json.hpp

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#pragma once
#include "djson/error.hpp"
#include "djson/string_table.hpp"
#include <expected>
#include <format>
#include <memory>
#include <span>
#include <string>
#include <utility>
 
namespace dj {
template <typename Type>
concept NumericT = std::integral<Type> || std::floating_point<Type>;

template <typename Type>
concept StringyT = std::convertible_to<Type, std::string_view>;

template <typename Type>
concept GettableT = std::same_as<Type, bool> || NumericT<Type> || StringyT<Type>;

template <typename Type>
concept SettableT = std::same_as<Type, std::nullptr_t> || GettableT<Type>;
 
class Json;

using Result = std::expected<Json, Error>;

enum class JsonType : std::int8_t { Null, Boolean, Number, String, Array, Object, COUNT_ };

struct SerializeFlag {
    // NOLINTNEXTLINE(cppcoreguidelines-use-enum-class)
    enum : std::uint8_t {
        None = 0,
        SortKeys = 1 << 0,
        TrailingNewline = 1 << 1,
        NoSpaces = 1 << 2,
    };
};
using SerializeFlags = decltype(std::to_underlying(SerializeFlag::None));
inline constexpr auto serialize_flags_v =
    static_cast<SerializeFlags>(SerializeFlag::SortKeys | SerializeFlag::TrailingNewline);

struct SerializeOptions {
    std::string_view indent{"  "};
    std::string_view newline{"\n"};
    SerializeFlags flags{serialize_flags_v};
};

enum class ParseMode : std::int8_t {
    Auto,
    Strict,
    Jsonc,
};
 
namespace detail {
struct Value;
class Parser;
} // namespace detail

class Json {
  public:
    using Type = JsonType;
 
    Json() = default;
    ~Json() = default;
 
    Json(Json&&) = default;
    auto operator=(Json&&) -> Json& = default;
 
    Json(Json const& other);
    auto operator=(Json const& other) -> Json&;
 
    explicit(false) Json(std::nullptr_t) noexcept {}
 
    template <SettableT Type>
    explicit(false) Json(Type const& value) {
        set(value);
    }

    [[nodiscard]] static auto parse(std::string_view text, ParseMode mode = ParseMode::Auto) -> Result;
    [[nodiscard]] static auto from_file(std::string_view path, ParseMode mode = ParseMode::Auto) -> Result;

    [[nodiscard]] static auto empty_array() -> Json const&;
    [[nodiscard]] static auto empty_object() -> Json const&;

    [[nodiscard]] auto get_type() const -> Type;
 
    [[nodiscard]] auto is_null() const -> bool { return get_type() == Type::Null; }
    [[nodiscard]] auto is_boolean() const -> bool { return get_type() == Type::Boolean; }
    [[nodiscard]] auto is_number() const -> bool { return get_type() == Type::Number; }
    [[nodiscard]] auto is_string() const -> bool { return get_type() == Type::String; }
    [[nodiscard]] auto is_array() const -> bool { return get_type() == Type::Array; }
    [[nodiscard]] auto is_object() const -> bool { return get_type() == Type::Object; }
 
    [[nodiscard]] auto as_bool(bool fallback = {}) const -> bool;
    [[nodiscard]] auto as_double(double fallback = {}) const -> double;
    [[nodiscard]] auto as_u64(std::uint64_t fallback = {}) const -> std::uint64_t;
    [[nodiscard]] auto as_i64(std::int64_t fallback = {}) const -> std::int64_t;
 
