is still physically present -- flush before it's safe to
     * remove (§F.10 decision 1). */
    blk_vm_flush_all((VM *)entry.vm_ptr);

    if (sk_repl_get_active_vm() == (VM *)entry.vm_ptr) {
        sk_repl_set_active_vm((VM *)0);
    }

    capsule_vm_kill(entry.name);
    g_wirebind_attached_valid       = 0;
    g_wirebind_attached_dev         = (struct blkio_dev *) 0;
    g_wirebind_attached_username[0] = '\0';

    console_puts("EJECT: ");
    console_puts(entry.name);
    console_println(" flushed and detached");
    return 0;
}

void capsule_wirebind_unclean_detach(struct blkio_dev *dev) {
    /* FABRIC-3.md §VII follow-on, 2026-09-06: same defect class as
     * capsule_zuse_boot_logout()'s own fix, found in the same live
     * verification session -- this used to take no device parameter at
     * all, so an unrelated device detaching (Zuse's own drive, or general-
     * purpose USB use) while a WIREBIND user stayed attached would
     * incorrectly tear down that user's session too. The single-USB-
     * device constraint this was written under never let a *different*
     * device be the one detaching while a WIREBIND user's own stayed live
     * -- stale now that genuine multi-device attach exists. */
    if (dev != g_wirebind_attached_dev) return;

    VMRegistryEntry entry;
    if (wirebind_resolve_attached(&entry) != 0) return;

    /* Device is already gone (§F.10 decision 2) -- no flush attempted;
     * data since the last flush is lost, matching real-OS unclean-removal
     * semantics. */
    if (sk_repl_get_active_vm() == (VM *)entry.vm_ptr) {
        sk_repl_set_active_vm((VM *)0);
    }

    capsule_vm_kill(entry.name);
    g_wirebind_attached_valid       = 0;
    g_wirebind_attached_dev         = (struct blkio_dev *) 0;
    g_wirebind_attached_username[0] = '\0';

    console_puts("WIREBIND: ");
    console_puts(entry.name);
    console_println(" detached without flush (device already gone)");
}

const char *capsule_wirebind_attached_username(void) {
    if (!g_wirebind_attached_valid) return (const char *)0;
    return g_wirebind_attached_username;
}

void capsule_wirebind_overflow_idle_check(void) {
    if (!g_wirebind_attached_valid || !g_wirebind_attached_dev) return;

    VMRegistryEntry entry;
    if (capsule_vm_registry_get(g_wirebind_attached_vm_id, &entry) != 0 ||
        entry.state != VM_STATE_LIVE || !entry.vm_ptr) {
        return;
    }

    uint64_t free_blocks, total_blocks;
    if (blk_get_device_free_blocks(g_wirebind_attached_dev, &free_blocks, &total_blocks)
        != BLK_OK || total_blocks == 0) {
        return;
    }

    if (free_blocks * 100u >= total_blocks * WIREBIND_OVERFLOW_FREE_THRESHOLD_PCT) {
        return; /* plenty of room left on the drive itself */
    }

    uint8_t owner_fp[8];
    memcpy(owner_fp, ((VM *)entry.vm_ptr)->identity.owner_pubkey, sizeof(owner_fp));

    if (blk_owner_has_claim(owner_fp)) {
        return; /* already extended once -- not a growth loop, see header doc */
    }

    uint32_t chain_head;
    if (blk_firsttouch_claim(owner_fp, WIREBIND_OVERFLOW_CLAIM_DEVBLOCKS, &chain_head)
        != BLK_OK) {
        console_println("WIREBIND: overflow trigger fired but Artemis has no room to extend into");
        return;
    }

    console_puts("WIREBIND: ");
    console_puts(g_wirebind_attached_username);
    console_println(" running low on drive space -- extended onto system-resident storage");
}