/*
Open Asset Import Library (assimp)
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*/

/** Helper structures for the Collada loader */

#ifndef AI_COLLADAHELPER_H_INC
#define AI_COLLADAHELPER_H_INC

#include <assimp/light.h>
#include <assimp/material.h>
#include <assimp/mesh.h>

#include <stdint.h>
#include <map>
#include <set>
#include <vector>

struct aiMaterial;

namespace Assimp {
namespace Collada {

/// Collada file versions which evolved during the years ...
enum FormatVersion {
    FV_1_5_n,
    FV_1_4_n,
    FV_1_3_n
};

/// Transformation types that can be applied to a node
enum TransformType {
    TF_LOOKAT,
    TF_ROTATE,
    TF_TRANSLATE,
    TF_SCALE,
    TF_SKEW,
    TF_MATRIX
};

/// Different types of input data to a vertex or face
enum InputType {
    IT_Invalid,
    IT_Vertex, // special type for per-index data referring to the <vertices> element carrying the per-vertex data.
    IT_Position,
    IT_Normal,
    IT_Texcoord,
    IT_Color,
    IT_Tangent,
    IT_Bitangent
};

/// Supported controller types
enum ControllerType {
    Skin,
    Morph
};

/// Supported morph methods
enum MorphMethod {
    Normalized,
    Relative
};

/// Common metadata keys as <Collada, Assimp>
using MetaKeyPair = std::pair<std::string, std::string>;
using MetaKeyPairVector = std::vector<MetaKeyPair>;

/// Collada as lower_case (native)
const MetaKeyPairVector &GetColladaAssimpMetaKeys();

// Collada as CamelCase (used by Assimp for consistency)
const MetaKeyPairVector &GetColladaAssimpMetaKeysCamelCase();

/// Convert underscore_separated to CamelCase "authoring_tool" becomes "AuthoringTool"
void ToCamelCase(std::string &text);

/// Contains all data for one of the different transformation types
struct Transform {
    std::string mID; ///< SID of the transform step, by which anim channels address their target node
    TransformType mType;
    ai_real f[16]; ///< Interpretation of data depends on the type of the transformation
};

/// A collada camera.
struct Camera {
    Camera() :
            mOrtho(false),
            mHorFov(10e10f),
            mVerFov(10e10f),
            mAspect(10e10f),
            mZNear(0.1f),
            mZFar(1000.f) {}

    /// Name of camera
    std::string mName;

    /// True if it is an orthographic camera
    bool mOrtho;

    /// Horizontal field of view in degrees
    ai_real mHorFov;

    /// Vertical field of view in degrees
    ai_real mVerFov;

    /// Screen aspect
    ai_real mAspect;

    /// Near& far z
    ai_real mZNear, mZFar;
};

#define ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET 1e9f

/** A collada light source. */
struct Light {
    Light() :
            mType(aiLightSource_UNDEFINED),
            mAttConstant(1.f),
            mAttLinear(0.f),
            mAttQuadratic(0.f),
            mFalloffAngle(180.f),
            mFalloffExponent(0.f),
            mPenumbraAngle(ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET),
            mOuterAngle(ASSIMP_COLLADA_LIGHT_ANGLE_NOT_SET),
            mIntensity(1.f) {}

    /// Type of the light source aiLightSourceType + ambient
    unsigned int mType;

    /// Color of the light
    aiColor3D mColor;

    /// Light attenuation
    ai_real mAttConstant, mAttLinear, mAttQuadratic;

    /// Spot light falloff
    ai_real mFalloffAngle;
    ai_real mFalloffExponent;

    // -----------------------------------------------------
    // FCOLLADA extension from here

    /// ... related stuff from maja and max extensions
    ai_real mPenumbraAngle;
    ai_real mOuterAngle;

    /// Common light intensity
    ai_real mIntensity;
};

/** Short vertex index description */
struct InputSemanticMapEntry {
    InputSemanticMapEntry() :
            mSet(0),
            mType(IT_Invalid) {}

    /// Index of set, optional
    unsigned int mSet;

    /// Type of referenced vertex input
    InputType mType;
};

/// Table to map from effect to vertex input semantics
struct SemanticMappingTable {
    /// Name of material
    std::string mMatName;

    /// List of semantic map commands, grouped by effect semantic name
    std::map<std::string, InputSemanticMapEntry> mMap;

    /// For std::find
    bool operator==(const std::string &s) const {
        return s == mMatName;
    }
};

/// A reference to a mesh inside a node, including materials assigned to the various subgroups.
/// The ID refers to either a mesh or a controller which specifies the mesh
struct MeshInstance {
    ///< ID of the mesh or controller to be instanced
    std::string mMeshOrController;

