#include <cassert>
#include <glad/glad.h>
#include <map>
#include <string>

#include "util.hpp"
#include "body.hpp"
#include "shaders.hpp"

using namespace std;

enum class ParserState {
    PREFIX,
    VERTEX,
    FACE,
    FACE_SKIP,
};

static map<string, ObjData> cache;

bool _parse_obj(ObjData* data, const char* obj_filepath);

bool load_body(Body* out_body, const char* obj_filepath) {
    ObjData data;
    if (auto it = cache.find(obj_filepath); it != cache.end()) {
        data = it->second;
    } else if (_parse_obj(&data, obj_filepath)) {
        cache[obj_filepath] = data;
    } else {
        return false;
    }

    // Need a good validation check here. This is a stand in.
    if (data.verts_len == 0 || data.faces_len == 0) {
        printf("Obj file appears incomplete or corrupted. Num verts %d. Num Faces %d.\n", data.verts_len,
            data.faces_len);
        return false;
    }

    uint vao, vbo, ebo;
    vao = 0;
    vbo = 0;
    ebo = 0;

    glGenVertexArrays(1, &vao);
    glGenBuffers(1, &vbo);
    glGenBuffers(1, &ebo);

    glBindVertexArray(vao);

    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, data.verts_len * sizeof(float), data.verts, GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, data.faces_len * sizeof(int), data.faces, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    *out_body = { .pose = glm::mat4(1), .ebo = ebo, .vao = vao, .vbo = vbo, .shader = 0, .data = data };
    return true;
}

void draw_body(const Body& b) {
    use_shader(b.shader);
    set_uniform(b.shader, "global_t", glm::scale(b.pose, glm::vec3(b.scale)));
    set_uniform(b.shader, "color", b.color);
    glBindVertexArray(b.vao);
    glDrawElements(GL_TRIANGLES, b.data.faces_len, GL_UNSIGNED_INT, 0);
}

void create_new_sphere(Body* b, float scale, glm::vec4 color) { 
    assert(load_body(b, "Icosphere.obj"));
    b->scale = scale;
    b->color = color;
}

// I need to write a good obj file parser at some point. This is basically garbage
bool _parse_obj(ObjData* data, const char* obj_filepath) {
    string source;
    if (!read_file(&source, obj_filepath)) {
        return {};
    }

    size_t num_verts = 0;
    size_t num_faces = 0;
    for (int i = 1; i < source.size(); i++) {
        if (source[i] == ' ' && source[i - 1] == 'v') {
            num_verts++;
        } else if (source[i] == ' ' && source[i - 1] == 'f') {
            num_faces++;
        }
    }

    float* verts = (float*)malloc(sizeof(float) * num_verts * 3);
    int* faces = (int*)malloc(sizeof(int) * num_faces * 3);

    int vert_i = 0;
    int face_i = 0;

    // Get ready for the parsing loop
    ParserState state = ParserState::PREFIX;
    int start = 0;

    for (int i = 1; i < source.size(); i++) {
        switch (state) {
        case ParserState::PREFIX:
            if (source[i - 1] == 'v' && source[i] == ' ') {
                state = ParserState::VERTEX;
                start = i + 1;
            } else if (i > 0 && source[i - 1] == 'f' && source[i] == ' ') {
                state = ParserState::FACE;
                start = i + 1;
            }
            break;
        case ParserState::VERTEX:
            if (iswspace(source[i])) {
                verts[vert_i++] = atof(&source[start]);
                start = i + 1;
            }
            break;
        case ParserState::FACE:
            if (source[i] == '/') {
                state = ParserState::FACE_SKIP;
                faces[face_i++] = atoi(&source[start]) - 1;
            }
            break;
        case ParserState::FACE_SKIP:
            if (iswspace(source[i])) {
                state = ParserState::FACE;
                start = i + 1;
            }
        }
        if (source[i] == '\n' || source[i] == '\r') {
            state = ParserState::PREFIX;
            continue;
        }
    }

    *data = { .verts = verts, .verts_len = vert_i, .faces = faces, .faces_len = face_i };
    return true;
}