#include <stdlib.h>
#include <string.h>

#include "src/common.h"

static void uv_link_def_alloc_cb(uv_link_t* link,
                                 size_t suggested_size,
                                 uv_buf_t* buf) {
  static const size_t kBufferSize = 16 * 1024;

  buf->base = malloc(kBufferSize);
  buf->len = kBufferSize;

  CHECK_NE(buf->base, NULL, "uv_link_t: alloc_cb failure");
}


static void uv_link_def_read_cb(uv_link_t* link,
                                ssize_t nread,
                                const uv_buf_t* buf) {
  if (buf != NULL)
    free(buf->base);
}


int uv_link_init(uv_link_t* link, uv_link_methods_t const* methods) {
  memset(link, 0, sizeof(*link));

  link->alloc_cb = uv_link_def_alloc_cb;
  link->read_cb = uv_link_def_read_cb;

  link->methods = methods;

  return 0;
}


static void uv_link_close_join(uv_link_t* link) {
  if (--link->close_waiting == 0)
    return link->saved_close_cb(link);
}


void uv_link_close(uv_link_t* link, uv_link_close_cb cb) {
  uv_link_propagate_close(link, link, cb);
}


void uv_link_propagate_close(uv_link_t* link, uv_link_t* source,
                             uv_link_close_cb cb) {
  uv_link_t* root;
  int count;

  CHECK_EQ(link->child, NULL, "uv_link_t: attempt to close chained link");

  /* Find root */
  count = 1;
  for (root = link; root->parent != NULL; root = root->parent)
    count++;

  /* NOTE: This is very important line. Only because we `+=` here the
   * recursive propagation is possible
   */
  source->close_waiting += count;

  source->saved_close_cb = cb;

  /* Go from the root to the leaf, disconnecting and closing everything */
  while (root != NULL) {
    uv_link_t* child;

    child = root->child;
    if (child != NULL)
      CHECK_EQ(uv_link_unchain(root, child), 0, "close unchain");

    root->methods->close(root, source, uv_link_close_join);
    root = child;
  }
}


int uv_link_chain(uv_link_t* from, uv_link_t* to) {
  if (from->child != NULL || to->parent != NULL)
    return UV_EINVAL;

  from->child = to;
  to->parent = from;

  from->saved_alloc_cb = from->alloc_cb;
  from->saved_read_cb = from->read_cb;
  from->alloc_cb = to->methods->alloc_cb_override;
  from->read_cb = to->methods->read_cb_override;

  return 0;
}


int uv_link_unchain(uv_link_t* from, uv_link_t* to) {
  if (from->child != to || to->parent != from)
    return UV_EINVAL;

  from->child = NULL;
  to->parent = NULL;

  from->alloc_cb = from->saved_alloc_cb;
  from->read_cb = from->saved_read_cb;
  from->saved_alloc_cb = NULL;
  from->saved_read_cb = NULL;

  return 0;
}


void uv_link_propagate_alloc_cb(uv_link_t* link,
                                size_t suggested_size,
                                uv_buf_t* buf) {
  uv_link_t* target;

  target = link;
  if (link->child != NULL)
    target = link->child;

  link->alloc_cb(target, suggested_size, buf);
}


void uv_link_propagate_read_cb(uv_link_t* link,
                               ssize_t nread,
                               const uv_buf_t* buf) {
  uv_link_t* target;

  target = link;
  if (link->child != NULL)
    target = link->child;

  link->read_cb(target, nread, buf);
}