// -*-c++-*-
// SPDX-License-Identifier: LGPL-2.1-only
// Copyright (C) 2021 James Hogan <james@albanarts.com>

#ifndef OSGXR_Settings
#define OSGXR_Settings 1

#include <osg/Referenced>

#include <osgXR/Export>
#include <osgXR/MirrorSettings>

#include <string>

namespace osgXR {

/// Encapsulates osgXR / OpenXR settings data.
class OSGXR_EXPORT Settings : public osg::Referenced
{
    public:

        /*
         * Instance management.
         */

        Settings();
        virtual ~Settings();

        /// Get the default/global instance of Settings.
        static Settings *instance();

        /*
         * OpenXR application information.
         */

        /**
         * Set the application's name and version to expose to OpenXR.
         * These will be used to create an OpenXR instance.
         * @param appName    Name of the application.
         * @param appVersion 32-bit version number of the application.
         */
        void setApp(const std::string &appName, uint32_t appVersion)
        {
            _appName = appName;
            _appVersion = appVersion;
        }

        /**
         * Set the application's name to expose to OpenXR.
         * This will be used to create an OpenXR instance.
         * @param appName    Name of the application.
         */
        void setAppName(const std::string &appName)
        {
            _appName = appName;
        }
        /// Get the application's name to expose to OpenXR.
        const std::string &getAppName() const
        {
            return _appName;
        }

        /**
         * Set the application's version to expose to OpenXR.
         * This will be used to create an OpenXR instance.
         * @param appVersion 32-bit version number of the application.
         */
        void setAppVersion(uint32_t appVersion)
        {
            _appVersion = appVersion;
        }
        /// Get the application's 32-bit version number to expose to OpenXR.
        uint32_t getAppVersion() const
        {
            return _appVersion;
        }


        /*
         * osgXR configuration settings.
         */

        /**
         * Set whether to try enabling OpenXR's validation layer.
         * This controls whether the OpenXR validation API layer (i.e.
         * XR_APILAYER_LUNARG_core_validation) will be enabled when creating an
         * OpenXR instance.
         * By default this is disabled.
         * @param validationLayer Whether to try enabling the validation layer.
         */
        void setValidationLayer(bool validationLayer)
        {
            _validationLayer = validationLayer;
        }
        /// Get whether to try enabling OpenXR's validation layer.
        bool getValidationLayer() const
        {
            return _validationLayer;
        }

        /**
         * Set whether to enable submission of depth information to OpenXR.
         * This controls whether the OpenXR instance depth information extension
         * (i.e XR_KHR_composition_layer_depth) will be used to submit depth
         * information to OpenXR to allow improved reprojection.
         * This is currently disabled by default.
         * @param depthInfo Whether to enable submission of depth information.
         */
        void setDepthInfo(bool depthInfo)
        {
            _depthInfo = depthInfo;
        }
        /// Get whether to enable submission of depth information to OpenXR.
        bool getDepthInfo() const
        {
            return _depthInfo;
        }

        /**
         * Set whether to create visibility masks.
         * This controls whether the OpenXR instance visibility mask extension
         * (i.e. XR_KHR_visibility_mask) will be used to create and update
         * visibility masks for each VR view in order to mask hidden fragments.
         * This is enabled by default.
         * @param visibilityMask Whether to create visibility masks.
         */
        void setVisibilityMask(bool visibilityMask)
        {
            _visibilityMask = visibilityMask;
        }
        /// Get whether to create visibility masks.
        bool getVisibilityMask() const
        {
            return _visibilityMask;
        }

        /// OpenXR system orm factors.
        typedef enum FormFactor
        {
            /// A display mounted to the user's head.
            HEAD_MOUNTED_DISPLAY,
            /// A display held in the user's hands.
            HANDHELD_DISPLAY,
        } FormFactor;
        /**
         * Set which OpenXR form factor to use.
         * This controls which OpenXR form factor to try to use. The default is
         * HEAD_MOUNTED_DISPLAY.
         * @param formFactor Form factor to use.
         */
        void setFormFactor(FormFactor formFactor)
        {
            _formFactor = formFactor;
        }
        /// Get which OpenXR form factor to use.
        FormFactor getFormFactor() const
        {
            return _formFactor;
        }

