/*
 * Copyright (C) 2022 Mikhail Burakov. This file is part of toolbox.
 *
 * toolbox is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * toolbox 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.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with toolbox.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "io_muxer.h"

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

struct IoMuxer_Closure {
  void (*callback)(void*);
  void* user;
};

static _Bool AppendRecord(struct IoMuxer* io_muxer) {
  if (io_muxer->size < io_muxer->alloc) return 1;
  size_t alloc = io_muxer->alloc + 1;
  struct pollfd* pfds = realloc(io_muxer->pfds, alloc * sizeof(struct pollfd));
  if (!pfds) return 0;
  io_muxer->pfds = pfds;
  struct IoMuxer_Closure* closures =
      realloc(io_muxer->closures, alloc * sizeof(struct IoMuxer_Closure));
  if (!closures) return 0;
  io_muxer->closures = closures;
  io_muxer->alloc = alloc;
  return 1;
}

static void CompressRecords(struct IoMuxer* io_muxer) {
  for (size_t forward = 0, reverse = io_muxer->size - 1; io_muxer->size;) {
    while (forward < reverse && !io_muxer->pfds[forward].revents) forward++;
    while (forward < reverse && io_muxer->pfds[reverse].revents) reverse--;
    if (forward == reverse) {
      if (!io_muxer->pfds[forward].revents) forward++;
      io_muxer->size = forward;
      return;
    }
    struct pollfd pfd = io_muxer->pfds[forward];
    io_muxer->pfds[forward] = io_muxer->pfds[reverse];
    io_muxer->pfds[reverse] = pfd;
    struct IoMuxer_Closure closure = io_muxer->closures[forward];
    io_muxer->closures[forward] = io_muxer->closures[reverse];
    io_muxer->closures[reverse] = closure;
  }
}

void IoMuxer_Create(struct IoMuxer* io_muxer) {
  memset(io_muxer, 0, sizeof(struct IoMuxer));
}

int IoMuxer_OnRead(struct IoMuxer* io_muxer, int fd,
                   void (*read_callback)(void*), void* user) {
  if (!AppendRecord(io_muxer)) return -1;
  struct pollfd pfd = {.fd = fd, .events = POLLIN};
  struct IoMuxer_Closure closure = {.callback = read_callback, .user = user};
  io_muxer->pfds[io_muxer->size] = pfd;
  io_muxer->closures[io_muxer->size] = closure;
  io_muxer->size++;
  return 0;
}

int IoMuxer_OnWrite(struct IoMuxer* io_muxer, int fd,
                    void (*write_callback)(void*), void* user) {
  if (!AppendRecord(io_muxer)) return -1;
  struct pollfd pfd = {.fd = fd, .events = POLLOUT};
  struct IoMuxer_Closure closure = {.callback = write_callback, .user = user};
  io_muxer->pfds[io_muxer->size] = pfd;
  io_muxer->closures[io_muxer->size] = closure;
  return 0;
}

int IoMuxer_Iterate(struct IoMuxer* io_muxer) {
  CompressRecords(io_muxer);
  int result = poll(io_muxer->pfds, io_muxer->size, -1);
  if (result <= 0) return -1;
  for (size_t i = 0; i < io_muxer->size; i++) {
    if (io_muxer->pfds[i].revents)
      io_muxer->closures[i].callback(io_muxer->closures[i].user);
  }
  return 0;
}

void IoMuxer_Destroy(struct IoMuxer* io_muxer) {
  free(io_muxer->pfds);
  free(io_muxer->closures);
}