/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2026 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the Starship License, Version 1.0 (SL-1.0) (the "License");
  you may not use this file except in compliance with the License.
*/

/**
 * vm_log_buffer.c - a VM's log records, on their way to Artemis's log ring.
 * See the header for the contract (FABRIC-3.md §XXXVIII, 2026-10-14).
 */

#ifdef __STARKERNEL__

#include "starkernel/vm_log_buffer.h"
#include "vm.h"
#include "log.h"                         /* LOG_ERROR, LOG_WARN */
#include "starkernel/vm/kernel_hermes.h" /* sk_hermes_send_one(), SK_HERMES_MSG_TYPE_LOG_BATCH */
#include "starkernel/capsule_birth.h"    /* capsule_vm_find_by_name_nocase(), capsule_vm_registry_get() */
#include "starkernel/log_region.h"       /* log_region_append() */
#include "starkernel/console.h"          /* console_println() -- never log_message() here */
#include "freestanding/stdio.h"          /* snprintf() */
#include <string.h>

#define REC_HEAD 11u /* level 1 + timestamp 8 + length 2 */

typedef char vm_log_buf_fits[(VM_LOG_BUF_SIZE + 64 <= SK_HERMES_CHUNK_MAX_PAYLOAD) ? 1 : -1];

/* Set while a record is being added or a buffer sent: a log line made from
 * inside that work (a kernel-Hermes refusal, say) must not re-enter it. */
static int g_busy;

static uint32_t put_record(uint8_t *at, uint8_t level, uint64_t ts,
                           const char *msg, uint16_t len) {
    at[0] = level;
    memcpy(at + 1, &ts, 8);
    memcpy(at + 9, &len, 2);
    memcpy(at + REC_HEAD, msg, len);
    return REC_HEAD + len;
}

static uint32_t count_records(const uint8_t *buf, uint32_t len) {
    uint32_t at = 0, n = 0;
    while (at + REC_HEAD <= len) {
        uint16_t l;
        memcpy(&l, buf + at + 9, 2);
        at += REC_HEAD + l;
        n++;
    }
    return n;
}

static int send_buffer(VM *vm) {
    uint8_t payload[SK_HERMES_CHUNK_MAX_PAYLOAD];
    uint32_t len = 0, records = count_records(vm->log_buf, vm->log_buf_len);
    VMRegistryEntry artemis;

    if (vm->log_buf_len == 0 && vm->log_lost == 0) return 0;

    if (vm->log_lost > 0) {
        char note[64];
        int n = snprintf(note, sizeof(note), "%u log records not sent: Artemis not ready",
                         (unsigned)vm->log_lost);
        if (n > 0) len += put_record(payload, LOG_WARN, 0, note, (uint16_t)n);
    }
    memcpy(payload + len, vm->log_buf, vm->log_buf_len);
    len += vm->log_buf_len;

    if (capsule_vm_find_by_name_nocase("Artemis", &artemis) != 0 || !artemis.vm_ptr ||
        (artemis.state != VM_STATE_LIVE && artemis.state != VM_STATE_SWITCHED_OUT) ||
        sk_hermes_send_one(vm->stadium_vm_id, artemis.vm_id, SK_HERMES_MSG_TYPE_LOG_BATCH,
                           0, payload, len) != 0) {
        vm->log_lost += records;
        vm->log_buf_len = 0;
        return -1;
    }
    vm->log_lost = 0;
    vm->log_buf_len = 0;
    return (int)records;
}

void vm_log_buffer_add(VM *vm, uint8_t level, uint64_t timestamp,
                       const char *msg, uint32_t len) {
    if (!vm || !msg) return;
    if (g_busy) { vm->log_lost++; return; }
    g_busy = 1;

    if (len > VM_LOG_BUF_SIZE - REC_HEAD) len = VM_LOG_BUF_SIZE - REC_HEAD;
    if (vm->log_buf_len + REC_HEAD + len > VM_LOG_BUF_SIZE) (void)send_buffer(vm);
    vm->log_buf_len = (uint16_t)(vm->log_buf_len +
        put_record(vm->log_buf + vm->log_buf_len, level, timestamp, msg, (uint16_t)len));
    if (level == LOG_ERROR) (void)send_buffer(vm);

    g_busy = 0;
}

int vm_log_buffer_flush(VM *vm) {
    int rc;
    if (!vm || g_busy) return -1;
    g_busy = 1;
    rc = send_buffer(vm);
    g_busy = 0;
    return rc;
}

int vm_log_batch_deliver(VM *vm, VMUuid from, const uint8_t *payload, uint32_t payload_len) {
    VMRegistryEntry artemis, sender;
    const char *source = "?";
    uint32_t at = 0;
    int written = 0, failed = 0;

    if (capsule_vm_find_by_name_nocase("Artemis", &artemis) != 0 || artemis.vm_ptr != (void *)vm) {
        return -1;
    }
    /* The source is the sender the kernel stamped on the message: a VM
     * cannot write a record under another's name. */
    if (capsule_vm_registry_get(from, &sender) == 0) source = sender.name;

    while (at + REC_HEAD <= payload_len) {
        uint8_t level = payload[at];
        uint64_t ts;
        uint16_t len;
        memcpy(&ts, payload + at + 1, 8);
        memcpy(&len, payload + at + 9, 2);
        if (at + REC_HEAD + len > payload_len) break; /* malformed tail: stop */
        if (log_region_append(level, ts, source, (uint32_t)strlen(source),
                              (const char *)payload + at + REC_HEAD, len) < 0) {
            failed++;
        } else {
            written++;
        }
        at += REC_HEAD + len;
    }
    if (failed) console_println("Artemis: log ring write failed -- records not kept");
    return written;
}

#endif /* __STARKERNEL__ */