/*
 * Deskflow -- mouse and keyboard sharing utility
 * SPDX-FileCopyrightText: (C) 2016 Symless Ltd.
 * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
 */

#include "platform/OSXUchrKeyResource.h"

#include <Carbon/Carbon.h>

//
// OSXUchrKeyResource
//

OSXUchrKeyResource::OSXUchrKeyResource(const void *resource, uint32_t keyboardType)
    : m_m(nullptr),
      m_cti(nullptr),
      m_sdi(nullptr),
      m_sri(nullptr),
      m_st(nullptr)
{
  m_resource = static_cast<const UCKeyboardLayout *>(resource);
  if (m_resource == nullptr) {
    return;
  }

  // find the keyboard info for the current keyboard type
  const UCKeyboardTypeHeader *th = nullptr;
  const UCKeyboardLayout *r = m_resource;
  for (ItemCount i = 0; i < r->keyboardTypeCount; ++i) {
    if (keyboardType >= r->keyboardTypeList[i].keyboardTypeFirst &&
        keyboardType <= r->keyboardTypeList[i].keyboardTypeLast) {
      th = r->keyboardTypeList + i;
      break;
    }
    if (r->keyboardTypeList[i].keyboardTypeFirst == 0) {
      // found the default.  use it unless we find a match.
      th = r->keyboardTypeList + i;
    }
  }
  if (th == nullptr) {
    // cannot find a suitable keyboard type
    return;
  }

  // get tables for keyboard type
  const uint8_t *const base = reinterpret_cast<const uint8_t *>(m_resource);
  m_m = reinterpret_cast<const UCKeyModifiersToTableNum *>(base + th->keyModifiersToTableNumOffset);
  m_cti = reinterpret_cast<const UCKeyToCharTableIndex *>(base + th->keyToCharTableIndexOffset);
  m_sdi = reinterpret_cast<const UCKeySequenceDataIndex *>(base + th->keySequenceDataIndexOffset);
  if (th->keyStateRecordsIndexOffset != 0) {
    m_sri = reinterpret_cast<const UCKeyStateRecordsIndex *>(base + th->keyStateRecordsIndexOffset);
  }
  if (th->keyStateTerminatorsOffset != 0) {
    m_st = reinterpret_cast<const UCKeyStateTerminators *>(base + th->keyStateTerminatorsOffset);
  }

  // find the space key, but only if it can combine with dead keys.
  // a dead key followed by a space yields the non-dead version of
  // the dead key.
  m_spaceOutput = 0xffffu;
  uint32_t table = getTableForModifier(0);
  for (uint32_t button = 0, n = getNumButtons(); button < n; ++button) {
    KeyID id = getKey(table, button);
    if (id == 0x20) {
      UCKeyOutput c = reinterpret_cast<const UCKeyOutput *>(base + m_cti->keyToCharTableOffsets[table])[button];
      if ((c & kUCKeyOutputTestForIndexMask) == kUCKeyOutputStateIndexMask) {
        m_spaceOutput = (c & kUCKeyOutputGetIndexMask);
        break;
      }
    }
  }
}

bool OSXUchrKeyResource::isValid() const
{
  return (m_m != nullptr);
}

uint32_t OSXUchrKeyResource::getNumModifierCombinations() const
{
  // only 32 (not 256) because the righthanded modifier bits are ignored
  return 32;
}

uint32_t OSXUchrKeyResource::getNumTables() const
{
  return m_cti->keyToCharTableCount;
}

uint32_t OSXUchrKeyResource::getNumButtons() const
{
  return m_cti->keyToCharTableSize;
}

uint32_t OSXUchrKeyResource::getTableForModifier(uint32_t mask) const
{
  if (mask >= m_m->modifiersCount) {
    return m_m->defaultTableNum;
  } else {
    return m_m->tableNum[mask];
  }
}

KeyID OSXUchrKeyResource::getKey(uint32_t table, uint32_t button) const
{
  assert(table < getNumTables());
  assert(button < getNumButtons());

  const uint8_t *const base = reinterpret_cast<const uint8_t *>(m_resource);
  const UCKeyOutput *cPtr = reinterpret_cast<const UCKeyOutput *>(base + m_cti->keyToCharTableOffsets[table]);

  const UCKeyOutput c = cPtr[button];

