json

/*
Copyright (C) 2018-2024 Geoffrey Daniels. https://gpdaniels.com/

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License only.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

#pragma once
#ifndef GTL_FILE_TEXT_JSON_HPP
#define GTL_FILE_TEXT_JSON_HPP

// Summary: A small json parser and composer. [wip]

#if defined(_MSC_VER)
#pragma warning(push, 0)
#endif

#include <cstdio>
#include <cstdlib>
#include <map>
#include <string>
#include <vector>

#if defined(_MSC_VER)
#pragma warning(pop)
#endif

namespace gtl {
    class json final {
    public:
        class value final {
        public:
            using null_type = decltype(nullptr);
            using bool_type = bool;
            using number_type = double;
            using string_type = std::string;
            using object_type = std::map<value::string_type, value>;
            using array_type = std::vector<value>;
        private:
            enum class contains {
                null_type,
                bool_type,
                number_type,
                string_type,
                object_type,
                array_type
            };
        private:
            contains type;
            union {
                null_type   null_value;
                bool_type   bool_value;
                number_type number_value;
                string_type string_value;
                object_type object_value;
                array_type  array_value;
            };
        public:
            ~value() {
                switch (this->type) {
                    case contains::null_type  : { null_value.~null_type(); } break;
                    case contains::bool_type  : { bool_value.~bool_type(); } break;
                    case contains::number_type: { number_value.~number_type(); } break;
                    case contains::string_type: { string_value.~string_type(); } break;
                    case contains::object_type: { object_value.~object_type(); } break;
                    case contains::array_type : { array_value.~array_type(); } break;
                }
            }
            value()
                : type(contains::null_type) {
                new (&null_value) null_type(nullptr);
            }
            value(const value& other)
                : type(other.type) {
                switch (this->type) {
                    case contains::null_type  : { new (&null_value) null_type(other.null_value); } break;
                    case contains::bool_type  : { new (&bool_value) bool_type(other.bool_value); } break;
                    case contains::number_type: { new (&number_value) number_type(other.number_value); } break;
                    case contains::string_type: { new (&string_value) string_type(other.string_value); } break;
                    case contains::object_type: { new (&object_value) object_type(other.object_value); } break;
                    case contains::array_type : { new (&array_value) array_type(other.array_value); } break;
                }
            }
            value(value&& other)
                : type(other.type) {
                switch (this->type) {
                    case contains::null_type  : { new (&null_value) null_type(static_cast<null_type&&>(other.null_value)); } break;
                    case contains::bool_type  : { new (&bool_value) bool_type(static_cast<bool_type&&>(other.bool_value)); } break;
                    case contains::number_type: { new (&number_value) number_type(static_cast<number_type&&>(other.number_value)); } break;
                    case contains::string_type: { new (&string_value) string_type(static_cast<string_type&&>(other.string_value)); } break;
                    case contains::object_type: { new (&object_value) object_type(static_cast<object_type&&>(other.object_value)); } break;
                    case contains::array_type : { new (&array_value) array_type(static_cast<array_type&&>(other.array_value)); } break;
                }
            }
            value& operator=(const value& other) {
                switch (this->type) {
                    case contains::null_type  : { null_value.~null_type(); } break;
                    case contains::bool_type  : { bool_value.~bool_type(); } break;
                    case contains::number_type: { number_value.~number_type(); } break;
                    case contains::string_type: { string_value.~string_type(); } break;
                    case contains::object_type: { object_value.~object_type(); } break;
                    case contains::array_type : { array_value.~array_type(); } break;
                }
                this->type = other.type;
                switch (this->type) {
                    case contains::null_type  : { new (&null_value) null_type(other.null_value); } break;
                    case contains::bool_type  : { new (&bool_value) bool_type(other.bool_value); } break;
                    case contains::number_type: { new (&number_value) number_type(other.number_value); } break;
                    case contains::string_type: { new (&string_value) string_type(other.string_value); } break;
                    case contains::object_type: { new (&object_value) object_type(other.object_value); } break;
                    case contains::array_type : { new (&array_value) array_type(other.array_value); } break;
                }
                return *this;
            }
            value& operator=(value&& other) {
                switch (this->type) {
                    case contains::null_type  : { null_value.~null_type(); } break;
                    case contains::bool_type  : { bool_value.~bool_type(); } break;
                    case contains::number_type: { number_value.~number_type(); } break;
                    case contains::string_type: { string_value.~string_type(); } break;
                    case contains::object_type: { object_value.~object_type(); } break;
                    case contains::array_type : { array_value.~array_type(); } break;
                }
                this->type = other.type;
                switch (this->type) {
                    case contains::null_type  : { new (&null_value) null_type(static_cast<null_type&&>(other.null_value)); } break;
                    case contains::bool_type  : { new (&bool_value) bool_type(static_cast<bool_type&&>(other.bool_value)); } break;
                    case contains::number_type: { new (&number_value) number_type(static_cast<number_type&&>(other.number_value)); } break;
