/*
  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.

 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.

 */

#include "io.h"
#include "log.h"

#include <string.h>

/** @} */

/**
 * @brief Initialize the IO subsystem
 * @param vm Pointer to VM instance
 *
 * Initializes the block device view over the unified VM memory.
 * Zeros out the entire VM memory space.
 */
void io_init(VM *vm) {
    if (!vm || !vm->memory) {
        log_message(LOG_ERROR, "io_init: VM or VM memory not initialized");
        return;
    }

    /* Zero the entire VM address space so blocks start clean. */
    memset(vm->memory, 0, VM_MEMORY_SIZE);

    log_message(LOG_INFO,
                "IO subsystem initialized with %d blocks of %d bytes",
                (int) MAX_BLOCKS, (int) BLOCK_SIZE);
}

/*
 * @brief Write a block to VM memory
 * @param vm Pointer to VM instance
 * @param block_num Block number to write (0 to MAX_BLOCKS-1)
 * @param buffer Source buffer containing block data
 * @return 0 on success, -1 on error
 */
/**
 * @brief Write a block to VM memory
 * @param vm Pointer to VM instance
 * @param block_num Block number to write (0 to MAX_BLOCKS-1)
 * @param buffer Source buffer containing block data
 * @return 0 on success, -1 on error
 *
 * Writes a BLOCK_SIZE chunk of data from the provided buffer into the VM's memory
 * at the specified block number offset. The block number must be within valid range.
 * The entire block is written atomically.
 *
 * @note The buffer must contain at least BLOCK_SIZE bytes of valid data
 */
int io_write_block(VM *vm, int block_num, const unsigned char *buffer) {
    if (!vm || !vm->memory || !buffer) {
        log_message(LOG_ERROR, "io_write_block: bad args");
        return -1;
    }
    if (block_num < 0 || block_num >= (int) MAX_BLOCKS) {
        log_message(LOG_ERROR, "io_write_block: invalid block number %d", block_num);
        return -1;
    }
    size_t off = (size_t) block_num * (size_t) BLOCK_SIZE;
    memcpy(&vm->memory[off], buffer, BLOCK_SIZE);
    log_message(LOG_DEBUG, "io_write_block: wrote block %d", block_num);
    return 0;
}