    ///< Map of materials by the subgroup ID they're applied to
    std::map<std::string, SemanticMappingTable> mMaterials;
};

/// A reference to a camera inside a node
struct CameraInstance {
    ///< ID of the camera
    std::string mCamera;
};

/// A reference to a light inside a node
struct LightInstance {
    ///< ID of the camera
    std::string mLight;
};

/// A reference to a node inside a node
struct NodeInstance {
    ///< ID of the node
    std::string mNode;
};

/// A node in a scene hierarchy
struct Node {
    std::string mName;
    std::string mID;
    std::string mSID;
    Node *mParent;
    std::vector<Node *> mChildren;

    /// Operations in order to calculate the resulting transformation to parent.
    std::vector<Transform> mTransforms;

    /// Meshes at this node
    std::vector<MeshInstance> mMeshes;

    /// Lights at this node
    std::vector<LightInstance> mLights;

    /// Cameras at this node
    std::vector<CameraInstance> mCameras;

    /// Node instances at this node
    std::vector<NodeInstance> mNodeInstances;

    /// Root-nodes: Name of primary camera, if any
    std::string mPrimaryCamera;

    /// Constructor. Begin with a zero parent
    Node() :
            mParent(nullptr) {
        // empty
    }

    /// Destructor: delete all children subsequently
    ~Node() {
        for (std::vector<Node *>::iterator it = mChildren.begin(); it != mChildren.end(); ++it) {
            delete *it;
        }
    }
};

/// Data source array: either floats or strings
struct Data {
    bool mIsStringArray;
    std::vector<ai_real> mValues;
    std::vector<std::string> mStrings;
};

/// Accessor to a data array
struct Accessor {
    size_t mCount; // in number of objects
    size_t mSize; // size of an object, in elements (floats or strings, mostly 1)
    size_t mOffset; // in number of values
    size_t mStride; // Stride in number of values
    std::vector<std::string> mParams; // names of the data streams in the accessors. Empty string tells to ignore.
    size_t mSubOffset[4]; // Sub-offset inside the object for the common 4 elements. For a vector, that's XYZ, for a color RGBA and so on.
            // For example, SubOffset[0] denotes which of the values inside the object is the vector X component.
    std::string mSource; // URL of the source array
    mutable const Data *mData; // Pointer to the source array, if resolved. nullptr else

    Accessor() {
        mCount = 0;
        mSize = 0;
        mOffset = 0;
        mStride = 0;
        mData = nullptr;
        mSubOffset[0] = mSubOffset[1] = mSubOffset[2] = mSubOffset[3] = 0;
    }
};

/// A single face in a mesh
struct Face {
    std::vector<size_t> mIndices;
};

/// An input channel for mesh data, referring to a single accessor
struct InputChannel {
    InputType mType; // Type of the data
    size_t mIndex; // Optional index, if multiple sets of the same data type are given
    size_t mOffset; // Index offset in the indices array of per-face indices. Don't ask, can't explain that any better.
    std::string mAccessor; // ID of the accessor where to read the actual values from.
    mutable const Accessor *mResolved; // Pointer to the accessor, if resolved. nullptr else

    InputChannel() {
        mType = IT_Invalid;
        mIndex = 0;
        mOffset = 0;
        mResolved = nullptr;
    }
};

/// Subset of a mesh with a certain material
struct SubMesh {
    std::string mMaterial; ///< subgroup identifier
    size_t mNumFaces; ///< number of faces in this sub-mesh
};

/// Contains data for a single mesh
struct Mesh {
    Mesh(const std::string &id) :
            mId(id) {
        for (unsigned int i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++i) {
            mNumUVComponents[i] = 2;
        }
    }

    const std::string mId;
    std::string mName;

    // just to check if there's some sophisticated addressing involved...
    // which we don't support, and therefore should warn about.
    std::string mVertexID;

    // Vertex data addressed by vertex indices
    std::vector<InputChannel> mPerVertexData;

    // actual mesh data, assembled on encounter of a <p> element. Verbose format, not indexed
    std::vector<aiVector3D> mPositions;
    std::vector<aiVector3D> mNormals;
    std::vector<aiVector3D> mTangents;
    std::vector<aiVector3D> mBitangents;
    std::vector<aiVector3D> mTexCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS];
    std::vector<aiColor4D> mColors[AI_MAX_NUMBER_OF_COLOR_SETS];

    unsigned int mNumUVComponents[AI_MAX_NUMBER_OF_TEXTURECOORDS];

    // Faces. Stored are only the number of vertices for each face.
    // 1 == point, 2 == line, 3 == triangle, 4+ == poly
    std::vector<size_t> mFaceSize;

