swift-sgf/Sources/SGF/SGFCursor.swift

//
//  SGFCursor.swift
//  ChildOfZero
//
//  Created by 市川雄二 on 2018/10/23.
//  Copyright © 2018 New 3 Rs. All rights reserved.
//

import Foundation

/// Cursor to traverse SGF collection
open class SGFCursor {
    public let collection: [SGFNode]
    public var current: SGFNode?
    public var history = [SGFNode]()
    public var moveNumber: Int {
        get {
            return history.count
        }
    }
    
    public init(_ collection: [SGFNode]) {
        self.collection = collection
        current = collection.first
    }
    
    @discardableResult
    open func forward(child: Int = 0) -> SGFNode? {
        if let c = current {
            if child >= c.children.count {
                return nil
            }
            history.append(c)
            current = c.children[child]
            return current
        } else {
            if child >= collection.count {
                return nil
            }
            current = collection[child]
            return current
        }
    }
    
    @discardableResult
    open func back() -> SGFNode? {
        if let node = history.popLast() {
            current = node
            return current
        } else {
            return nil
        }
    }

    open func toTop() {
        history = []
        current = collection[0]
    }

    /// 該当の手があれば進めて、なければ変化を追加する。
    open func play(color: String, value: String) {
        guard let c = current else {
            return
        }
        if let i = c.children.firstIndex(where: { $0.properties[color]?.first == value }) {
            forward(child: i)
        } else if c.children.count > 0 && c.children.allSatisfy({ $0.properties["B"] == nil && $0.properties["W"] == nil }) {
            // FGなどは先に進める
            forward()
            play(color: color, value: value)
        } else {
            history.append(c)
            let node = SGFNode()
            node.properties[color] = [value]
            c.children.append(node)
            current = node
        }
    }
    
    open func hasNext() -> Bool {
        guard let c = current else {
            return false
        }
        return c.children.count > 0
    }

    open func hasParent() -> Bool {
        return !history.isEmpty
    }

    @discardableResult
    open func removeCurrent() -> SGFNode? {
        let c = current
        if back() == nil {
            return nil
        }
        current?.children.removeAll { $0 === c }
        return c
    }
    
    open func toSgf() -> String {
        var root: SGFNode?
        if let copied: SGFNode = history.reduce(nil, { parent, node in
            let copied = SGFNode()
            copied.properties = node.properties
            if let p = parent {
                p.children.append(copied)
            } else {
                root = copied
            }
            return copied
        }) {
            let current = SGFNode()
            current.properties = self.current!.properties
            copied.children.append(current)
        } else {
            let node = SGFNode()
            node.properties = self.current!.properties
            root = node
        }
        return SGFEncoder.encode(collection: [root!])
    }
    
    open func shallowCopy() -> SGFCursor {
        let cursor = SGFCursor(collection)
        cursor.current = current
        cursor.history = history
        return cursor
    }
}