#pragma once

#include <string>
#include <iostream>

#include <assimp/Importer.hpp>      // C++ importer interface
#include <assimp/scene.h>           // Output data structure
#include <assimp/postprocess.h>     // Post processing flags

#include <epoxy/gl.h>
#include <epoxy/glx.h>

class PolygonModel {
    public:
        PolygonModel(const std::string &filename) : m_filename(filename)
        {
            clear();
        }

        void clear()
        {
            // TODO: delete buffers if there's data

            m_loaded_from_file = false;
            m_loaded_to_opengl = false;

            m_data_position.clear();
            m_data_normal.clear();

            m_vbo_id_position = 0;
            m_vbo_id_normal   = 0;
            m_numVertices     = 0;
        }

        bool import()
        {
            clear();

            // Create an instance of the Importer class
            Assimp::Importer importer;
            // And have it read the given file with some example postprocessing
            // Usually - if speed is not the most important aspect for you - you'll
            // propably to request more postprocessing than we do in this example.
            const aiScene* scene = importer.ReadFile(m_filename,
                    aiProcess_CalcTangentSpace       |
                    aiProcess_Triangulate            |
                    aiProcess_JoinIdenticalVertices  |
                    aiProcess_SortByPType);

            // If the import failed, report it
            if (!scene) {
                std::cout<<"[polygonmodel] loading file "
                    << m_filename << " failed with: "
                    << importer.GetErrorString() << std::endl;

                return false;
            }

            // Now we can access the file's contents.
            copyVertices(scene);

            m_loaded_from_file = true;

            // We're done. Everything will be cleaned up by the importer destructor
            return true;
        }

        bool uploadToOpenGl()
        {
            if (!m_loaded_from_file) {
                std::cerr<<"[polygonmodel] warning: try to upload model data "
                    << "to OpenGL but no data is loaded!" << std::endl;

                exit(-1);
                return false;
            }

            glEnableVertexAttribArray(0);

            glGenBuffers(1, &m_vbo_id_position);            // Generate buffer
            glBindBuffer(GL_ARRAY_BUFFER, m_vbo_id_position); // Bind buffer

            glVertexAttribPointer(0,
                    3, // three floats per vertex
                    GL_FLOAT,  // Data is floating point type
                    GL_FALSE,  // No fixed point scaling
                    0,         // stride: no
                    NULL);     // No offset

            // fill buffer with the loaded mesh position data
            glBufferData(
                    GL_ARRAY_BUFFER,                    // Buffer target
                    3 * m_numVertices * sizeof(float),  // Buffer data size
                    m_data_position.data(),             // Buffer data pointer
                    GL_STATIC_DRAW);                    // Usage - Data never changes;

            // TODO
#if 0
        // 2 holds normal data
        glEnableVertexAttribArray(2);
        glGenBuffers(1, &(model->vbo_normal));            // Generate buffer
        glBindBuffer(GL_ARRAY_BUFFER, model->vbo_normal); // Bind buffer

        glVertexAttribPointer(2,
            3,         // three floats per normal
            GL_FLOAT,  // Data is floating point type
            GL_FALSE,  // No fixed point scaling
            0,         // stride: no
            NULL);     // No offset

        // Fill bound buffer
        glBufferData(
            GL_ARRAY_BUFFER,                    // Buffer target
            3*model->numVertices*sizeof(float), // Buffer data size
            model->normals,                     // Buffer data pointer
            GL_STATIC_DRAW);                    // Usage - Data never changes;
#endif
            m_loaded_to_opengl = true;

            return true;
        }

        bool bind()
        {
            // TODO: check whether this vbo is bound!
            if (!m_loaded_to_opengl) {
                std::cout<<"[polygonmodel] warning: try to bind model vbo "
                    << "which was not uploaded to OpenGL!" << std::endl;

                exit(-1);
                return false;
            }

            // bind position vbo
            glEnableVertexAttribArray(0);
            glBindBuffer(GL_ARRAY_BUFFER, m_vbo_id_position);
            glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);

            // TODO
#if 0
            // bind normal vbo
            GLuint normalLoc = glGetAttribLocation(program, "attr_normal");
            glEnableVertexAttribArray(normalLoc);
            glBindBuffer(GL_ARRAY_BUFFER, mesh->vbo_normal);
            glVertexAttribPointer(normalLoc, 3, GL_FLOAT, GL_FALSE, 0, NULL);
#endif

            m_binding_active = true;

            return true;
        }

        bool render()
        {
            if (!m_binding_active || !m_loaded_to_opengl) {
                std::cout<<"[polygonmodel] warning: try to render model without bind()" << std::endl;
                exit(-1);
                return false;
            }

            glDrawArrays(GL_TRIANGLES, 0, m_numVertices);
            return true;
        }

    private:
        bool copyVertices(const aiScene *scene)
        {
            if (scene->mMeshes == 0) {
                std::cout << "[polygonmodel : no meshes loaded for " << m_filename << std::endl;
                return false;
            }

            aiNode *node = scene->mRootNode;
            const aiMesh* mesh = scene->mMeshes[node->mMeshes[0]];

            // 3 vertices per face, 3 floats per vertex
            m_numVertices = mesh->mNumFaces*3;

            m_data_position.reserve(m_numVertices);
            m_data_normal.reserve(m_numVertices);

            size_t t, i;
            for (t=0; t<mesh->mNumFaces; ++t) {
                const aiFace* face = &mesh->mFaces[t];
                if (face->mNumIndices != 3) {
                    std::cout << "[polygonmodel] need triangles, got something different with: "
                        << face->mNumIndices  << " vertices" << std::endl;

                    return false;
                }

                for (i=0; i<face->mNumIndices; i++) {
                    const size_t index = face->mIndices[i];
                    m_data_position.push_back(mesh->mVertices[index].x);
                    m_data_position.push_back(mesh->mVertices[index].y);
                    m_data_position.push_back(mesh->mVertices[index].z);

                    m_data_normal.push_back(mesh->mNormals[index].x);
                    m_data_normal.push_back(mesh->mNormals[index].y);
                    m_data_normal.push_back(mesh->mNormals[index].z);
                }
            }

            size_t totalBytes = 3*m_numVertices*sizeof(float);
            std::cout<<"[polygonmodel] loaded file " << m_filename
                << " with "  << m_numVertices << " vertices ("
                << totalBytes << " bytes)" << std::endl;

            return true;
        }

        const std::string &filename() const { return m_filename; }

    private:
        std::string m_filename;
        bool        m_loaded_from_file;
        bool        m_loaded_to_opengl;
        bool        m_binding_active;

        // both will hold 3 * numVertices floats
        std::vector<float> m_data_position;
        std::vector<float> m_data_normal;

        size_t      m_numVertices;

        GLuint      m_vbo_id_position;
        GLuint      m_vbo_id_normal;
};