Kelsidavis-WoWee/include/pipeline/m2_loader.hpp

#pragma once

#include <vector>
#include <string>
#include <glm/glm.hpp>
#include <glm/gtc/quaternion.hpp>

namespace wowee {
namespace pipeline {

/**
 * M2 Model Format (WoW Character/Creature Models)
 *
 * M2 files contain:
 * - Skeletal animated meshes
 * - Multiple texture units and materials
 * - Animation sequences
 * - Bone hierarchy
 * - Particle emitters, ribbon emitters, etc.
 *
 * Reference: https://wowdev.wiki/M2
 */

// Animation sequence data
struct M2Sequence {
    uint32_t id;                    // Animation ID
    uint32_t variationIndex;        // Sub-animation index
    uint32_t duration;              // Length in milliseconds
    float movingSpeed;              // Speed during animation
    uint32_t flags;                 // Animation flags
    int16_t frequency;              // Probability weight
    uint32_t replayMin;             // Minimum replay delay
    uint32_t replayMax;             // Maximum replay delay
    uint32_t blendTime;             // Blend time in ms
    glm::vec3 boundMin;             // Bounding box
    glm::vec3 boundMax;
    float boundRadius;              // Bounding sphere radius
    int16_t nextAnimation;          // Next animation in chain
    uint16_t aliasNext;             // Alias for next animation
};

// Animation track with per-sequence keyframe data
struct M2AnimationTrack {
    uint16_t interpolationType = 0; // 0=none, 1=linear, 2=hermite, 3=bezier
    int16_t globalSequence = -1;    // -1 if not a global sequence

    struct SequenceKeys {
        std::vector<uint32_t> timestamps;   // Milliseconds
        std::vector<glm::vec3> vec3Values;  // For translation/scale tracks
        std::vector<glm::quat> quatValues;  // For rotation tracks
        std::vector<float> floatValues;     // For float tracks (particle emitters)
    };
    std::vector<SequenceKeys> sequences;    // One per animation sequence

    bool hasData() const { return !sequences.empty(); }
};

// Bone data for skeletal animation
struct M2Bone {
    int32_t keyBoneId;              // Bone ID (-1 = not key bone)
    uint32_t flags;                 // Bone flags
    int16_t parentBone;             // Parent bone index (-1 = root)
    uint16_t submeshId;             // Submesh ID
    glm::vec3 pivot;                // Pivot point

    M2AnimationTrack translation;   // Position keyframes per sequence
    M2AnimationTrack rotation;      // Rotation keyframes per sequence
    M2AnimationTrack scale;         // Scale keyframes per sequence
};

// Vertex with skinning data
struct M2Vertex {
    glm::vec3 position;
    uint8_t boneWeights[4];         // Bone weights (0-255)
    uint8_t boneIndices[4];         // Bone indices
    glm::vec3 normal;
    glm::vec2 texCoords[2];         // Two UV sets
};

// Texture unit
struct M2Texture {
    uint32_t type;                  // Texture type
    uint32_t flags;                 // Texture flags
    std::string filename;           // Texture filename (from FileData or embedded)
};

// Render batch (submesh)
struct M2Batch {
    uint8_t flags;
    int8_t priorityPlane;
    uint16_t shader;                // Shader ID
    uint16_t skinSectionIndex;      // Submesh index
    uint16_t colorIndex;            // Color animation index
    uint16_t materialIndex;         // Material index
    uint16_t materialLayer;         // Material layer
    uint16_t textureCount;          // Number of textures
    uint16_t textureIndex;          // First texture lookup index
    uint16_t textureUnit;           // Texture unit
    uint16_t transparencyIndex;     // Transparency animation index
    uint16_t textureAnimIndex;      // Texture animation index

    // Render data
    uint32_t indexStart;            // First index
    uint32_t indexCount;            // Number of indices
    uint32_t vertexStart;           // First vertex
    uint32_t vertexCount;           // Number of vertices

    // Geoset info (from submesh)
    uint16_t submeshId = 0;         // Submesh/geoset ID (determines body part group)
    uint16_t submeshLevel = 0;      // Submesh level (0=base, 1+=LOD/alternate mesh)
};

// Material / render flags (per-batch blend mode)
struct M2Material {
    uint16_t flags;       // Render flags (unlit, unfogged, two-sided, etc.)
    uint16_t blendMode;   // 0=Opaque, 1=AlphaKey, 2=Alpha, 3=Add, 4=Mod, 5=Mod2x, 6=BlendAdd, 7=Screen
};

// Texture transform (UV animation) data
struct M2TextureTransform {
    M2AnimationTrack translation;   // UV translation keyframes
    M2AnimationTrack rotation;      // UV rotation keyframes (quat)
    M2AnimationTrack scale;         // UV scale keyframes
};

// Attachment point (bone-anchored position for weapons, effects, etc.)
struct M2Attachment {
    uint32_t id;        // 0=Head, 1=RightHand, 2=LeftHand, etc.
    uint16_t bone;      // Bone index
    glm::vec3 position; // Offset from bone pivot
};

