//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

@exported import CoreAudio // Clang module

extension UnsafeBufferPointer {
  /// Initialize an `UnsafeBufferPointer<T>` from an `AudioBuffer`.
  init(_ audioBuffer: AudioBuffer) {
    // FIXME: this API should be public, but it can't be because of a compiler
    // limitation: can't declare a public extension on a generic type from
    // another module.  rdar://16974298
    self.init(
      start: UnsafePointer<T>(audioBuffer.mData),
      count: Int(audioBuffer.mDataByteSize) / strideof(T))
  }
}

// The API above can't be public yet.  We expose it through this function for
// the sake of testing so that the code does not bitrot.
public // @testable
func _convertAudioBufferToUnsafeBufferPointer<T>(
  audioBuffer: AudioBuffer) -> UnsafeBufferPointer<T> {
  return UnsafeBufferPointer(audioBuffer)
}

extension UnsafeMutableBufferPointer {
  /// Initialize an `UnsafeMutableBufferPointer<T>` from an `AudioBuffer`.
  init(_ audioBuffer: AudioBuffer) {
    // FIXME: this API should be public, but it can't be because of a compiler
    // limitation: can't declare a public extension on a generic type from
    // another module.  rdar://16974298
    self.init(
      start: UnsafeMutablePointer<T>(audioBuffer.mData),
      count: Int(audioBuffer.mDataByteSize) / strideof(T))
  }
}

// The API above can't be public yet.  We expose it through this function for
// the sake of testing so that the code does not bitrot.
public // @testable
func _convertAudioBufferToUnsafeMutableBufferPointer<T>(
  audioBuffer: AudioBuffer) -> UnsafeMutableBufferPointer<T> {
  return UnsafeMutableBufferPointer(audioBuffer)
}

extension AudioBuffer {
  /// Initialize an `AudioBuffer` from an `UnsafeMutableBufferPointer<T>`.
  public init<T>(
    _ typedBuffer: UnsafeMutableBufferPointer<T>, numberOfChannels: Int) {
    self.mNumberChannels = UInt32(numberOfChannels)
    self.mData = UnsafeMutablePointer<Void>(typedBuffer.baseAddress)
    self.mDataByteSize = UInt32(typedBuffer.count * strideof(T))
  }
}

extension AudioBufferList {
  /// :returns: the size in bytes of an `AudioBufferList` that can hold up to
  /// `maximumBuffers` `AudioBuffer`\ s.
  public static func sizeInBytes(#maximumBuffers: Int) -> Int {
    _precondition(maximumBuffers >= 1,
      "AudioBufferList should contain at least one AudioBuffer")
    return sizeof(AudioBufferList) +
      (maximumBuffers - 1) * strideof(AudioBuffer)
  }

  /// Allocate an `AudioBufferList` with a capacity for the specified number of
  /// `AudioBuffer`\ s.
  ///
  /// The `count` property of the new `AudioBufferList` is initialized to
  /// `maximumBuffers`.
  ///
  /// The memory should be freed with `free()`.
  public static func allocate(#maximumBuffers: Int)
    -> UnsafeMutableAudioBufferListPointer {
    let byteSize = UInt(sizeInBytes(maximumBuffers: maximumBuffers))
    let ablMemory = calloc(byteSize, 1)
    _precondition(ablMemory != nil,
      "failed to allocate memory for an AudioBufferList")

    let abl = UnsafeMutableAudioBufferListPointer(
        UnsafeMutablePointer<AudioBufferList>(ablMemory))
    abl.count = maximumBuffers
    return abl
  }
}

/// A wrapper for a pointer to an `AudioBufferList`.
///
/// Like `UnsafeMutablePointer`, this type provides no automated memory
/// management and the user must therefore take care to allocate and free
/// memory appropriately.
public struct UnsafeMutableAudioBufferListPointer {
  /// Construct from an `AudioBufferList` pointer.
  public init(_ p: UnsafeMutablePointer<AudioBufferList>) {
    unsafeMutablePointer = p
  }

  /// The number of `AudioBuffer`\ s in the `AudioBufferList`
  /// (`mNumberBuffers`).
  public var count: Int {
    get {
      return Int(unsafeMutablePointer.memory.mNumberBuffers)
    }
    nonmutating set(newValue) {
      unsafeMutablePointer.memory.mNumberBuffers = UInt32(newValue)
    }
  }

  /// The pointer to the first `AudioBuffer` in this `AudioBufferList`.
  internal var _audioBuffersPointer: UnsafeMutablePointer<AudioBuffer> {
    // AudioBufferList has one AudioBuffer in a "flexible array member".
    // Position the pointer after that, and skip one AudioBuffer back.  This
    // brings us to the start of AudioBuffer array.
    return UnsafeMutablePointer<AudioBuffer>(unsafeMutablePointer + 1) - 1
  }

  // FIXME: the properties 'unsafePointer' and 'unsafeMutablePointer' should
  // be initializers on UnsafePointer and UnsafeMutablePointer, but they can't
  // because of a compiler limitation: can't declare a public extension on a
  // generic type from another module.  rdar://16974298

  /// The pointer to the wrapped `AudioBufferList`.
  public var unsafePointer: UnsafePointer<AudioBufferList> {
    return UnsafePointer(unsafeMutablePointer)
  }

  /// The pointer to the wrapped `AudioBufferList`.
  public var unsafeMutablePointer: UnsafeMutablePointer<AudioBufferList>
}

extension UnsafeMutableAudioBufferListPointer : MutableCollectionType {
  public func generate()
    -> IndexingGenerator<UnsafeMutableAudioBufferListPointer> {
    return IndexingGenerator(self)
  }

  /// Always zero, which is the index of the first `AudioBuffer`.
  public var startIndex: Int {
    return 0
  }

  /// The "past the end" position; always identical to `count`.
  public var endIndex: Int {
    return count
  }

  /// Access an indexed `AudioBuffer` (`mBuffers[i]`).
  public subscript(index: Int) -> AudioBuffer {
    get {
      _precondition(index >= 0 && index < self.count,
        "subscript index out of range")
      return (_audioBuffersPointer + index).memory
    }
    nonmutating set(newValue) {
      _precondition(index >= 0 && index < self.count,
        "subscript index out of range")
      (_audioBuffersPointer + index).memory = newValue
    }
  }
}