import Foundation

enum MonthlyContributionStore {
    private static let key = "monthlyContributions"

    static func contribution(for sourceId: UUID) -> Decimal? {
        let dict = load()
        guard let raw = dict[sourceId.uuidString] else { return nil }
        return Decimal(raw)
    }

    static func setContribution(_ amount: Decimal?, for sourceId: UUID) {
        var dict = load()
        if let amount, amount > 0 {
            dict[sourceId.uuidString] = NSDecimalNumber(decimal: amount).doubleValue
        } else {
            dict.removeValue(forKey: sourceId.uuidString)
        }
        save(dict)
    }

    private static func load() -> [String: Double] {
        guard let data = UserDefaults.standard.data(forKey: key),
              let decoded = try? JSONDecoder().decode([String: Double].self, from: data) else { return [:] }
        return decoded
    }

    private static func save(_ dict: [String: Double]) {
        if let data = try? JSONEncoder().encode(dict) {
            UserDefaults.standard.set(data, forKey: key)
        }
    }
}