#pragma once

#include <mbgl/util/peer.hpp>
#include <mbgl/util/immutable.hpp>
#include <mbgl/util/optional.hpp>
#include <mbgl/style/layer_type.hpp>
#include <mbgl/style/types.hpp>
#include <mbgl/style/conversion.hpp>

#include <cassert>
#include <memory>
#include <string>
#include <stdexcept>

namespace mbgl {
namespace style {

class FillLayer;
class LineLayer;
class CircleLayer;
class SymbolLayer;
class RasterLayer;
class HillshadeLayer;
class BackgroundLayer;
class CustomLayer;
class FillExtrusionLayer;
class HeatmapLayer;
class LayerObserver;
class Filter;

/**
 * The runtime representation of a [layer](https://www.mapbox.com/mapbox-gl-style-spec/#layers) from the Mapbox Style
 * Specification.
 *
 * `Layer` is an abstract base class; concrete derived classes are provided for each layer type. `Layer` contains
 * functionality that is common to all layer types:
 *
 * * Runtime type information: type predicates and casting
 * * Accessors for properties common to all layer types: ID, visibility, etc.
 * * Cloning and copying
 *
 * All other functionality lives in the derived classes. To instantiate a layer, create an instance of the desired
 * type, passing the ID:
 *
 *     auto circleLayer = std::make_unique<CircleLayer>("my-circle-layer");
 */
class Layer {
public:
    Layer(const Layer& ) = delete;
    Layer& operator=(const Layer&) = delete;

    virtual ~Layer();

    // Check whether this layer is of the given subtype.
    template <class T>
    bool is() const;

    // Dynamically cast this layer to the given subtype.
    template <class T>
    T* as() {
        return is<T>() ? reinterpret_cast<T*>(this) : nullptr;
    }

    template <class T>
    const T* as() const {
        return is<T>() ? reinterpret_cast<const T*>(this) : nullptr;
    }

    LayerType getType() const;
    std::string getID() const;
    // Source
    std::string getSourceID() const;
    std::string getSourceLayer() const;
    void setSourceLayer(const std::string& sourceLayer);

    // Filter
    const Filter& getFilter() const;
    void setFilter(const Filter&);

    // Visibility
    VisibilityType getVisibility() const;
    void setVisibility(VisibilityType);

    // Zoom range
    float getMinZoom() const;
    float getMaxZoom() const;
    void setMinZoom(float);
    void setMaxZoom(float);

    // Dynamic properties
    virtual optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) = 0;
    virtual optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) = 0;
    optional<conversion::Error> setVisibility(const conversion::Convertible& value);

    // Private implementation
    // TODO : We should not have public mutable data members.
    class Impl;
    Immutable<Impl> baseImpl;

    // Create a layer, copying all properties except id and paint properties from this layer.
    virtual std::unique_ptr<Layer> cloneRef(const std::string& id) const = 0;

    
    void setObserver(LayerObserver*);

    // For use in SDK bindings, which store a reference to a platform-native peer
    // object here, so that separately-obtained references to this object share
    // identical platform-native peers.
    util::peer peer;
protected:
    Layer(Immutable<Impl>);   
    virtual Mutable<Impl> mutableBaseImpl() const = 0;

    LayerObserver* observer = nullptr;
};

} // namespace style
} // namespace mbgl