/** @file

  A brief file description

  @section license License

  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
 */

#include "HuffmanCodec.h"
#include "libts.h"

struct huffman_entry
{
  uint32_t code_as_hex;
  uint32_t bit_len;
};

static const huffman_entry huffman_table[] = {
  {0x1ff8, 13},
  {0x7fffd8, 23},
  {0xfffffe2, 28},
  {0xfffffe3, 28},
  {0xfffffe4, 28},
  {0xfffffe5, 28},
  {0xfffffe6, 28},
  {0xfffffe7, 28},
  {0xfffffe8, 28},
  {0xffffea, 24},
  {0x3ffffffc, 30},
  {0xfffffe9, 28},
  {0xfffffea, 28},
  {0x3ffffffd, 30},
  {0xfffffeb, 28},
  {0xfffffec, 28},
  {0xfffffed, 28},
  {0xfffffee, 28},
  {0xfffffef, 28},
  {0xffffff0, 28},
  {0xffffff1, 28},
  {0xffffff2, 28},
  {0x3ffffffe, 30},
  {0xffffff3, 28},
  {0xffffff4, 28},
  {0xffffff5, 28},
  {0xffffff6, 28},
  {0xffffff7, 28},
  {0xffffff8, 28},
  {0xffffff9, 28},
  {0xffffffa, 28},
  {0xffffffb, 28},
  {0x14, 6},
  {0x3f8, 10},
  {0x3f9, 10},
  {0xffa, 12},
  {0x1ff9, 13},
  {0x15, 6},
  {0xf8, 8},
  {0x7fa, 11},
  {0x3fa, 10},
  {0x3fb, 10},
  {0xf9, 8},
  {0x7fb, 11},
  {0xfa, 8},
  {0x16, 6},
  {0x17, 6},
  {0x18, 6},
  {0x0, 5},
  {0x1, 5},
  {0x2, 5},
  {0x19, 6},
  {0x1a, 6},
  {0x1b, 6},
  {0x1c, 6},
  {0x1d, 6},
  {0x1e, 6},
  {0x1f, 6},
  {0x5c, 7},
  {0xfb, 8},
  {0x7ffc, 15},
  {0x20, 6},
  {0xffb, 12},
  {0x3fc, 10},
  {0x1ffa, 13},
  {0x21, 6},
  {0x5d, 7},
  {0x5e, 7},
  {0x5f, 7},
  {0x60, 7},
  {0x61, 7},
  {0x62, 7},
  {0x63, 7},
  {0x64, 7},
  {0x65, 7},
  {0x66, 7},
  {0x67, 7},
  {0x68, 7},
  {0x69, 7},
  {0x6a, 7},
  {0x6b, 7},
  {0x6c, 7},
  {0x6d, 7},
  {0x6e, 7},
  {0x6f, 7},
  {0x70, 7},
  {0x71, 7},
  {0x72, 7},
  {0xfc, 8},
  {0x73, 7},
  {0xfd, 8},
  {0x1ffb, 13},
  {0x7fff0, 19},
  {0x1ffc, 13},
  {0x3ffc, 14},
  {0x22, 6},
  {0x7ffd, 15},
  {0x3, 5},
  {0x23, 6},
  {0x4, 5},
  {0x24, 6},
  {0x5, 5},
  {0x25, 6},
  {0x26, 6},
  {0x27, 6},
  {0x6, 5},
  {0x74, 7},
  {0x75, 7},
  {0x28, 6},
  {0x29, 6},
  {0x2a, 6},
  {0x7, 5},
  {0x2b, 6},
  {0x76, 7},
  {0x2c, 6},
  {0x8, 5},
  {0x9, 5},
  {0x2d, 6},
  {0x77, 7},
  {0x78, 7},
  {0x79, 7},
  {0x7a, 7},
  {0x7b, 7},
  {0x7ffe, 15},
  {0x7fc, 11},
  {0x3ffd, 14},
  {0x1ffd, 13},
  {0xffffffc, 28},
  {0xfffe6, 20},
  {0x3fffd2, 22},
  {0xfffe7, 20},
  {0xfffe8, 20},
  {0x3fffd3, 22},
  {0x3fffd4, 22},
  {0x3fffd5, 22},
  {0x7fffd9, 23},
  {0x3fffd6, 22},
  {0x7fffda, 23},
  {0x7fffdb, 23},
  {0x7fffdc, 23},
  {0x7fffdd, 23},
  {0x7fffde, 23},
  {0xffffeb, 23},
  {0x7fffdf, 23},
  {0xffffec, 24},
  {0xffffed, 24},
  {0x3fffd7, 22},
  {0x7fffe0, 23},
  {0xffffee, 24},
  {0x7fffe1, 23},
  {0x7fffe2, 23},
  {0x7fffe3, 23},
  {0x7fffe4, 23},
  {0x1fffdc, 21},
  {0x3fffd8, 22},
  {0x7fffe5, 23},
  {0x3fffd9, 22},
  {0x7fffe6, 23},
  {0x7fffe7, 23},
  {0xffffef, 24},
  {0x3fffda, 22},
  {0x1fffdd, 21},
  {0xfffe9, 20},
  {0x3fffdb, 22},
  {0x3fffdc, 22},
  {0x7fffe8, 23},
  {0x7fffe9, 23},
  {0x1fffde, 21},
  {0x7fffde, 23},
  {0x3fffdd, 22},
  {0x3fffde, 22},
  {0xfffff0, 24},
  {0x1fffdf, 21},
  {0x3fffdf, 22},
  {0x7fffeb, 23},
  {0x7fffec, 23},
  {0x1fffe0, 21},
  {0x1fffe1, 21},
  {0x3fffe0, 22},
  {0x1fffe2, 21},
  {0x7fffed, 23},
  {0x3fffe1, 22},
  {0x7fffee, 23},
  {0x7fffef, 23},
  {0xfffea, 20},
  {0x3fffe2, 22},
  {0x3fffe3, 22},
  {0x3fffe4, 22},
  {0x7ffff0, 23},
  {0x3fffe5, 22},
  {0x3fffe6, 22},
  {0x7ffff1, 23},
  {0x3ffffe0, 26},
  {0x3ffffe1, 26},
  {0xfffeb, 20},
  {0x7fff1, 19},
  {0x3fffe7, 22},
  {0x7ffff2, 23},
  {0x3fffe8, 22},
  {0x1ffffec, 25},
  {0x3ffffe2, 26},
  {0x3ffffe3, 26},
  {0x3ffffe4, 26},
  {0x7ffffde, 27},
  {0x7ffffdf, 27},
  {0x3ffffe5, 26},
  {0xfffff1, 24},
  {0x1ffffed, 25},
  {0x7fff2, 19},
  {0x1fffe3, 21},
  {0x3ffffe6, 26},
  {0x7ffffe0, 27},
  {0x7ffffe1, 27},
  {0x3ffffe7, 26},
  {0x3ffffe2, 27},
  {0xfffff2, 24},
  {0x1fffe4, 21},
  {0x1fffe5, 21},
  {0x3ffffe8, 26},
  {0x3ffffe9, 26},
  {0xffffffd, 28},
  {0x7ffffe3, 27},
  {0x7ffffe4, 27},
  {0x7ffffe5, 27},
  {0xfffec, 20},
  {0xfffff3, 24},
  {0xfffed, 20},
  {0x1fffe6, 21},
  {0x3fffe9, 22},
  {0x1fffe7, 21},
  {0x1fffe8, 21},
  {0x7ffff3, 23},
  {0x3fffea, 22},
  {0x3fffeb, 22},
  {0x1ffffee, 25},
  {0x1ffffef, 25},
  {0xfffff4, 24},
  {0xfffff5, 24},
  {0x3ffffea, 26},
  {0x7ffff4, 23},
  {0x3ffffeb, 26},
  {0x7ffffe6, 27},
  {0x3ffffec, 26},
  {0x3ffffed, 26},
  {0x7ffffe7, 27},
  {0x7ffffe8, 27},
  {0x7ffffe9, 27},
  {0x7ffffea, 27},
  {0x7ffffeb, 27},
  {0xffffffe, 28},
  {0x7ffffec, 27},
  {0x7ffffed, 27},
  {0x7ffffee, 27},
  {0x7ffffef, 27},
  {0x7fffff0, 27},
  {0x3ffffee, 26},
  {0x3fffffff, 30}
};

