path: root/src/client/render/model.hh

#ifndef CLIENT_RENDER_MODEL_HH_
#define CLIENT_RENDER_MODEL_HH_

#include <string>
#include <vector>

#include <epoxy/glx.h>

#include <glm/glm.hpp>
#include <glm/gtc/type_ptr.hpp>

#include <assimp/Importer.hpp>
#include <assimp/postprocess.h>
#include <assimp/scene.h>

#include "client/render/program.hh"
#include "client/render/texture.hh"

namespace client {
namespace render {

struct vertex {
    glm::vec3 position;
    glm::vec3 normal;
    glm::vec2 texture;
};
struct texture_info {
    unsigned id;
    std::string type;
    std::string path;
};

class model {
private:
    struct mesh {
    private:
        GLuint vao;
        GLuint vbo;
        GLuint ebo;

    public:
        std::vector<vertex> vertices;
        std::vector<unsigned> indices;
        std::vector<texture_info> textures;

    private:
        void setup() noexcept {
            glGenVertexArrays(1, &this->vao);
            glGenBuffers(1, &this->vbo);
            glGenBuffers(1, &this->ebo);

            glBindVertexArray(vao);

            glBindBuffer(GL_ARRAY_BUFFER, vbo);
            glBufferData(GL_ARRAY_BUFFER,
                         std::size(this->vertices) * sizeof(vertex),
                         std::data(this->vertices), GL_STATIC_DRAW);

            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
            glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                         std::size(this->indices) * sizeof(GLuint),
                         std::data(this->indices), GL_STATIC_DRAW);

            // The reinterpret casts might be wrong here.
            // positions
            glEnableVertexAttribArray(0);
            glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(vertex),
                                  nullptr);
            // normals LMAO
            glEnableVertexAttribArray(1);
            glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(vertex),
                                  reinterpret_cast<void*>(sizeof(glm::vec3)));
            // texture
            glEnableVertexAttribArray(2);
            glVertexAttribPointer(
                2, 2, GL_FLOAT, GL_FALSE, sizeof(vertex),
                reinterpret_cast<void*>(sizeof(glm::vec3) + sizeof(glm::vec3)));
        }

    public:
        mesh(const std::vector<vertex>& v, const std::vector<unsigned>& i,
             const std::vector<texture_info>& t) noexcept
            : vertices(v), indices(i), textures(t) {
            setup();
        }

        // Not going to bother with textures yet.
        void draw(const client::render::program& program,
                  const glm::mat4& matrix) const noexcept {

            glUseProgram(program);
            static const GLint u_matrix{
                glGetUniformLocation(program, "_u_matrix")};
            glBindVertexArray(this->vao);

            glUniformMatrix4fv(u_matrix, 1, GL_FALSE, glm::value_ptr(matrix));

            glDrawElements(GL_TRIANGLES, std::size(this->indices),
                           GL_UNSIGNED_INT, nullptr);
        }
    };

private:
    std::vector<mesh> meshes;
    std::string directory;

private:
    unsigned int texture_from_file(const std::string& path,
                                   const std::string& dir) noexcept {
        const std::string filename = dir + '/' + path;

        const client::render::texture texture{filename};

        unsigned int tex;
        glGenTextures(1, &tex);
        glBindTexture(GL_TEXTURE_2D, tex);

        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);

        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texture.width, texture.height,
                     0, texture.channels == 3 ? GL_RGB : GL_RGBA,
                     GL_UNSIGNED_BYTE, texture.image);
        glGenerateMipmap(GL_TEXTURE_2D);

        return tex;
    }

    std::vector<texture_info>
    load_material_textures(const aiMaterial* const material,
                           const aiTextureType type,
                           const std::string& name) noexcept {
        std::vector<texture_info> textures;
        for (unsigned i = 0; i < material->GetTextureCount(type); ++i) {
            aiString str;
            material->GetTexture(type, i, &str);

            struct texture_info texture;
            texture.id = texture_from_file(str.C_Str(), directory);
            texture.type = name;
            texture.path = str.data;

            textures.push_back(std::move(texture));
        }
        return textures;
    }
    mesh process_mesh(const aiMesh* mesh, const aiScene* scene) noexcept {
        std::vector<vertex> vertices;
        std::vector<unsigned> indices;
        std::vector<texture_info> textures;

        for (unsigned i = 0; i < mesh->mNumVertices; ++i) {
            vertex v;

            glm::vec3 vector;
            vector.x = mesh->mVertices[i].x;
            vector.y = mesh->mVertices[i].y;
            vector.z = mesh->mVertices[i].z;

            v.position = vector;

            vector.x = mesh->mNormals[i].x;
            vector.y = mesh->mNormals[i].y;
            vector.z = mesh->mNormals[i].z;

            v.normal = vector;

            if (mesh->mTextureCoords[0]) {
                glm::vec2 vec;
                vec.x = mesh->mTextureCoords[0][i].x;
                vec.y = mesh->mTextureCoords[0][i].x;
                v.texture = vec;
            } else {
                v.texture = glm::vec2{0.0f};
            }

            vector.x = mesh->mNormals[i].x;
            vector.y = mesh->mNormals[i].y;
            vector.z = mesh->mNormals[i].z;

            vertices.push_back(std::move(v));
        }

        for (unsigned i = 0; i < mesh->mNumFaces; ++i) {
            aiFace face = mesh->mFaces[i];
            for (unsigned j = 0; j < face.mNumIndices; ++j) {
                indices.push_back(face.mIndices[j]);
            }
        }

        if (mesh->mMaterialIndex >= 0) {
            const aiMaterial* const material =
                scene->mMaterials[mesh->mMaterialIndex];
            std::ranges::copy(load_material_textures(material,
                                                     aiTextureType_DIFFUSE,
                                                     "texture_diffuse"),
                              std::back_inserter(textures));
            std::ranges::copy(load_material_textures(material,
                                                     aiTextureType_SPECULAR,
                                                     "texture_specular"),
                              std::back_inserter(textures));
        }

        return {vertices, indices, textures};
    }
    void process_node(const aiNode* node, const aiScene* scene) noexcept {
        for (unsigned i = 0; i < node->mNumMeshes; ++i) {
            const aiMesh* const mesh = scene->mMeshes[node->mMeshes[i]];
            meshes.push_back(process_mesh(mesh, scene));
        }
        for (unsigned i = 0; i < node->mNumChildren; ++i) {
            process_node(node->mChildren[i], scene);
        }
    }
    void load(const std::string& path) noexcept {
        Assimp::Importer importer;

        const aiScene* scene =
            importer.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);
        if (scene == nullptr || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE ||
            scene->mRootNode == nullptr) {
            throw std::runtime_error("assimp error: " +
                                     std::string(importer.GetErrorString()));
        }

        directory = path; // AHHHHHHHhh
        process_node(scene->mRootNode, scene);
    }

public:
    model(const std::string& path) noexcept { load(path); }
    void draw(const client::render::program& program,
              const glm::mat4& matrix) noexcept {
        for (const auto& mesh : meshes) {
            mesh.draw(program, matrix);
        }
    }
};

} // namespace render

} // namespace client

#endif