#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

typedef struct Layer {
    int neuron_count;
    float* neurons;
    float* weights;
} Layer;

typedef struct Network {
    struct Layer* layers;
    int layer_count;
} Network;

Layer create_layer(int count, int next) {
    Layer layer;
    layer.neuron_count = count;
    layer.neurons = calloc(sizeof(float), count);
    layer.weights = calloc(sizeof(float), count * next);
    return layer;
}

Network* create_network(int input, int hidden, int output) {
    Network* network = calloc(sizeof(Network), 1);
    network->layer_count = 3;
    network->layers = calloc(sizeof(Layer), 3);
    network->layers[0] = create_layer(input, hidden);
    network->layers[1] = create_layer(hidden, output);
    network->layers[2] = create_layer(output, 0);

    return network;
}

float activation_func(float in) {
    return 1.0f / (1.0f + powf(2.71828f, -in));
}

float randomf() {
    return (rand() % 1000) / 1000.0f;
}

int main() {
    srand(time(NULL));

    Network* net = create_network(2, 3, 1);

    for(int i = 0; i < net->layer_count - 1; i++) {
        for(int j = 0; j < net->layers[i].neuron_count; j++) {
            for(int m = 0; m < net->layers[i + 1].neuron_count; m++) {
                net->layers[i].weights[j * net->layers[i + 1].neuron_count + m] = (randomf() - 0.5f) * 2.0f;
            }
        }
    }

    net->layers[0].neurons[0] = 1.0f;
    net->layers[0].neurons[1] = 0.0f;

    for(int layer = 1; layer < net->layer_count; layer++) {
        for(int n = 0; n < net->layers[layer].neuron_count; n++) {
            float sum = 0.0f;
            Layer l_back = net->layers[layer - 1];

            for(int n_back = 0; n_back < l_back.neuron_count; n_back++) {
                sum += l_back.neurons[n_back] * 
                    l_back.weights[n_back * l_back.neuron_count + n];
            }

            net->layers[layer].neurons[n] = activation_func(sum);
            printf("layer[%d].neurons[%d] = %f\n", layer, n, net->layers[layer].neurons[n]);
        }
    }
}