#include "storage.hpp"
#include "../../num/safe_cast.hpp"
#include <fstream>
#include <concepts>
#include <type_traits>

#define TYPES ::yycc::carton::binstore::types
#define CFG ::yycc::carton::binstore::configuration
#define SERDES ::yycc::carton::binstore::serializer
#define SAFECAST ::yycc::num::safe_cast

namespace yycc::carton::binstore::storage {

#pragma region Read and Write Helper Functions

    static bool read_buffer(std::istream& s, void* buffer, size_t length) {
        // Cast length
        auto rv_length = SAFECAST::try_to<std::streamsize>(length);
        if (!rv_length.has_value()) return false;
        auto cast_length = rv_length.value();

        // Read data.
        s.read(static_cast<std::istream::char_type*>(buffer), cast_length);
        // Check read count.
        if (s.gcount() != cast_length) return false;
        // Return IO status.
        return s.good();
    }

    template<typename T>
    requires std::is_pod_v<T>
    static bool read_pod(std::istream& s, T& val) {
        return read_buffer(s, &val, sizeof(T));
    }

    static bool read_byte_array(std::istream& s, TYPES::ByteArray& ba) {
        size_t length = 0;
        if (!read_pod(s, length)) return false;

        // Resize byte array.
        // There is an exception may be thrown that resized length is too large.
        // We need capture it and return error.
        try {
            ba.resize_data(length);
        } catch (const std::exception&) {
            return false;
        }
        // Read data into byte array.
        read_buffer(s, ba.get_data_ptr(), length);
        // Okey
        return true;
    }

    static bool write_buffer(std::ostream& s, const void* buffer, size_t length) {
        // Cast length
        auto rv_length = SAFECAST::try_to<std::streamsize>(length);
        if (!rv_length.has_value()) return false;
        auto cast_length = rv_length.value();

        // Write data.
        s.write(static_cast<const std::istream::char_type*>(buffer), cast_length);
        // There is no function to tell how many data was written,
        // so directly return.
        return s.good();
    }

    template<typename T>
        requires std::is_pod_v<T>
    static bool write_pod(std::ostream& s, const T& val) {
        return write_buffer(s, &val, sizeof(T));
    }

    static bool write_byte_array(std::ostream& s, const TYPES::ByteArray& ba) {
        // Write length header.
        auto length = ba.get_data_size();
        if (!write_pod(s, length)) return false;
        // Write body
        return write_buffer(s, ba.get_data_ptr(), length);
    }

#pragma endregion

#pragma region Storage Class

    Storage::Storage(CFG::Configuration&& cfg) : cfg(std::move(cfg)), raws() {}

    Storage::~Storage() {}

    TYPES::BinstoreResult<void> Storage::load_from_file(const std::filesystem::path& fpath, LoadStrategy strategy) {
        std::ifstream fs(fpath, std::ios::binary);
        if (fs.is_open()) {
            auto rv = this->load(fs, strategy);
            fs.close();
            return rv;
        } else {
            return std::unexpected(TYPES::BinstoreError::Io);
        }
    }

    TYPES::BinstoreResult<void> Storage::load(std::istream& s, LoadStrategy strategy) {
        return TYPES::BinstoreResult<void>();
    }

    TYPES::BinstoreResult<void> Storage::save_into_file(const std::filesystem::path& fpath) {
        std::ofstream fs(fpath, std::ios::binary);
        if (fs.is_open()) {
            auto rv = this->save(fs);
            fs.close();
            return rv;
        } else {
            return std::unexpected(TYPES::BinstoreError::Io);
        }
    }

    TYPES::BinstoreResult<void> Storage::save(std::ostream& s) {
        return TYPES::BinstoreResult<void>();
    }

    bool Storage::has_setting(TYPES::Token token) const {
        return this->cfg.get_settings().has_setting(token);
    }

    bool Storage::is_setting_stored(TYPES::Token token) const {
        if (!this->has_setting(token)) throw std::logic_error("given setting token is invalid");
        return this->raws.contains(token);
    }

    const TYPES::ByteArray& Storage::get_raw_value(TYPES::Token token) const {
        if (!this->has_setting(token)) throw std::logic_error("given setting token is invalid");
        auto finder = this->raws.find(token);
        if (finder != this->raws.end()) {
            return finder->second;
        } else {
            throw std::logic_error("given setting has not been stored yet");
        }
    }

    void Storage::set_raw_value(TYPES::Token token, TYPES::ByteArray&& ba) {
        if (!this->has_setting(token)) throw std::logic_error("given setting token is invalid");
        this->raws.insert_or_assign(token, std::move(ba));
    }

#pragma endregion

} // namespace yycc::carton::binstore::storage