%# -*- mode: swift -*-
//===--- Arrays.swift.gyb - ContiguousArray, Array, and Slice -----------------===//
//
// 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<T> is a fast, contiguous array of T with a known
//    backing store.
//
//  - Slice<T> presents an arbitrary subsequence of some contiguous sequence
//    of Ts.
//
//  - Array<T> is like ContiguousArray<T> when T is not an ObjC type.
//    Otherwise, it may use an NSArray bridged from Cocoa for storage
//
//===----------------------------------------------------------------------===//

% for Self in ['ContiguousArray', 'Slice', 'Array']:
struct ${Self}<T> : MutableCollection, Sliceable {
  typealias Element = T
  var startIndex: Int {
    return 0
  }

  var endIndex: Int {
    return buffer.count
  }

  subscript(index: Int) -> Element {
    get {
      assert(index < count, "Array index out of range")
      return buffer[index]
    }
    nonmutating set {
      assert(index < count, "Array index out of range")
      buffer[index] = newValue
    }
  }

  func generate() -> IndexingGenerator<${Self}> {
    return IndexingGenerator(self)
  }
  
  typealias SliceType = Slice<T>
  subscript(subRange: Range<Int>) -> SliceType {
    get {
      return Slice(buffer[subRange])
    }
    set {
      if self[subRange] !== newValue {
        replace(&self, subRange, newValue)
      }
    }
  }

  //===--- private --------------------------------------------------------===//
  typealias Buffer = ${'Array' if Self.startswith('New') else Self}Buffer<T>

  init(_ buffer: Buffer) {
    self.buffer = buffer
  }

  var buffer: Buffer
}

extension ${Self} : ArrayLiteralConvertible {
  static func convertFromArrayLiteral(elements: Element...) -> ${Self} {
    return ${Self}(_extractOrCopyToNativeArrayBuffer(elements.buffer))
  }
}

extension ${Self} {
  func _asCocoaArray() -> _CocoaArray {
    return buffer._asCocoaArray()
  }
}

extension ${Self} : ArrayType {
  /// Construct an empty ${Self}
  init() {
    buffer = Buffer()
  }

  init<S: Sequence where S.GeneratorType.Element == Buffer.Element>(_ s: S) {
    self = ${Self}(Buffer(s~>_copyToNativeArrayBuffer()))
  }

  /// Construct an array of count elements, each initialized to value
  init(count: Int, value: T) {
    assert(count >= 0)
    buffer = Buffer()
    reserveCapacity(count)
    var p = buffer.elementStorage
    for _ in 0..count {
      p++.initialize(value)
    }
    buffer.count = count
  }
  
  /// How many elements the ${Self} stores
  var count: Int {
    return buffer.count
  }

  /// How many elements the ${Self} can store without reallocation
  var capacity: Int {
    return buffer.capacity
  }

  /// true if and only if the ${Self} is empty
  var isEmpty: Bool {
    return count == 0
  }
  
  /// An object that guarantees the lifetime of this array's elements
  var owner: AnyObject? {
    return buffer.owner
  }
  
  /// If the elements are stored contiguously, a pointer to the first
  /// element. Otherwise, nil.
  var elementStorage: UnsafePointer<Element> {
    return buffer.elementStorage
  }
  
  //===--- basic mutations ------------------------------------------------===//


  /// Returns a new array that does not share the underlying storage with this
  /// array.
  /// Complexity: O(N)
  func copy() -> ${Self} {
    var result = self
    result.reserveCapacity(0)
    return result
  }

  /// Ensure the uniqueness of the array.
  /// Complexity: O(N)
  mutating func unshare() {
    reserveCapacity(0)
  }

  /// Ensure the array has enough mutable contiguous storage to store
  /// newCapacity elements in.  Note: does not affect count.
  /// Complexity: O(N)
  mutating func reserveCapacity(newCapacity: Int) {
    if !buffer.requestUniqueMutableBuffer(newCapacity) {
      var newBuffer = ContiguousArrayBuffer<T>(count: count, minimumCapacity: newCapacity)
      buffer._uninitializedCopy(0..count, target: newBuffer.elementStorage)
      buffer = Buffer(newBuffer)
    }
    assert(capacity >= newCapacity)
  }
  
  /// Append newElement to the ${Self} in O(1) (amortized)
  mutating func append(newElement: T) {
    _arrayAppend(&buffer, newElement)
  }
  
  /// Remove an element from the end of the ${Self} in O(1).
  /// Requires: count > 0
  mutating func popLast() -> T {
    assert(count > 0, "can't pop from an empty ${Self}")
    let c = count
    let result = self[c - 1]
    replace(&self, (c - 1)..c, EmptyCollection())
    return result
  }
  
