import Foundation

enum MoveValidator {
    /// True if the two cards have alternating colors (one red, one black).
    static func isAlternatingColor(_ card: Card, with other: Card) -> Bool {
        card.color != other.color
    }

    /// True if both cards share the same suit.
    static func isSameSuit(_ card: Card, as other: Card) -> Bool {
        card.suit == other.suit
    }

    /// True if card's rank is exactly one higher than target (for foundation building A→K).
    static func isAscending(_ card: Card, onto target: Card) -> Bool {
        card.rank.rawValue == target.rank.rawValue + 1
    }

    /// True if card's rank is exactly one lower than target (for tableau stacking K→A).
    static func isDescending(_ card: Card, onto target: Card) -> Bool {
        card.rank.rawValue == target.rank.rawValue - 1
    }

    /// True if the card is an Ace.
    static func isAce(_ card: Card) -> Bool {
        card.rank == .ace
    }

    /// True if the card is a King.
    static func isKing(_ card: Card) -> Bool {
        card.rank == .king
    }

    /// True if the card can be placed on a foundation pile (same suit, ascending).
    static func canPlaceOnFoundation(_ card: Card, topCard: Card?) -> Bool {
        guard let topCard else {
            return isAce(card)
        }
        return isSameSuit(card, as: topCard) && isAscending(card, onto: topCard)
    }
}