/*
 * 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
 */

#include <libavutil/avassert.h>

#include "cbs/cbs.h"
#include "cbs/cbs_mpeg2.h"

#include "cbs_internal.h"


#define HEADER(name)                \
  do {                              \
    ff_cbs_trace_header(ctx, name); \
  } while(0)

#define CHECK(call) \
  do {              \
    err = (call);   \
    if(err < 0)     \
      return err;   \
  } while(0)

#define FUNC_NAME(rw, codec, name) cbs_##codec##_##rw##_##name
#define FUNC_MPEG2(rw, name) FUNC_NAME(rw, mpeg2, name)
#define FUNC(name) FUNC_MPEG2(READWRITE, name)

#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]) { subs, __VA_ARGS__ }) : NULL)

#define ui(width, name) \
  xui(width, name, current->name, 0, MAX_UINT_BITS(width), 0, )
#define uir(width, name) \
  xui(width, name, current->name, 1, MAX_UINT_BITS(width), 0, )
#define uis(width, name, subs, ...) \
  xui(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define uirs(width, name, subs, ...) \
  xui(width, name, current->name, 1, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define xui(width, name, var, range_min, range_max, subs, ...) \
  xuia(width, #name, var, range_min, range_max, subs, __VA_ARGS__)
#define sis(width, name, subs, ...) \
  xsi(width, name, current->name, subs, __VA_ARGS__)

#define marker_bit() \
  bit("marker_bit", 1)
#define bit(string, value)                   \
  do {                                       \
    av_unused uint32_t bit = value;          \
    xuia(1, string, bit, value, value, 0, ); \
  } while(0)


#define READ
#define READWRITE read
#define RWContext GetBitContext

#define xuia(width, string, var, range_min, range_max, subs, ...) \
  do {                                                            \
    uint32_t value;                                               \
    CHECK(ff_cbs_read_unsigned(ctx, rw, width, string,            \
      SUBSCRIPTS(subs, __VA_ARGS__),                              \
      &value, range_min, range_max));                             \
    var = value;                                                  \
  } while(0)

#define xsi(width, name, var, subs, ...)            \
  do {                                              \
    int32_t value;                                  \
    CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), &value,        \
      MIN_INT_BITS(width),                          \
      MAX_INT_BITS(width)));                        \
    var = value;                                    \
  } while(0)

#define nextbits(width, compare, var) \
  (get_bits_left(rw) >= width &&      \
    (var = show_bits(rw, width)) == (compare))

#define infer(name, value) \
  do {                     \
    current->name = value; \
  } while(0)

#include "cbs_mpeg2_syntax_template.c"

#undef READ
#undef READWRITE
#undef RWContext
#undef xuia
#undef xsi
#undef nextbits
#undef infer


#define WRITE
#define READWRITE write
#define RWContext PutBitContext

#define xuia(width, string, var, range_min, range_max, subs, ...) \
  do {                                                            \
    CHECK(ff_cbs_write_unsigned(ctx, rw, width, string,           \
      SUBSCRIPTS(subs, __VA_ARGS__),                              \
      var, range_min, range_max));                                \
  } while(0)

#define xsi(width, name, var, subs, ...)             \
  do {                                               \
    CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), var,            \
      MIN_INT_BITS(width),                           \
      MAX_INT_BITS(width)));                         \
  } while(0)

#define nextbits(width, compare, var) (var)

#define infer(name, value)                                                              \
  do {                                                                                  \
    if(current->name != (value)) {                                                      \
      av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: "                                  \
                                           "%s does not match inferred value: "         \
                                           "%" PRId64 ", but should be %" PRId64 ".\n", \
        #name, (int64_t)current->name, (int64_t)(value));                               \
    }                                                                                   \
  } while(0)

#include "cbs_mpeg2_syntax_template.c"