  /// Insert an element at the given index in O(N).  Requires: atIndex
  /// <= count
  mutating func insert(atIndex: Int, newElement: T) {
    replace(&self, atIndex..atIndex, CollectionOfOne(newElement))
  }

  /// Remove the element at the given index.  Worst case complexity:
  /// O(N).  Requires: index < count
  mutating func removeAt(index: Int) -> T {
    let result = self[index]
    replace(&self, index..(index + 1), EmptyCollection())
    return result
  }

  /// Erase all the elements and release the storage
  mutating func clear() {
    buffer = Buffer()
  }

  /// Erase all the elements.  If keepStorage is true, capacity will not change
  mutating func clear(keepStorage: Bool) {
    if !keepStorage {
      clear()
    }
    else {
      replace(&self, indices(self), EmptyCollection())
    }
  }
  
  //===--- algorithms -----------------------------------------------------===//
  func reduce<U>(initial: U, combine: (U, T)->U) -> U {
    return Swift.reduce(self, initial, combine)
  }

  mutating func sort(isOrderedBefore: (T, T)->Bool) {
    quickSort(&self, indices(self), isOrderedBefore)
  }

  func map<U>(transform: (T)->U) -> ${Self}<U> {
    var result = ${Self}<U>()

    let count = self.count
    result.reserveCapacity(count)
    var p = result.buffer.elementStorage
    for i in 0..count {
      p++.initialize( transform(self[i]) )
    }
    result.buffer.count = count
    
    return result
  }
}

extension ${Self} : Reflectable {
  func getMirror() -> Mirror {
    return _ArrayTypeMirror(self)
  }
}

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

  var description: String {
    return _makeDescription(isDebug: false)
  }

  var debugDescription: String {
    return _makeDescription(isDebug: true)
  }
}

extension ${Self} {
  @transparent
  func _cPointerArgs() -> (AnyObject?, Builtin.RawPointer) {
    let p = elementStorage
    if _fastPath(p != nil || count == 0) {
      return (owner, p.value)
    }
    let n = _extractOrCopyToNativeArrayBuffer(self.buffer)
    return (n.owner, n.elementStorage.value)
  }
  
  // Conversion to C pointer arguments
  @transparent @conversion
  func __conversion() -> CConstPointer<T> {
    return CConstPointer(_cPointerArgs())
  }
  
  @transparent @conversion
  func __conversion() -> CConstVoidPointer {
    return CConstVoidPointer(_cPointerArgs())
  }
}

%if Self != 'Array': # // Array does not necessarily have contiguous storage
extension ${Self} {
  func withUnsafePointerToElements<R>(body: (UnsafePointer<T>)->R) -> R {
    return buffer.withUnsafePointerToElements(body)
  }
}
%end

%end

extension Array {
  /// This function "seeds" the ArrayLiteralConvertible protocol
  static func convertFromHeapArray(
    base: Builtin.RawPointer,
    owner: Builtin.NativeObject,
    count: Builtin.Word
  ) -> Array {
    let elements = UnsafeArray(
      start: reinterpretCast(base) as UnsafePointer<T>,
      length: reinterpretCast(count) as Int
    )
    let r = Array(elements)
    _fixLifetime(owner)
    return r
  }
}

struct _InitializeMemoryFromCollection<C: Collection> : PointerFunction {
  func call(rawMemory: UnsafePointer<C.GeneratorType.Element>) {
    var p = rawMemory
    for x in newValues {
      p++.initialize(x)
    }    
  }

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

  var newValues: C
}

func replace<
  A: ArrayType, C: Collection
  where C.GeneratorType.Element == A.Buffer.Element, A.IndexType == Int
  >(
  inout target: A, subRange: Range<Int>, newValues: C
) {
  assert(subRange.startIndex >= 0)
  assert(subRange.endIndex >= subRange.startIndex)
  assert(subRange.endIndex <= target.endIndex)
  
  let oldCount = target.count
  let eraseCount = countElements(subRange)
  let insertCount = numericCast(countElements(newValues)) as Int
  var newBuffer = _demandUniqueMutableBuffer(
    &target.buffer, oldCount + insertCount - eraseCount)

  if _fastPath(!newBuffer) {
    let growth = insertCount - eraseCount
    
    let elements = target.buffer.elementStorage
    assert(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++])
      }
    }
    else { // We're not growing the buffer
      // Assign all the new elements into the start of the subRange
      var i = subRange.startIndex
      for j in indices(newValues) {
        elements[i++] = newValues[j]
      }