  KeySequence keys;
  switch (c & kUCKeyOutputTestForIndexMask) {
  case kUCKeyOutputStateIndexMask:
    if (!getDeadKey(keys, c & kUCKeyOutputGetIndexMask)) {
      return kKeyNone;
    }
    break;

  case kUCKeyOutputSequenceIndexMask:
  default:
    if (!addSequence(keys, c)) {
      return kKeyNone;
    }
    break;
  }

  // XXX -- no support for multiple characters
  if (keys.size() != 1) {
    return kKeyNone;
  }

  return keys.front();
}

bool OSXUchrKeyResource::getDeadKey(KeySequence &keys, uint16_t index) const
{
  if (m_sri == nullptr || index >= m_sri->keyStateRecordCount) {
    // XXX -- should we be using some other fallback?
    return false;
  }

  uint16_t state = 0;
  if (!getKeyRecord(keys, index, state)) {
    return false;
  }
  if (state == 0) {
    // not a dead key
    return true;
  }

  // no dead keys if we couldn't find the space key
  if (m_spaceOutput == 0xffffu) {
    return false;
  }

  // the dead key should not have put anything in the key list
  if (!keys.empty()) {
    return false;
  }

  // get the character generated by pressing the space key after the
  // dead key.  if we're still in a compose state afterwards then we're
  // confused so we bail.
  if (!getKeyRecord(keys, m_spaceOutput, state) || state != 0) {
    return false;
  }

  // convert keys to their dead counterparts
  for (KeySequence::iterator i = keys.begin(); i != keys.end(); ++i) {
    *i = deskflow::KeyMap::getDeadKey(*i);
  }

  return true;
}

bool OSXUchrKeyResource::getKeyRecord(KeySequence &keys, uint16_t index, uint16_t &state) const
{
  const uint8_t *const base = reinterpret_cast<const uint8_t *>(m_resource);
  const UCKeyStateRecord *sr = reinterpret_cast<const UCKeyStateRecord *>(base + m_sri->keyStateRecordOffsets[index]);
  const UCKeyStateEntryTerminal *kset = reinterpret_cast<const UCKeyStateEntryTerminal *>(sr->stateEntryData);

  uint16_t nextState = 0;
  bool found = false;
  if (state == 0) {
    found = true;
    nextState = sr->stateZeroNextState;
    if (!addSequence(keys, sr->stateZeroCharData)) {
      return false;
    }
  } else {
    // we have a next entry
    switch (sr->stateEntryFormat) {
    case kUCKeyStateEntryTerminalFormat:
      for (uint16_t j = 0; j < sr->stateEntryCount; ++j) {
        if (kset[j].curState == state) {
          if (!addSequence(keys, kset[j].charData)) {
            return false;
          }
          nextState = 0;
          found = true;
          break;
        }
      }
      break;

    case kUCKeyStateEntryRangeFormat:
      // XXX -- not supported yet
      break;

    default:
      // XXX -- unknown format
      return false;
    }
  }
  if (!found) {
    // use a terminator
    if (m_st != nullptr && state < m_st->keyStateTerminatorCount) {
      if (!addSequence(keys, m_st->keyStateTerminators[state - 1])) {
        return false;
      }
    }
    nextState = sr->stateZeroNextState;
    if (!addSequence(keys, sr->stateZeroCharData)) {
      return false;
    }
  }

  // next
  state = nextState;

  return true;
}

bool OSXUchrKeyResource::addSequence(KeySequence &keys, UCKeyCharSeq c) const
{
  if ((c & kUCKeyOutputTestForIndexMask) == kUCKeyOutputSequenceIndexMask) {
    uint16_t index = (c & kUCKeyOutputGetIndexMask);
    if (index < m_sdi->charSequenceCount &&
        m_sdi->charSequenceOffsets[index] != m_sdi->charSequenceOffsets[index + 1]) {
      // XXX -- sequences not supported yet
      return false;
    }
  }

  if (c != 0xfffe && c != 0xffff) {
    KeyID id = unicharToKeyID(c);
    if (id != kKeyNone) {
      keys.push_back(id);
    }
  }

  return true;
}