    // Position indices for all faces in the sequence given in mFaceSize -
    // necessary for bone weight assignment
    std::vector<size_t> mFacePosIndices;

    // Sub-meshes in this mesh, each with a given material
    std::vector<SubMesh> mSubMeshes;
};

/// Which type of primitives the ReadPrimitives() function is going to read
enum PrimitiveType {
    Prim_Invalid,
    Prim_Lines,
    Prim_LineStrip,
    Prim_Triangles,
    Prim_TriStrips,
    Prim_TriFans,
    Prim_Polylist,
    Prim_Polygon
};

/// A skeleton controller to deform a mesh with the use of joints
struct Controller {
    // controller type
    ControllerType mType;

    // Morphing method if type is Morph
    MorphMethod mMethod;

    // the URL of the mesh deformed by the controller.
    std::string mMeshId;

    // accessor URL of the joint names
    std::string mJointNameSource;

    ///< The bind shape matrix, as array of floats. I'm not sure what this matrix actually describes, but it can't be ignored in all cases
    ai_real mBindShapeMatrix[16];

    // accessor URL of the joint inverse bind matrices
    std::string mJointOffsetMatrixSource;

    // input channel: joint names.
    InputChannel mWeightInputJoints;
    // input channel: joint weights
    InputChannel mWeightInputWeights;

    // Number of weights per vertex.
    std::vector<size_t> mWeightCounts;

    // JointIndex-WeightIndex pairs for all vertices
    std::vector<std::pair<size_t, size_t>> mWeights;

    std::string mMorphTarget;
    std::string mMorphWeight;
};

/// A collada material. Pretty much the only member is a reference to an effect.
struct Material {
    std::string mName;
    std::string mEffect;
};

/// Type of the effect param
enum ParamType {
    Param_Sampler,
    Param_Surface
};

/// A param for an effect. Might be of several types, but they all just refer to each other, so I summarize them
struct EffectParam {
    ParamType mType;
    std::string mReference; // to which other thing the param is referring to.
};

/// Shading type supported by the standard effect spec of Collada
enum ShadeType {
    Shade_Invalid,
    Shade_Constant,
    Shade_Lambert,
    Shade_Phong,
    Shade_Blinn
};

/// Represents a texture sampler in collada
struct Sampler {
    Sampler() :
            mWrapU(true),
            mWrapV(true),
            mMirrorU(),
            mMirrorV(),
            mOp(aiTextureOp_Multiply),
            mUVId(UINT_MAX),
            mWeighting(1.f),
            mMixWithPrevious(1.f) {}

    /// Name of image reference
    std::string mName;

    /// Wrap U?
    bool mWrapU;

    /// Wrap V?
    bool mWrapV;

    /// Mirror U?
    bool mMirrorU;

    /// Mirror V?
    bool mMirrorV;

    /// Blend mode
    aiTextureOp mOp;

    /// UV transformation
    aiUVTransform mTransform;

    /// Name of source UV channel
    std::string mUVChannel;

    /// Resolved UV channel index or UINT_MAX if not known
    unsigned int mUVId;

    // OKINO/MAX3D extensions from here
    // -------------------------------------------------------

    /// Weighting factor
    ai_real mWeighting;

    /// Mixing factor from OKINO
    ai_real mMixWithPrevious;
};

/// A collada effect. Can contain about anything according to the Collada spec,
/// but we limit our version to a reasonable subset.
struct Effect {
    /// Shading mode
    ShadeType mShadeType;

    /// Colors
    aiColor4D mEmissive, mAmbient, mDiffuse, mSpecular,
            mTransparent, mReflective;

    /// Textures
    Sampler mTexEmissive, mTexAmbient, mTexDiffuse, mTexSpecular,
            mTexTransparent, mTexBump, mTexReflective;

    /// Scalar factory
    ai_real mShininess, mRefractIndex, mReflectivity;
    ai_real mTransparency;
    bool mHasTransparency;
    bool mRGBTransparency;
    bool mInvertTransparency;

    /// local params referring to each other by their SID
    using ParamLibrary = std::map<std::string, Collada::EffectParam>;
    ParamLibrary mParams;

    // MAX3D extensions
    // ---------------------------------------------------------
    // Double-sided?
    bool mDoubleSided, mWireframe, mFaceted;

