/*

  * Copyright (C) 2007 Vitor Sessak <vitor1001@gmail.com>

  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * @file

  * Codebook Generator using the ELBG algorithm
  */
 
 #include <string.h>
 

 #include "libavutil/lfg.h"

 #include "elbg.h"
 #include "avcodec.h"
 
 #define DELTA_ERR_MAX 0.1  ///< Precision of the ELBG algorithm (as percentual error)
 
 /**
  * In the ELBG jargon, a cell is the set of points that are closest to a
  * codebook entry. Not to be confused with a RoQ Video cell. */
 typedef struct cell_s {
     int index;
     struct cell_s *next;
 } cell;
 
 /**
  * ELBG internal data
  */
 typedef struct{
     int error;
     int dim;
     int numCB;
     int *codebook;
     cell **cells;
     int *utility;
     int *utility_inc;
     int *nearest_cb;
     int *points;

     AVLFG *rand_state;

     int *scratchbuf;

 } elbg_data;
 
 static inline int distance_limited(int *a, int *b, int dim, int limit)
 {
     int i, dist=0;
     for (i=0; i<dim; i++) {
         dist += (a[i] - b[i])*(a[i] - b[i]);
         if (dist > limit)
             return INT_MAX;
     }
 
     return dist;
 }
 
 static inline void vect_division(int *res, int *vect, int div, int dim)
 {
     int i;
     if (div > 1)
         for (i=0; i<dim; i++)
             res[i] = ROUNDED_DIV(vect[i],div);
     else if (res != vect)
         memcpy(res, vect, dim*sizeof(int));
 
 }
 
 static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)
 {
     int error=0;
     for (; cells; cells=cells->next)
         error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX);
 
     return error;
 }
 
 static int get_closest_codebook(elbg_data *elbg, int index)
 {
     int i, pick=0, diff, diff_min = INT_MAX;
     for (i=0; i<elbg->numCB; i++)
         if (i != index) {
             diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min);
             if (diff < diff_min) {
                 pick = i;
                 diff_min = diff;
             }
         }
     return pick;
 }
 
 static int get_high_utility_cell(elbg_data *elbg)
 {
     int i=0;
     /* Using linear search, do binary if it ever turns to be speed critical */

     int r = av_lfg_get(elbg->rand_state)%elbg->utility_inc[elbg->numCB-1] + 1;

     while (elbg->utility_inc[i] < r)
         i++;

 
     assert(!elbg->cells[i]);
 

     return i;
 }
 
 /**
  * Implementation of the simple LBG algorithm for just two codebooks
  */

 static int simple_lbg(elbg_data *elbg,
                       int dim,

                       int *centroid[3],

                       int newutility[3],
                       int *points,
                       cell *cells)
 {
     int i, idx;
     int numpoints[2] = {0,0};

     int *newcentroid[2] = {
         elbg->scratchbuf + 3*dim,
         elbg->scratchbuf + 4*dim
     };

     cell *tempcell;
 

     memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0]));

 
     newutility[0] =
     newutility[1] = 0;
 
     for (tempcell = cells; tempcell; tempcell=tempcell->next) {
         idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>=
               distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX);
         numpoints[idx]++;
         for (i=0; i<dim; i++)
             newcentroid[idx][i] += points[tempcell->index*dim + i];
     }
 
     vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
     vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
 
     for (tempcell = cells; tempcell; tempcell=tempcell->next) {
         int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX),
                        distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)};
         int idx = dist[0] > dist[1];
         newutility[idx] += dist[idx];
     }
 
     return newutility[0] + newutility[1];
 }
 
 static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i,
                               int *newcentroid_p)
 {
     cell *tempcell;

     int *min = newcentroid_i;
     int *max = newcentroid_p;

     int i;
 
     for (i=0; i< elbg->dim; i++) {
         min[i]=INT_MAX;
         max[i]=0;
     }
 
     for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next)
         for(i=0; i<elbg->dim; i++) {
             min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]);
             max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]);
         }
 
     for (i=0; i<elbg->dim; i++) {

         int ni = min[i] + (max[i] - min[i])/3;
         int np = min[i] + (2*(max[i] - min[i]))/3;
         newcentroid_i[i] = ni;
         newcentroid_p[i] = np;

     }
 }
 
 /**
  * Add the points in the low utility cell to its closest cell. Split the high
  * utility cell, putting the separed points in the (now empty) low utility
  * cell.
  *
  * @param elbg         Internal elbg data
  * @param indexes      {luc, huc, cluc}
  * @param newcentroid  A vector with the position of the new centroids
  */
 static void shift_codebook(elbg_data *elbg, int *indexes,

                            int *newcentroid[3])

 {
     cell *tempdata;
     cell **pp = &elbg->cells[indexes[2]];
 
     while(*pp)
         pp= &(*pp)->next;
 
     *pp = elbg->cells[indexes[0]];
 
     elbg->cells[indexes[0]] = NULL;
     tempdata = elbg->cells[indexes[1]];
     elbg->cells[indexes[1]] = NULL;
 
     while(tempdata) {
         cell *tempcell2 = tempdata->next;
         int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
                            newcentroid[0], elbg->dim, INT_MAX) >
                   distance_limited(elbg->points + tempdata->index*elbg->dim,
                            newcentroid[1], elbg->dim, INT_MAX);
 
         tempdata->next = elbg->cells[indexes[idx]];
         elbg->cells[indexes[idx]] = tempdata;
         tempdata = tempcell2;
     }
 }
 
 static void evaluate_utility_inc(elbg_data *elbg)
 {
     int i, inc=0;
 
     for (i=0; i < elbg->numCB; i++) {
         if (elbg->numCB*elbg->utility[i] > elbg->error)
             inc += elbg->utility[i];
         elbg->utility_inc[i] = inc;
     }
 }
 
 
 static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
 {
     cell *tempcell;
 
     elbg->utility[idx] = newutility;
     for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next)
         elbg->nearest_cb[tempcell->index] = idx;
 }
 