                    case contains::string_type: { new (&string_value) string_type(static_cast<string_type&&>(other.string_value)); } break;
                    case contains::object_type: { new (&object_value) object_type(static_cast<object_type&&>(other.object_value)); } break;
                    case contains::array_type : { new (&array_value) array_type(static_cast<array_type&&>(other.array_value)); } break;
                }
                return *this;
            }
            value(null_type value)          : type(contains::null_type)   { new (&null_value) null_type(value); }
            value(bool_type value)          : type(contains::bool_type)   { new (&bool_value) bool_type(value); }
            value(number_type value)        : type(contains::number_type) { new (&number_value) number_type(value); }
            value(const string_type& value) : type(contains::string_type) { new (&string_value) string_type(value); }
            value(const object_type& value) : type(contains::object_type) { new (&object_value) object_type(value); }
            value(const array_type& value)  : type(contains::array_type)  { new (&array_value) array_type(value); }
        private:
            template <typename contains_type>
            class convert_to_contains_enum;
        public:
            template <typename is_type>
            bool is() const {
                return (this->type == convert_to_contains_enum<is_type>::type);
            }
        public:
            template <typename as_type>
            const as_type& as() const {
                if constexpr (convert_to_contains_enum<as_type>::type == contains::null_type) { return null_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::bool_type) { return bool_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::number_type) { return number_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::string_type) { return string_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::object_type) { return object_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::array_type) { return array_value; }
            }
            template <typename as_type>
            as_type& as() {
                if constexpr (convert_to_contains_enum<as_type>::type == contains::null_type) { return null_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::bool_type) { return bool_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::number_type) { return number_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::string_type) { return string_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::object_type) { return object_value; }
                else if constexpr (convert_to_contains_enum<as_type>::type == contains::array_type) { return array_value; }
            }
        public:
            string_type to_string() const {
                constexpr static const auto replace = [](string_type& string, const string_type& from, const string_type& to){
                    string_type::size_type position = 0;
                    while(true) {
                        string_type::size_type start = string.find(from, position);
                        if(start == string_type::npos) {
                            return;
                        }
                        string.replace(start, from.size(), to);
                        position += to.size();
                    }
                };
                switch (this->type) {
                    case contains::null_type  : {
                        return "null";
                    } break;
                    case contains::bool_type  : {
                        if (bool_value) {
                            return "true";
                        }
                        return "false";
                    } break;
                    case contains::number_type: {
                        char buffer[25] = {};
                        const int length = std::snprintf(&buffer[0], 25, "%g", number_value);
                        if ((length < 0) || (length >= 25)) {
                            return "";
                        }
                        return std::string(&buffer[0]);
                    } break;
                    case contains::string_type: {
                        string_type string = this->string_value;
                        replace(string, "\\", "\\\\");
                        replace(string, "\b", "\\\b");
                        replace(string, "\f", "\\\f");
                        replace(string, "\n", "\\\n");
                        replace(string, "\r", "\\\r");
                        replace(string, "\t", "\\\t");
                        replace(string, "\"", "\\\"");
                        return "\"" + string + "\"";
                    } break;
                    case contains::object_type: {
                        string_type string = "{";
                        for (const auto& [key, item] : this->object_value) {
                            string_type key_escaped = key;
                            replace(key_escaped, "\\", "\\\\");
                            replace(key_escaped, "\b", "\\\b");
                            replace(key_escaped, "\f", "\\\f");
                            replace(key_escaped, "\n", "\\\n");
                            replace(key_escaped, "\r", "\\\r");
                            replace(key_escaped, "\t", "\\\t");
                            replace(key_escaped, "\"", "\\\"");
                            if (string.size() == 1) {
                                string += "\"" + key_escaped + "\":" + item.to_string();
                            }
                            else {
                                string += ",\"" + key_escaped + "\":" + item.to_string();
                            }
                        }
                        return string + "}";
                    } break;
                    case contains::array_type : {
                        string_type string = "[";
                        for (const auto& value : this->array_value) {
                            if (string.size() == 1) {
                                string += value.to_string();
                            }
                            else {
                                string += "," + value.to_string();
                            }
                        }
                        return string + "]";
                    } break;
                }
                return "";
            }
        };

