//===--- Arrays.swift.gyb -------------------------------------*- swift -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//  Three generic, mutable array-like types with value semantics.
//
//  - `ContiguousArray<Element>` is a fast, contiguous array of `Element` with
//    a known backing store.
//
//  - `ArraySlice<Element>` presents an arbitrary subsequence of some
//    contiguous sequence of `Element`s.
//
//  - `Array<Element>` is like `ContiguousArray<Element>` when `Element` is not
//    an reference type or an Objective-C existential.  Otherwise, it may use
//    an `NSArray` bridged from Cocoa for storage.
//
//===----------------------------------------------------------------------===//


%{
  arrayTypes = [
    ('ContiguousArray', 'a ContiguousArray'),
    ('ArraySlice', 'an `ArraySlice`'),
    ('Array', 'an `Array`'),
  ]
}%

% for (Self, a_Self) in arrayTypes:

%{
if True:
    O1 = ("O(1) unless `self`'s storage is"
       + ' shared with another live array; O(`count`) '
       + ('if `self` does not wrap a bridged `NSArray`; '
       + 'otherwise the efficiency is unspecified.'
         if Self == 'Array' else 'otherwise.'))

    contiguousCaveat = (
      ' If no such storage exists, it is first created.' if Self == 'Array'
      else '')

    if Self == 'ContiguousArray':
      SelfDocComment = """\
/// A fast, contiguously-stored array of `Element`.
///
/// Efficiency is equivalent to that of `Array`, unless `Element` is a
/// `class` or `@objc` `protocol` type, in which case using
/// `ContiguousArray` may be more efficient.  Note, however, that
/// `ContiguousArray` does not bridge to Objective-C.  See `Array`,
/// with which `ContiguousArray` shares most properties, for more
/// detail."""
    elif Self == 'ArraySlice':
      SelfDocComment = """\
/// The `Array`-like type that represents a sub-sequence of any
/// `Array`, `ContiguousArray`, or other `ArraySlice`.
///
/// `ArraySlice` always uses contiguous storage and does not bridge to
/// Objective-C.
///
/// - Warning: Long-term storage of `ArraySlice` instances is discouraged.
///
/// Because a `ArraySlice` presents a *view* onto the storage of some
/// larger array even after the original array's lifetime ends,
/// storing the slice may prolong the lifetime of elements that are
/// no longer accessible, which can manifest as apparent memory and
/// object leakage.  To prevent this effect, use `ArraySlice` only for
/// transient computation."""
    elif Self == 'Array':
      SelfDocComment = '''\
/// `Array` is an efficient, tail-growable random-access
/// collection of arbitrary elements.
///
/// Common Properties of Array Types
/// ================================
///
/// The information in this section applies to all three of Swift's
/// array types, `Array<Element>`, `ContiguousArray<Element>`, and
/// `ArraySlice<Element>`.  When you read the word "array" here in
/// a normal typeface, it applies to all three of them.
///
/// Value Semantics
/// ---------------
///
/// Each array variable, `let` binding, or stored property has an
/// independent value that includes the values of all of its elements.
/// Therefore, mutations to the array are not observable through its
/// copies:
///
///     var a = [1, 2, 3]
///     var b = a
///     b[0] = 4
///     print("a=\(a), b=\(b)")     // a=[1, 2, 3], b=[4, 2, 3]
///
/// (Of course, if the array stores `class` references, the objects
/// are shared; only the values of the references are independent.)
///
/// Arrays use Copy-on-Write so that their storage and elements are
/// only copied lazily, upon mutation, when more than one array
/// instance is using the same buffer.  Therefore, the first in any
/// sequence of mutating operations may cost `O(N)` time and space,
/// where `N` is the length of the array.
///
/// Growth and Capacity
/// -------------------
///
/// When an array's contiguous storage fills up, new storage must be
/// allocated and elements must be moved to the new storage.  `Array`,
/// `ContiguousArray`, and `ArraySlice` share an exponential growth
/// strategy that makes `append` a constant time operation *when
/// amortized over many invocations*.  In addition to a `count`
/// property, these array types have a `capacity` that reflects their
/// potential to store elements without reallocation, and when you
/// know how many elements you'll store, you can call
/// `reserveCapacity` to pre-emptively reallocate and prevent
/// intermediate reallocations.
///
/// Objective-C Bridge
/// ==================
///
/// The main distinction between `Array` and the other array types is
/// that it interoperates seamlessly and efficiently with Objective-C.
///
/// `Array<Element>` is considered bridged to Objective-C iff `Element`
/// is bridged to Objective-C.
///
/// When `Element` is a `class` or `@objc` protocol type, `Array` may
/// store its elements in an `NSArray`.  Since any arbitrary subclass
/// of `NSArray` can become an `Array`, there are no guarantees about
/// representation or efficiency in this case (see also
/// `ContiguousArray`).  Since `NSArray` is immutable, it is just as
/// though the storage was shared by some copy: the first in any
/// sequence of mutating operations causes elements to be copied into
/// unique, contiguous storage which may cost `O(N)` time and space,
/// where `N` is the length of the array (or more, if the underlying
/// `NSArray` is has unusual performance characteristics).
///
/// Bridging to Objective-C
/// -----------------------
///
/// Any bridged `Array` can be implicitly converted to an `NSArray`.
/// When `Element` is a `class` or `@objc` protocol, bridging takes O(1)
/// time and O(1) space.  Other `Array`s must be bridged
/// element-by-element, allocating a new object for each element, at a
/// cost of at least O(`count`) time and space.
///
/// Bridging from Objective-C
/// -------------------------
///
/// An `NSArray` can be implicitly or explicitly converted to any
/// bridged `Array<Element>`.  This conversion calls `copyWithZone`
/// on the `NSArray`, to ensure it won't be modified, and stores the
/// result in the `Array`.  Type-checking, to ensure the `NSArray`'s
/// elements match or can be bridged to `Element`, is deferred until the
/// first element access.'''
# FIXME: Write about Array up/down-casting.
    else:
      raise AssertionError('Unhandled case: ' + Self)
}%