      // 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)
      }
    }
  }
  else {
    _arrayOutOfPlaceUpdate(
      &target.buffer, &newBuffer,
      subRange.startIndex, insertCount,
      _InitializeMemoryFromCollection(newValues)
    )
  }
}

@assignment
func += <
  A: ArrayType, S: Sequence
  where S.GeneratorType.Element == A.Buffer.Element
>(inout lhs: A, rhs: S) {
  _arrayAppendSequence(&lhs.buffer, rhs)
}

@assignment
func += <
  A: ArrayType, C: Collection
where C.GeneratorType.Element == A.Buffer.Element
>(inout lhs: A, rhs: C) {
  let rhsCount = numericCast(countElements(rhs)) 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, capacity * 2) : newCount)
  var p = lhs.buffer.elementStorage + oldCount
  for x in rhs {
    (p++).initialize(x)
  }
  lhs.buffer.count = newCount
}

@assignment
func += <
  A: ArrayType
>(inout lhs: A, rhs: A.Buffer.Element) {
  lhs += CollectionOfOne(rhs)
}

//===--- generic helpers --------------------------------------------------===//
/// Ensure there's a ContiguousArrayBuffer capable of storing
/// max(newCount, minimumCapacity) elements, with count set to
/// newCount.
///
/// If source has sufficient capacity, returns nil.  Otherwise,
/// returns a new buffer.
///
/// NOTE: does not initialize or destroy any elements.  In general,
/// the buffer that satisfies the capacity request now has a count
/// that does not match its number of initialized elements, and that
/// needs to be corrected before the buffer can go back into circulation.
func _demandUniqueMutableBuffer<Buffer: ArrayBufferType>(
  inout source: Buffer, newCount: Int, minimumCapacity: Int = 0)
-> ContiguousArrayBuffer<Buffer.Element>? {

  assert(newCount >= 0)
  
  let requiredCapacity = max(newCount, minimumCapacity)
  
  if let b = source.requestUniqueMutableBuffer(requiredCapacity) {
    source.count = newCount
    return nil
  }

  let newCapacity = max(
    requiredCapacity,
    newCount > source.capacity ? source.capacity * 2 : source.capacity)

  return ContiguousArrayBuffer(count: newCount, minimumCapacity: newCapacity)
}

protocol PointerFunction {
  typealias Element
  func call(UnsafePointer<Element>)
}

/// 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.
func _arrayOutOfPlaceUpdate<
  Buffer: ArrayBufferType, Initializer: PointerFunction
    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
) {
  assert(headCount >= 0)
  assert(newCount >= 0)
  
  // Count of trailing source elements to copy/move
  let tailCount = dest!.count - headCount - newCount
  assert(headCount + tailCount <= source.count)
  
  let sourceCount = source.count
  let oldCount = sourceCount - headCount - tailCount
  let destStart = dest!.elementStorage
  let newStart = destStart + headCount
  let newEnd = newStart + newCount
  
  // Check to see if we have storage we can move from
  if let backing = source.requestUniqueMutableBuffer(sourceCount) {
    let sourceStart = source.elementStorage
    let oldStart = sourceStart + headCount
    
    // Destroy any items that may be lurking in a SliceBuffer before
    // its real first element
    let backingStart = backing.elementStorage
    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)

    // 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(sourceEnd - backingEnd)
    backing.count = 0
  }
  else {
    let newStart = source._uninitializedCopy(0..headCount, target: destStart)
    initializeNewElements.call(newStart)
    source._uninitializedCopy(headCount + oldCount..sourceCount, 
                              target: newEnd)
  }
  source = Buffer(dest!)
}

struct InitializePointer<T> : PointerFunction {
  func call(rawMemory: UnsafePointer<T>) {
    // FIXME: maybe we should move here instead of copying?
    rawMemory.initialize(newValue)
  }

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

  var newValue: T
}

func _arrayAppend<Buffer: ArrayBufferType>(
  inout buffer: Buffer, newValue: Buffer.Element
) {
  let oldCount = buffer.count
  var newBuffer = _demandUniqueMutableBuffer(&buffer, oldCount + 1)
  if _fastPath(!newBuffer) {
    (buffer.elementStorage + oldCount).initialize(newValue)
  }
  else {
    _arrayOutOfPlaceUpdate(
      &buffer, &newBuffer, oldCount, 1, InitializePointer(newValue))
  }
}

struct IgnorePointer<T> : PointerFunction {
  func call(_:UnsafePointer<T>) {}
}

func _arrayReserve<Buffer: ArrayBufferType>(
  inout buffer: Buffer, newCapacity: Int
) {
  let oldCount = buffer.count
  var newBuffer = _demandUniqueMutableBuffer(&buffer, oldCount, minimumCapacity: newCapacity)
  if _slowPath(newBuffer) {
    _arrayOutOfPlaceUpdate(&buffer, &newBuffer, oldCount, 1, IgnorePointer())
  }
}

func _extractOrCopyToNativeArrayBuffer<
  Buffer: ArrayBufferType where Buffer.GeneratorType.Element == Buffer.Element
>(source: Buffer) 
  -> ContiguousArrayBuffer<Buffer.Element> 
{
  if let n = source.requestNativeBuffer() {
    return n
  }
  return _copyCollectionToNativeArrayBuffer(source)
}