#undef WRITE
#undef READWRITE
#undef RWContext
#undef xuia
#undef xsi
#undef nextbits
#undef infer

static const uint8_t *avpriv_find_start_code(const uint8_t *restrict p,
  const uint8_t *end,
  uint32_t *restrict state) {
  int i;

  av_assert0(p <= end);
  if(p >= end)
    return end;

  for(i = 0; i < 3; i++) {
    uint32_t tmp = *state << 8;
    *state       = tmp + *(p++);
    if(tmp == 0x100 || p == end)
      return p;
  }

  while(p < end) {
    if(p[-1] > 1) p += 3;
    else if(p[-2])
      p += 2;
    else if(p[-3] | (p[-1] - 1))
      p++;
    else {
      p++;
      break;
    }
  }

  p      = FFMIN(p, end) - 4;
  *state = AV_RB32(p);

  return p + 4;
}

static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
  CodedBitstreamFragment *frag,
  int header) {
  const uint8_t *start, *end;
  CodedBitstreamUnitType unit_type;
  uint32_t start_code = -1;
  size_t unit_size;
  int err, i, final = 0;

  start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
    &start_code);
  if(start_code >> 8 != 0x000001) {
    // No start code found.
    return AVERROR_INVALIDDATA;
  }

  for(i = 0;; i++) {
    unit_type = start_code & 0xff;

    if(start == frag->data + frag->data_size) {
      // The last four bytes form a start code which constitutes
      // a unit of its own.  In this situation avpriv_find_start_code
      // won't modify start_code at all so modify start_code so that
      // the next unit will be treated as the last unit.
      start_code = 0;
    }

    end = avpriv_find_start_code(start--, frag->data + frag->data_size,
      &start_code);

    // start points to the byte containing the start_code_identifier
    // (may be the last byte of fragment->data); end points to the byte
    // following the byte containing the start code identifier (or to
    // the end of fragment->data).
    if(start_code >> 8 == 0x000001) {
      // Unit runs from start to the beginning of the start code
      // pointed to by end (including any padding zeroes).
      unit_size = (end - 4) - start;
    }
    else {
      // We didn't find a start code, so this is the final unit.
      unit_size = end - start;
      final     = 1;
    }

    err = ff_cbs_insert_unit_data(frag, i, unit_type, (uint8_t *)start,
      unit_size, frag->data_ref);
    if(err < 0)
      return err;

    if(final)
      break;

    start = end;
  }

  return 0;
}

static int cbs_mpeg2_read_unit(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit) {
  GetBitContext gbc;
  int err;

  err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
  if(err < 0)
    return err;

  err = ff_cbs_alloc_unit_content2(ctx, unit);
  if(err < 0)
    return err;

  if(MPEG2_START_IS_SLICE(unit->type)) {
    MPEG2RawSlice *slice = unit->content;
    int pos, len;

    err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
    if(err < 0)
      return err;

    if(!get_bits_left(&gbc))
      return AVERROR_INVALIDDATA;

    pos = get_bits_count(&gbc);
    len = unit->data_size;

    slice->data_size = len - pos / 8;
    slice->data_ref  = av_buffer_ref(unit->data_ref);
    if(!slice->data_ref)
      return AVERROR(ENOMEM);
    slice->data = unit->data + pos / 8;

    slice->data_bit_start = pos % 8;
  }
  else {
    switch(unit->type) {
#define START(start_code, type, read_func, free_func)             \
  case start_code: {                                              \
    type *header = unit->content;                                 \
    err          = cbs_mpeg2_read_##read_func(ctx, &gbc, header); \
    if(err < 0)                                                   \
      return err;                                                 \
  } break;
      START(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
        picture_header, &cbs_mpeg2_free_picture_header);
      START(MPEG2_START_USER_DATA, MPEG2RawUserData,
        user_data, &cbs_mpeg2_free_user_data);
      START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader,
        sequence_header, NULL);
      START(MPEG2_START_EXTENSION, MPEG2RawExtensionData,
        extension_data, NULL);
      START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
        group_of_pictures_header, NULL);
      START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd,
        sequence_end, NULL);
#undef START
    default:
      return AVERROR(ENOSYS);
    }
  }

  return 0;
}

static int cbs_mpeg2_write_header(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit,
  PutBitContext *pbc) {
  int err;

  switch(unit->type) {
#define START(start_code, type, func)                      \
  case start_code:                                         \
    err = cbs_mpeg2_write_##func(ctx, pbc, unit->content); \
    break;
    START(MPEG2_START_PICTURE, MPEG2RawPictureHeader, picture_header);
    START(MPEG2_START_USER_DATA, MPEG2RawUserData, user_data);
    START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader, sequence_header);
    START(MPEG2_START_EXTENSION, MPEG2RawExtensionData, extension_data);
    START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
      group_of_pictures_header);
    START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd, sequence_end);
#undef START
  default:
    av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
                                       "code %02" PRIx32 ".\n",
      unit->type);
    return AVERROR_PATCHWELCOME;
  }

