//===--- 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"

}%

//===----------------------------------------------------------------------===//
// isEmpty
//===----------------------------------------------------------------------===//

extension CollectionType {
  /// Returns `true` iff `self` is empty.
  final public var _prext_isEmpty: Bool {
    // FIXME: dynamic dispatch for Set and Dictionary.
    return startIndex == endIndex
  }
}

//===----------------------------------------------------------------------===//
// 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]
  }
}

//===----------------------------------------------------------------------===//
// 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)
  }
}