 /**
  * Evaluate if a shift lower the error. If it does, call shift_codebooks
  * and update elbg->error, elbg->utility and elbg->nearest_cb.
  *
  * @param elbg  Internal elbg data

  * @param idx   {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}

  */
 static void try_shift_candidate(elbg_data *elbg, int idx[3])
 {
     int j, k, olderror=0, newerror, cont=0;
     int newutility[3];

     int *newcentroid[3] = {
         elbg->scratchbuf,
         elbg->scratchbuf + elbg->dim,
         elbg->scratchbuf + 2*elbg->dim
     };

     cell *tempcell;
 
     for (j=0; j<3; j++)
         olderror += elbg->utility[idx[j]];
 
     memset(newcentroid[2], 0, elbg->dim*sizeof(int));
 
     for (k=0; k<2; k++)
         for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) {
             cont++;
             for (j=0; j<elbg->dim; j++)
                 newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
         }
 
     vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
 
     get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
 
     newutility[2]  = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
     newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
 
     newerror = newutility[2];
 

     newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points,

                            elbg->cells[idx[1]]);
 
     if (olderror > newerror) {

         shift_codebook(elbg, idx, newcentroid);

 
         elbg->error += newerror - olderror;
 
         for (j=0; j<3; j++)
             update_utility_and_n_cb(elbg, idx[j], newutility[j]);
 
         evaluate_utility_inc(elbg);
     }
  }
 
 /**
  * Implementation of the ELBG block
  */
 static void do_shiftings(elbg_data *elbg)
 {
     int idx[3];
 
     evaluate_utility_inc(elbg);
 
     for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
         if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
             if (elbg->utility_inc[elbg->numCB-1] == 0)
                 return;
 

             idx[1] = get_high_utility_cell(elbg);

             idx[2] = get_closest_codebook(elbg, idx[0]);
 

             if (idx[1] != idx[0] && idx[1] != idx[2])
                 try_shift_candidate(elbg, idx);

         }
 }
 
 #define BIG_PRIME 433494437LL
 
 void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
                   int numCB, int max_steps, int *closest_cb,

                   AVLFG *rand_state)

 {
     int i, k;
 
     if (numpoints > 24*numCB) {
         /* ELBG is very costly for a big number of points. So if we have a lot
            of them, get a good initial codebook to save on iterations       */
         int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int));
         for (i=0; i<numpoints/8; i++) {
             k = (i*BIG_PRIME) % numpoints;
             memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int));
         }
 
         ff_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
         ff_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
 
         av_free(temp_points);
 
     } else  // If not, initialize the codebook with random positions
         for (i=0; i < numCB; i++)
             memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim,
                    dim*sizeof(int));
 
 }
 
 void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
                 int numCB, int max_steps, int *closest_cb,

                 AVLFG *rand_state)

 {
     int dist;
     elbg_data elbg_d;
     elbg_data *elbg = &elbg_d;
     int i, j, k, last_error, steps=0;
     int *dist_cb = av_malloc(numpoints*sizeof(int));
     int *size_part = av_malloc(numCB*sizeof(int));
     cell *list_buffer = av_malloc(numpoints*sizeof(cell));
     cell *free_cells;

     int best_dist, best_idx = 0;

 
     elbg->error = INT_MAX;
     elbg->dim = dim;
     elbg->numCB = numCB;
     elbg->codebook = codebook;
     elbg->cells = av_malloc(numCB*sizeof(cell *));
     elbg->utility = av_malloc(numCB*sizeof(int));
     elbg->nearest_cb = closest_cb;
     elbg->points = points;
     elbg->utility_inc = av_malloc(numCB*sizeof(int));

     elbg->scratchbuf = av_malloc(5*dim*sizeof(int));

 
     elbg->rand_state = rand_state;
 
     do {
         free_cells = list_buffer;
         last_error = elbg->error;
         steps++;
         memset(elbg->utility, 0, numCB*sizeof(int));
         memset(elbg->cells, 0, numCB*sizeof(cell *));
 
         elbg->error = 0;
 
         /* This loop evaluate the actual Voronoi partition. It is the most
            costly part of the algorithm. */
         for (i=0; i < numpoints; i++) {

             best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX);

             for (k=0; k < elbg->numCB; k++) {

                 dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist);
                 if (dist < best_dist) {
                     best_dist = dist;
                     best_idx = k;

                 }
             }

             elbg->nearest_cb[i] = best_idx;
             dist_cb[i] = best_dist;

             elbg->error += dist_cb[i];
             elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
             free_cells->index = i;
             free_cells->next = elbg->cells[elbg->nearest_cb[i]];
             elbg->cells[elbg->nearest_cb[i]] = free_cells;
             free_cells++;
         }
 
         do_shiftings(elbg);
 
         memset(size_part, 0, numCB*sizeof(int));
 
         memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
 
         for (i=0; i < numpoints; i++) {
             size_part[elbg->nearest_cb[i]]++;
             for (j=0; j < elbg->dim; j++)
                 elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
                     elbg->points[i*elbg->dim + j];
         }
 
         for (i=0; i < elbg->numCB; i++)
             vect_division(elbg->codebook + i*elbg->dim,
                           elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
 
     } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
             (steps < max_steps));
 
     av_free(dist_cb);
     av_free(size_part);
     av_free(elbg->utility);
     av_free(list_buffer);
     av_free(elbg->cells);
     av_free(elbg->utility_inc);

     av_free(elbg->scratchbuf);

 }