        /// Modes for blending layers onto the user's view of the real world.
        typedef enum BlendMode
        {
            // Matches XrEnvironmentBlendMode
            /// Display layers with no view of physical world behind.
            BLEND_MODE_OPAQUE = 1,
            /// Additively blend layers with view of physical world behind.
            BLEND_MODE_ADDITIVE = 2,
            /// Alpha blend layers with view of physical world behind.
            BLEND_MODE_ALPHA_BLEND = 3,
        } BlendMode;
        /**
         * Specify a preferred environment blend mode.
         * The chosen environment blend mode is allowed for use, and will be
         * chosen in preference to any other supported environment blend modes
         * specified by allowEnvBlendMode() if supported by OpenXR.
         * @param mode Environment blend mode to prefer.
         */
        void preferEnvBlendMode(BlendMode mode)
        {
            uint32_t mask = (1u << (unsigned int)mode);
            _preferredEnvBlendModeMask |= mask;
            _allowedEnvBlendModeMask |= mask;
        }
        /**
         * Specify an allowed environment blend mode.
         * The chosen environment blend mode is allowed for use, and may be
         * chosen if supported by OpenXR when none of the preferred environment
         * blend modes specified by preferEnvBlendMode() are supported by
         * OpenXR.
         * @param mode Environment blend mode to prefer.
         */
        void allowEnvBlendMode(BlendMode mode)
        {
            uint32_t mask = (1u << (unsigned int)mode);
            _allowedEnvBlendModeMask |= mask;
        }
        /// Get the bitmask of preferred environment blend modes.
        uint32_t getPreferredEnvBlendModeMask() const
        {
            return _preferredEnvBlendModeMask;
        }
        /// Set the bitmask of preferred environment blend modes.
        void setPreferredEnvBlendModeMask(uint32_t preferredEnvBlendModeMask)
        {
            _preferredEnvBlendModeMask = preferredEnvBlendModeMask;
        }
        /// Get the bitmask of allowed environment blend modes.
        uint32_t getAllowedEnvBlendModeMask() const
        {
            return _allowedEnvBlendModeMask;
        }
        /// Set the bitmask of allowed environment blend modes.
        void setAllowedEnvBlendModeMask(uint32_t allowedEnvBlendModeMask)
        {
            _allowedEnvBlendModeMask = allowedEnvBlendModeMask;
        }

        /// Techniques for rendering multiple views.
        typedef enum VRMode
        {
            /// Choose automatically.
            VRMODE_AUTOMATIC,
            /** Create a slave camera for each view.
             * Either separate swapchains, or single with multiple viewports.
             */
            VRMODE_SLAVE_CAMERAS,
            /** Use the OSG SceneView stereo functionality.
             * No extra slave cameras.
             * Only supports SWAPCHAIN_SINGLE with stereo.
             */
            VRMODE_SCENE_VIEW,
        } VRMode;
        /// Set the rendering technique to use.
        void setVRMode(VRMode mode)
        {
            _vrMode = mode;
        }
        /// Get the rendering technique to use.
        VRMode getVRMode() const
        {
            return _vrMode;
        }

        /// Techniques for managing swapchains.
        typedef enum SwapchainMode
        {
            /// Choose automatically.
            SWAPCHAIN_AUTOMATIC,
            /// Create a 2D swapchain per view.
            SWAPCHAIN_MULTIPLE,
            /** Create a single 2D swapchain with a viewport per view.
             * Stack them horizontally.
             */
            SWAPCHAIN_SINGLE,
        } SwapchainMode;
        /// Set the swapchain management technique to use.
        void setSwapchainMode(SwapchainMode mode)
        {
            _swapchainMode = mode;
        }
        /// Get the swapchain management technique to use.
        SwapchainMode getSwapchainMode() const
        {
            return _swapchainMode;
        }