${SelfDocComment}
public struct ${Self}<Element>
  : CollectionType, MutableCollectionType, _DestructorSafeContainer {

  @available(*, unavailable, renamed="Element")
  public typealias T = Element

  /// Always zero, which is the index of the first element when non-empty.
  public var startIndex: Int {
    return 0
  }

  /// A "past-the-end" element index; the successor of the last valid
  /// subscript argument.
  public var endIndex: Int {
    return _getCount()
  }

#if _runtime(_ObjC)
  // FIXME: Code is duplicated here between the Objective-C and non-Objective-C
  // runtimes because config blocks can't appear inside a subscript function
  // without causing parse errors. When this is fixed, they should be merged
  // as described in the comment below.
  // rdar://problem/19553956

  /// Access the `index`th element. Reading is O(1).  Writing is
  /// ${O1}.
  public subscript(index: Int) -> Element {
%if Self == 'Array':
    get {
      let isNativeNoTypeCheck = _getArrayPropertyIsNativeNoTypeCheck()
      _checkSubscript(index,
                      hoistedIsNativeNoTypeCheckBuffer: isNativeNoTypeCheck)
      return _getElement(index,
                         hoistedIsNativeNoTypeCheckBuffer: isNativeNoTypeCheck)
    }
    // on non-Objective-C, this should just be NativeOwner for all other
    // cases, including ArraySlice.
%elif Self == 'ArraySlice':
    addressWithOwner {
      _checkSubscript(index, hoistedIsNativeBuffer: true)
      return (UnsafePointer(_buffer.baseAddress + index),
              Builtin.castToUnknownObject(_buffer.owner))
    }
%else:
    addressWithNativeOwner {
      _checkSubscript(index, hoistedIsNativeBuffer: true)
      return (UnsafePointer(_buffer.baseAddress + index),
              Builtin.castToNativeObject(_buffer.owner))
    }
%end
    mutableAddressWithPinnedNativeOwner {
      _makeMutableAndUniqueOrPinned()
      // When an array was made mutable we know it is a backed by a native array
      // buffer.
      _checkSubscript(index, hoistedIsNativeBuffer: true)

      // We are hiding the access to '_buffer.owner' behind a semantic function
      // to help the compiler hoist uniqueness checks in the case of class or
      // objective c existential typed array elements. In the value typed case
      // the extra call to _getOwner hinders optimization so we perform a check
      // and select based on the element type below.
      return (_getElementAddress(index),
              Builtin.tryPin(
                !_isClassOrObjCExistential(Element.self) ?
                  Builtin.castToNativeObject(_buffer.owner) : _getOwner()))
    }
  }
#else
  /// Access the `index`th element. Reading is O(1).  Writing is
  /// ${O1}.
  public subscript(index: Int) -> Element {
    addressWithNativeOwner {
      _checkSubscript(index, hoistedIsNativeBuffer: true)
      return (UnsafePointer(_buffer.baseAddress + index),
              Builtin.castToNativeObject(_buffer.owner))
    }
    mutableAddressWithPinnedNativeOwner {
      _makeMutableAndUniqueOrPinned()
      // When an array was made mutable we know it is a backed by a native array
      // buffer.
      _checkSubscript(index, hoistedIsNativeBuffer: true)
      return (_getElementAddress(index),
              Builtin.tryPin(Builtin.castToNativeObject(_buffer.owner)))
    }
  }
#endif

  /// Access the elements indicated by the given half-open `subRange`.
  ///
  /// - Complexity: O(1).
  public subscript(subRange: Range<Int>) -> ArraySlice<Element> {
    get {
      _checkIndex(subRange.startIndex)
      _checkIndex(subRange.endIndex)
      return ArraySlice(_buffer[subRange])
    }
    set(rhs) {
      _checkIndex(subRange.startIndex)
      _checkIndex(subRange.endIndex)
      if self[subRange]._buffer.identity != rhs._buffer.identity {
        self.replaceRange(subRange, with: rhs)
      }
    }
  }

  //===--- private --------------------------------------------------------===//

  @_semantics("array.props.isNative")
  public // @testable
  func _getArrayPropertyIsNative() -> Bool {
   return _buffer.arrayPropertyIsNative
  }

  /// Returns true if the array is native and does not need a deferred type
  /// check.
  @_semantics("array.props.isNativeNoTypeCheck")
  public // @testable
  func _getArrayPropertyIsNativeNoTypeCheck() -> Bool {
   return _buffer.arrayPropertyIsNativeNoTypeCheck
  }

  @_semantics("array.get_count")
  internal func _getCount() -> Int {
    return _buffer.count
  }
  @_semantics("array.get_capacity")
  internal func _getCapacity() -> Int {
    return _buffer.capacity
  }

  /// - Requires: The array has a native buffer.
  @_semantics("array.owner")
  internal func _getOwner() -> Builtin.NativeObject {
    return Builtin.castToNativeObject(_buffer.nativeOwner)
  }