    private:
        value root;

    private:
        value parse_recursive(const std::string& data, std::string::size_type& index) {
            skip_whitespace(data, index);
            if (parse_null(data, index)) { return value(nullptr); }
            value::bool_type boolean;
            if (parse_bool(data, index, boolean)) { return value(boolean); }
            value::number_type number;
            if (parse_number(data, index, number)) { return value(number); }
            value::string_type string;
            if (parse_string(data, index, string)) { return value(string); }
            value::object_type object;
            if (parse_object(data, index, object)) { return value(object); }
            value::array_type array;
            if (parse_array(data, index, array)) { return value(array); }
            return value(nullptr);
        }
        void skip_whitespace(const std::string& data, std::string::size_type& index) {
            for (; index < data.size(); ++index) {
                switch (data[index]) {
                    case '\f': break;
                    case '\n': break;
                    case '\r': break;
                    case '\t': break;
                    case ' ': break;
                    default: return;
                }
            }
        }
        bool parse_null(const std::string& data, std::string::size_type& index) {
            if (data.substr(index, 4) == "null") {
                index += 4;
                return true;
            }
            return false;
        }
        bool parse_bool(const std::string& data, std::string::size_type& index, value::bool_type& boolean) {
            if (data.substr(index, 4) == "true") {
                boolean = true;
                index += 4;
                return true;
            }
            if (data.substr(index, 5) == "false") {
                boolean = false;
                index += 5;
                return true;
            }
            return false;
        }
        bool parse_number(const std::string& data, std::string::size_type& index, value::number_type& number) {
            std::string valid_number_characters = "0123456789-+eE.";
            std::string::size_type length = 0;
            while ((index + length < data.size()) && (valid_number_characters.find(data[index + length]) < valid_number_characters.size())) {
                ++length;
            }
            if (length == 0) {
                return false;
            }
            char* end_pointer = nullptr;
            std::string number_string = data.substr(index, length);
            number = std::strtod(number_string.c_str(), &end_pointer);
            if ((end_pointer != nullptr) && (*end_pointer == 0)) {
                index += length;
                return true;
            }
            return false;
        }
        bool parse_string(const std::string& data, std::string::size_type& index, value::string_type& string) {
            if (data[index] != '"') {
                return false;
            }
            std::string::size_type length = 1;
            while ((index + length < data.size()) && ((data[index + length] != '"') || ((data[index + length - 1] == '\\') && (data[index + length] == '"')))) {
                if (data[index + length] == '\b') {
                    return false;
                }
                if (data[index + length] == '\f') {
                    return false;
                }
                if (data[index + length] == '\n') {
                    return false;
                }
                if (data[index + length] == '\r') {
                    return false;
                }
                if (data[index + length] == '\t') {
                    return false;
                }
                ++length;
            }
            if (index + length == data.size()) {
                return false;
            }
            string = data.substr(index + 1, length - 1);
            index += length + 1;
            return true;
        }
        bool parse_object(const std::string& data, std::string::size_type& index, value::object_type& object) {
            if (data[index] != '{') {
                return false;
            }
            std::string::size_type index_object = index + 1;
            object = value::object_type();
            if (index_object >= data.size()) {
                return false;
            }
            if (data[index_object] == '}') {
                index = index_object + 1;
                return true;
            }
            while (index_object < data.size()) {
                skip_whitespace(data, index_object);
                value::string_type key;
                if (!parse_string(data, index_object, key)) {
                    return false;
                }
                skip_whitespace(data, index_object);
                if ((index_object >= data.size()) || (data[index_object] != ':')) {
                    return false;
                }
                ++index_object;
                skip_whitespace(data, index_object);
                value item = parse_recursive(data, index_object);
                object.insert({key, item});
                skip_whitespace(data, index_object);
                if (index_object >= data.size()) {
                    return false;
                }
                if (data[index_object] == '}') {
                    index = index_object + 1;
                    return true;
                }
                if (data[index_object] != ',') {
                    return false;
                }
                ++index_object;
            }
            return false;
        }
        bool parse_array(const std::string& data, std::string::size_type& index, value::array_type& array) {
            if (data[index] != '[') {
                return false;
            }
            std::string::size_type index_array = index + 1;
            array = value::array_type();
            if (index_array >= data.size()) {
                return false;
            }
            if (data[index_array] == ']') {
                index = index_array + 1;
                return true;
            }
            while (index_array < data.size()) {
                skip_whitespace(data, index_array);
                value item = parse_recursive(data, index_array);
                array.push_back(item);
                skip_whitespace(data, index_array);
                if (index_array >= data.size()) {
                    return false;
                }
                if (data[index_array] == ']') {
                    index = index_array + 1;
                    return true;
                }
                if (data[index_array] != ',') {
                    return false;
                }
                ++index_array;
            }
            return false;
        }

    public:
        bool parse(const std::string& data) {
            std::string::size_type index = 0;
            this->root = parse_recursive(data, index);
            return (index == data.size());
        }

        std::string compose() const {
            return this->root.to_string();
        }

        value& document() {
            return this->root;
        }
    };

    template <typename contains_type>
    class json::value::convert_to_contains_enum<const contains_type> final { public: constexpr static const json::value::contains type = json::value::convert_to_contains_enum<contains_type>::type; };
    template <> class json::value::convert_to_contains_enum<json::value::null_type> final { public: constexpr static const json::value::contains type = json::value::contains::null_type; };
    template <> class json::value::convert_to_contains_enum<json::value::bool_type> final { public: constexpr static const json::value::contains type = json::value::contains::bool_type; };
    template <> class json::value::convert_to_contains_enum<json::value::number_type> final { public: constexpr static const json::value::contains type = json::value::contains::number_type; };
    template <> class json::value::convert_to_contains_enum<json::value::string_type> final { public: constexpr static const json::value::contains type = json::value::contains::string_type; };
    template <> class json::value::convert_to_contains_enum<json::value::object_type> final { public: constexpr static const json::value::contains type = json::value::contains::object_type; };
    template <> class json::value::convert_to_contains_enum<json::value::array_type> final { public: constexpr static const json::value::contains type = json::value::contains::array_type; };
}

#endif // GTL_FILE_TEXT_JSON_HPP