IMessage.hpp

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// Copyright (C) 2022 Numendacil and contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
#ifndef MIRAI_MESSAGE_INTERFACE_HPP_
#define MIRAI_MESSAGE_INTERFACE_HPP_
 
 
#include <memory>
#include <string>
#include <type_traits>
 
#include <libmirai/Types/MessageTypes.hpp>
 
namespace Mirai
{
 
/**
 * @brief Common interface for all message types
 * 
 */
class IMessage
{
protected:
    IMessage() = default;
 
    virtual MessageTypes GetType_() const = 0;
    virtual bool isSendSupported_() const = 0;
    virtual bool isValid_() const = 0;
 
public:
    virtual ~IMessage() = default;
 
    virtual std::unique_ptr<IMessage> clone() const = 0;
 
    /**
     * @brief Return the type of the class
     * 
     * @return `MessageTypes`
     */
    MessageTypes type() const { return this->GetType_(); }
 
    /**
     * @brief 检查消息是否可以用于发送
     * 
     * 部分消息仅支持接收
     * @return `bool`
     */
    bool allowSend() const { return this->isSendSupported_(); }
 
    /**
     * @brief 检查消息是否有效
     * 
     * 发送无效消息( `valid() = false` )会导致mirai-api-http返回400或500错误，并抛出异常。
     * 检测的内容靠测试经验和mirai-api-http源码确定， `valid() = true` 不保证一定能发送成功。
     * @return `bool`
     */
    bool valid() const { return this->isValid_(); }  
};
 
/**
 * @brief CRTP helper layer
 * 
 */
template <class Message>
class IMessageImpl : public IMessage
{
protected:
    // Better not to set default value to avoid errors
    // static constexpr bool SUPPORT_SEND_ = true;
    // static constexpr MessageTypes TYPE_ = MessageTypes::ENUM_END;
 
    IMessageImpl() = default;
 
    MessageTypes GetType_() const override { return Message::TYPE_; }
    
    bool isSendSupported_() const override { return Message::SUPPORT_SEND_; }
 
private:
    Message& top_() { return *static_cast<Message*>(this); }
    const Message& top_() const { return *static_cast<const Message*>(this); }
 
public:
    static constexpr MessageTypes GetType() { return Message::TYPE_; }
 
    static constexpr bool isSendSupported() { return Message::SUPPORT_SEND_; }
 
    std::unique_ptr<IMessage> clone() const override
    {
        return std::make_unique<Message>(top_());
    }
};
 
} // namespace Mirai
 
 
#endif