        /// RGB(A) / depth encodings.
        typedef enum Encoding
        {
            /** Discrete linear encoding of RGB(A).
             * The OpenXR runtime may perform its own conversion from RGB to
             * sRGB for display on HMD, so the app should ensure it leaves RGB
             * values linear to avoid an over-bright image.
             */
            ENCODING_LINEAR = 0,
            /** Floating-point linear encoding of RGB(A).
             * The OpenXR runtime may perform its own conversion from RGB to
             * sRGB for display on HMD, so the app should ensure it leaves RGB
             * values linear to avoid an over-bright image.
             */
            ENCODING_FLOAT = 1,
            /** Discrete non-linear sRGB encoding with linear (A).
             * Linear RGB values should be converted to sRGB, for example with
             * GL_FRAMEBUFFER_SRGB or via fragment shader code, as the OpenXR
             * runtime will treat them as non-linear.
             * Not applicable to depth/stencil swapchains.
             */
            ENCODING_SRGB = 2,
        } Encoding;

        /**
         * Specify a preferred RGB(A) encoding.
         * The chosen RGB(A) encoding is allowed for use, and a format with this
         * encoding will be chosen in preference to other allowed encodings
         * specified by allowRGBEncoding() if possible.
         * @param encoding RGB(A) encoding to prefer.
         */
        void preferRGBEncoding(Encoding encoding)
        {
            uint32_t mask = (1u << (unsigned int)encoding);
            _preferredRGBEncodingMask |= mask;
            _allowedRGBEncodingMask |= mask;
        }
        /**
         * Specify an allowed RGB(A) encoding.
         * The chosen RGB(A) encoding is allowed for use, and a format with this
         * encoding may be chosen when none of the preferred color encodings
         * specified by preferRGBEncoding() are useable.
         * @param encoding RGB(A) encoding to permit.
         */
        void allowRGBEncoding(Encoding encoding)
        {
            uint32_t mask = (1u << (unsigned int)encoding);
            _allowedRGBEncodingMask |= mask;
        }
        /// Get the bitmask of preferred RGB(A) encodings.
        uint32_t getPreferredRGBEncodingMask() const
        {
            return _preferredRGBEncodingMask;
        }
        /// Set the bitmask of preferred RGB(A) encodings.
        void setPreferredRGBEncodingMask(uint32_t preferredRGBEncodingMask)
        {
            _preferredRGBEncodingMask = preferredRGBEncodingMask;
        }
        /// Get the bitmask of allowed RGB(A) encodings.
        uint32_t getAllowedRGBEncodingMask() const
        {
            return _allowedRGBEncodingMask;
        }
        /// Set the bitmask of allowed RGB(A) encodings.
        void setAllowedRGBEncodingMask(uint32_t allowedRGBEncodingMask)
        {
            _allowedRGBEncodingMask = allowedRGBEncodingMask;
        }

        /**
         * Specify a preferred depth encoding.
         * The chosen depth encoding is allowed for use, and a format with this
         * encoding will be chosen in preference to other allowed encodings
         * specified by allowDepthEncoding() if possible.
         * @param encoding Depth encoding to prefer.
         */
        void preferDepthEncoding(Encoding encoding)
        {
            uint32_t mask = (1u << (unsigned int)encoding);
            _preferredDepthEncodingMask |= mask;
            _allowedDepthEncodingMask |= mask;
        }
        /**
         * Specify an allowed depth encoding.
         * The chosen depth encoding is allowed for use, and a format with this
         * encoding may be chosen when none of the preferred color encodings
         * specified by preferDepthEncoding() are useable.
         * @param encoding Depth encoding to permit.
         */
        void allowDepthEncoding(Encoding encoding)
        {
            uint32_t mask = (1u << (unsigned int)encoding);
            _allowedDepthEncodingMask |= mask;
        }
        /// Get the bitmask of preferred depth encodings.
        uint32_t getPreferredDepthEncodingMask() const
        {
            return _preferredDepthEncodingMask;
        }
        /// Set the bitmask of preferred depth encodings.
        void setPreferredDepthEncodingMask(uint32_t preferredDepthEncodingMask)
        {
            _preferredDepthEncodingMask = preferredDepthEncodingMask;
        }
        /// Get the bitmask of allowed depth encodings.
        uint32_t getAllowedDepthEncodingMask() const
        {
            return _allowedDepthEncodingMask;
        }
        /// Set the bitmask of allowed depth encodings.
        void setAllowedDepthEncodingMask(uint32_t allowedDepthEncodingMask)
        {
            _allowedDepthEncodingMask = allowedDepthEncodingMask;
        }

