//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

/// A C++ type that represents a vector of values.
///
/// C++ standard library type `std::vector` conforms to this protocol.
public protocol CxxVector<Element>: ExpressibleByArrayLiteral {
  associatedtype Element
  associatedtype RawIterator: UnsafeCxxRandomAccessIterator
    where RawIterator.Pointee == Element
  associatedtype Size: BinaryInteger

  init()

  mutating func push_back(_ element: Element)

  func size() -> Size
  func __dataUnsafe() -> UnsafePointer<Element>?
}

extension CxxVector {
  /// Creates a C++ vector containing the elements of a Swift Sequence.
  ///
  /// This initializes the vector by copying every element of the sequence.
  ///
  /// - Complexity: O(*n*), where *n* is the number of elements in the Swift
  ///   sequence
  @inlinable
  public init<S: Sequence>(_ sequence: __shared S) where S.Element == Element {
    self.init()
    for item in sequence {
      self.push_back(item)
    }
  }
}

extension CxxVector {
  @inlinable
  public init(arrayLiteral elements: Element...) {
    self.init(elements)
  }
}

@available(SwiftStdlib 6.2, *)
extension CxxVector {
  public var span: Span<Element> {
    @lifetime(borrow self)
    @_alwaysEmitIntoClient
    borrowing get {
      let buffer = unsafe UnsafeBufferPointer(start: self.__dataUnsafe(), count: Int(self.size()))
      let span = unsafe Span(_unsafeElements: buffer)
      return unsafe _cxxOverrideLifetime(span, borrowing: self)
    }
  }
}