/*
 * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
 *
 * This program is free software: you can use, redistribute, and/or modify
 * it under the terms of the GNU Affero General Public License, version 3
 * or later ("AGPL"), as published by the Free Software Foundation.
 *
 * This program 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.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
#include "index_fst_util.h"
#include "index_fst_common.h"

// A sentinel value used to indicate an empty final state
const CompiledAddr EMPTY_ADDRESS = 0;
/// A sentinel value used to indicate an invalid state.
const CompiledAddr NONE_ADDRESS = 1;

// This version number is written to every finite state transducer created by
// this crate. When a finite state transducer is read, its version number is
// checked against this value.
const uint64_t VERSION = 3;
// The threshold (in number of transitions) at which an index is created for
// a node's transitions. This speeds up lookup time at the expense of FST size

const uint64_t TRANS_INDEX_THRESHOLD = 32;

// uint8_t commonInput(uint8_t idx) {
//  if (idx == 0) { return -1; }
//  else {
//    return COMMON_INPUTS_INV[idx - 1];
//  }
//}
//
// uint8_t commonIdx(uint8_t v, uint8_t max) {
//  uint8_t v = ((uint16_t)tCOMMON_INPUTS[v] + 1)%256;
//  return v > max ? 0: v;
//}

uint8_t packSize(uint64_t n) {
  if (n < (1u << 8)) {
    return 1;
  } else if (n < (1u << 16)) {
    return 2;
  } else if (n < (1u << 24)) {
    return 3;
  } else if (n < ((uint64_t)(1) << 32)) {
    return 4;
  } else if (n < ((uint64_t)(1) << 40)) {
    return 5;
  } else if (n < ((uint64_t)(1) << 48)) {
    return 6;
  } else if (n < ((uint64_t)(1) << 56)) {
    return 7;
  } else {
    return 8;
  }
}

uint64_t unpackUint64(uint8_t *ch, uint8_t sz) {
  uint64_t n = 0;
  for (uint8_t i = 0; i < sz; i++) {
    n = n | (ch[i] << (8 * i));
  }
  return n;
}
uint8_t packDeltaSize(CompiledAddr nodeAddr, CompiledAddr transAddr) {
  if (transAddr == EMPTY_ADDRESS) {
    return packSize(EMPTY_ADDRESS);
  } else {
    return packSize(nodeAddr - transAddr);
  }
}
CompiledAddr unpackDelta(char *data, uint64_t len, uint64_t nodeAddr) {
  uint64_t delta = unpackUint64(data, len);
  // delta_add = u64_to_usize
  if (delta == EMPTY_ADDRESS) {
    return EMPTY_ADDRESS;
  } else {
    return nodeAddr - delta;
  }
}

// fst slice func
//

FstSlice fstSliceCreate(uint8_t *data, uint64_t len) {
  FstString *str = (FstString *)malloc(sizeof(FstString));
  str->ref = 1;
  str->len = len;
  str->data = malloc(len * sizeof(uint8_t));
  memcpy(str->data, data, len);

  FstSlice s = {.str = str, .start = 0, .end = len - 1};
  return s;
}
// just shallow copy
FstSlice fstSliceCopy(FstSlice *s, int32_t start, int32_t end) {
  FstString *str = s->str;
  str->ref++;
  // uint8_t *buf = fstSliceData(s, &alen);
  // start = buf + start - (buf - s->start);
  // end   = buf + end - (buf - s->start);

  FstSlice t = {.str = str, .start = start + s->start, .end = end + s->start};
  return t;
}
FstSlice fstSliceDeepCopy(FstSlice *s, int32_t start, int32_t end) {
  int32_t  tlen = end - start + 1;
  int32_t  slen;
  uint8_t *data = fstSliceData(s, &slen);
  assert(tlen <= slen);

  uint8_t *buf = malloc(sizeof(uint8_t) * tlen);
  memcpy(buf, data + start, tlen);

  FstString *str = malloc(sizeof(FstString));
  str->data = buf;
  str->len = tlen;
  str->ref = 1;

  FstSlice ans;
  ans.str = str;
  ans.start = 0;
  ans.end = tlen - 1;
  return ans;
}
bool fstSliceIsEmpty(FstSlice *s) { return s->str == NULL || s->str->len == 0 || s->start < 0 || s->end < 0; }

uint8_t *fstSliceData(FstSlice *s, int32_t *size) {
  FstString *str = s->str;
  if (size != NULL) {
    *size = s->end - s->start + 1;
  }
  return str->data + s->start;
}
void fstSliceDestroy(FstSlice *s) {
  FstString *str = s->str;
  str->ref--;
  if (str->ref <= 0) {
    free(str->data);
    free(str);
    s->str = NULL;
  }
}

int fstSliceCompare(FstSlice *a, FstSlice *b) {
  int32_t  alen, blen;
  uint8_t *aBuf = fstSliceData(a, &alen);
  uint8_t *bBuf = fstSliceData(b, &blen);

  uint32_t i, j;
  for (i = 0, j = 0; i < alen && j < blen; i++, j++) {
    uint8_t x = aBuf[i];
    uint8_t y = bBuf[j];
    if (x == y) {
      continue;
    } else if (x < y) {
      return -1;
    } else {
      return 1;
    };
  }
  if (i < alen) {
    return 1;
  } else if (j < blen) {
    return -1;
  } else {
    return 0;
  }
}

// FstStack* fstStackCreate(size_t elemSize, StackFreeElem freeFn) {
//  FstStack *s = calloc(1, sizeof(FstStack));
//  if (s == NULL) { return NULL; }
//  s->
//  s->freeFn
//
//}
// void  *fstStackPush(FstStack *s, void *elem);
// void  *fstStackTop(FstStack *s);
// size_t fstStackLen(FstStack *s);
// void  *fstStackGetAt(FstStack *s, size_t i);
// void   fstStackDestory(FstStack *);