/// Append items from newItems to buffer
func _arrayAppendSequence<
  Buffer: ArrayBufferType,
  S: Sequence where S.GeneratorType.Element == Buffer.Element
>(
  inout buffer: Buffer, newItems: S
) {
  var stream = newItems.generate()
  var nextItem = stream.next()

  if !nextItem {
    return
  }

  // This will force uniqueness
  _arrayAppend(&buffer, nextItem!)
  var count = buffer.count
  nextItem = stream.next()
  while nextItem {
    let capacity = buffer.capacity
    let base = buffer.elementStorage
    
    while nextItem && count < capacity {
      (base + count++).initialize(nextItem!)
      nextItem = stream.next()
    }
    buffer.count = count
    if nextItem {
      _arrayReserve(&buffer, capacity * 2)
    }
  }
}

/// Returns true iff these arrays reference exactly the same elements.
func ===<T: ArrayType, U: ArrayType>(lhs: T, rhs: U) -> Bool {
  let lhsCount = lhs.count
  if lhsCount != rhs.count {
    return false
  }

  return lhsCount == 0 || lhs.buffer.identity == rhs.buffer.identity
}

/// Returns false iff these arrays reference exactly the same
/// elements.
func !==<T: ArrayType, U: ArrayType>(lhs: T, rhs: U) -> Bool {
  return !(lhs === rhs)
}

% for Self in ['ContiguousArray', 'Slice', 'Array']:
// NOTE: The '==' and '!=' below only handles array types
// that are the same, e.g. Array<Int> and Array<Int>, not
// Slice<Int> and Array<Int>.

/// Returns true if these arrays contain the same elements.
func ==<T: Equatable>(lhs: ${Self}<T>, rhs: ${Self}<T>) -> 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 {
    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.
func !=<T: Equatable>(lhs: ${Self}<T>, rhs: ${Self}<T>) -> Bool {
  return !(lhs == rhs)
}
%end

/// 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.
func _arrayUpCast<Derived, Base>(a: Array<Derived>) -> Array<Base> {
  return Array(a.buffer.castToBufferOf(Base.self))
}

/// Implements the semantics of `x as Derived[]` where `x` has type
/// `Base[]` and `Derived` is a verbatim-bridged trivial subtype of
/// `Base`.
///
/// Returns an Array<Derived> containing the same elements as a in
/// O(1) iff a's buffer elements are dynamically known to have
/// type Derived or a type derived from Derived.
func _arrayCheckedDownCast<Base, Derived>(a: Array<Base>) -> Derived[]? {
  _sanityCheck(isBridgedVerbatimToObjectiveC(Base.self))
  _sanityCheck(isBridgedVerbatimToObjectiveC(Derived.self))
  
  if _fastPath(!a.isEmpty) {
    let native = a.buffer.requestNativeBuffer()
    
    if _fastPath(native) {
      if native!.storesOnlyElementsOfType(Derived.self) {
        return Array(a.buffer.castToBufferOf(Derived.self))
      }
      return nil
    }
    
    // slow path: we store an NSArray
    
    // We can skip the check if Derived happens to be AnyObject
    if !(AnyObject.self is Derived.Type) {
      for element in a {
        if !(element is Derived) {
          return nil
        }
      }
    }
    return Array(a.buffer.castToBufferOf(Derived.self))
  }
  return []
}

/// Convert a to its corresponding bridged array type.
/// Precondition: T is bridged to objective C
/// O(1) if T is bridged verbatim, O(N) otherwise
func _arrayBridgeToObjectiveC<BridgesToDerived, Base>(
  source: Array<BridgesToDerived>
) -> Array<Base> {
  var buf = ContiguousArrayBuffer<Base>(count: source.count, minimumCapacity: 0)
  var p = buf._unsafeElementStorage
  for value in source {
    let bridged: AnyObject? = bridgeToObjectiveC(value)
    _precondition(bridged, "array element cannot be bridged to Objective-C")
    p++.initialize(reinterpretCast(bridged!))
  }
  return Array(ArrayBuffer(buf))
}

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