stringify.c

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/*
 * 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 stringify.c
 * @brief VM opcode snippet for converting a Fun Value to a JSON string.
 *
 * Implements the OP_JSON_STRINGIFY instruction. Expects a boolean/integer flag
 * indicating pretty-printing and a Value to serialize. Uses json-c to build a
 * json_object from the Value and then renders it to a string, which is pushed
 * back to the stack.
 *
 * Build gating: compiled only when FUN_WITH_JSON is enabled. Otherwise the
 * opcode consumes its two arguments and pushes the string "null".
 *
 * Stack effect (with FUN_WITH_JSON):
 * - Pops: pretty (bool/int), value (any)
 * - Pushes: string (JSON representation)
 *
 * Errors and edge cases:
 * - If conversion to json_object fails, an empty string is pushed.
 * - Pretty printing selects JSON_C_TO_STRING_PRETTY; otherwise plain output.
 */
 
/* JSON_STRINGIFY */
case OP_JSON_STRINGIFY: {
#ifdef FUN_WITH_JSON
  Value vpretty = pop_value(vm);
  Value any = pop_value(vm);
  int pretty = (vpretty.type == VAL_BOOL || vpretty.type == VAL_INT) ? (vpretty.i != 0) : 0;
  json_object *j = fun_to_json(&any);
  int flags = pretty ? JSON_C_TO_STRING_PRETTY : JSON_C_TO_STRING_PLAIN;
  const char *js = json_object_to_json_string_ext(j, flags);
  push_value(vm, make_string(js ? js : ""));
  json_object_put(j);
  free_value(vpretty);
  free_value(any);
#else
  /* Fallback: consume two args, push "null" */
  Value vpretty = pop_value(vm);
  free_value(vpretty);
  Value any = pop_value(vm);
  free_value(any);
  push_value(vm, make_string("null"));
#endif
  break;
}