//
//  StatusInfoView.swift
//  Feels
//
//  Created by Trey Tartt on 7/8/22.
//

import SwiftUI
import StoreKit

struct StatusInfoView: View {
    @EnvironmentObject var iapManager: IAPManager

    let product: Product
    let status: Product.SubscriptionInfo.Status
    
    var body: some View {
        ScrollView {
            Text(statusDescription())
                .frame(maxWidth: .infinity, alignment: .center)
                .font(.body)
        }
        .frame(maxWidth: .infinity)
        .frame(height: 75)
    }
    
    //Build a string description of the subscription status to display to the user.
    fileprivate func statusDescription() -> String {
        guard case .verified(let renewalInfo) = status.renewalInfo,
              case .verified(let transaction) = status.transaction else {
            return "The App Store could not verify your subscription status."
        }
        
        var description = ""
        
        switch status.state {
        case .subscribed:
            let renewToProduct: Product?
            let renewalInfo: RenewalInfo?
            
            renewalInfo = try? iapManager.checkVerified(status.renewalInfo)
            renewToProduct = iapManager.subscriptions.first(where: {
                $0.key.id == renewalInfo?.autoRenewPreference
            })?.key

            description = subscribedDescription(expirationDate: transaction.expirationDate,
                                                willRenew: renewalInfo?.willAutoRenew ?? false,
                                                willRenewTo: renewToProduct)
        case .expired:
            if let expirationDate = transaction.expirationDate,
               let expirationReason = renewalInfo.expirationReason {
                description = expirationDescription(expirationReason, expirationDate: expirationDate)
            }
        case .revoked:
            if let revokedDate = transaction.revocationDate {
                description = "The App Store refunded your subscription to \(product.displayName) on \(revokedDate.formattedDate())."
            }
        case .inGracePeriod:
            description = gracePeriodDescription(renewalInfo)
        case .inBillingRetryPeriod:
            description = billingRetryDescription()
        default:
            break
        }
        return description
    }
    
    fileprivate func billingRetryDescription() -> String {
        var description = "The App Store could not confirm your billing information for \(product.displayName)."
        description += " Please verify your billing information to resume service."
        return description
    }
    
    fileprivate func gracePeriodDescription(_ renewalInfo: RenewalInfo) -> String {
        var description = "The App Store could not confirm your billing information for \(product.displayName)."
        if let untilDate = renewalInfo.gracePeriodExpirationDate {
            description += " Please verify your billing information to continue service after \(untilDate.formattedDate())"
        }
        
        return description
    }
    
    fileprivate func subscribedDescription(expirationDate: Date?, willRenew: Bool, willRenewTo: Product?) -> String {
        var description = "You are currently subscribed to \(product.displayName)"
        
        if let expirationDate = expirationDate {
            description += ", which will expire on \(expirationDate.formattedDate()),"
        }
        
        if willRenew {
            if let willRenewTo = willRenewTo {
                if willRenewTo == product {
                    description += " and will auto renew."
                } else {
                    description += " and will auto renew to \(willRenewTo.displayName) at \(willRenewTo.displayPrice)."
                }
            }
        } else {
            description += " and will NOT auto renew."
        }
        
        return description
    }
    
    fileprivate func renewalDescription(_ renewalInfo: RenewalInfo, _ expirationDate: Date) -> String {
        var description = ""
        
        if let newProductID = renewalInfo.autoRenewPreference {
            if let newProduct = iapManager.subscriptions.first(where: { $0.key.id == newProductID }) {
                description += "\nYour subscription to \(newProduct.key.displayName)"
                description += " will begin when your current subscription expires on \(expirationDate.formattedDate())."
            }
        } else if renewalInfo.willAutoRenew {
            description += "\nWill auto renew on: \(expirationDate.formattedDate())."
        }
        
        return description
    }
    
    //Build a string description of the `expirationReason` to display to the user.
    fileprivate func expirationDescription(_ expirationReason: RenewalInfo.ExpirationReason, expirationDate: Date) -> String {
        var description = ""
        
        switch expirationReason {
        case .autoRenewDisabled:
            if expirationDate > Date() {
                description += "Your subscription to \(product.displayName) will expire on \(expirationDate.formattedDate())."
            } else {
                description += "Your subscription to \(product.displayName) expired on \(expirationDate.formattedDate())."
            }
        case .billingError:
            description = "Your subscription to \(product.displayName) was not renewed due to a billing error."
        case .didNotConsentToPriceIncrease:
            description = "Your subscription to \(product.displayName) was not renewed due to a price increase that you disapproved."
        case .productUnavailable:
            description = "Your subscription to \(product.displayName) was not renewed because the product is no longer available."
        default:
            description = "Your subscription to \(product.displayName) was not renewed."
        }
        
        return description
    }
}