environment.h

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#ifndef GEOGRAM_BASIC_ENVIRONMENT
#define GEOGRAM_BASIC_ENVIRONMENT
 
#include <geogram/basic/common.h>
#include <geogram/basic/smart_pointer.h>
#include <geogram/basic/counted.h>
#include <string>
#include <vector>
#include <map>
 
namespace GEO {
 
    class Environment;
    
    /************************************************************************/
 
    class GEOGRAM_API VariableObserver {
    public:
        VariableObserver(const std::string& var_name);
 
        virtual void value_changed(const std::string& new_value) = 0;
 
        virtual ~VariableObserver();
 
        const std::string& observed_variable() const {
            return observed_variable_;
        }
 
    private:
        std::string observed_variable_;
        Environment* environment_;
    };
 
    /************************************************************************/
 
    class GEOGRAM_API VariableObserverList {
    public:
        VariableObserverList() :
            block_notify_(false) {
        }
 
        void notify_observers(const std::string& value);
 
        void add_observer(VariableObserver* observer);
 
        void remove_observer(VariableObserver* observer);
 
    private:
        typedef std::vector<VariableObserver*> Observers;
        Observers observers_;
        bool block_notify_;
    };
 
    /************************************************************************/
 
    class GEOGRAM_API Environment : public Counted {
    public:
        static Environment* instance();
 
        static void terminate();
 
        virtual bool add_environment(Environment* env);
 
        bool has_value(const std::string& name) const;
 
        virtual bool get_value(
            const std::string& name, std::string& value
        ) const;
 
        std::string get_value(const std::string& name) const;
 
        virtual bool set_value(
            const std::string& name, const std::string& value
        );
 
        virtual Environment* find_environment(const std::string& name);
        
        virtual bool add_observer(
            const std::string& name, VariableObserver* observer
        );
 
        virtual bool remove_observer(
            const std::string& name, VariableObserver* observer
        );
 
        virtual bool notify_observers(
            const std::string& name, bool recursive = false
        );
 
    protected:
         ~Environment() override;
 
        virtual bool get_local_value(
            const std::string& name, std::string& value
        ) const = 0;
 
        virtual bool set_local_value(
            const std::string& name, const std::string& value
        ) = 0;
 
        bool notify_observers(
            const std::string& name, const std::string& value,
            bool recursive
        );
 
        bool notify_local_observers(
            const std::string& name, const std::string& value
        );
 
    private:
        typedef SmartPointer<Environment> Environment_var;
 
        typedef std::vector<Environment_var> Environments;
 
        typedef std::map<std::string, VariableObserverList> ObserverMap;
 
        static Environment_var instance_;
        Environments environments_;
        ObserverMap observers_;
    };
 
    /************************************************************************/
 
    class SystemEnvironment : public Environment {
    protected:
        ~SystemEnvironment() override;
 
        bool set_local_value(
            const std::string& name, const std::string& value
        ) override;
 
        bool get_local_value(
            const std::string& name, std::string& value
        ) const override;
    };
}
 
#endif