//===--- CollectionAlgorithms.swift.gyb -----------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

%{

# We know we will eventually get a SequenceType.Element type.  Define
# a shorthand that we can use today.
GElement = "Generator.Element"

}%

//===----------------------------------------------------------------------===//
// first
//===----------------------------------------------------------------------===//

extension CollectionType {
  /// Returns the first element of `self`, or `nil` if `self` is empty.
  final public var _prext_first: Generator.Element? {
    return _prext_isEmpty ? nil : self[startIndex]
  }
}

//===----------------------------------------------------------------------===//
// last
//===----------------------------------------------------------------------===//

extension CollectionType where Self.Index : BidirectionalIndexType {
  final public var _prext_last: Generator.Element? {
    return _prext_isEmpty ? nil : self[endIndex.predecessor()]
  }
}

//===----------------------------------------------------------------------===//
// find()
//===----------------------------------------------------------------------===//

extension CollectionType where Self.${GElement} : Equatable {
  /// Returns the first index where `value` appears in `self` or `nil` if
  /// `value` is not found.
  ///
  /// - complexity: O(`self.count()`)
  final public func _prext_find(element: ${GElement}) -> Index? {
    if let result? = _customFindEquatableElement(element) {
      return result
    }

    for i in self._prext_indices {
      if self[i] == element {
        return i
      }
    }
    return nil
  }
}

extension CollectionType {
  /// Returns the first index where `predicate` returns `true` for the
  /// corresponding value, or `nil` if such value is not found.
  ///
  /// - complexity: O(`self.count()`)
  final public func _prext_find(
    @noescape predicate: (${GElement}) -> Bool
  ) -> Index? {
    for i in indices(self) {
      if predicate(self[i]) {
        return i
      }
    }
    return nil
  }
}

//===----------------------------------------------------------------------===//
// indices()
//===----------------------------------------------------------------------===//

extension CollectionType {
  /// Return the range of valid index values.
  ///
  /// The result's `endIndex` is the same as that of `self`.  Because
  /// `Range` is half-open, iterating the values of the result produces
  /// all valid subscript arguments for `self`, omitting its `endIndex`.
  final public var _prext_indices: Range<Index> {
    return Range(start: startIndex, end: endIndex)
  }
}

//===----------------------------------------------------------------------===//
// MutableCollectionType
//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//
// partition()
//===----------------------------------------------------------------------===//

%{

partitionDocComment = """\
  /// Re-order the given `range` of elements in `self` and return
  /// a pivot index *p*.
  ///
  /// Postcondition: for all *i* in `range.startIndex..<`\ *p*, and *j*
  /// in *p*\ `..<range.endIndex`, `less(self[`\ *i*\ `],
  /// self[`\ *j*\ `]) && !less(self[`\ *j*\ `], self[`\ *p*\ `])`.
  /// Only returns `range.endIndex` when `self` is empty."""

orderingRequirementForPredicate = """\
  /// Requires: `isOrderedBefore` is a `strict weak ordering
  /// <http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings>`__
  /// over `self`."""

orderingRequirementForComparable = """\
  /// Requires: The less-than operator (`func <`) defined in the `Comparable`
  /// conformance is a `strict weak ordering
  /// <http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings>`__
  /// over `self`."""

}%

extension MutableCollectionType
  where Self.Index : RandomAccessIndexType, Self.${GElement} : Comparable {

${partitionDocComment}
  ///
${orderingRequirementForComparable}
  final public mutating func _prext_partition(range: Range<Index>) -> Index {
    return _partition(&self, range)
  }
}

extension MutableCollectionType where Self.Index : RandomAccessIndexType {

${partitionDocComment}
  ///
${orderingRequirementForPredicate}
  final public mutating func _prext_partition(
    range: Range<Index>,
    var isOrderedBefore: (${GElement}, ${GElement}) -> Bool
  ) -> Index {
    return _partition(&self, range, &isOrderedBefore)
  }
}