cello_value.h

/*
    Copyright (c) 2023 Brett g Porter
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
    The above copyright notice and this permission notice shall be included in all
    copies or substantial portions of the Software.
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
    SOFTWARE.
*/
 
#pragma once
 
#include <optional>
 
#include "cello_update_source.h"
 
namespace cello
{
 
class Object;
 
class ValueBase : public UpdateSource
{
public:
    juce::Identifier getId () const { return id; }
 
protected:
    ValueBase (const juce::Identifier& id_)
    : id { id_ }
    {
    }
 
protected:
    const juce::Identifier id;
};

template <typename T> class Value : public ValueBase
{
public:
    using ValidateGetFn = std::function<T (const T&)>;

    using ValidateSetFn = std::function<std::optional<T> (const T&)>;

    Value (Object& data, const juce::Identifier& id_, T initVal = {}, ValidateGetFn getFn = nullptr,
           ValidateSetFn setFn = nullptr)
    : ValueBase { id_ }
    , onSet { setFn }
    , onGet { getFn }
    , object { data }
    {
        // if the object doesn't have this value yet, add it and set it
        // to the initial value. This will happen as part of initializing a
        // new Object, but may also happen if new values are added to an existing
        // type.
        if (!object.hasattr (id))
            object.setattr<T> (id, initVal);
    }

    Value& operator= (const T& val)
    {
        set (val);
        return *this;
    }

    void set (const T& val)
    {
        if (onSet != nullptr)
        {
            const auto validated { onSet (val) };
            if (validated.has_value ())
                doSet (validated.value ());
        }
        else
            doSet (val);
    }

    operator T () const { return get (); }

    T get () const
    {
        if (onGet != nullptr)
            return onGet (doGet ());
        return doGet ();
    }

    class Cached
    {
    public:
        Cached (Value<T>& val)
        : value { val }
        , cachedValue { static_cast<T> (value) }
        {
            // when the underlying value changes, cache it here so it can
            // be used without needing to look it up, go through validation, etc.
            value.onPropertyChange ([this] (const juce::Identifier& /*id*/) { cachedValue = static_cast<T> (value); });
        }
 
        ~Cached () { value.onPropertyChange (nullptr); }

        T get () const { return cachedValue; }

        operator T () const { return get (); }
 
    private:
        Value<T>& value;
        T cachedValue;
    };

    Cached getCached () { return Cached (*this); }

    ValidateSetFn onSet;

    ValidateGetFn onGet;

    void excludeListener (juce::ValueTree::Listener* listener) { excludedListener = listener; }

    void onPropertyChange (PropertyUpdateFn callback) { object.onPropertyChange (getId (), callback); }
 
private:
    void doSet (const T& val)
    {
        juce::ValueTree tree { object };
 
        // check if this call should change the current value.
        if (notEqualTo (val))
        {
            // check if this value or our parent object have a listener to exclude
            // from updates.
            auto* excluded = (excludedListener != nullptr) ? excludedListener : object.getExcludedListener ();
            const auto asVar { juce::VariantConverter<T>::toVar (val) };
            if (excluded)
                tree.setPropertyExcludingListener (excluded, id, asVar, object.getUndoManager ());
            else
                tree.setProperty (id, asVar, object.getUndoManager ());
        }
        else
        {
            // check if we or our parent object want us to always send
            // a property change callback for this value.
            if (shouldForceUpdate () || object.shouldForceUpdate ())
                tree.sendPropertyChangeMessage (id);
        }
    }
 
    T doGet () const
    {
        juce::ValueTree tree { object };
        return juce::VariantConverter<T>::fromVar (tree.getProperty (id));
    }

    bool notEqualTo (const T& newValue)
    {
        if constexpr (std::is_floating_point_v<T>)
            return std::fabs (newValue - doGet ()) > epsilon;
        else
            return (newValue != doGet ());
    }
 
public:
    static inline float epsilon { 0.001f };
 
private:
    Object& object;

    juce::ValueTree::Listener* excludedListener { nullptr };
};
 
template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
Value<T>& operator+= (Value<T>& val, const T& rhs)
{
    val = val.get () + rhs;
    return val;
}
 
template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
Value<T>& operator-= (Value<T>& val, const T& rhs)
{
    val = val.get () - rhs;
    return val;
}
 
template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
Value<T>& operator*= (Value<T>& val, const T& rhs)
{
    val = val.get () * rhs;
    return val;
}
 
template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
Value<T>& operator/= (Value<T>& val, const T& rhs)
{
    jassert (rhs != 0);
    val = val.get () / rhs;
    return val;
}

template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
T operator++ (Value<T>& val)
{
    const auto newVal { val.get () + static_cast<int> (1) };
    val = newVal;
    return newVal;
}

template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
T operator++ (Value<T>& val, int)
{
    const auto original { val.get () };
    val.set (original + static_cast<T> (1));
    return original;
}

template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
T operator-- (Value<T>& val)
{
    const auto newVal { val.get () - static_cast<T> (1) };
    val.set (newVal);
    return newVal;
}

template <typename T, // the actual type
          typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
T operator-- (Value<T>& val, int)
{
    const auto original { val.get () };
    val.set (original - static_cast<T> (1));
    return original;
}
 
} // namespace cello

// clang-format off
#define MAKE_VALUE_MEMBER(type, name, init)                  \
    static const inline juce::Identifier name##Id { #name }; \
    cello::Value<type> name { *this, name##Id, init }
 
// ...also pass in a ValidateGetFn callable at construction time. 
#define MAKE_VALUE_MEMBER_GET(type, name, init, getFn) \
    static const inline juce::Identifier name##Id { #name }; \
    cello::Value<type> name { *this, name##Id, init, getFn }
 
// ...pass in Validation functions for get and set.
#define MAKE_VALUE_MEMBER_GET_SET(type, name, init, getFn, setFn) \
    static const inline juce::Identifier name##Id { #name }; \
    cello::Value<type> name { *this, name##Id, init, getFn, setFn }
 
// clang-format on
 
// clang-format off
#define CACHED_VALUE(name, value)  decltype(value.getCached()) name { value }
// clang-format on