// FBlock: particle lifetime curve (color/alpha/scale over particle life)
struct M2FBlock {
    std::vector<float> timestamps;      // Normalized 0..1
    std::vector<float> floatValues;     // For alpha/scale
    std::vector<glm::vec3> vec3Values;  // For color RGB
};

// Particle emitter definition parsed from M2
struct M2ParticleEmitter {
    int32_t particleId;
    uint32_t flags;
    glm::vec3 position;
    uint16_t bone;
    uint16_t texture;
    uint8_t blendingType;   // 0=opaque,1=alphakey,2=alpha,4=add
    uint8_t emitterType;    // 1=plane,2=sphere,3=spline
    int16_t textureTileRotation = 0;
    uint16_t textureRows = 1;
    uint16_t textureCols = 1;
    M2AnimationTrack emissionSpeed;
    M2AnimationTrack speedVariation;
    M2AnimationTrack verticalRange;
    M2AnimationTrack horizontalRange;
    M2AnimationTrack gravity;
    M2AnimationTrack lifespan;
    M2AnimationTrack emissionRate;
    M2AnimationTrack emissionAreaLength;
    M2AnimationTrack emissionAreaWidth;
    M2AnimationTrack deceleration;
    M2FBlock particleColor;   // vec3 RGB at 3 timestamps
    M2FBlock particleAlpha;   // float (from uint16/32767) at 3 timestamps
    M2FBlock particleScale;   // float (x component of vec2) at 3 timestamps
    bool enabled = true;
};

// Complete M2 model structure
struct M2Model {
    // Model metadata
    std::string name;
    uint32_t version;
    glm::vec3 boundMin;             // Model bounding box
    glm::vec3 boundMax;
    float boundRadius;              // Bounding sphere

    // Geometry data
    std::vector<M2Vertex> vertices;
    std::vector<uint16_t> indices;

    // Skeletal animation
    std::vector<M2Bone> bones;
    std::vector<M2Sequence> sequences;
    std::vector<uint32_t> globalSequenceDurations;  // Per-global-sequence loop durations (ms)

    // Bone lookup table (vertex bone indices reference this to get global bone index)
    std::vector<uint16_t> boneLookupTable;

    // Rendering
    std::vector<M2Batch> batches;
    std::vector<M2Texture> textures;
    std::vector<uint16_t> textureLookup;  // Batch texture index lookup
    std::vector<M2Material> materials;    // Render flags / blend modes

    // Texture transforms (UV animation)
    std::vector<M2TextureTransform> textureTransforms;
    std::vector<uint16_t> textureTransformLookup;

    // Texture weights (per-batch opacity, from M2Track<fixed16>)
    // Each entry is the "at-rest" opacity value (0=transparent, 1=opaque).
    // batch.transparencyIndex → textureTransformLookup[idx] → textureWeights[trackIdx]
    std::vector<float> textureWeights;

    // Color animation alpha values (from M2Color.alpha M2Track<fixed16>)
    // One entry per color animation slot; batch.colorIndex indexes directly into this.
    // Value 0=transparent, 1=opaque. Independent from textureWeights.
    std::vector<float> colorAlphas;

    // Attachment points (for weapon/effect anchoring)
    std::vector<M2Attachment> attachments;
    std::vector<uint16_t> attachmentLookup; // attachment ID → index

    // Particle emitters
    std::vector<M2ParticleEmitter> particleEmitters;

    // Collision mesh (simplified geometry for physics)
    std::vector<glm::vec3> collisionVertices;
    std::vector<uint16_t> collisionIndices;      // 3 per triangle
    std::vector<glm::vec4> collisionNormals;     // xyz=normal, w=distance; one per triangle

    // Flags
    uint32_t globalFlags;

    bool isValid() const {
        return !vertices.empty() && !indices.empty();
    }
};

class M2Loader {
public:
    /**
     * Load M2 model from raw file data
     *
     * @param m2Data Raw M2 file bytes
     * @return Parsed M2 model
     */
    static M2Model load(const std::vector<uint8_t>& m2Data);

    /**
     * Load M2 skin file (contains submesh/batch data)
     *
     * @param skinData Raw M2 skin file bytes
     * @param model Model to populate with skin data
     * @return True if successful
     */
    static bool loadSkin(const std::vector<uint8_t>& skinData, M2Model& model);

    /**
     * Load external .anim file data into model bone tracks
     *
     * @param m2Data Original M2 file bytes (contains track headers)
     * @param animData Raw .anim file bytes
     * @param sequenceIndex Which sequence index this .anim file provides data for
     * @param model Model to patch with animation data
     */
    static void loadAnimFile(const std::vector<uint8_t>& m2Data,
                             const std::vector<uint8_t>& animData,
                             uint32_t sequenceIndex,
                             M2Model& model);
};

} // namespace pipeline
} // namespace wowee