  return err;
}

static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit,
  PutBitContext *pbc) {
  MPEG2RawSlice *slice = unit->content;
  int err;

  err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
  if(err < 0)
    return err;

  if(slice->data) {
    size_t rest  = slice->data_size - (slice->data_bit_start + 7) / 8;
    uint8_t *pos = slice->data + slice->data_bit_start / 8;

    av_assert0(slice->data_bit_start >= 0 &&
               slice->data_size > slice->data_bit_start / 8);

    if(slice->data_size * 8 + 8 > put_bits_left(pbc))
      return AVERROR(ENOSPC);

    // First copy the remaining bits of the first byte
    if(slice->data_bit_start % 8)
      put_bits(pbc, 8 - slice->data_bit_start % 8,
        *pos++ & MAX_UINT_BITS(8 - slice->data_bit_start % 8));

    if(put_bits_count(pbc) % 8 == 0) {
      // If the writer is aligned at this point,
      // memcpy can be used to improve performance.
      // This is the normal case.
      flush_put_bits(pbc);
      memcpy(put_bits_ptr(pbc), pos, rest);
      skip_put_bytes(pbc, rest);
    }
    else {
      // If not, we have to copy manually:
      for(; rest > 3; rest -= 4, pos += 4)
        put_bits32(pbc, AV_RB32(pos));

      for(; rest; rest--, pos++)
        put_bits(pbc, 8, *pos);

      // Align with zeros
      put_bits(pbc, 8 - put_bits_count(pbc) % 8, 0);
    }
  }

  return 0;
}

static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit,
  PutBitContext *pbc) {
  if(MPEG2_START_IS_SLICE(unit->type))
    return cbs_mpeg2_write_slice(ctx, unit, pbc);
  else
    return cbs_mpeg2_write_header(ctx, unit, pbc);
}

static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
  CodedBitstreamFragment *frag) {
  uint8_t *data;
  size_t size, dp;
  int i;

  size = 0;
  for(i = 0; i < frag->nb_units; i++)
    size += 3 + frag->units[i].data_size;

  frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
  if(!frag->data_ref)
    return AVERROR(ENOMEM);
  data = frag->data_ref->data;

  dp = 0;
  for(i = 0; i < frag->nb_units; i++) {
    CodedBitstreamUnit *unit = &frag->units[i];

    data[dp++] = 0;
    data[dp++] = 0;
    data[dp++] = 1;

    memcpy(data + dp, unit->data, unit->data_size);
    dp += unit->data_size;
  }

  av_assert0(dp == size);

  memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  frag->data      = data;
  frag->data_size = size;

  return 0;
}

static const CodedBitstreamUnitTypeDescriptor cbs_mpeg2_unit_types[] = {
  CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
    extra_information_picture.extra_information),

  {
    .nb_unit_types         = CBS_UNIT_TYPE_RANGE,
    .unit_type_range_start = 0x01,
    .unit_type_range_end   = 0xaf,

    .content_type   = CBS_CONTENT_TYPE_INTERNAL_REFS,
    .content_size   = sizeof(MPEG2RawSlice),
    .nb_ref_offsets = 2,
    .ref_offsets    = { offsetof(MPEG2RawSlice, header.extra_information_slice.extra_information),
      offsetof(MPEG2RawSlice, data) },
  },

  CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_USER_DATA, MPEG2RawUserData,
    user_data),

  CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader),
  CBS_UNIT_TYPE_POD(MPEG2_START_EXTENSION, MPEG2RawExtensionData),
  CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd),
  CBS_UNIT_TYPE_POD(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader),

  CBS_UNIT_TYPE_END_OF_LIST
};

const CodedBitstreamType ff_cbs_type_mpeg2 = {
  .codec_id = AV_CODEC_ID_MPEG2VIDEO,

  .priv_data_size = sizeof(CodedBitstreamMPEG2Context),

  .unit_types = cbs_mpeg2_unit_types,

  .split_fragment    = &cbs_mpeg2_split_fragment,
  .read_unit         = &cbs_mpeg2_read_unit,
  .write_unit        = &cbs_mpeg2_write_unit,
  .assemble_fragment = &cbs_mpeg2_assemble_fragment,
};