  // Don't inline copyBuffer - this would inline the copy loop into the current
  // path preventing retains/releases to be matched accross that region.
  @inline(never)
  internal func _copyBuffer(inout buffer: _Buffer) {
    let newBuffer = _ContiguousArrayBuffer<Element>(
      count: buffer.count, minimumCapacity: buffer.count)
    buffer._uninitializedCopy(
      0..<count, target: newBuffer.baseAddress)
    buffer = _Buffer(newBuffer)
  }

  @_semantics("array.make_mutable")
  internal mutating func _makeMutableAndUnique() {
    if _slowPath(!_buffer.isMutableAndUniquelyReferenced()) {
      _copyBuffer(&_buffer)
    }
  }

  @_semantics("array.make_mutable")
  internal mutating func _makeMutableAndUniqueOrPinned() {
    if _slowPath(!_buffer.isMutableAndUniquelyReferencedOrPinned()) {
      _copyBuffer(&_buffer)
    }
  }

  /// Check that the given `index` is valid for subscripting, i.e. `0
  /// ≤ index < count`.
  @_semantics("array.check_subscript")
  public // @testable
  func _checkSubscript(index: Int, hoistedIsNativeBuffer: Bool) {
    _precondition(_buffer._isValidSubscript(index,
                                  hoistedIsNativeBuffer: hoistedIsNativeBuffer),
                  "${Self} index out of range")
  }

%if Self == 'Array':
  /// Check that the given `index` is valid for subscripting, i.e. `0
  /// ≤ index < count`.
  @_semantics("array.check_subscript")
  public // @testable
  func _checkSubscript(index: Int, hoistedIsNativeNoTypeCheckBuffer: Bool) {
    // Using this specialized version of ArrayBuffer._isValidSubscript (for
    // the Array subscript-getter) ensures that CSE can eliminate the
    // _precondition checks in _isValidSubscript in most cases.
    _precondition(_buffer._isValidSubscript(index,
          hoistedIsNativeNoTypeCheckBuffer: hoistedIsNativeNoTypeCheckBuffer),
          "${Self} index out of range")
  }
%end

  /// Check that the given `index` is valid, i.e. `0 ≤ index ≤ count`.
  @_semantics("array.check_index")
  internal func _checkIndex(index: Int) {
    _precondition(index <= count, "${Self} index out of range")
    _precondition(index >= 0, "Negative ${Self} index is out of range")
  }

  @_semantics("array.get_element")
  @inline(__always)
  public // @testable
  func _getElement(index: Int, hoistedIsNativeNoTypeCheckBuffer : Bool)
      -> Element {
    return _buffer.getElement(index,
      hoistedIsNativeNoTypeCheckBuffer : hoistedIsNativeNoTypeCheckBuffer)
  }

  @_semantics("array.get_element_address")
  internal func _getElementAddress(index: Int) -> UnsafeMutablePointer<Element> {
    return _buffer._getBaseAddress() + index
  }

%if Self == 'Array':
#if _runtime(_ObjC)
  public typealias _Buffer = _ArrayBuffer<Element>
#else
  public typealias _Buffer = _ContiguousArrayBuffer<Element>
#endif
%elif Self == 'ArraySlice':
  public typealias _Buffer = _SliceBuffer<Element>
%else:
  public typealias _Buffer = _${Self.strip('_')}Buffer<Element>
%end

  /// Initialization from an existing buffer does not have "array.init"
  /// semantics because the caller may retain an alias to buffer.
  public init(_ _buffer: _Buffer) {
    self._buffer = _buffer
  }

  public var _buffer: _Buffer
}

extension ${Self} : ArrayLiteralConvertible {
%if Self == 'Array':
  // Optimized implementation for Array
  /// Create an instance containing `elements`.
  public init(arrayLiteral elements: Element...) {
    self = elements
  }
%else:
  /// Create an instance containing `elements`.
  public init(arrayLiteral elements: Element...) {
    self.init(_extractOrCopyToNativeArrayBuffer(elements._buffer))
  }
%end
}

// Referenced by the compiler to allocate array literals.
@_semantics("array.uninitialized")
public func _allocateUninitialized${Self}<Element>(count: Builtin.Word)
    -> (${Self}<Element>, Builtin.RawPointer) {
  let (array, ptr) = ${Self}<Element>._allocateUninitialized(Int(count))
  return (array, ptr._rawValue)
}

%if Self == 'Array':
// Referenced by the compiler to deallocate array literals on the
// error path.
@_semantics("array.dealloc_uninitialized")
public func _deallocateUninitialized${Self}<Element>(
  var array: ${Self}<Element>
) {
  array._deallocateUninitialized()
}
%end

extension ${Self} : _ArrayType {
  /// Construct an empty ${Self}.
  @_semantics("array.init")
  public init() {
    _buffer = _Buffer()
  }

  /// Construct from an arbitrary sequence with elements of type `Element`.
  public init<
    S: SequenceType where S.Generator.Element == _Buffer.Element
  >(_ s: S) {
    self = ${Self}(_Buffer(s._copyToNativeArrayBuffer()))
  }

  /// Construct a ${Self} of `count` elements, each initialized to
  /// `repeatedValue`.
  @_semantics("array.init")
  public init(count: Int, repeatedValue: Element) {
    var p: UnsafeMutablePointer<Element>
    (self, p) = ${Self}._allocateUninitialized(count)
    for _ in 0..<count {
      p++.initialize(repeatedValue)
    }
  }

