//
// Created by Lenn on 2025/12/2.
//

#ifndef COORDINATE_SYSTEM_PROJECT_MESH_HH
#define COORDINATE_SYSTEM_PROJECT_MESH_HH
#include <assimp/material.h>
#include <assimp/mesh.h>
#include <assimp/types.h>
#include <cstring>
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>
#include <iostream>
#include <vector>
#include "myshader.hh"
#include "stb_image.h"

#define MAX_BONE_INFLUENCE 4

struct Vertex {
    glm::vec3 Position;
    glm::vec3 Normal;
    glm::vec2 TexCoords;
    glm::vec3 Tangent;
    glm::vec3 Bitangent;
    int       BoneIDs[MAX_BONE_INFLUENCE];
    float     Weights[MAX_BONE_INFLUENCE];
};

struct Texture {
    unsigned int id;
    std::string  type;
    std::string  path;
};
class Mesh {
  public:
    std::vector<Vertex>       vertices;
    std::vector<unsigned int> indices;
    std::vector<Texture>      textures;
    // unsigned int VAO;

    Mesh(std::vector<Vertex> vertices, std::vector<unsigned int> indices, std::vector<Texture> textures) {
        vertices_ = vertices;
        indices_  = indices;
        textures_ = textures;
        setup_mesh();
    }
    void draw(Shader& shader) {
        unsigned int diffuse_nr  = 1;
        unsigned int specular_nr = 1;
        for (unsigned int i = 0; i < textures.size(); i++) {
            glActiveTexture(GL_TEXTURE0 + i);
            std::string number;
            std::string name = textures[i].type;
            if (name == "texture_diffuse")
                number = std::to_string(diffuse_nr++);
            else if (name == "texture_specular")
                number = std::to_string(specular_nr++);

            shader.setInt(("material." + name + number).c_str(), i);
            glBindTexture(GL_TEXTURE_2D, textures[i].id);
        }
        glActiveTexture(GL_TEXTURE0);
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES, static_cast<unsigned int>(indices.size()), GL_UNSIGNED_INT, 0);
        glBindVertexArray(0);
    }

  private:
    unsigned int              VAO, VBO, EBO;
    std::vector<Vertex>       vertices_;
    std::vector<unsigned int> indices_;
    std::vector<Texture>      textures_;
    void                      setup_mesh() {
        glGenVertexArrays(1, &VAO);
        glGenBuffers(1, &VBO);
        glGenBuffers(1, &EBO);

        glBindVertexArray(VAO);
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(Vertex), &vertices[0], GL_STATIC_DRAW);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(unsigned int), &indices[0], GL_STATIC_DRAW);

        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)0);
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, Normal));
        glEnableVertexAttribArray(2);
        glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, TexCoords));
        glEnableVertexAttribArray(3);
        glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, Tangent));
        glEnableVertexAttribArray(4);
        glVertexAttribPointer(4, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, Bitangent));
        glEnableVertexAttribArray(5);
        glVertexAttribPointer(5, 4, GL_INT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, BoneIDs));
        glEnableVertexAttribArray(6);
        glVertexAttribPointer(6, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, Weights));
        glBindVertexArray(0);
    }
};

unsigned int TextureFromFile(const char* path, const std::string& directory, bool gamma = false);

class Model {
  public:
    Model(char* path) {
    }

    void draw(Shader shader) {
        for (unsigned int i = 0; i < meshes_.size(); i++) {
            meshes_[i].draw(shader);
        }
    }

  private:
    std::vector<Texture> textures_;
    std::vector<Mesh>    meshes_;
    std::string          directory_;
    bool gamma_correction_;
    void                 loadModel(std::string path) {
        Assimp::Importer importer;
        const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_GenSmoothNormals);
        if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) {
            std::cout << "ERROR:ASSIMP::" << importer.GetErrorString();
            return;
        }
        
        directory_ = path.substr(0, path.find_last_of('/'));
        processNode(scene->mRootNode, scene);
    }
    void                 processNode(aiNode* node, const aiScene* scene) {
        // 处理节点所有的网格（如果有的话）
        for (unsigned int i = 0; i < node->mNumMeshes; i++) {
            aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];
            meshes_.push_back(processMesh(mesh, scene));
        }
        // 接下来对它的子节点重复这一过程
        for (unsigned int i = 0; i < node->mNumChildren; i++) {
            processNode(node->mChildren[i], scene);
        }
    }

