import Foundation

/// A `Sendable` snapshot of a buyer's offer on a listing.
public struct Offer: Sendable, Equatable {

    // MARK: Constants

    /// The share of the asking price under which an offer is declined outright.
    public static let floorShare = 0.8

    /// How long an offer binds its buyer: 48 hours.
    public static let lifetime: TimeInterval = 172_800

    // MARK: Properties

    /// The offer's identifier.
    public let id: UUID
    /// The identifier of the conversation the offer was made in.
    public let conversationID: UUID
    /// The listing offered on.
    public let listing: Listing
    /// The account offering.
    public let buyer: User
    /// The amount offered, in euro cents.
    public let amountCents: Int
    /// Where the offer stands; an open offer past its expiry reads as expired.
    public let status: Status
    /// When the offer was made.
    public let createdAt: Date
    /// When the offer stops binding its buyer.
    public let expiresAt: Date

    // MARK: Initializers

    public init(
        id: UUID,
        conversationID: UUID,
        listing: Listing,
        buyer: User,
        amountCents: Int,
        status: Status,
        createdAt: Date,
        expiresAt: Date
    ) {
        self.id = id
        self.conversationID = conversationID
        self.listing = listing
        self.buyer = buyer
        self.amountCents = amountCents
        self.status = status
        self.createdAt = createdAt
        self.expiresAt = expiresAt
    }

}

// MARK: - Enumerations

public extension Offer {
    /// Where an offer stands.
    enum Status: String, Sendable {
        /// Waiting for the seller's answer.
        case open
        /// Accepted: a sale record was opened.
        case accepted
        /// Declined by the seller.
        case declined
        /// Left unanswered past its expiry, or overtaken by a sale of the listing.
        case expired
    }
}

// MARK: - Extensions

public extension Offer {

    // MARK: Methods

    /// The lowest offer a listing's seller hears, in euro cents: ``floorShare`` of the asking price, rounded up to a whole euro.
    /// - Parameter askingCents: the listing's asking price, in euro cents.
    static func floor(
        forAsking askingCents: Int
    ) -> Int {
        Int((Double(askingCents) * floorShare / 100).rounded(.up)) * 100
    }

}