  /// Construct a ${Self} of `count` uninitialized elements.
  internal init(_uninitializedCount count: Int) {
    _precondition(count >= 0, "Can't construct ${Self} with count < 0")
    _buffer = _Buffer()

    // Performance optimization: avoid reserveCapacity call if not needed.
    if count > 0 {
      reserveCapacity(count)
    }
    _buffer.count = count
  }

  /// Entry point for `Array` literal construction; builds and returns
  /// a ${Self} of `count` uninitialized elements.
  internal static func _allocateUninitialized(
    count: Int
  ) -> (${Self}, UnsafeMutablePointer<Element>) {
    let result = ${Self}(_uninitializedCount: count)
    return (result, result._buffer.baseAddress)
  }

%if Self == 'Array':
  /// Entry point for aborting literal construction: deallocates
  /// a ${Self} containing only uninitialized elements.
  internal mutating func _deallocateUninitialized() {
    // Set the count to zero and just release as normal.
    // Somewhat of a hack.
    _buffer.count = 0
  }
%end

  /// The number of elements the ${Self} stores.
  public var count: Int {
    return _getCount()
  }

  /// The number of elements the `${Self}` can store without reallocation.
  public var capacity: Int {
    return _getCapacity()
  }

  /// An object that guarantees the lifetime of this array's elements.
  public // @testable
  var _owner: AnyObject? {
    return _buffer.owner
  }

  /// If the elements are stored contiguously, a pointer to the first
  /// element. Otherwise, `nil`.
  public var _baseAddressIfContiguous: UnsafeMutablePointer<Element> {
    return _buffer.baseAddress
  }

%if Self != 'Array': # // Array does not necessarily have contiguous storage
  internal var _baseAddress: UnsafeMutablePointer<Element> {
    return _buffer.baseAddress
  }
%end
  //===--- basic mutations ------------------------------------------------===//


  /// Reserve enough space to store `minimumCapacity` elements.
  ///
  /// - Postcondition: `capacity >= minimumCapacity` and the array has
  ///   mutable contiguous storage.
  ///
  /// - Complexity: O(`count`).
  @_semantics("array.mutate_unknown")
  public mutating func reserveCapacity(minimumCapacity: Int) {
    if _buffer.requestUniqueMutableBackingBuffer(minimumCapacity) == nil {

      let newBuffer = _ContiguousArrayBuffer<Element>(
        count: count, minimumCapacity: minimumCapacity)

      _buffer._uninitializedCopy(0..<count, target: newBuffer.baseAddress)
      _buffer = _Buffer(newBuffer)
    }
    _sanityCheck(capacity >= minimumCapacity)
  }

  /// Append `newElement` to the ${Self}.
  ///
  /// - Complexity: Amortized ${O1}.
  @_semantics("array.mutate_unknown")
  public mutating func append(newElement: Element) {
    // Checking for the isNative fast-path in the outermost if-statement helps
    // the optimizer to eliminate subsequent isNative checks, e.g. when
    // accessing _buffer.count.
    if _fastPath(_buffer.arrayPropertyIsNative) {
      let oldCount = _buffer.count
      if _buffer.requestUniqueMutableBackingBuffer(oldCount + 1) != nil {
        _buffer.count = oldCount + 1
        (_buffer.baseAddress + oldCount).initialize(newElement)
        return
      }
    }
    _arrayAppendSlowPath(&_buffer, initializePointer: _InitializePointer(newElement))
  }

  @inline(never)
  internal func _arrayAppendSlowPath<_Buffer: _ArrayBufferType>(
    inout buffer: _Buffer, initializePointer: _InitializePointer<_Buffer.Element>
  ) {
    let oldCount = buffer.count
    var newBuffer = Optional(
                      _forceCreateUniqueMutableBuffer(
                        &buffer,
                        oldCount + 1,
                        oldCount + 1))
    _arrayOutOfPlaceUpdate(
      &buffer, &newBuffer, oldCount, 1, initializePointer)
  }

  /// Append the elements of `newElements` to `self`.
  ///
  /// - Complexity: O(*length of result*).
  public mutating func appendContentsOf<
      S : SequenceType
      where S.Generator.Element == Element
  >(newElements: S) {
    self += newElements
  }

  // An overload of `appendContentsOf()` that uses the += that is optimized for
  // collections.
  /// Append the elements of `newElements` to `self`.
  ///
  /// - Complexity: O(*length of result*).
  public mutating func appendContentsOf<
      C : CollectionType
      where C.Generator.Element == Element
  >(newElements: C) {
    self += newElements
  }

  /// Remove an element from the end of the ${Self} in O(1).
  ///
  /// - Requires: `count > 0`.
  public mutating func removeLast() -> Element {
    _precondition(count > 0, "can't removeLast from an empty ${Self}")
    let c = count
    // We don't check for "c - 1"  underflow because C is known to be positive.
    let result = self[c &- 1]
    self.replaceRange((c &- 1)..<c, with: EmptyCollection())
    return result
  }

  /// Insert `newElement` at index `i`.
  ///
  /// - Requires: `i <= count`.
  ///
  /// - Complexity: O(`count`).
  public mutating func insert(newElement: Element, atIndex i: Int) {
    _checkIndex(i)
    self.replaceRange(i..<i, with: CollectionOfOne(newElement))
  }

