JsonReader.hpp

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#pragma once
 
#include <initializer_list>
#include <limits>
#include <string>
 
#include <nlohmann/json.hpp>
 
namespace ppforest2 {
  class JsonReader {
  public:
    JsonReader(nlohmann::json const& j, std::string path);

    void require_object() const;

    JsonReader at(std::string const& key) const;

    template<typename T> T require(std::string const& key) const;

    template<typename T> T optional(std::string const& key, T fallback) const;

    bool contains(std::string const& key) const;

    std::string require_enum(std::string const& key, std::initializer_list<char const*> allowed) const;

    long long require_int(
        std::string const& key,
        long long min = std::numeric_limits<long long>::min(),
        long long max = std::numeric_limits<long long>::max()
    ) const;

    double require_number(
        std::string const& key,
        double min = -std::numeric_limits<double>::infinity(),
        double max = std::numeric_limits<double>::infinity()
    ) const;

    void only_keys(std::initializer_list<char const*> allowed) const;

    void require_keys(std::initializer_list<char const*> keys) const;

    nlohmann::json const& require_array(std::string const& key) const;

    void require_string_array(std::string const& key, bool non_empty = false) const;

    void forbid_key(std::string const& key, std::string const& reason) const;

    void expect_enum(std::string const& key, std::initializer_list<char const*> allowed) const {
      (void)require_enum(key, allowed);
    }
    void expect_int(
        std::string const& key,
        long long min = std::numeric_limits<long long>::min(),
        long long max = std::numeric_limits<long long>::max()
    ) const {
      (void)require_int(key, min, max);
    }
    void expect_number(
        std::string const& key,
        double min = -std::numeric_limits<double>::infinity(),
        double max = std::numeric_limits<double>::infinity()
    ) const {
      (void)require_number(key, min, max);
    }
    void expect_array(std::string const& key) const { (void)require_array(key); }

    nlohmann::json const& json() const { return j_; }

    std::string const& path() const { return path_; }
 
  private:
    nlohmann::json const& j_;
    std::string path_;
 
    std::string child_path(std::string const& key) const;
    nlohmann::json const& require_present(std::string const& key) const;
  };
}