/*-------------------------------------------------------------------------
This source file is a part of OGRE
(Object-oriented Graphics Rendering Engine)

For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2014 Torus Knot Software Ltd
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
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The above copyright notice and this permission notice shall be included in
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-------------------------------------------------------------------------*/

#ifndef _Font_H__
#define _Font_H__

#include "OgreOverlayPrerequisites.h"
#include "OgreResource.h"
#include "OgreCommon.h"
#include "OgreSharedPtr.h"
#include "OgreColourValue.h"
#include "OgreException.h"

namespace Ogre
{
    class BillboardSet;

    /** \addtogroup Optional
    *  @{
    */
    /** \addtogroup Overlays
    *  @{
    */
    class Font;
    typedef SharedPtr<Font> FontPtr;

    /// decode UTF8 encoded bytestream to uint32 codepoints
    _OgreOverlayExport std::vector<uint32> utftoc32(String str);

    /** Enumerates the types of Font usable in the engine. */
    enum FontType
    {
        /// Generated from a truetype (.ttf) font
        FT_TRUETYPE = 1,
        /// Loaded from an image created by an artist
        FT_IMAGE = 2
    };


    /// Information about the position and size of a glyph in a texture
    struct GlyphInfo
    {
        typedef uint32 CodePoint;
        typedef FloatRect UVRect;

        CodePoint codePoint;
        UVRect uvRect;
        float aspectRatio; // width/ height
        float bearing; // bearingX/ height
        float advance; // advanceX/ height
    };

    /** Class representing a font in the system.

    This class is simply a way of getting a font texture into the OGRE system and
    to easily retrieve the texture coordinates required to accurately render them.
    Fonts can either be loaded from precreated textures, or the texture can be generated
    using a truetype font. You can either create the texture manually in code, or you
    can use a .fontdef script to define it (probably more practical since you can reuse
    the definition more easily)
    @note
    This class extends both Resource and ManualResourceLoader since it is
    both a resource in it's own right, but it also provides the manual load
    implementation for the Texture it creates.
    */
    class _OgreOverlayExport Font final : public Resource, public ManualResourceLoader
    {
    protected:
        /// The type of font
        FontType mType;

        /// Source of the font (either an image name or a truetype font)
        String mSource;

        /// Size of the truetype font, in points
        Real mTtfSize;
        /// Resolution (dpi) of truetype font
        uint mTtfResolution;
        /// Max distance to baseline of this (truetype) font
        int mTtfMaxBearingY;


    public:
        typedef GlyphInfo::CodePoint CodePoint;
        typedef GlyphInfo::UVRect UVRect;
        /// A range of code points, inclusive on both ends
        typedef std::pair<CodePoint, CodePoint> CodePointRange;
        typedef std::vector<CodePointRange> CodePointRangeList;
    protected:
        /// Map from unicode code point to texture coordinates
        typedef std::map<CodePoint, GlyphInfo> CodePointMap;
        CodePointMap mCodePointMap;

        /// The material which is generated for this font
        MaterialPtr mMaterial;

        /// Texture pointer
        TexturePtr mTexture;

        /// For TRUE_TYPE font only
        bool mAntialiasColour;

        /// Range of code points to generate glyphs for (truetype only)
        CodePointRangeList mCodePointRangeList;

        std::vector<FontPtr> mMergeFonts;

        /// Internal method for loading from ttf
        void createTextureFromFont(void);

        void loadImpl() override;
        void unloadImpl() override;
        size_t calculateSize(void) const override { return 0; } // permanent resource is in the texture

        friend class ImGuiOverlay;
        DataStreamPtr _getTTFData();

        void* _prepareFont(void* context, uint32& glyphCount, int32& max_height, int32& max_width);
        void _loadGlyphs(void* font, int32 max_height, Image& img, uint32& l, uint32& m);

    public:

        /** Constructor.
        @see Resource
        */
        Font(ResourceManager* creator, const String& name, ResourceHandle handle,
            const String& group, bool isManual = false, ManualResourceLoader* loader = 0);
        virtual ~Font();

        /** Sets the type of font. Must be set before loading. */
        void setType(FontType ftype);

        /** Gets the type of font. */
        FontType getType(void) const;

        /** Sets the source of the font.

            If you have created a font of type FT_IMAGE, this method tells the
            Font which image to use as the source for the characters. So the parameter 
            should be the name of an appropriate image file. Note that when using an image
            as a font source, you will also need to tell the font where each character is
            located using setGlyphTexCoords (for each character).
        @par
            If you have created a font of type FT_TRUETYPE, this method tells the
            Font which .ttf file to use to generate the text. You will also need to call 
            setTrueTypeSize and setTrueTypeResolution, and call addCodePointRange
            as many times as required to define the range of glyphs you want to be
            available.
        @param source An image file or a truetype font, depending on the type of this font
        */
        void setSource(const String& source);

        /** Gets the source this font (either an image or a truetype font).
        */
        const String& getSource(void) const;

        /** Sets the size of a truetype font (only required for FT_TRUETYPE). 
        @param ttfSize The size of the font in points. Note that the
            size of the font does not affect how big it is on the screen, just how large it is in
            the texture and thus how detailed it is.
        */
        void setTrueTypeSize(Real ttfSize);
        /** Gets the resolution (dpi) of the font used to generate the texture
        (only required for FT_TRUETYPE).
        @param ttfResolution The resolution in dpi
        */
        void setTrueTypeResolution(uint ttfResolution);

        /** Gets the point size of the font used to generate the texture.

            Only applicable for FT_TRUETYPE Font objects.
            Note that the size of the font does not affect how big it is on the screen, 
            just how large it is in the texture and thus how detailed it is.            
        */
        Real getTrueTypeSize(void) const;
        /** Gets the resolution (dpi) of the font used to generate the texture.

