//
//  BlackjackEngine.swift
//  Blackjack
//
//  Core game logic for Blackjack.
//

import Foundation
import CasinoKit

/// Manages the Blackjack game rules and shoe.
@Observable
@MainActor
final class BlackjackEngine {
    // MARK: - Properties
    
    /// The card shoe.
    private(set) var shoe: Deck
    
    /// Number of decks in the shoe.
    let deckCount: Int
    
    /// Settings reference for rule variations.
    private let settings: GameSettings
    
    /// Cards remaining in shoe.
    var cardsRemaining: Int {
        shoe.cardsRemaining
    }
    
    /// Whether the shoe needs reshuffling (below 25% remaining).
    var needsReshuffle: Bool {
        let threshold = (52 * deckCount) / 4
        return cardsRemaining < threshold
    }
    
    // MARK: - Initialization
    
    init(settings: GameSettings) {
        self.settings = settings
        self.deckCount = settings.deckCount.rawValue
        self.shoe = Deck(deckCount: deckCount)
        shoe.shuffle()
    }
    
    // MARK: - Shoe Management
    
    /// Reshuffles the shoe.
    func reshuffle() {
        shoe = Deck(deckCount: deckCount)
        shoe.shuffle()
    }
    
    /// Deals a single card from the shoe.
    func dealCard() -> Card? {
        shoe.draw()
    }
    
    // MARK: - Hand Evaluation
    
    /// Determines if dealer should hit based on rules.
    func dealerShouldHit(hand: BlackjackHand) -> Bool {
        let value = hand.value
        
        if value < 17 {
            return true
        }
        
        if value == 17 && hand.isSoft && settings.dealerHitsSoft17 {
            return true
        }
        
        return false
    }
    
    /// Determines the result of a player hand against dealer.
    func determineResult(playerHand: BlackjackHand, dealerHand: BlackjackHand) -> HandResult {
        let playerValue = playerHand.value
        let dealerValue = dealerHand.value
        
        // Player busted
        if playerHand.isBusted {
            return .bust
        }
        
        // Player has blackjack
        if playerHand.isBlackjack {
            if dealerHand.isBlackjack {
                return .push
            }
            return .blackjack
        }
        
        // Dealer busted
        if dealerHand.isBusted {
            return .win
        }
        
        // Dealer has blackjack (player doesn't)
        if dealerHand.isBlackjack {
            return .lose
        }
        
        // Compare values
        if playerValue > dealerValue {
            return .win
        } else if playerValue < dealerValue {
            return .lose
        } else {
            return .push
        }
    }
    
    /// Calculates payout for a hand result.
    func calculatePayout(bet: Int, result: HandResult, isDoubled: Bool) -> Int {
        let effectiveBet = isDoubled ? bet * 2 : bet
        
        switch result {
        case .blackjack:
            return Int(Double(bet) * settings.blackjackPayout) + bet
        case .win:
            return effectiveBet * 2
        case .push:
            return effectiveBet
        case .lose, .bust:
            return 0
        case .surrender:
            return bet / 2
        case .insuranceWin:
            return bet * 3  // 2:1 + original bet
        case .insuranceLose:
            return 0
        }
    }
    
    // MARK: - Action Availability
    
    /// Whether player can double down on this hand.
    func canDoubleDown(hand: BlackjackHand, balance: Int) -> Bool {
        guard hand.cards.count == 2 else { return false }
        guard !hand.isDoubledDown else { return false }
        guard balance >= hand.bet else { return false }
        
        // After split, check DAS rule
        if hand.isSplit && !settings.doubleAfterSplit {
            return false
        }
        
        return true
    }
    
    /// Whether player can split this hand.
    func canSplit(hand: BlackjackHand, balance: Int, currentSplitCount: Int) -> Bool {
        guard hand.canSplit else { return false }
        guard balance >= hand.bet else { return false }
        guard currentSplitCount < 3 else { return false }  // Max 4 hands
        
        // Check resplit aces
        if hand.isSplit && hand.cards.first?.rank == .ace && !settings.resplitAces {
            return false
        }
        
        return true
    }
    
    /// Whether player can surrender.
    func canSurrender(hand: BlackjackHand) -> Bool {
        guard settings.lateSurrender else { return false }
        guard hand.cards.count == 2 else { return false }
        guard !hand.isSplit else { return false }
        return true
    }
    
    /// Whether insurance should be offered.
    func shouldOfferInsurance(dealerUpCard: Card) -> Bool {
        settings.insuranceAllowed && dealerUpCard.rank == .ace
    }
    
    // MARK: - Basic Strategy Hint
    
    /// Returns the basic strategy recommendation.
    func getHint(playerHand: BlackjackHand, dealerUpCard: Card) -> String {
        let playerValue = playerHand.value
        let dealerValue = dealerUpCard.blackjackValue
        let isSoft = playerHand.isSoft
        let canDouble = playerHand.cards.count == 2
        
        // Pairs
        if playerHand.canSplit {
            let pairRank = playerHand.cards[0].rank
            switch pairRank {
            case .ace, .eight:
                return String(localized: "Split")
            case .ten, .jack, .queen, .king:
                return String(localized: "Stand")
            case .five:
                return canDouble ? String(localized: "Double") : String(localized: "Hit")
            case .four:
                return (dealerValue == 5 || dealerValue == 6) ? String(localized: "Split") : String(localized: "Hit")
            case .two, .three, .seven:
                return dealerValue <= 7 ? String(localized: "Split") : String(localized: "Hit")
            case .six:
                return dealerValue <= 6 ? String(localized: "Split") : String(localized: "Hit")
            case .nine:
                return (dealerValue == 7 || dealerValue >= 10) ? String(localized: "Stand") : String(localized: "Split")
            }
        }
        
        // Soft hands
        if isSoft {
            if playerValue >= 19 {
                return String(localized: "Stand")
            }
            if playerValue == 18 {
                if dealerValue >= 9 {
                    return String(localized: "Hit")
                }
                return String(localized: "Stand")
            }
            // Soft 17 or less
            return String(localized: "Hit")
        }
        
        // Hard hands
        if playerValue >= 17 {
            return String(localized: "Stand")
        }
        if playerValue >= 13 && dealerValue <= 6 {
            return String(localized: "Stand")
        }
        if playerValue == 12 && dealerValue >= 4 && dealerValue <= 6 {
            return String(localized: "Stand")
        }
        if playerValue == 11 && canDouble {
            return String(localized: "Double")
        }
        if playerValue == 10 && dealerValue <= 9 && canDouble {
            return String(localized: "Double")
        }
        if playerValue == 9 && dealerValue >= 3 && dealerValue <= 6 && canDouble {
            return String(localized: "Double")
        }
        
        return String(localized: "Hit")
    }
}