    Effect() :
            mShadeType(Shade_Phong),
            mEmissive(0, 0, 0, 1),
            mAmbient(0.1f, 0.1f, 0.1f, 1),
            mDiffuse(0.6f, 0.6f, 0.6f, 1),
            mSpecular(0.4f, 0.4f, 0.4f, 1),
            mTransparent(0, 0, 0, 1),
            mShininess(10.0f),
            mRefractIndex(1.f),
            mReflectivity(0.f),
            mTransparency(1.f),
            mHasTransparency(false),
            mRGBTransparency(false),
            mInvertTransparency(false),
            mDoubleSided(false),
            mWireframe(false),
            mFaceted(false) {
    }
};

/// An image, meaning texture
struct Image {
    std::string mFileName;

    /// Embedded image data
    std::vector<uint8_t> mImageData;

    /// File format hint of embedded image data
    std::string mEmbeddedFormat;
};

/// An animation channel.
struct AnimationChannel {
    /// URL of the data to animate. Could be about anything, but we support only the
    /// "NodeID/TransformID.SubElement" notation
    std::string mTarget;

    /// Source URL of the time values. Collada calls them "input". Meh.
    std::string mSourceTimes;
    /// Source URL of the value values. Collada calls them "output".
    std::string mSourceValues;
    /// Source URL of the IN_TANGENT semantic values.
    std::string mInTanValues;
    /// Source URL of the OUT_TANGENT semantic values.
    std::string mOutTanValues;
    /// Source URL of the INTERPOLATION semantic values.
    std::string mInterpolationValues;
};

/// An animation. Container for 0-x animation channels or 0-x animations
struct Animation {
    /// Anim name
    std::string mName;

    /// the animation channels, if any
    std::vector<AnimationChannel> mChannels;

    /// the sub-animations, if any
    std::vector<Animation *> mSubAnims;

    /// Destructor
    ~Animation() {
        for (std::vector<Animation *>::iterator it = mSubAnims.begin(); it != mSubAnims.end(); ++it) {
            delete *it;
        }
    }

    /// Collect all channels in the animation hierarchy into a single channel list.
    void CollectChannelsRecursively(std::vector<AnimationChannel> &channels) {
        channels.insert(channels.end(), mChannels.begin(), mChannels.end());

        for (std::vector<Animation *>::iterator it = mSubAnims.begin(); it != mSubAnims.end(); ++it) {
            Animation *pAnim = (*it);
            pAnim->CollectChannelsRecursively(channels);
        }
    }

    /// Combine all single-channel animations' channel into the same (parent) animation channel list.
    void CombineSingleChannelAnimations() {
        CombineSingleChannelAnimationsRecursively(this);
    }

    void CombineSingleChannelAnimationsRecursively(Animation *pParent) {
        std::set<std::string> childrenTargets;
        bool childrenAnimationsHaveDifferentChannels = true;

        for (std::vector<Animation *>::iterator it = pParent->mSubAnims.begin(); it != pParent->mSubAnims.end();) {
            Animation *anim = *it;
            CombineSingleChannelAnimationsRecursively(anim);

            if (childrenAnimationsHaveDifferentChannels && anim->mChannels.size() == 1 &&
                    childrenTargets.find(anim->mChannels[0].mTarget) == childrenTargets.end()) {
                childrenTargets.insert(anim->mChannels[0].mTarget);
            } else {
                childrenAnimationsHaveDifferentChannels = false;
            }

            ++it;
        }

        // We only want to combine animations if they have different channels
        if (childrenAnimationsHaveDifferentChannels) {
            for (std::vector<Animation *>::iterator it = pParent->mSubAnims.begin(); it != pParent->mSubAnims.end();) {
                Animation *anim = *it;

                pParent->mChannels.push_back(anim->mChannels[0]);

                it = pParent->mSubAnims.erase(it);

                delete anim;
                continue;
            }
        }
    }
};

/// Description of a collada animation channel which has been determined to affect the current node
struct ChannelEntry {
    const Collada::AnimationChannel *mChannel; ///< the source channel
    std::string mTargetId;
    std::string mTransformId; // the ID of the transformation step of the node which is influenced
    size_t mTransformIndex; // Index into the node's transform chain to apply the channel to
    size_t mSubElement; // starting index inside the transform data

    // resolved data references
    const Collada::Accessor *mTimeAccessor; ///> Collada accessor to the time values
    const Collada::Data *mTimeData; ///> Source data array for the time values
    const Collada::Accessor *mValueAccessor; ///> Collada accessor to the key value values
    const Collada::Data *mValueData; ///> Source datat array for the key value values

    ChannelEntry() :
            mChannel(),
            mTransformIndex(),
            mSubElement(),
            mTimeAccessor(),
            mTimeData(),
            mValueAccessor(),
            mValueData() {}
};

} // end of namespace Collada
} // end of namespace Assimp

#endif // AI_COLLADAHELPER_H_INC