    Mesh processMesh(aiMesh* mesh, const aiScene* scene) {
        std::vector<Vertex>       vertices;
        std::vector<unsigned int> indices;
        std::vector<Texture>      textures;

        for (unsigned int i = 0; i < mesh->mNumVertices; i++) {
            Vertex    vertex;
            glm::vec3 vector;
            vector.x        = mesh->mVertices[i].x;
            vector.y        = mesh->mVertices[i].y;
            vector.z        = mesh->mVertices[i].z;
            vertex.Position = vector;
            if (mesh->HasNormals()) {
                vector.x      = mesh->mNormals[i].x;
                vector.y      = mesh->mNormals[i].y;
                vector.z      = mesh->mNormals[i].z;
                vertex.Normal = vector;
            }
            if (mesh->mTextureCoords[0]) {
                glm::vec2 vec;
                vec.x            = mesh->mTextureCoords[0][i].x;
                vec.y            = mesh->mTextureCoords[0][i].y;
                vertex.TexCoords = vec;

                vector.x       = mesh->mTangents[i].x;
                vector.y       = mesh->mTangents[i].y;
                vector.z       = mesh->mTangents[i].z;
                vertex.Tangent = vector;

                vector.x         = mesh->mBitangents[i].x;
                vector.y         = mesh->mBitangents[i].y;
                vector.z         = mesh->mBitangents[i].z;
                vertex.Bitangent = vector;
            }
            else
                vertex.TexCoords = glm::vec2(0.0f, 0.0f);

            vertices.push_back(vertex);
        }

        for (unsigned int i = 0; i < mesh->mNumFaces; i++) {
            aiFace face = mesh->mFaces[i];
            for (unsigned int j = 0; j < face.mNumIndices; j++) {
                indices.push_back(face.mIndices[j]);
            }
        }
        aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];

        std::vector<Texture> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
        textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
        std::vector<Texture> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
        textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
        std::vector<Texture> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal");
        textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
        std::vector<Texture> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height");
        textures.insert(textures.end(), textures.begin(), heightMaps.end());

        return Mesh(vertices, indices, textures);
    }

    std::vector<Texture> loadMaterialTextures(aiMaterial* mat, aiTextureType type, std::string type_name) {
        std::vector<Texture> textures;
        for (unsigned int i = 0; i < mat->GetTextureCount(type); i++) {
            aiString str;
            mat->GetTexture(type, i, &str);
            bool skip = false;
            for (unsigned int j = 0; j < textures_.size(); j++) {
                if (std::strcmp(textures_[j].path.data(), str.C_Str()) == 0) {
                    textures.push_back(textures_[j]);
                    skip = true;
                    break;
                }
            }
            if (!skip) {
                Texture texture;
                texture.id   = textureFromFile(str.C_Str(), this->directory_, false);
                texture.type = type_name;
                texture.path = str.C_Str();
                textures.push_back(texture);
                textures_.push_back(texture);
            }
        }

        return textures;
    }

    unsigned int textureFromFile(const char* path, const std::string& directory, bool gamma) {
        std::string filename = std::string(path);
        filename             = directory + '/' + filename;
        unsigned int textureID;
        glGenTextures(1, &textureID);
        int            width, height, nrComponents;
        unsigned char* data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
        if (data) {
            GLenum fromat;
            if (nrComponents == 1) {
                fromat = GL_RED;
            }
            else if (nrComponents == 3) {
                fromat = GL_RGB;
            }
            else if (nrComponents == 4) {
                fromat = GL_RGBA;
            }

            glBindTexture(GL_TEXTURE_2D, textureID);
            glTexImage2D(GL_TEXTURE_2D, 0, fromat, width, height, 0, fromat, GL_UNSIGNED_BYTE, data);
            glGenerateMipmap(GL_TEXTURE_2D);

            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

            stbi_image_free(data);
        }
        else {
            std::cout << "Texture failed to load at path: " << path << std::endl;
            stbi_image_free(data);
        }

        return textureID;
    }
};

#endif // COORDINATE_SYSTEM_PROJECT_MESH_HH