typedef struct node {
  node *left, *right;
  char ascii_code;
} Node;

Node* HUFFMAN_TREE_ROOT;

static Node*
make_huffman_tree_node()
{
  Node *n = static_cast<Node *>(ats_malloc(sizeof(Node)));
  n->left = NULL;
  n->right = NULL;
  n->ascii_code = '\0';
  return n;
}

static Node*
make_huffman_tree()
{
  Node* root = make_huffman_tree_node();
  Node* current;
  uint32_t bit_len;
  // insert leafs for each ascii code
  for (unsigned i = 0; i < countof(huffman_table); i++){
    bit_len = huffman_table[i].bit_len;
    current = root;
    while (bit_len > 0){
      if (huffman_table[i].code_as_hex & (1 << (bit_len-1))) {
        if (!current->right)
          current->right = make_huffman_tree_node();
        current = current->right;
      } else {
        if (!current->left)
          current->left = make_huffman_tree_node();
        current = current->left;
      }
      bit_len--;
    }
    current->ascii_code = i;
  }
  return root;
}

static void
free_huffman_tree(Node* node)
{
  if (node->left)
    free_huffman_tree(node->left);
  if (node->right)
    free_huffman_tree(node->right);

  ats_free(node);
}

void hpack_huffman_init()
{
  if (!HUFFMAN_TREE_ROOT)
    HUFFMAN_TREE_ROOT = make_huffman_tree();
}

void hpack_huffman_fin()
{
  if (HUFFMAN_TREE_ROOT)
    free_huffman_tree(HUFFMAN_TREE_ROOT);
}

int64_t
huffman_decode(char* dst_start, const uint8_t* src, uint32_t src_len)
{
  char* dst_end = dst_start;
  uint8_t shift = 7;
  Node* current = HUFFMAN_TREE_ROOT;

  while (src_len) {
    if (*src & (1 << shift)) {
      current = current->right;
    } else {
      current = current->left;
    }

    if (current->ascii_code) {
      *dst_end = current->ascii_code;
      ++dst_end;
      current = HUFFMAN_TREE_ROOT;
    }
    if (shift) {
      --shift;
    } else {
      shift = 7;
      ++src;
      --src_len;
    }
  }

  return dst_end - dst_start;
}