            Only applicable for FT_TRUETYPE Font objects.
        */
        uint getTrueTypeResolution(void) const;
        /** Gets the maximum baseline distance of all glyphs used in the texture.

            Only applicable for FT_TRUETYPE Font objects.
            The baseline is the vertical origin of horizontal based glyphs.  The bearingY
            attribute is the distance from the baseline (origin) to the top of the glyph's 
            bounding box.
        @note
            This value is only available after the font has been loaded.
        */
        int getTrueTypeMaxBearingY() const;


        /** Returns the texture coordinates of the associated glyph. 
            @remarks Parameter is a short to allow both ASCII and wide chars.
            @param id The code point (unicode)
            @return A rectangle with the UV coordinates, or null UVs if the
                code point was not present
        */
        const UVRect& getGlyphTexCoords(CodePoint id) const { return getGlyphInfo(id).uvRect; }

        /** Sets the texture coordinates of a glyph.

            You only need to call this if you're setting up a font loaded from a texture manually.
        @note
            Also sets the aspect ratio (width / height) of this character. textureAspect
            is the width/height of the texture (may be non-square)
        */
        void setGlyphInfoFromTexCoords(CodePoint id, const UVRect& rect, float textureAspect = 1.0)
        {
            auto glyphAspect = textureAspect * rect.width()  / rect.height();
            setGlyphInfo({id, rect, glyphAspect, 0, glyphAspect});
        }

        void setGlyphInfo(const GlyphInfo& info) { mCodePointMap[info.codePoint] = info; }

        /** Gets the aspect ratio (width / height) of this character. */
        float getGlyphAspectRatio(CodePoint id) const { return getGlyphInfo(id).aspectRatio; }
        /** Sets the aspect ratio (width / height) of this character.

            You only need to call this if you're setting up a font loaded from a 
            texture manually.
        */
        void setGlyphAspectRatio(CodePoint id, Real ratio)
        {
            CodePointMap::iterator i = mCodePointMap.find(id);
            if (i != mCodePointMap.end())
            {
                i->second.aspectRatio = ratio;
            }
        }

        /** Gets the information available for a glyph corresponding to a
            given code point, or throws an exception if it doesn't exist;
        */
        const GlyphInfo& getGlyphInfo(CodePoint id) const
        {
            CodePointMap::const_iterator i = mCodePointMap.find(id);
            if (i == mCodePointMap.end())
            {
                // Try a fallback first.
                i = mCodePointMap.find(static_cast<CodePoint>('?'));

                if (i == mCodePointMap.end())
                {
                    OGRE_EXCEPT(Exception::ERR_ITEM_NOT_FOUND, StringUtil::format(
                        "Code point %d and fallback 63 not found in font %s", id, mName.c_str()));
                }
            }
            return i->second;
        }

        /** Adds a range of code points to the list of code point ranges to generate
            glyphs for, if this is a truetype based font.

            In order to save texture space, only the glyphs which are actually
            needed by the application are generated into the texture. Before this
            object is loaded you must call this method as many times as necessary
            to define the code point range that you need.
        */
        void addCodePointRange(const CodePointRange& range)
        {
            mCodePointRangeList.push_back(range);
        }

        /** Clear the list of code point ranges.
        */
        void clearCodePointRanges()
        {
            mCodePointRangeList.clear();
        }
        /** Get a const reference to the list of code point ranges to be used to
            generate glyphs from a truetype font.
        */
        const CodePointRangeList& getCodePointRangeList() const
        {
            return mCodePointRangeList;
        }

        /** Add a font to merge with this one.

            This is useful when you want to use a font for most of the characters, but
            fall back to another font for characters not present in the current font. e.g. icons.
        */
        void addMergeFont(const FontPtr& font) { mMergeFonts.push_back(font); }

        const std::vector<FontPtr>& getMergeFontList() const { return mMergeFonts; }

        /** Gets the material generated for this font, as a weak reference. 

            This will only be valid after the Font has been loaded. 
        */
        inline const MaterialPtr& getMaterial() const
        {
            return mMaterial;
        }

        /**
         * Write a text into a BillboardSet for positioning in Space
         *
         * Text is laid out in the x-y plane, running into x+ and using y+ as up
         * @param bbs the target BillboardSet
         * @param text text to write
         * @param height character height in world units
         * @param colour text colour
         */
        void putText(BillboardSet* bbs, String text, float height, const ColourValue& colour = ColourValue::White);

        /** Sets whether the colour of this font is multiplied with alpha as it is generated
            from a true type font.

            This is valid only for a FT_TRUETYPE font. If you are planning on using 
            alpha blending to draw your font, then set this to
            false (which is the default), otherwise the darkening of the font will combine
            with the fading out of the alpha around the edges and make your font look thinner
            than it should. However, if you intend to use premultipled alpha or a colour blending
            mode (add or modulate for example) then set this to true, in
            order to soften your font edges.
        */
        inline void setAntialiasColour(bool enabled)
        {
            mAntialiasColour = enabled;
        }

        /** Gets whether or not the colour of this font is antialiased as it is generated
        from a true type font.
        */
        inline bool getAntialiasColour(void) const
        {
            return mAntialiasColour;
        }

        /** Implementation of ManualResourceLoader::loadResource, called
            when the Texture that this font creates needs to (re)load.
        */
        void loadResource(Resource* resource) override;

        /** Manually set the material used for this font.

            This should only be used when the font is being loaded from a
            ManualResourceLoader.
        */
        void _setMaterial(const MaterialPtr& mat);
    };
    /** @} */
    /** @} */
}

#endif