  /// Remove and return the element at index `i`.
  ///
  /// Invalidates all indices with respect to `self`.
  ///
  /// - Complexity: O(`count`).
  public mutating func removeAtIndex(index: Int) -> Element {
    let result = self[index]
    self.replaceRange(index..<(index + 1), with: EmptyCollection())
    return result
  }

  /// Remove all elements.
  ///
  /// - Postcondition: `capacity == 0` iff `keepCapacity` is `false`.
  ///
  /// - Complexity: O(`self.count`).
  public mutating func removeAll(keepCapacity keepCapacity: Bool = false) {
    if !keepCapacity {
      _buffer = _Buffer()
    }
    else {
      self.replaceRange(self.indices, with: EmptyCollection())
    }
  }

  //===--- algorithms -----------------------------------------------------===//

  public mutating func _withUnsafeMutableBufferPointerIfSupported<R>(
    @noescape body: (inout UnsafeMutableBufferPointer<Element>) throws -> R
  ) rethrows -> R? {
    // FIXME: Can't write simple code because of:
    // <rdar://problem/20735802> Assertion failure while emitting SIL for
    // _withUnsafeMutableBufferPointerIfSupported

    //return withUnsafeMutableBufferPointer { body($0) }

    return try withUnsafeMutableBufferPointer {
      (bufferPointer) -> R in
      let r = try body(&bufferPointer)
      return r
    }
  }

  /// Interpose `self` between each consecutive pair of `elements`,
  /// and concatenate the elements of the resulting sequence.  For
  /// example, `[-1, -2].join([[1, 2, 3], [4, 5, 6], [7, 8, 9]])`
  /// yields `[1, 2, 3, -1, -2, 4, 5, 6, -1, -2, 7, 8, 9]`.
  public func join<
      S : SequenceType where S.Generator.Element == ${Self}<Element>
  >(elements: S) -> ${Self}<Element> {
    return Swift.join(self, elements)
  }

  /// Returns a copy of `self` that has been sorted according to
  /// `isOrderedBefore`.
  ///
  /// - Requires: `isOrderedBefore` induces a
  /// [strict weak ordering](http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings)
  /// over the elements.
  @available(*, unavailable, message="call the 'sort()' method on the array")
  public func sorted(isOrderedBefore: (Element, Element) -> Bool) -> ${Self} {
    fatalError("unavailable function can't be called")
  }
  
  public func _copyToNativeArrayBuffer() -> _ContiguousArrayBuffer<Element> {
    return _extractOrCopyToNativeArrayBuffer(self._buffer)
  }
}

extension ${Self} : _Reflectable {
  /// Returns a mirror that reflects `self`.
  public func _getMirror() -> _MirrorType {
    return _ArrayTypeMirror(self)
  }
}

extension ${Self} : CustomStringConvertible, CustomDebugStringConvertible {
  internal func _makeDescription(isDebug isDebug: Bool) -> String {
    var result = "["
    var first = true
    for item in self {
      if first {
        first = false
      } else {
        result += ", "
      }
      if isDebug {
        debugPrint(item, &result, appendNewline: false)
      } else {
        print(item, &result, appendNewline: false)
      }
    }
    result += "]"
    return result
  }

  /// A textual representation of `self`.
  public var description: String {
    return _makeDescription(isDebug: false)
  }

  /// A textual representation of `self`, suitable for debugging.
  public var debugDescription: String {
    return _makeDescription(isDebug: true)
  }
}

extension ${Self} {
  @transparent
  internal func _cPointerArgs() -> (AnyObject?, Builtin.RawPointer) {
    let p = _baseAddressIfContiguous
    if _fastPath(p != nil || isEmpty) {
      return (_owner, p._rawValue)
    }
    let n = _extractOrCopyToNativeArrayBuffer(self._buffer)
    return (n.owner, n.baseAddress._rawValue)
  }

}

extension ${Self} {
  /// Call `body(p)`, where `p` is a pointer to the `${Self}`'s
  /// contiguous storage.${contiguousCaveat}
  ///
  /// Often, the optimizer can eliminate bounds checks within an
  /// array algorithm, but when that fails, invoking the
  /// same algorithm on `body`'s argument lets you trade safety for
  /// speed.
  public func withUnsafeBufferPointer<R>(
    @noescape body: (UnsafeBufferPointer<Element>) throws -> R
  ) rethrows -> R {
    return try _buffer.withUnsafeBufferPointer(body)
  }

  /// Call `body(p)`, where `p` is a pointer to the `${Self}`'s
  /// mutable contiguous storage.${contiguousCaveat}
  ///
  /// Often, the optimizer can eliminate bounds- and uniqueness-checks
  /// within an array algorithm, but when that fails, invoking the
  /// same algorithm on `body`'s argument lets you trade safety for
  /// speed.
  ///
  /// - Warning: Do not rely on anything about `self` (the `${Self}`
  ///   that is the target of this method) during the execution of
  ///   `body`: it may not appear to have its correct value.  Instead,
  ///   use only the `UnsafeMutableBufferPointer` argument to `body`.
  public mutating func withUnsafeMutableBufferPointer<R>(
    @noescape body: (inout UnsafeMutableBufferPointer<Element>) throws -> R
  ) rethrows -> R {
    // Ensure unique storage
    _arrayReserve(&_buffer, 0)

    // Ensure that body can't invalidate the storage or its bounds by
    // moving self into a temporary working array.
    var work = ${Self}()
    swap(&work, &self)

