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//
// Move.swift
// Sage
//
// Copyright 2016-2017 Nikolai Vazquez
// Modified by SuperGeroy
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
/// A chess move from a start `Square` to an end `Square`.
public struct Move: Hashable, CustomStringConvertible {
/// The move's start square.
public var start: Square
/// The move's end square.
public var end: Square
/// The move's change in file.
public var fileChange: Int {
return end.file.rawValue - start.file.rawValue
}
/// The move's change in rank.
public var rankChange: Int {
return end.rank.rawValue - start.rank.rawValue
}
/// The move is a real change in location.
public var isChange: Bool {
return start != end
}
/// The move is diagonal.
public var isDiagonal: Bool {
let fileChange = self.fileChange
return fileChange != 0 && abs(fileChange) == abs(rankChange)
}
/// The move is horizontal.
public var isHorizontal: Bool {
return start.file != end.file && start.rank == end.rank
}
/// The move is vertical.
public var isVertical: Bool {
return start.file == end.file && start.rank != end.rank
}
/// The move is horizontal or vertical.
public var isAxial: Bool {
return isHorizontal || isVertical
}
/// The move is leftward.
public var isLeftward: Bool {
return end.file < start.file
}
/// The move is rightward.
public var isRightward: Bool {
return end.file > start.file
}
/// The move is downward.
public var isDownward: Bool {
return end.rank < start.rank
}
/// The move is upward.
public var isUpward: Bool {
return end.rank > start.rank
}
/// The move is a knight jump two spaces horizontally and one space vertically, or two spaces vertically and one
/// space horizontally.
public var isKnightJump: Bool {
let fileChange = abs(self.fileChange)
let rankChange = abs(self.rankChange)
return (fileChange == 2 && rankChange == 1)
|| (rankChange == 2 && fileChange == 1)
}
/// The move's direction in file, if any.
public var fileDirection: File.Direction? {
if self.isLeftward {
return .left
} else if self.isRightward {
return .right
} else {
return .none
}
}
/// The move's direction in rank, if any.
public var rankDirection: Rank.Direction? {
if self.isUpward {
return .up
} else if self.isDownward {
return .down
} else {
return .none
}
}
/// A textual representation of `self`.
public var description: String {
return "\(start) >>> \(end)"
}
/// The hash value.
public func hash(into hasher: inout Hasher) {
hasher.combine(start)
hasher.combine(end)
}
/// Create a move with start and end squares.
public init(start: Square, end: Square) {
self.start = start
self.end = end
}
/// Create a move with start and end locations.
public init(start: Location, end: Location) {
self.start = Square(location: start)
self.end = Square(location: end)
}
/// A castle move for `color` in `direction`.
public init(castle color: Color, direction: File.Direction) {
let rank: Rank = color.isWhite ? 1 : 8
self = Move(start: Square(file: .e, rank: rank), end: Square(file: direction == .left ? .c : .g, rank: rank))
}
/// Returns the castle squares for a rook.
internal func _castleSquares() -> (old: Square, new: Square) {
let rank = start.rank
let movedLeft = self.isLeftward
let old = Square(file: movedLeft ? .a : .h, rank: rank)
let new = Square(file: movedLeft ? .d : .f, rank: rank)
return (old, new)
}
/// Returns a move with the end and start of `self` reversed.
public func reversed() -> Move {
return Move(start: end, end: start)
}
/// Returns the result of rotating `self` 180 degrees.
public func rotated() -> Move {
let start = Square(file: self.start.file.opposite(),
rank: self.start.rank.opposite())
let end = Square(file: self.end.file.opposite(),
rank: self.end.rank.opposite())
return start >>> end
}
/// Returns `true` if `self` is castle move for `color`.
///
/// - parameter color: The color to check the rank against. If `nil`, the rank can be either 1 or 8. The default
/// value is `nil`.
public func isCastle(for color: Color? = nil) -> Bool {
let startRank = start.rank
if let color = color {
guard startRank == Rank(startFor: color) else { return false }
} else {
guard startRank == 1 || startRank == 8 else { return false }
}
let endFile = end.file
return startRank == end.rank
&& start.file == ._e
&& (endFile == ._c || endFile == ._g)
}
}
infix operator >>>
/// Returns `true` if both moves are the same.
public func == (lhs: Move, rhs: Move) -> Bool {
return lhs.start == rhs.start && lhs.end == rhs.end
}
/// Returns a `Move` from the two squares.
public func >>> (start: Square, end: Square) -> Move {
return Move(start: start, end: end)
}
/// Returns a `Move` from the two locations.
public func >>> (start: Location, rhs: Location) -> Move {
return Square(location: start) >>> Square(location: rhs)
}
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