/*

 *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.

 *

 *  Use of this source code is governed by a BSD-style license

 *  that can be found in the LICENSE file in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

 */

#include "vpx_dsp/bitwriter.h"

#include "vp9/common/vp9_common.h"

#include "vp9/common/vp9_entropy.h"

#include "vp9/encoder/vp9_cost.h"

#include "vp9/encoder/vp9_subexp.h"

static const uint8_t update_bits[255] = {

  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  6,  6,  6,

  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  6,  8,  8,  8,  8,  8,  8,

  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,  8,

  8,  8,  8,  8,  8,  8,  8,  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,

  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,

  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,

  10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,

  11, 11, 11, 11, 11, 11, 11, 0,

};

#define MIN_DELP_BITS 5

static int recenter_nonneg(int v, int m) {

  if (v > (m << 1))

    return v;

  else if (v >= m)

    return ((v - m) << 1);

  else

    return ((m - v) << 1) - 1;

}

static int remap_prob(int v, int m) {

  int i;

  static const uint8_t map_table[MAX_PROB - 1] = {

    // generated by:

    //   map_table[j] = split_index(j, MAX_PROB - 1, MODULUS_PARAM);

    20,  21,  22,  23,  24,  25,  0,   26,  27,  28,  29,  30,  31,  32,  33,

    34,  35,  36,  37,  1,   38,  39,  40,  41,  42,  43,  44,  45,  46,  47,

    48,  49,  2,   50,  51,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,

    3,   62,  63,  64,  65,  66,  67,  68,  69,  70,  71,  72,  73,  4,   74,

    75,  76,  77,  78,  79,  80,  81,  82,  83,  84,  85,  5,   86,  87,  88,

    89,  90,  91,  92,  93,  94,  95,  96,  97,  6,   98,  99,  100, 101, 102,

    103, 104, 105, 106, 107, 108, 109, 7,   110, 111, 112, 113, 114, 115, 116,

    117, 118, 119, 120, 121, 8,   122, 123, 124, 125, 126, 127, 128, 129, 130,

    131, 132, 133, 9,   134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144,

    145, 10,  146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 11,

    158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 12,  170, 171,

    172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 13,  182, 183, 184, 185,

    186, 187, 188, 189, 190, 191, 192, 193, 14,  194, 195, 196, 197, 198, 199,

    200, 201, 202, 203, 204, 205, 15,  206, 207, 208, 209, 210, 211, 212, 213,

    214, 215, 216, 217, 16,  218, 219, 220, 221, 222, 223, 224, 225, 226, 227,

    228, 229, 17,  230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,

    18,  242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 19,

  };

  v--;

  m--;

  assert(m >= 0);

  if ((m << 1) <= MAX_PROB)

    i = recenter_nonneg(v, m) - 1;

  else

    i = recenter_nonneg(MAX_PROB - 1 - v, MAX_PROB - 1 - m) - 1;

  assert(i >= 0 && (size_t)i < sizeof(map_table));

  i = map_table[i];

  return i;

}

static int prob_diff_update_cost(vpx_prob newp, vpx_prob oldp) {

  int delp = remap_prob(newp, oldp);

  return update_bits[delp] << VP9_PROB_COST_SHIFT;

}

static void encode_uniform(vpx_writer *w, int v) {

  const int l = 8;

  const int m = (1 << l) - 191;

  if (v < m) {

    vpx_write_literal(w, v, l - 1);

  } else {

    vpx_write_literal(w, m + ((v - m) >> 1), l - 1);

    vpx_write_literal(w, (v - m) & 1, 1);

  }

}

static INLINE int write_bit_gte(vpx_writer *w, int word, int test) {

  vpx_write_literal(w, word >= test, 1);

  return word >= test;

}

static void encode_term_subexp(vpx_writer *w, int word) {

  if (!write_bit_gte(w, word, 16)) {

    vpx_write_literal(w, word, 4);

  } else if (!write_bit_gte(w, word, 32)) {

    vpx_write_literal(w, word - 16, 4);

