/**
 * 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 neq.c
 * @brief Implements the OP_NEQ opcode for inequality comparison in the VM.
 *
 * This file handles the OP_NEQ instruction, which checks if two values are not equal.
 * The values are popped from the stack, and the result (1 or 0) is pushed back.
 *
 * Behavior:
 * - Pops two values from the stack.
 * - Checks if the values are not equal.
 * - Pushes 1 (true) or 0 (false) onto the stack.
 *
 * Error Handling:
 * - Exits with an error if the operands are of incompatible types.
 *
 * Example:
 * // Bytecode: OP_NEQ
 * // Stack before: [42, 10]
 * // Stack after: [1]
 *
 * @author Johannes Findeisen
 * @date 2025-10-16
 */

case OP_NEQ: {
  Value b = pop_value(vm);
  Value a = pop_value(vm);
  int neq = 1;
  if (a.type == b.type) {
    switch (a.type) {
    case VAL_INT:
      neq = (a.i != b.i);
      break;
    case VAL_BOOL:
      neq = ((a.i != 0) != (b.i != 0));
      break;
    case VAL_STRING:
      neq = (a.s && b.s) ? (strcmp(a.s, b.s) != 0) : (a.s != b.s);
      break;
    case VAL_FUNCTION:
      neq = (a.fn != b.fn);
      break;
    case VAL_NIL:
      neq = 0;
      break;
    default:
      neq = 1;
      break;
    }
  } else {
    /* interop: bool vs int (0/1) */
    if ((a.type == VAL_BOOL && b.type == VAL_INT) || (a.type == VAL_INT && b.type == VAL_BOOL)) {
      int ai = (a.type == VAL_BOOL) ? (a.i != 0) : (a.i != 0);
      int bi = (b.type == VAL_BOOL) ? (b.i != 0) : (b.i != 0);
      neq = (ai != bi);
    } else {
      neq = 1;
    }
  }
  push_value(vm, make_bool(neq));
  free_value(a);
  free_value(b);
  break;
}