#ifndef NNLAYER_INC_C

#define NNLAYER_INC_C

#include <math.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

typedef struct NeuralLayer {

  struct NeuralLayer *prev, *next;

  int size;

  double trainRatio;

  double *a, *b, *d, *da, *w;

} NeuralLayer;

NeuralLayer* nlNew(NeuralLayer *prev, int size, double trainRatio) {

  assert(size > 0);

  while(prev && prev->next) prev = prev->next;

  NeuralLayer *nl = calloc(sizeof(NeuralLayer), 1);

  nl->size = size;

  nl->prev = prev;

  nl->trainRatio = trainRatio;

  nl->a = calloc(sizeof(*nl->a), size*4);

  nl->d = nl->a + size;

  nl->da = nl->d + size;

  if (prev) {

    assert(prev->size > 0);

    nl->b = calloc(sizeof(*nl->b), size*(1 + prev->size));

    nl->w = nl->b + size;

    for(double *p = nl->b, *e = p + size*(1 + prev->size); p < e; ++p)

      *p = rand()/(double)RAND_MAX*2 - 1;

    prev->next = nl;

  }

  return nl;

}

void nlFree(NeuralLayer *nl) {

  if (nl->next) nlFree(nl->next);

  if (nl->prev) nl->prev->next = NULL;

  free(nl->a);

  if (nl->prev) free(nl->b);

  free(nl);

}

NeuralLayer* nlFront(NeuralLayer *nl)

  { while(nl->prev) nl = nl->prev; return nl; }

NeuralLayer* nlBack(NeuralLayer *nl)

  { while(nl->next) nl = nl->next; return nl; }

int nlToStream(NeuralLayer *nl, FILE *f) {

  if (nl->prev)

    if (!fwrite(nl->b, sizeof(double) * nl->size * (1 + nl->prev->size), 1, f))

      return 0;

  return nl->next ? nlToStream(nl->next, f) : 1;

}

int nlFromStream(NeuralLayer *nl, FILE *f) {

  if (nl->prev)

    if (!fread(nl->b, sizeof(double) * nl->size * (1 + nl->prev->size), 1, f))

      return 0;

  return nl->next ? nlFromStream(nl->next, f) : 1;

}

int nlSave(NeuralLayer *nl, const char *filename) {

  FILE *f = fopen(filename, "wb");

  if (!f)

    return printf("cannot open file '%s' for write\n", filename), 0;

  if (!nlToStream(nl, f))

    return printf("cannot write to file '%s'\n", filename), fclose(f), 0;

  fclose(f);

  return 1;

}

int nlLoad(NeuralLayer *nl, const char *filename) {

  FILE *f = fopen(filename, "rb");

  if (!f)

    return printf("cannot open file '%s' for read\n", filename), 0;

  if (!nlFromStream(nl, f))

    return printf("cannot read from file '%s'\n", filename), fclose(f), 0;

  fclose(f);

  return 1;

}

NeuralLayer* nlPass(NeuralLayer *nl) {

  NeuralLayer *nlp = nl->prev;

  if (nlp) {

    double *nlpa = nlp->a, *ee = nlpa + nlp->size;

    double *w = nl->w;

    for(double *a = nl->a, *b = nl->b, *d = nl->d, *e = a + nl->size; a < e; ++a, ++b, ++d) {

      double s = *b;

      for(double *pa = nlpa; pa < ee; ++pa, ++w)

        s += *w * *pa;

      double ex = exp(-s);

      double ex1 = ex + 1;

      double ex2 = 1/ex1;

      *a = ex2;        // sigmoid

      *d = ex*ex2*ex2; // sigmoid derivation

    }

  }

  return nl->next ? nlPass(nl->next) : nl;

}

NeuralLayer* nlBackpass(NeuralLayer *nl) {

  NeuralLayer *nlp = nl->prev;

  if (nlp) {

    double tr = nl->trainRatio;

    double *nlpa = nlp->a, *nlpda = nlp->da, *ee = nlpa + nlp->size;

    double *w = nl->w;

    if (nlp->prev) {

      memset(nlp->da, 0, sizeof(*nlp->da) * nlp->size);

      for(double *b = nl->b, *d = nl->d, *da = nl->da, *e = b + nl->size; b < e; ++b, ++d, ++da) {

        double ds = *d * *da;

        double dst = ds*tr;

        *b -= dst;

        for(double *pa = nlpa, *pda = nlpda; pa < ee; ++pa, ++pda, ++w) {

          *pda += ds * *w;

          *w += dst * *pa;

        }

      }

    } else {

      for(double *b = nl->b, *d = nl->d, *da = nl->da, *e = b + nl->size; b < e; ++b, ++d, ++da) {

        double dst = *d * *da * tr;

        *b -= dst;

        for(double *pa = nlpa; pa < ee; ++pa, ++w)

          *w += dst * *pa;

      }

    }

    return nlBackpass(nlp);

  }

  return nl;

}

double nlTrainPass(NeuralLayer *nl, double *x, double *y, double qmin) {

  assert(!nl->prev);

  double *fa = nl->a;

  nl->a = x;

  NeuralLayer *nlb = nlPass(nl);

  double qmax = 0;

  for(double *a = nlb->a, *da = nlb->da, *e = a + nlb->size; a < e; ++a, ++da, ++y) {

    double d = *y - *a;

    *da = d;

    double q = fabs(d);

    if (qmax < q) qmax = q;

  }

  if (qmax > qmin) nlBackpass(nlb);

  nl->a = fa;

  return qmax;

}

#endif