/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "src/core/ext/transport/chttp2/transport/stream_map.h"

#include <string.h>

#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/useful.h>

void grpc_chttp2_stream_map_init(grpc_chttp2_stream_map *map,
                                 size_t initial_capacity) {
  GPR_ASSERT(initial_capacity > 1);
  map->keys = gpr_malloc(sizeof(uint32_t) * initial_capacity);
  map->values = gpr_malloc(sizeof(void *) * initial_capacity);
  map->count = 0;
  map->free = 0;
  map->capacity = initial_capacity;
}

void grpc_chttp2_stream_map_destroy(grpc_chttp2_stream_map *map) {
  gpr_free(map->keys);
  gpr_free(map->values);
}

static size_t compact(uint32_t *keys, void **values, size_t count) {
  size_t i, out;

  for (i = 0, out = 0; i < count; i++) {
    if (values[i]) {
      keys[out] = keys[i];
      values[out] = values[i];
      out++;
    }
  }

  return out;
}

void grpc_chttp2_stream_map_add(grpc_chttp2_stream_map *map, uint32_t key,
                                void *value) {
  size_t count = map->count;
  size_t capacity = map->capacity;
  uint32_t *keys = map->keys;
  void **values = map->values;

  GPR_ASSERT(count == 0 || keys[count - 1] < key);
  GPR_ASSERT(value);

  if (count == capacity) {
    if (map->free > capacity / 4) {
      count = compact(keys, values, count);
      map->free = 0;
    } else {
      /* resize when less than 25% of the table is free, because compaction
         won't help much */
      map->capacity = capacity = 3 * capacity / 2;
      map->keys = keys = gpr_realloc(keys, capacity * sizeof(uint32_t));
      map->values = values = gpr_realloc(values, capacity * sizeof(void *));
    }
  }

  keys[count] = key;
  values[count] = value;
  map->count = count + 1;
}

void grpc_chttp2_stream_map_move_into(grpc_chttp2_stream_map *src,
                                      grpc_chttp2_stream_map *dst) {
  /* if src is empty we dont need to do anything */
  if (src->count == src->free) {
    return;
  }
  /* if dst is empty we simply need to swap */
  if (dst->count == dst->free) {
    GPR_SWAP(grpc_chttp2_stream_map, *src, *dst);
    return;
  }
  /* the first element of src must be greater than the last of dst...
   * however the maps may need compacting for this property to hold */
  if (src->keys[0] <= dst->keys[dst->count - 1]) {
    src->count = compact(src->keys, src->values, src->count);
    src->free = 0;
    dst->count = compact(dst->keys, dst->values, dst->count);
    dst->free = 0;
  }
  GPR_ASSERT(src->keys[0] > dst->keys[dst->count - 1]);
  /* if dst doesn't have capacity, resize */
  if (dst->count + src->count > dst->capacity) {
    dst->capacity = GPR_MAX(dst->capacity * 3 / 2, dst->count + src->count);
    dst->keys = gpr_realloc(dst->keys, dst->capacity * sizeof(uint32_t));
    dst->values = gpr_realloc(dst->values, dst->capacity * sizeof(void *));
  }
  memcpy(dst->keys + dst->count, src->keys, src->count * sizeof(uint32_t));
  memcpy(dst->values + dst->count, src->values, src->count * sizeof(void *));
  dst->count += src->count;
  dst->free += src->free;
  src->count = 0;
  src->free = 0;
}

static void **find(grpc_chttp2_stream_map *map, uint32_t key) {
  size_t min_idx = 0;
  size_t max_idx = map->count;
  size_t mid_idx;
  uint32_t *keys = map->keys;
  void **values = map->values;
  uint32_t mid_key;

  if (max_idx == 0) return NULL;

  while (min_idx < max_idx) {
    /* find the midpoint, avoiding overflow */
    mid_idx = min_idx + ((max_idx - min_idx) / 2);
    mid_key = keys[mid_idx];

    if (mid_key < key) {
      min_idx = mid_idx + 1;
    } else if (mid_key > key) {
      max_idx = mid_idx;
    } else /* mid_key == key */
    {
      return &values[mid_idx];
    }
  }

  return NULL;
}

void *grpc_chttp2_stream_map_delete(grpc_chttp2_stream_map *map, uint32_t key) {
  void **pvalue = find(map, key);
  void *out = NULL;
  if (pvalue != NULL) {
    out = *pvalue;
    *pvalue = NULL;
    map->free += (out != NULL);
    /* recognize complete emptyness and ensure we can skip
     * defragmentation later */
    if (map->free == map->count) {
      map->free = map->count = 0;
    }
  }
  return out;
}

void *grpc_chttp2_stream_map_find(grpc_chttp2_stream_map *map, uint32_t key) {
  void **pvalue = find(map, key);
  return pvalue != NULL ? *pvalue : NULL;
}

size_t grpc_chttp2_stream_map_size(grpc_chttp2_stream_map *map) {
  return map->count - map->free;
}

void grpc_chttp2_stream_map_for_each(grpc_chttp2_stream_map *map,
                                     void (*f)(void *user_data, uint32_t key,
                                               void *value),
                                     void *user_data) {
  size_t i;

  for (i = 0; i < map->count; i++) {
    if (map->values[i]) {
      f(user_data, map->keys[i], map->values[i]);
    }
  }
}