    // Create an UnsafeBufferPointer over work that we can pass to body
    let pointer = work._buffer.baseAddress
    let count = work.count
    var inoutBufferPointer = UnsafeMutableBufferPointer(
      start: pointer, count: count)

    // Put the working array back before returning.
    defer {
      _precondition(
        inoutBufferPointer.baseAddress == pointer &&
        inoutBufferPointer.count == count,
        "${Self} withUnsafeMutableBufferPointer: replacing the buffer is not allowed")

      swap(&work, &self)
    }

    // Invoke the body.
    return try body(&inoutBufferPointer)
  }
}
%end

internal struct _InitializeMemoryFromCollection<
  C: CollectionType
> : _PointerFunctionType {
  func call(rawMemory: UnsafeMutablePointer<C.Generator.Element>, count: Int) {
    var p = rawMemory
    var q = newValues.startIndex
    for _ in 0..<count {
      p++.initialize(newValues[q++])
    }
    _expectEnd(q, newValues)
  }

  init(_ newValues: C) {
    self.newValues = newValues
  }

  var newValues: C
}

@inline(never)
internal func _arrayOutOfPlaceReplace<
  B : _ArrayBufferType, C : CollectionType
    where C.Generator.Element == B.Element
>(
  inout source: B, _ subRange: Range<Int>, _ newValues: C, _ insertCount: Int
) {
  let growth = insertCount - subRange.count
  let newCount = source.count + growth
  var newBuffer = Optional(
    _forceCreateUniqueMutableBuffer(&source, newCount, newCount))

  _arrayOutOfPlaceUpdate(
    &source, &newBuffer,
    subRange.startIndex, insertCount,
    _InitializeMemoryFromCollection(newValues)
  )
}

/// A _debugPrecondition check that `i` has exactly reached the end of
/// `s`.  This test is never used to ensure memory safety; that is
/// always guaranteed by measuring `s` once and re-using that value.
internal func _expectEnd<C : CollectionType>(
  i: C.Index, _ s: C
) {
  _debugPrecondition(
    i == s.endIndex,
      "invalid CollectionType: count differed in successive traversals"
    )
}

internal func _arrayNonSliceInPlaceReplace<
  B : _ArrayBufferType, C : CollectionType
  where C.Generator.Element == B.Element
>(inout target: B, _ subRange: Range<Int>, _ insertCount: Int, _ newValues: C) {
  let oldCount = target.count
  let eraseCount = subRange.count

  let growth = insertCount - eraseCount
  target.count = oldCount + growth

  let elements = target.baseAddress
  _sanityCheck(elements != nil)

  let oldTailIndex = subRange.endIndex
  let oldTailStart = elements + oldTailIndex
  let newTailIndex = oldTailIndex + growth
  let newTailStart = oldTailStart + growth
  let tailCount = oldCount - subRange.endIndex

  if growth > 0 {
    // Slide the tail part of the buffer forwards, in reverse order
    // so as not to self-clobber.
    newTailStart.moveInitializeBackwardFrom(oldTailStart, count: tailCount)

    // Assign over the original subRange
    var i = newValues.startIndex
    for j in subRange {
      elements[j] = newValues[i++]
    }
    // Initialize the hole left by sliding the tail forward
    for j in oldTailIndex..<newTailIndex {
      (elements + j).initialize(newValues[i++])
    }
    _expectEnd(i, newValues)
  }
  else { // We're not growing the buffer
    // Assign all the new elements into the start of the subRange
    var i = subRange.startIndex
    var j = newValues.startIndex
    for _ in 0..<insertCount {
      elements[i++] = newValues[j++]
    }
    _expectEnd(j, newValues)

    // If the size didn't change, we're done.
    if growth == 0 {
      return
    }

    // Move the tail backward to cover the shrinkage.
    let shrinkage = -growth
    if tailCount > shrinkage {   // If the tail length exceeds the shrinkage

      // Assign over the rest of the replaced range with the first
      // part of the tail.
      newTailStart.moveAssignFrom(oldTailStart, count: shrinkage)

      //  slide the rest of the tail back
      oldTailStart.moveInitializeFrom(
        oldTailStart + shrinkage, count: tailCount - shrinkage)
    }
    else {                      // tail fits within erased elements
      // Assign over the start of the replaced range with the tail
      newTailStart.moveAssignFrom(oldTailStart, count: tailCount)

      // destroy elements remaining after the tail in subRange
      (newTailStart + tailCount).destroy(shrinkage - tailCount)
    }
  }
}

internal func _growArrayCapacity(capacity: Int) -> Int {
  return capacity * 2
}

% for (Self, a_Self) in arrayTypes:
extension ${Self} {
  /// Replace the given `subRange` of elements with `newElements`.
  ///
  /// - Complexity: O(`subRange.count`) if `subRange.endIndex
  ///   == self.endIndex` and `isEmpty(newElements)`, O(N) otherwise.
  @_semantics("array.mutate_unknown")
  public mutating func replaceRange<
    C: CollectionType where C.Generator.Element == _Buffer.Element
  >(
    subRange: Range<Int>, with newElements: C
  ) {
    _precondition(subRange.startIndex >= 0,
      "${Self} replace: subRange start is negative")

