full_json.cpp

#include "json.h"

#include <cctype>
#include <cmath>
#include <unordered_map>

using namespace std::string_literals;

namespace json {

namespace {

const std::unordered_map<char, char> kEscapeSymbolsDirectOrder{
    {'\n', 'n'}, {'\t', 't'}, {'\r', 'r'}, {'\\', '\\'}, {'\"', '"'}};

const std::unordered_map<char, char> kEscapeSymbolsReversedOrder{
    {'\\', '\\'}, {'"', '"'}, {'n', '\n'}, {'t', '\t'}, {'r', '\r'}};

struct NodeContainerPrinter {
    std::ostream& out;

    void operator()(std::nullptr_t /* value */) const {
        out << "null"s;
    }
    void operator()(bool value) const {
        out << (value ? "true"s : "false"s);
    }
    void operator()(int value) const {
        out << value;
    }
    void operator()(double value) const {
        out << value;
    }
    void operator()(const std::string& value) const {
        out << '"';

        for (const char symbol : value) {
            if (kEscapeSymbolsDirectOrder.count(symbol) > 0) {
                out << '\\' << kEscapeSymbolsDirectOrder.at(symbol);
            } else {
                out << symbol;
            }
        }

        out << '"';
    }
    void operator()(const Dict& map) const {
        out << '{';
        int id{0};
        for (const auto& [key, value] : map) {
            if (id++ != 0)
                out << ", "s;
            out << '"' << key << '"';
            out << ':';
            std::visit(NodeContainerPrinter{out}, value.AsPureNodeContainer());
        }
        out << '}';
    }
    void operator()(const Array& array) const {
        out << '[';

        int id{0};
        for (const auto& value : array) {
            if (id++ != 0)
                out << ", "s;
            std::visit(NodeContainerPrinter{out}, value.AsPureNodeContainer());
        }

        out << ']';
    }
};

/* Load methods */

std::string LoadLetters(std::istream& input) {
    std::string result;
    while (std::isalpha(input.peek()))
        result.push_back(static_cast<char>(input.get()));

    return result;
}

Node LoadNode(std::istream& input);

Node LoadNull(std::istream& input) {
    if (auto value = LoadLetters(input); value == "null"s)
        return Node{nullptr};

    throw ParsingError(R"(Incorrect format for Null Node parsing. "null" expected)"s);
}

Node LoadBool(std::istream& input) {
    std::string value = LoadLetters(input);
    if (value == "true"s)
        return Node{true};
    if (value == "false"s)
        return Node{false};

    throw ParsingError(R"(Incorrect format for Boolean Node parsing. "true" or "false" expected)"s);
}

Node LoadArray(std::istream& input) {
    Array result;

    for (char symbol; input >> symbol && symbol != ']';) {
        if (symbol != ',')
            input.putback(symbol);

        result.emplace_back(LoadNode(input));

        if (input >> symbol) {
            // Break if this is the end of array
            if (symbol == ']')
                break;
            // If parsed element was not last, but there is no "," afterwards
            if (symbol != ',')
                throw ParsingError(R"(All elements of the Array should be separated with the "," symbol)"s);
        } else {
            throw ParsingError(R"(During Array Node parsing expected "," or "]" symbols)"s);
        }
    }

    if (!input)
        throw ParsingError("Incorrect format for Array Node parsing"s);

    return Node{std::move(result)};
}

Node LoadNumber(std::istream& input) {
    std::string parsed_num;

    // Считывает в parsed_num очередной символ из input
    auto read_char = [&parsed_num, &input] {
        parsed_num += static_cast<char>(input.get());
        if (!input) {
            throw ParsingError("Failed to read number from stream"s);
        }
    };

    // Считывает одну или более цифр в parsed_num из input
    auto read_digits = [&input, read_char] {
        if (!std::isdigit(input.peek())) {
            throw ParsingError("A digit is expected"s);
        }
        while (std::isdigit(input.peek())) {
            read_char();
        }
    };

    if (input.peek() == '-') {
        read_char();
    }
    // Парсим целую часть числа
    if (input.peek() == '0') {
        read_char();
        // После 0 в JSON не могут идти другие цифры
    } else {
        read_digits();
    }

    bool is_int = true;
    // Парсим дробную часть числа
    if (input.peek() == '.') {
        read_char();
        read_digits();
        is_int = false;
    }

    // Парсим экспоненциальную часть числа
    if (int ch = input.peek(); ch == 'e' || ch == 'E') {
        read_char();
        if (ch = input.peek(); ch == '+' || ch == '-') {
            read_char();
        }
        read_digits();
        is_int = false;
    }

    try {
        if (is_int) {
            // Сначала пробуем преобразовать строку в int
            try {
                return Node{std::stoi(parsed_num)};
            } catch (...) {
                // В случае неудачи, например, при переполнении,
                // код ниже попробует преобразовать строку в double
            }
        }
        return Node{std::stod(parsed_num)};
    } catch (...) {
        throw ParsingError("Failed to convert "s + parsed_num + " to number"s);
    }
}

Node LoadString(std::istream& input) {
    if (!input)
        throw ParsingError("Incorrect format for String Node parsing. Unexpected EOF"s);

    input >> std::noskipws;
    std::string result;

    char current;
    char escape_symbol;

    while (input >> current) {
        // If " is not a part of \" symbol - this is the end of the line
        if (current == '"')
            break;