    [[nodiscard]] auto as_string_view(std::string_view fallback = {}) const -> std::string_view;
    [[nodiscard]] auto as_string(std::string_view const fallback = {}) const -> std::string {
        return std::string{as_string_view(fallback)};
    }
 
    template <NumericT Type>
    [[nodiscard]] auto as_number(Type const fallback = {}) const -> Type {
        if constexpr (std::signed_integral<Type>) {
            return static_cast<Type>(as_i64(static_cast<std::int64_t>(fallback)));
        } else if constexpr (std::unsigned_integral<Type>) {
            return static_cast<Type>(as_u64(static_cast<std::uint64_t>(fallback)));
        } else {
            return static_cast<Type>(as_double(static_cast<double>(fallback)));
        }
    }
 
    template <GettableT Type>
    [[nodiscard]] auto as(Type const& fallback = {}) const -> Type {
        if constexpr (std::same_as<Type, bool>) {
            return as_bool(fallback);
        } else if constexpr (NumericT<Type>) {
            return as_number(fallback);
        } else if constexpr (std::same_as<Type, std::string_view>) {
            return as_string_view(fallback);
        } else {
            return as_string(fallback);
        }
    }
 
    [[nodiscard]] auto as_array() const -> std::span<dj::Json const>;
    [[nodiscard]] auto as_object() const -> StringTable<dj::Json> const&;
 
    void set_null();
    void set_boolean(bool value);
    void set_string(std::string_view value);
    void set_number(std::int64_t value);
    void set_number(std::uint64_t value);
    void set_number(double value);
    void set_value(Json value);
 
    template <NumericT Type>
    void set_number(Type const value) {
        if constexpr (std::signed_integral<Type>) {
            set_number(static_cast<std::int64_t>(value));
        } else if constexpr (std::unsigned_integral<Type>) {
            set_number(static_cast<std::uint64_t>(value));
        } else {
            set_number(static_cast<double>(value));
        }
    }
 
    template <SettableT Type>
    void set(Type const& value) {
        if constexpr (std::same_as<Type, std::nullptr_t>) {
            set_null();
        } else if constexpr (std::same_as<Type, bool>) {
            set_boolean(value);
        } else if constexpr (NumericT<Type>) {
            set_number(value);
        } else {
            set_string(value);
        }
    }

    void set_array();
    void set_object();

    auto push_back(Json value = {}) -> Json&;
    auto insert_or_assign(std::string key, Json value) -> Json&;

    [[nodiscard]] auto at(std::string_view key) const -> Json const&;
    [[nodiscard]] auto at(std::string_view key) -> Json&;
    [[nodiscard]] auto at(std::size_t index) const -> Json const&;
    [[nodiscard]] auto at(std::size_t index) -> Json&;
 
    [[nodiscard]] auto& operator[](this auto&& self, std::string_view const key) { return self.at(key); }
    [[nodiscard]] auto& operator[](this auto&& self, std::size_t const index) { return self.at(index); }

    [[nodiscard]] auto serialize(SerializeOptions const& options = {}) const -> std::string;
    [[nodiscard]] auto to_file(std::string_view path, SerializeOptions const& options = {}) const -> bool;
 
    friend void swap(Json& a, Json& b) noexcept { std::swap(a.m_value, b.m_value); }
 
    explicit operator bool() const { return m_value != nullptr; }
 
  private:
    struct Serializer;
 
    struct Deleter {
        void operator()(detail::Value* ptr) const noexcept;
    };
 
    void ensure_impl();
 
    std::unique_ptr<detail::Value, Deleter> m_value;
 
    friend class detail::Parser;
};
 
[[nodiscard]] inline auto to_string(Json const& json, SerializeOptions const& options = {}) {
    return json.serialize(options);
}

[[nodiscard]] auto make_escaped(std::string_view text) -> std::string;

template <GettableT Type>
void from_json(Json const& json, Type& value, Type const fallback = {}) {
    value = json.as<Type>(fallback);
}

template <SettableT Type>
void to_json(Json& json, Type const& value) {
    json.set(value);
}
} // namespace dj

template <>
struct std::formatter<dj::Json> {
    template <typename FormatParseContext>
    constexpr auto parse(FormatParseContext& pc) const {
        return pc.begin();
    }
 
    static auto format(dj::Json const& json, std::format_context& fc) -> std::format_context::iterator;
};