/*
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2025 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */

/**
 * @file len.c
 * @brief Implements the OP_LEN opcode for getting the length of arrays or strings in the VM.
 *
 * This file handles the OP_LEN instruction, which retrieves the length of an array or string.
 * The array or string is popped from the stack, and the length is pushed back.
 *
 * Behavior:
 * - Pops the array or string from the stack.
 * - Retrieves the length of the array or string.
 * - Pushes the length onto the stack.
 *
 * Error Handling:
 * - Exits with an error if the operand is not an array or string.
 *
 * Example:
 * - Bytecode: OP_LEN
 * - Stack before: ["hello"]
 * - Stack after: [5]
 */

case OP_LEN: {
  Value a = pop_value(vm);
  int len = 0;
  if (a.type == VAL_STRING) {
    len = (int)(a.s ? (int)strlen(a.s) : 0);
  } else if (a.type == VAL_ARRAY) {
    len = array_length(&a);
    if (len < 0) len = 0;
  } else {
    /* Be lenient: for non-array/non-string, treat length as 0 */
    push_value(vm, make_int(0));
  }
  free_value(a);
  push_value(vm, make_int(len));
  break;
}