        // If string starts with '\\' -> this is an escape symbol
        if (current == '\\') {
            // If it is possible to read escape symbol (// is not the end of the string)
            if (input >> escape_symbol) {
                if (kEscapeSymbolsReversedOrder.count(escape_symbol) > 0) {
                    result += kEscapeSymbolsReversedOrder.at(escape_symbol);
                } else {
                    throw ParsingError("Unknown escape symbol: \\"s + std::string{escape_symbol});
                }
            } else {
                throw ParsingError("Incorrect input String for parsing"s);
            }
        } else {
            result += current;
        }
    }

    input >> std::skipws;

    if (!input)
        throw ParsingError("Incorrect input String for parsing"s);

    return Node{std::move(result)};
}

Node LoadDict(std::istream& input) {
    Dict result;

    for (char symbol; input >> symbol && symbol != '}';) {
        if (symbol == '"') {
            std::string key = LoadString(input).AsString();
            if (result.count(key) > 0)
                throw ParsingError("Key "s + key + " is already exists in the Dict"s);

            if (input >> symbol && symbol != ':')
                throw ParsingError(R"(Dict "key" should be separated from "value" with ":" symbol)"s);

            result.emplace(std::move(key), LoadNode(input));
        } else if (symbol != ',') {
            throw ParsingError(R"(Dict {"key":value} pairs should be separated with "," symbol)"s);
        }
    }

    if (!input)
        throw ParsingError("Incorrect format for Dict Node parsing"s);

    return Node{std::move(result)};
}

Node LoadNode(std::istream& input) {
    char symbol;
    if (!(input >> symbol))
        throw ParsingError("Incorrect format for Node parsing. Unexpected EOF"s);

    if (symbol == 'n') {
        input.putback(symbol);
        return LoadNull(input);
    } else if (symbol == 't' || symbol == 'f') {
        input.putback(symbol);
        return LoadBool(input);
    } else if (symbol == '[') {
        return LoadArray(input);
    } else if (symbol == '{') {
        return LoadDict(input);
    } else if (symbol == '"') {
        return LoadString(input);
    } else {
        input.putback(symbol);
        return LoadNumber(input);
    }
}

}  // namespace

/* Constructors */

Node::Node(bool value) : data_(value) {}
Node::Node(std::nullptr_t /* value*/) : Node() {}
Node::Node(int value) : data_(value) {}
Node::Node(double value) : data_(value) {}
Node::Node(std::string value) : data_(std::move(value)) {}
Node::Node(Dict map) : data_(std::move(map)) {}
Node::Node(Array array) : data_(std::move(array)) {}

/* Is-like methods */

bool Node::IsNull() const {
    return std::holds_alternative<std::nullptr_t>(data_);
}
bool Node::IsBool() const {
    return std::holds_alternative<bool>(data_);
}
bool Node::IsInt() const {
    return std::holds_alternative<int>(data_);
}
bool Node::IsDouble() const {
    return std::holds_alternative<double>(data_) || std::holds_alternative<int>(data_);
}
bool Node::IsPureDouble() const {
    double integral_part{0.};
    return !std::holds_alternative<int>(data_) && std::fmod(std::get<double>(data_), integral_part) != 0.;
}
bool Node::IsString() const {
    return std::holds_alternative<std::string>(data_);
}
bool Node::IsArray() const {
    return std::holds_alternative<Array>(data_);
}
bool Node::IsMap() const {
    return std::holds_alternative<Dict>(data_);
}

/* As-like methods */

const NodeContainer& Node::AsPureNodeContainer() const {
    return data_;
}

bool Node::AsBool() const {
    if (auto* value = std::get_if<bool>(&data_))
        return *value;
    throw std::logic_error("Impossible to parse node as Boolean"s);
}

int Node::AsInt() const {
    if (auto* value = std::get_if<int>(&data_))
        return *value;
    throw std::logic_error("Impossible to parse node as Int "s);
}

double Node::AsDouble() const {
    if (auto* value = std::get_if<double>(&data_))
        return *value;

    if (auto* value = std::get_if<int>(&data_))
        return static_cast<double>(*value);

    throw std::logic_error("Impossible to parse node as Double "s);
}

const std::string& Node::AsString() const {
    if (auto* value = std::get_if<std::string>(&data_))
        return *value;
    throw std::logic_error("Impossible to parse node as String"s);
}

const Array& Node::AsArray() const {
    if (auto* value = std::get_if<Array>(&data_))
        return *value;
    throw std::logic_error("Impossible to parse node as Array"s);
}

const Dict& Node::AsMap() const {
    if (auto* value = std::get_if<Dict>(&data_))
        return *value;
    throw std::logic_error("Impossible to parse node as Dict"s);
}

/* Operators */

bool operator==(const Node& left, const Node& right) {
    return left.data_ == right.data_;
}

bool operator!=(const Node& left, const Node& right) {
    return !(left == right);
}

/* Document */

Document::Document(Node root) : root_(std::move(root)) {}

const Node& Document::GetRoot() const {
    return root_;
}

bool operator==(const Document& left, const Document& right) {
    return left.GetRoot() == right.GetRoot();
}

bool operator!=(const Document& left, const Document& right) {
    return !(left == right);
}

Document Load(std::istream& input) {
    return Document{LoadNode(input)};
}

void Print(const Document& doc, std::ostream& output) {
    std::visit(NodeContainerPrinter{output}, doc.GetRoot().AsPureNodeContainer());

    // Реализуйте функцию самостоятельно
}

}  // namespace json