/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim:set ts=2 sw=2 sts=2 et cindent: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/dom/MIDITypes.h"

#include "mozilla/dom/MIDIUtils.h"

// Taken from MIDI IMPLEMENTATION CHART INSTRUCTIONS, MIDI Spec v1.0, Pg. 97

static const uint8_t kCommandByte = 0x80;

static const uint8_t kSysexMessageStart = 0xF0;

static const uint8_t kSystemMessage = 0xF0;

static const uint8_t kSysexMessageEnd = 0xF7;

static const uint8_t kSystemRealtimeMessage = 0xF8;

// Represents the length of all possible command messages.

// Taken from MIDI Spec, Pg. 101v 1.0, Table 2

static const uint8_t kCommandLengths[] = {3, 3, 3, 3, 2, 2, 3};

// Represents the length of all possible system messages. The length of sysex

// messages is variable, so we just put zero since it won't be checked anyways.

// Taken from MIDI Spec v1.0, Pg. 105, Table 5

static const uint8_t kSystemLengths[] = {0, 2, 3, 2, 1, 1, 1, 1};

namespace mozilla {

namespace dom {

namespace MIDIUtils {

// Checks validity of MIDIMessage passed to it. Throws debug warnings and

// returns false if message is not valid.

bool

IsValidMessage(const MIDIMessage* aMsg)

{

  if (NS_WARN_IF(!aMsg)) {

    return false;

  }

  // Assert on parser problems

  MOZ_ASSERT(aMsg->data().Length() > 0,

             "Created a MIDI Message of Length 0. This should never happen!");

  uint8_t cmd = aMsg->data()[0];

  // If first byte isn't a command, something is definitely wrong.

  MOZ_ASSERT((cmd & kCommandByte) == kCommandByte,

             "Constructed a MIDI packet where first byte is not command!");

  if (cmd == kSysexMessageStart) {

    // All we can do with sysex is make sure it starts and  ends with the correct

    // command bytes.

    if (aMsg->data()[aMsg->data().Length() - 1] != kSysexMessageEnd) {

      NS_WARNING("Last byte of Sysex Message not 0xF7!");

      return false;

    }

    return true;

  }

  // For system realtime messages, the length should always be 1.

  if ((cmd & kSystemRealtimeMessage) == kSystemRealtimeMessage) {

    return aMsg->data().Length() == 1;

  }

  // Otherwise, just use the correct array for testing lengths. We can't tell

  // much about message validity other than that.

  if ((cmd & kSystemMessage) == kSystemMessage) {

    if (cmd - kSystemMessage >= static_cast<uint8_t>(ArrayLength(kSystemLengths))) {

      NS_WARNING("System Message Command byte not valid!");

      return false;

    }

    return aMsg->data().Length() == kSystemLengths[cmd - kSystemMessage];

  }

  // For non system commands, we only care about differences in the high nibble

  // of the first byte. Shift this down to give the index of the expected packet

  // length.

  uint8_t cmdIndex = (cmd - kCommandByte) >> 4;

  if (cmdIndex >= ArrayLength(kCommandLengths)) {

    // If our index is bigger than our array length, command byte is unknown;

    NS_WARNING("Unknown MIDI command!");

    return false;

  }

  return aMsg->data().Length() == kCommandLengths[cmdIndex];

}

uint32_t

ParseMessages(const nsTArray<uint8_t>& aByteBuffer,

              const TimeStamp& aTimestamp,

              nsTArray<MIDIMessage>& aMsgArray)

{

  uint32_t bytesRead = 0;

  bool inSysexMessage = false;

  nsAutoPtr<MIDIMessage> currentMsg;

  for (auto& byte : aByteBuffer) {

    bytesRead++;

    if ((byte & kSystemRealtimeMessage) == kSystemRealtimeMessage) {

      MIDIMessage rt_msg;

      rt_msg.data().AppendElement(byte);

      rt_msg.timestamp() = aTimestamp;

      aMsgArray.AppendElement(rt_msg);

      continue;

    }

    if (byte == kSysexMessageEnd) {

      if (!inSysexMessage) {

        MOZ_ASSERT(inSysexMessage);

        NS_WARNING("Got sysex message end with no sysex message being processed!");

      }

      inSysexMessage = false;

    } else if (byte & kCommandByte) {

      if (currentMsg && IsValidMessage(currentMsg)) {

        aMsgArray.AppendElement(*currentMsg);

      }

      currentMsg = new MIDIMessage();

      currentMsg->timestamp() = aTimestamp;

    }

    currentMsg->data().AppendElement(byte);

    if (byte == kSysexMessageStart) {

      inSysexMessage = true;

    }

  }

  if (currentMsg && IsValidMessage(currentMsg)) {

    aMsgArray.AppendElement(*currentMsg);

  }

  return bytesRead;

}

bool

IsSysexMessage(const MIDIMessage& aMsg)

{

  if (aMsg.data().Length() == 0) {

    return false;

  }

  if (aMsg.data()[0] == kSysexMessageStart) {

    return true;

  }

  return false;

}

}

} // namespace dom

} // namespace mozilla