#include "mesh.h"
#include "vertex.h"
#include "mikktspace.h"

#include <glad/gl.h>
#include <stdlib.h>

void compute_tangents(mons_vertex *vertex_array, int vertex_count, int *index_array, int index_count);

mons_mesh mons_create_mesh(mons_vertex *vertex_array, int vertex_count, int *index_array, int index_count) {
    compute_tangents(vertex_array, vertex_count, index_array, index_count);
    // VAO & VBO
    unsigned int vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);
    unsigned int vbo;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(mons_vertex) * vertex_count, vertex_array, GL_STATIC_DRAW);
    unsigned int ebo;
    glGenBuffers(1, &ebo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(unsigned int) * index_count, index_array, GL_STATIC_DRAW);
    // Set up vertex attributes
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(mons_vertex), 0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(mons_vertex), (void*)(sizeof(mons_vec3)));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, sizeof(mons_vertex), (void*)(sizeof(mons_vec3) * 2));
    glEnableVertexAttribArray(2);
    glVertexAttribPointer(3, 2, GL_FLOAT, GL_FALSE, sizeof(mons_vertex), (void*)(sizeof(mons_vec3) * 2 + sizeof(mons_vec4)));
    glEnableVertexAttribArray(3);
    return (mons_mesh) {
        .vao = vao,
        .element_count = index_count,
    };
}

struct mesh_data {
    mons_vertex *vertex_array;
    int vertex_count;
    int *index_array;
    int index_count;
};

int get_vertex_index(const SMikkTSpaceContext *context, int i_face, int i_vert) {
    struct mesh_data *mesh_data = context->m_pUserData;
    int index_index = (i_face * 3) + i_vert;
    int index = mesh_data->index_array[index_index];
    return index;
}

int get_num_faces(const SMikkTSpaceContext *context) {
    struct mesh_data *mesh_data = context->m_pUserData;
    return mesh_data->index_count / 3;
}

int get_num_vertices_of_face(const SMikkTSpaceContext *context, int i_face) {
    return 3;
}

void get_position(const SMikkTSpaceContext *context, float *outpos, int i_face, int i_vert) {
    struct mesh_data *mesh_data = context->m_pUserData;
    int index = get_vertex_index(context, i_face, i_vert);
    mons_vertex vertex = mesh_data->vertex_array[index];

    outpos[0] = vertex.position.x;
    outpos[1] = vertex.position.y;
    outpos[2] = vertex.position.z;
}

void get_normal(const SMikkTSpaceContext *context, float *outnormal, int i_face, int i_vert) {
    struct mesh_data *mesh_data = context->m_pUserData;
    int index = get_vertex_index(context, i_face, i_vert);
    mons_vertex vertex = mesh_data->vertex_array[index];

    outnormal[0] = vertex.normal.x;
    outnormal[1] = vertex.normal.y;
    outnormal[2] = vertex.normal.z;
}

void get_tex_coords(const SMikkTSpaceContext *context, float *outuv, int i_face, int i_vert) {
    struct mesh_data *mesh_data = context->m_pUserData;
    int index = get_vertex_index(context, i_face, i_vert);
    mons_vertex vertex = mesh_data->vertex_array[index];

    outuv[0] = vertex.texture_coords.x;
    outuv[1] = vertex.texture_coords.y;
}

void set_tspace_basic(const SMikkTSpaceContext *context, const float *tangentu, float f_sign, int i_face, int i_vert) {
    struct mesh_data *mesh_data = context->m_pUserData;
    int index = get_vertex_index(context, i_face, i_vert);
    mons_vertex *vertex = &mesh_data->vertex_array[index];

    vertex->tangent.x = tangentu[0];
    vertex->tangent.y = tangentu[1];
    vertex->tangent.z = tangentu[2];
    vertex->tangent.w = f_sign;
}

void compute_tangents(mons_vertex *vertex_array, int vertex_count, int *index_array, int index_count) {
    static SMikkTSpaceInterface iface = {
        .m_getNumFaces = get_num_faces,
        .m_getNumVerticesOfFace = get_num_vertices_of_face,
        .m_getNormal = get_normal,
        .m_getPosition = get_position,
        .m_getTexCoord = get_tex_coords,
        .m_setTSpaceBasic = set_tspace_basic,
    };
    struct mesh_data mesh_data = {
        vertex_array,
        vertex_count,
        index_array,
        index_count,
    };
    SMikkTSpaceContext context = {
        .m_pInterface = &iface,
        .m_pUserData = &mesh_data,
    };

    genTangSpaceDefault(&context);
}