/*
 * BRLTTY - A background process providing access to the console screen (when in
 *          text mode) for a blind person using a refreshable braille display.
 *
 * Copyright (C) 1995-2023 by The BRLTTY Developers.
 *
 * BRLTTY comes with ABSOLUTELY NO WARRANTY.
 *
 * This is free software, placed under the terms of the
 * GNU Lesser General Public License, as published by the Free Software
 * Foundation; either version 2.1 of the License, or (at your option) any
 * later version. Please see the file LICENSE-LGPL for details.
 *
 * Web Page: http://brltty.app/
 *
 * This software is maintained by Dave Mielke <dave@mielke.cc>.
 */

#include "prologue.h"

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/msg.h>
#include <sys/shm.h>

#include "log.h"
#include "scr_terminal.h"

int
makeTerminalKey (key_t *key, const char *path) {
  key_t result = ftok(path, 't');
  int gotKey = result != -1;

  if (gotKey) {
    *key = result;
  } else {
    logSystemError("ftok");
  }

  return gotKey;
}

int
getMessageQueue (int *queue, key_t key) {
  int result = msgget(key, 0);
  int foundQueue = result != -1;

  if (foundQueue) {
    *queue = result;
  } else if (errno != ENOENT) {
    logSystemError("msgget");
  }

  return foundQueue;
}

int
getScreenSegment (int *identifier, key_t key) {
  int result = shmget(key, 0, 0);
  int foundSegment = result != -1;

  if (foundSegment) {
    *identifier = result;
  } else if (errno != ENOENT) {
    logSystemError("shmget");
  }

  return foundSegment;
}

ScreenSegmentHeader *
attachScreenSegment (int identifier) {
  void *address = shmat(identifier, NULL, 0);
  if (address != (void *)-1) return address;

  logSystemError("shmat");
  return NULL;
}

int
detachScreenSegment (ScreenSegmentHeader *segment) {
  if (shmdt(segment) != -1) return 1;
  logSystemError("shmdt");
  return 0;
}

ScreenSegmentHeader *
getScreenSegmentForKey (key_t key) {
  int identifier;

  if (getScreenSegment(&identifier, key)) {
    ScreenSegmentHeader *segment = attachScreenSegment(identifier);
    if (segment) return segment;
  }

  return NULL;
}

ScreenSegmentHeader *
getScreenSegmentForPath (const char *path) {
  key_t key;
  if (!makeTerminalKey(&key, path)) return NULL;
  return getScreenSegmentForKey(key);
}

void
logScreenSegment (const ScreenSegmentHeader *segment) {
  const void *const address = segment;
  const unsigned char *const bytes = address;

  uint32_t offset = 0;
  const uint32_t end = segment->segmentSize;
  unsigned int increment = 0X10;
  const int width = snprintf(NULL, 0, "%X", end);

  while (offset < end) {
    {
      const uint32_t count = end - offset;
      if (increment > count) increment = count;
    }

    logBytes(LOG_NOTICE, "screen segment: %0*X", &bytes[offset], increment, width, offset);
    offset += increment;
  }
}

void *
getScreenItem (ScreenSegmentHeader *segment, uint32_t offset) {
  void *address = segment;
  address += offset;
  return address;
}

ScreenSegmentRow *
getScreenRowArray (ScreenSegmentHeader *segment) {
  return getScreenItem(segment, segment->rowsOffset);
}

ScreenSegmentCharacter *
getScreenCharacterArray (ScreenSegmentHeader *segment, const ScreenSegmentCharacter **end) {
  ScreenSegmentCharacter *array = getScreenItem(segment, segment->charactersOffset);
  if (end) *end = array + getScreenCharacterCount(segment);
  return array;
}

ScreenSegmentCharacter *
getScreenRow (ScreenSegmentHeader *segment, unsigned int row, const ScreenSegmentCharacter **end) {
  void *address = segment;

  if (haveScreenRowArray(segment)) {
    address += getScreenRowArray(segment)[row].charactersOffset;
  } else {
    address += segment->charactersOffset;
    address += row * getScreenRowWidth(segment);
  }

  if (end) {
    *end = address + getScreenRowWidth(segment);
  }

  return address;
}

ScreenSegmentCharacter *
getScreenCharacter (ScreenSegmentHeader *segment, unsigned int row, unsigned int column, const ScreenSegmentCharacter **end) {
  void *address = getScreenRow(segment, row, end);
  address += column * segment->characterSize;
  return address;
}