        /**
         * Get number of desired bits for each RGB channel in RGB(A) swapchain.
         * This only applies to linear RGB formats, not sRGB formats.
         */
        int getRGBBits() const
        {
            return _rgbBits;
        }
        /**
         * Set number of desired bits for each RGB channel in RGB(A) swapchain.
         * This only applies to linear RGB formats, not sRGB formats.
         */
        void setRGBBits(int rgbBits = -1)
        {
            _rgbBits = rgbBits;
        }

        /// Get number of desired alpha bits in RGB(A) swapchain.
        int getAlphaBits() const
        {
            return _alphaBits;
        }
        /// Set the number of desired alpha bits in RGB(A) swapchain.
        void setAlphaBits(int alphaBits = -1)
        {
            _alphaBits = alphaBits;
        }

        /// Get number of desired depth bits in depth/stencil swapchain.
        int getDepthBits() const
        {
            return _depthBits;
        }
        /// Set the number of desired depth bits in depth/stencil swapchain.
        void setDepthBits(int depthBits = -1)
        {
            _depthBits = depthBits;
        }

        /// Get number of desired stencil bits in depth/stencil swapchain.
        int getStencilBits() const
        {
            return _stencilBits;
        }
        /// Set the number of desired stenil bits in depth/stencil swapchain.
        void setStencilBits(int stencilBits = -1)
        {
            _stencilBits = stencilBits;
        }

        /// Get mirror settings.
        MirrorSettings &getMirrorSettings()
        {
            return _mirrorSettings;
        }
        /// Get mirror settings.
        const MirrorSettings &getMirrorSettings() const
        {
            return _mirrorSettings;
        }

        /**
         * Set the number of virtual world units to fit per real world meter.
         * This controls the size of the user relative to the virtual world, by
         * scaling down the size of the world.
         * @param unitsPerMeter The number of units per real world meter.
         */
        void setUnitsPerMeter(float unitsPerMeter)
        {
            _unitsPerMeter = unitsPerMeter;
        }
        /// Get the number of virtual world units to fit per real world meter.
        float getUnitsPerMeter() const
        {
            return _unitsPerMeter;
        }

        // Internal APIs

        typedef enum {
            DIFF_NONE             = 0,
            DIFF_APP_INFO         = (1u << 0),
            DIFF_VALIDATION_LAYER = (1u << 1),
            DIFF_DEPTH_INFO       = (1u << 2),
            DIFF_VISIBILITY_MASK  = (1u << 3),
            DIFF_FORM_FACTOR      = (1u << 4),
            DIFF_BLEND_MODE       = (1u << 5),
            DIFF_VR_MODE          = (1u << 6),
            DIFF_SWAPCHAIN_MODE   = (1u << 7),
            DIFF_RGB_ENCODING     = (1u << 8),
            DIFF_DEPTH_ENCODING   = (1u << 9),
            DIFF_RGB_BITS         = (1u << 10),
            DIFF_ALPHA_BITS       = (1u << 11),
            DIFF_DEPTH_BITS       = (1u << 12),
            DIFF_STENCIL_BITS     = (1u << 13),
            DIFF_MIRROR           = (1u << 14),
            DIFF_SCALE            = (1u << 15),
        } _ChangeMask;

        unsigned int _diff(const Settings &other) const;

    private:

        /*
         * Internal data.
         */

        // For XrInstance creation
        std::string _appName;
        uint32_t _appVersion;
        bool _validationLayer;
        bool _depthInfo;
        bool _visibilityMask;

        // To get XrSystem
        FormFactor _formFactor;

        // For choosing environment blend mode
        uint32_t _preferredEnvBlendModeMask;
        uint32_t _allowedEnvBlendModeMask;

        // VR/swapchain modes to use
        VRMode _vrMode;
        SwapchainMode _swapchainMode;

        // Swapchain requirements
        uint32_t _preferredRGBEncodingMask;
        uint32_t _allowedRGBEncodingMask;
        uint32_t _preferredDepthEncodingMask;
        uint32_t _allowedDepthEncodingMask;
        // These default to -1: get bit depths from graphics window traits
        int _rgbBits;  // for linear RGB formats, per channel
        int _alphaBits;
        int _depthBits;
        int _stencilBits;

        // Mirror settings
        MirrorSettings _mirrorSettings;

        // How big the world
        float _unitsPerMeter;
};

}

#endif