  } else if (!write_bit_gte(w, word, 64)) {

    vpx_write_literal(w, word - 32, 5);

  } else {

    encode_uniform(w, word - 64);

  }

}

void vp9_write_prob_diff_update(vpx_writer *w, vpx_prob newp, vpx_prob oldp) {

  const int delp = remap_prob(newp, oldp);

  encode_term_subexp(w, delp);

}

int64_t vp9_prob_diff_update_savings_search(const unsigned int *ct,

                                            vpx_prob oldp, vpx_prob *bestp,

                                            vpx_prob upd) {

  const int64_t old_b = cost_branch256(ct, oldp);

  int64_t bestsavings = 0;

  vpx_prob newp, bestnewp = oldp;

  const int step = *bestp > oldp ? -1 : 1;

  const int upd_cost = vp9_cost_one(upd) - vp9_cost_zero(upd);

  if (old_b > upd_cost + (MIN_DELP_BITS << VP9_PROB_COST_SHIFT)) {

    for (newp = *bestp; newp != oldp; newp += step) {

      const int64_t new_b = cost_branch256(ct, newp);

      const int64_t update_b = prob_diff_update_cost(newp, oldp) + upd_cost;

      const int64_t savings = old_b - new_b - update_b;

      if (savings > bestsavings) {

        bestsavings = savings;

        bestnewp = newp;

      }

    }

  }

  *bestp = bestnewp;

  return bestsavings;

}

int64_t vp9_prob_diff_update_savings_search_model(const unsigned int *ct,

                                                  const vpx_prob oldp,

                                                  vpx_prob *bestp, vpx_prob upd,

                                                  int stepsize) {

  int64_t i, old_b, new_b, update_b, savings, bestsavings;

  int64_t newp;

  const int64_t step_sign = *bestp > oldp ? -1 : 1;

  const int64_t step = stepsize * step_sign;

  const int64_t upd_cost = vp9_cost_one(upd) - vp9_cost_zero(upd);

  const vpx_prob *newplist, *oldplist;

  vpx_prob bestnewp;

  oldplist = vp9_pareto8_full[oldp - 1];

  old_b = cost_branch256(ct + 2 * PIVOT_NODE, oldp);

  for (i = UNCONSTRAINED_NODES; i < ENTROPY_NODES; ++i)

    old_b += cost_branch256(ct + 2 * i, oldplist[i - UNCONSTRAINED_NODES]);

  bestsavings = 0;

  bestnewp = oldp;

  assert(stepsize > 0);

  if (old_b > upd_cost + (MIN_DELP_BITS << VP9_PROB_COST_SHIFT)) {

    for (newp = *bestp; (newp - oldp) * step_sign < 0; newp += step) {

      if (newp < 1 || newp > 255) continue;

      newplist = vp9_pareto8_full[newp - 1];

      new_b = cost_branch256(ct + 2 * PIVOT_NODE, (vpx_prob)newp);

      for (i = UNCONSTRAINED_NODES; i < ENTROPY_NODES; ++i)

        new_b += cost_branch256(ct + 2 * i, newplist[i - UNCONSTRAINED_NODES]);

      update_b = prob_diff_update_cost((vpx_prob)newp, oldp) + upd_cost;

      savings = old_b - new_b - update_b;

      if (savings > bestsavings) {

        bestsavings = savings;

        bestnewp = (vpx_prob)newp;

      }

    }

  }

  *bestp = bestnewp;

  return bestsavings;

}

void vp9_cond_prob_diff_update(vpx_writer *w, vpx_prob *oldp,

                               const unsigned int ct[2]) {

  const vpx_prob upd = DIFF_UPDATE_PROB;

  vpx_prob newp = get_binary_prob(ct[0], ct[1]);

  const int64_t savings =

      vp9_prob_diff_update_savings_search(ct, *oldp, &newp, upd);

  assert(newp >= 1);

  if (savings > 0) {

    vpx_write(w, 1, upd);

    vp9_write_prob_diff_update(w, newp, *oldp);

    *oldp = newp;

  } else {

    vpx_write(w, 0, upd);

  }

}