    _precondition(subRange.endIndex <= self._buffer.endIndex,
      "${Self} replace: subRange extends past the end")

    let oldCount = self._buffer.count
    let eraseCount = subRange.count
    let insertCount = numericCast(newElements.count) as Int
    let growth = insertCount - eraseCount

    if self._buffer.requestUniqueMutableBackingBuffer(oldCount + growth) != nil {
      self._buffer.replace(subRange: subRange, with: insertCount, elementsOf: newElements)
    } else {
      _arrayOutOfPlaceReplace(&self._buffer, subRange, newElements, insertCount)
    }
  }
}

/// Extend `lhs` with the elements of `rhs`.
public func += <
  Element, S : SequenceType
  where S.Generator.Element == Element
>(inout lhs: ${Self}<Element>, rhs: S) {
  let oldCount = lhs.count
  let capacity = lhs.capacity
  let newCount = oldCount + rhs.underestimateCount()

  if newCount > capacity {
    lhs.reserveCapacity(
      max(newCount, _growArrayCapacity(capacity)))
  }
  _arrayAppendSequence(&lhs._buffer, rhs)
}

/// Extend `lhs` with the elements of `rhs`.
public func += <
  Element, C : CollectionType
  where C.Generator.Element == Element
>(inout lhs: ${Self}<Element>, rhs: C) {
  let rhsCount = numericCast(rhs.count) as Int

  let oldCount = lhs.count
  let capacity = lhs.capacity
  let newCount = oldCount + rhsCount

  // Ensure uniqueness, mutability, and sufficient storage.  Note that
  // for consistency, we need unique lhs even if rhs is empty.
  lhs.reserveCapacity(
    newCount > capacity ?
    max(newCount, _growArrayCapacity(capacity))
    : newCount)

  (lhs._buffer.baseAddress + oldCount).initializeFrom(rhs)
  lhs._buffer.count = newCount
}
% end

//===--- generic helpers --------------------------------------------------===//

@inline(never)
internal func _forceCreateUniqueMutableBuffer<_Buffer : _ArrayBufferType>(
  inout source: _Buffer, _ newCount: Int, _ requiredCapacity: Int
) -> _ContiguousArrayBuffer<_Buffer.Element> {
  _sanityCheck(newCount >= 0)
  _sanityCheck(requiredCapacity >= newCount)

  let minimumCapacity = max(
    requiredCapacity,
    newCount > source.capacity
      ? _growArrayCapacity(source.capacity) : source.capacity)

  return _ContiguousArrayBuffer(
    count: newCount, minimumCapacity: minimumCapacity)
}

internal protocol _PointerFunctionType {
  typealias Element
  func call(_: UnsafeMutablePointer<Element>, count: Int)
}

/// Initialize the elements of dest by copying the first headCount
/// items from source, calling initializeNewElements on the next
/// uninitialized element, and finally by copying the last N items
/// from source into the N remaining uninitialized elements of dest.
///
/// As an optimization, may move elements out of source rather than
/// copying when it isUniquelyReferenced.
internal func _arrayOutOfPlaceUpdate<
  _Buffer : _ArrayBufferType, Initializer : _PointerFunctionType
  where Initializer.Element == _Buffer.Element
>(
  inout source: _Buffer,
  inout _ dest: _ContiguousArrayBuffer<_Buffer.Element>?,
  _ headCount: Int, // Count of initial source elements to copy/move
  _ newCount: Int,  // Count of new elements to insert
  _ initializeNewElements: Initializer
) {
  _sanityCheck(headCount >= 0)
  _sanityCheck(newCount >= 0)

  // Count of trailing source elements to copy/move
  let tailCount = dest!.count - headCount - newCount
  _sanityCheck(headCount + tailCount <= source.count)

  let sourceCount = source.count
  let oldCount = sourceCount - headCount - tailCount
  let destStart = dest!.baseAddress
  let newStart = destStart + headCount
  let newEnd = newStart + newCount

  // Check to see if we have storage we can move from
  if let backing = source.requestUniqueMutableBackingBuffer(sourceCount) {
    let sourceStart = source.baseAddress
    let oldStart = sourceStart + headCount

    // Destroy any items that may be lurking in a _SliceBuffer before
    // its real first element
    let backingStart = backing.baseAddress
    let sourceOffset = sourceStart - backingStart
    backingStart.destroy(sourceOffset)

    // Move the head items
    destStart.moveInitializeFrom(sourceStart, count: headCount)

    // Destroy unused source items
    oldStart.destroy(oldCount)

    initializeNewElements.call(newStart, count: newCount)

    // Move the tail items
    newEnd.moveInitializeFrom(oldStart + oldCount, count: tailCount)

    // Destroy any items that may be lurking in a _SliceBuffer after
    // its real last element
    let backingEnd = backingStart + backing.count
    let sourceEnd = sourceStart + sourceCount
    sourceEnd.destroy(backingEnd - sourceEnd)
    backing.count = 0
  }
  else {
    let newStart = source._uninitializedCopy(0..<headCount, target: destStart)
    initializeNewElements.call(newStart, count: newCount)
    source._uninitializedCopy(headCount + oldCount..<sourceCount,
                              target: newEnd)
  }
  source = _Buffer(dest!)
}

internal struct _InitializePointer<T> : _PointerFunctionType {
  internal func call(rawMemory: UnsafeMutablePointer<T>, count: Int) {
    _sanityCheck(count == 1)
    // FIXME: it would be better if we could find a way to move, here
    rawMemory.initialize(newValue)
  }

