json-validator/include/jvalidate/validator.h

#pragma once

#include <regex>
#include <unordered_map>

#include <jvalidate/detail/on_block_exit.h>
#include <jvalidate/forward.h>
#include <jvalidate/status.h>
#include <jvalidate/validation_config.h>
#include <jvalidate/validation_visitor.h>

namespace jvalidate::detail {
/**
 * @brief An implementation of a regular expression "engine", for use with
 * constraints like "pattern" and "patternProperties".
 * Uses std::regex as its underlying implementation.
 *
 * While being std::regex means that it is the most sensible choice for a
 * default RegexEngine, the performance of std::regex is generally the worst
 * among C++ regex utilities, and it struggles to compile several patterns.
 * See https://stackoverflow.com/questions/70583395/ for an explaination.
 *
 * If you need to use complicated patterns in your json schema, provide a
 * RegexEngine compatible wrapper for a different library, such as re2.
 */
class StdRegexEngine {
private:
  std::unordered_map<std::string, std::regex> cache_;

public:
  static bool is_valid(std::string const & regex) {
    try {
      [[maybe_unused]] std::regex _{regex};
      return true;
    } catch (...) { return false; }
  }

  bool search(std::string const & regex, std::string const & text) {
    // TODO: detail::regex_escape
    auto const & re = cache_.try_emplace(regex, regex).first->second;
    return std::regex_search(text, re);
  }
};

/**
 * @brief An implementation of an "Extension Constraint Visitor" plugin that
 * does nothing.
 */
struct StubExtensionVisitor {};
}

namespace jvalidate {
/**
 * @brief A validator is the tool by which a JSON object is actually validated
 * against a schema.
 *
 * @tparam RE A type that can be used to solve regular expressions
 */
template <RegexEngine RE = detail::StdRegexEngine,
          typename ExtensionVisitor = detail::StubExtensionVisitor>
class Validator {
private:
  schema::Node const & schema_;
  ValidationConfig cfg_;
  ExtensionVisitor extension_;
  RE regex_;

public:
  /**
   * @brief Construct a Validator
   *
   * @param schema The root schema being validated against. Must outlive this.
   *
   * @param cfg Any special (runtime) configuration rules being applied to the
   * validator.
   */
  Validator(schema::Node const & schema, ExtensionVisitor extension = {},
            ValidationConfig const & cfg = {})
      : schema_(schema), cfg_(cfg), extension_(extension) {}

  Validator(schema::Node const & schema, ValidationConfig const & cfg)
      : schema_(schema), cfg_(cfg) {}

  template <typename... Args> Validator(schema::Node &&, Args &&...) = delete;

  /**
   * @brief Run validation on the given JSON
   *
   * @tparam A Any Adapter type, in principle a subclass of adapter::Adapter.
   * Disallows mutation via ValidationConfig.construct_default_values
   *
   * @param json The value being validated
   *
   * @param result An optional out-param of detailed information about
   * validation failures. If result is not provided, then the validator will
   * terminate on the first error. Otherwise it will run through the entire
   * schema to provide a record of all of the failures.
   */
  template <Adapter A>
    requires(not MutableAdapter<A>)
  bool validate(A const & json, ValidationResult * result = nullptr) {
    EXPECT_M(not cfg_.construct_default_values,
             "Cannot perform mutations on an immutable JSON Adapter");
    detail::OnBlockExit _ = [&result, this]() { post_process(result); };
    return static_cast<bool>(
        ValidationVisitor(schema_, cfg_, regex_, extension_, result).validate(json));
  }

  /**
   * @brief Run validation on the given JSON
   *
   * @tparam A Any Adapter type that supports assignment, in principle a
   * subclass of adapter::Adapter.
   *
   * @param json The value being validated. Because A is a reference-wrapper,
   * the underlying value may be mutated.
   *
   * @param result An optional out-param of detailed information about
   * validation failures. If result is not provided, then the validator will
   * terminate on the first error. Otherwise it will run through the entire
   * schema to provide a record of all of the failures.
   */
  template <MutableAdapter A> bool validate(A const & json, ValidationResult * result = nullptr) {
    detail::OnBlockExit _ = [&result, this]() { post_process(result); };
    return static_cast<bool>(
        ValidationVisitor(schema_, cfg_, regex_, extension_, result).validate(json));
  }

  /**
   * @brief Run validation on the given JSON
   *
   * @tparam JSON A concrete JSON type. Will be turned into an Adapter, or a
   * MutableAdapter (if json is non-const and exists).
   *
   * @param json The value being validated.
   *
   * @param result An optional out-param of detailed information about
   * validation failures. If result is not provided, then the validator will
   * terminate on the first error. Otherwise it will run through the entire
   * schema to provide a record of all of the failures.
   */
  template <typename JSON>
    requires(not Adapter<JSON>)
  bool validate(JSON & json, ValidationResult * result = nullptr) {
    return validate(adapter::AdapterFor<JSON>(json), result);
  }

private:
  void post_process(ValidationResult *& result) const {
    if (result == nullptr) {
      return;
    }
    if (cfg_.only_return_results_with_error) {
      *result = result->only_errors();
    }
  }
};
}