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

#include "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) {
  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;
}


void uv_link_close(uv_link_t* link) {
  link->alloc_cb = NULL;
  link->read_cb = NULL;
  link->methods = NULL;
}


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_invoke_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_invoke_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);
}