  @transparent
  internal init(_ newValue: T) {
    self.newValue = newValue
  }

  internal var newValue: T
}

internal struct _IgnorePointer<T> : _PointerFunctionType {
  internal func call(_: UnsafeMutablePointer<T>, count: Int) {
    _sanityCheck(count == 0)
  }
}

internal func _arrayReserve<_Buffer : _ArrayBufferType>(
  inout buffer: _Buffer, _ minimumCapacity: Int
) {
  let count = buffer.count
  let requiredCapacity = max(count, minimumCapacity)

  if _fastPath(
      buffer.requestUniqueMutableBackingBuffer(requiredCapacity) != nil) {
    return
  }

  var newBuffer = Optional(_forceCreateUniqueMutableBuffer(&buffer, count,
                                                           requiredCapacity))
  _arrayOutOfPlaceUpdate(&buffer, &newBuffer, count, 0, _IgnorePointer())
}

public // SPI(Foundation)
func _extractOrCopyToNativeArrayBuffer<
  Buffer : _ArrayBufferType
  where
  Buffer.Generator.Element == Buffer.Element
>(source: Buffer)
  -> _ContiguousArrayBuffer<Buffer.Generator.Element>
{
  if let n = source.requestNativeBuffer() {
    return n
  }
  return _copyCollectionToNativeArrayBuffer(source)
}

/// Append items from `newItems` to `buffer`.
internal func _arrayAppendSequence<
  Buffer : _ArrayBufferType,
  S : SequenceType where S.Generator.Element == Buffer.Element
>(
  inout buffer: Buffer, _ newItems: S
) {
  var stream = newItems.generate()
  var nextItem = stream.next()

  if nextItem == nil {
    return
  }

  // This will force uniqueness
  var count = buffer.count
  _arrayReserve(&buffer, count + 1)
  while true {
    let capacity = buffer.capacity
    let base = buffer.baseAddress

    while (nextItem != nil) && count < capacity {
      (base + count++).initialize(nextItem!)
      nextItem = stream.next()
    }
    buffer.count = count
    if nextItem == nil {
      return
    }
    _arrayReserve(&buffer, _growArrayCapacity(capacity))
  }
}

% for (Self, a_Self) in arrayTypes:
// NOTE: The '==' and '!=' below only handles array types
// that are the same, e.g. Array<Int> and Array<Int>, not
// ArraySlice<Int> and Array<Int>.

/// Returns true if these arrays contain the same elements.
public func == <Element : Equatable>(
  lhs: ${Self}<Element>, rhs: ${Self}<Element>
) -> Bool {
  let lhsCount = lhs.count
  if lhsCount != rhs.count {
    return false
  }

  // Test referential equality.
  if lhsCount == 0 || lhs._buffer.identity == rhs._buffer.identity {
    return true
  }

  var streamLHS = lhs.generate()
  var streamRHS = rhs.generate()

  var nextLHS = streamLHS.next()
  while nextLHS != nil {
    let nextRHS = streamRHS.next()
    if nextLHS != nextRHS {
      return false
    }
    nextLHS = streamLHS.next()
  }

  return true
}

/// Returns true if the arrays do not contain the same elements.
public func != <Element : Equatable>(
  lhs: ${Self}<Element>, rhs: ${Self}<Element>
) -> Bool {
  return !(lhs == rhs)
}
%end

#if _runtime(_ObjC)
/// Returns an `Array<Base>` containing the same elements as `a` in
/// O(1).
///
/// - Requires: `Base` is a base class or base `@objc` protocol (such
///   as `AnyObject`) of `Derived`.
public func _arrayUpCast<Derived, Base>(a: Array<Derived>) -> Array<Base> {
  // FIXME: Dynamic casting is currently not possible without the objc runtime:
  // rdar://problem/18801510
  return Array(a._buffer.castToBufferOf(Base.self))
}
#endif

#if _runtime(_ObjC)
extension Array {
  /// Try to downcast the source `NSArray` as our native buffer type.
  /// If it succeeds, create a new `Array` around it and return that.
  /// Return `nil` otherwise.
  // Note: this function exists here so that Foundation doesn't have
  // to know Array's implementation details.
  public static func _bridgeFromObjectiveCAdoptingNativeStorage(
    source: AnyObject
  ) -> Array? {
    if let deferred = source as? _SwiftDeferredNSArray {
      if let nativeStorage =
        deferred._nativeStorage as? _ContiguousArrayStorage<Element> {
        return Array(_ContiguousArrayBuffer(nativeStorage))
      }
    }
    return nil
  }

  /// Private initializer used for bridging.
  ///
  /// Only use this initializer when both conditions are true:
  ///
  /// * it is statically known that the given `NSArray` is immutable;
  /// * `Element` is bridged verbatim to Objective-C (i.e.,
  ///   is a reference type).
  public init(_immutableCocoaArray: _NSArrayCoreType) {
    self = Array(_ArrayBuffer(nsArray: _immutableCocoaArray))
  }
}
#endif

extension Array {
  /// If `!self.isEmpty`, remove the last element and return it, otherwise
  /// return `nil`.
  ///
  /// - Complexity: O(`self.count`) if the array is bridged,
  ///   otherwise O(1).
  public mutating func popLast() -> Element? {
    guard !isEmpty else { return nil }
    return removeLast()
  }
}

extension ContiguousArray {
  /// If `!self.isEmpty`, remove the last element and return it, otherwise
  /// return `nil`.
  ///
  /// - Complexity: O(1)
  public mutating func popLast() -> Element? {
    guard !isEmpty else { return nil }
    return removeLast()
  }
}

// ${'Local Variables'}:
// eval: (read-only-mode 1)
// End: