import Foundation

class SampleDataService {
    static let shared = SampleDataService()

    private init() {}

    func seedSampleData() {
        let context = CoreDataStack.shared.viewContext
        let sourceRepository = InvestmentSourceRepository(context: context)
        guard sourceRepository.sourceCount == 0 else { return }

        let categoryRepository = CategoryRepository(context: context)
        categoryRepository.createDefaultCategoriesIfNeeded()

        let accountRepository = AccountRepository(context: context)
        let account = accountRepository.createDefaultAccountIfNeeded()

        let snapshotRepository = SnapshotRepository(context: context)
        let goalRepository = GoalRepository(context: context)
        let transactionRepository = TransactionRepository(context: context)

        let categories = categoryRepository.categories
        let stocksCategory = categories.first { $0.name == "Stocks" } ?? categories.first!
        let cryptoCategory = categories.first { $0.name == "Crypto" } ?? categories.first!
        let realEstateCategory = categories.first { $0.name == "Real Estate" } ?? categories.first!

        let stocks = sourceRepository.createSource(
            name: "Index Fund",
            category: stocksCategory,
            account: account
        )
        let crypto = sourceRepository.createSource(
            name: "BTC",
            category: cryptoCategory,
            account: account
        )
        let realEstate = sourceRepository.createSource(
            name: "Rental Property",
            category: realEstateCategory,
            account: account
        )

        seedSnapshots(for: stocks, baseValue: 12000, monthlyIncrease: 450, repository: snapshotRepository)
        seedSnapshots(for: crypto, baseValue: 3000, monthlyIncrease: 250, repository: snapshotRepository)
        seedSnapshots(for: realEstate, baseValue: 80000, monthlyIncrease: 600, repository: snapshotRepository)

        seedMonthlyNotes()

        transactionRepository.createTransaction(
            source: stocks,
            type: .buy,
            date: Calendar.current.date(byAdding: .month, value: -3, to: Date()) ?? Date(),
            shares: 10,
            price: 400,
            amount: nil,
            notes: "Sample buy"
        )

        _ = goalRepository.createGoal(
            name: "1M Goal",
            targetAmount: 1_000_000,
            targetDate: nil,
            account: account
        )
    }

    private func seedSnapshots(
        for source: InvestmentSource,
        baseValue: Decimal,
        monthlyIncrease: Decimal,
        repository: SnapshotRepository
    ) {
        let calendar = Calendar.current
        for monthOffset in (0..<6).reversed() {
            let date = calendar.date(byAdding: .month, value: -monthOffset, to: Date()) ?? Date()
            let value = baseValue + Decimal(monthOffset) * monthlyIncrease
            repository.createSnapshot(
                for: source,
                date: date,
                value: value,
                contribution: monthOffset == 0 ? monthlyIncrease : nil,
                notes: nil
            )
        }
    }

    private func seedMonthlyNotes() {
        let calendar = Calendar.current
        let notes = [
            "Rebalanced slightly toward equities. Stayed calm despite noise.",
            "Focused on contributions. No major changes.",
            "Reviewed allocation drift and decided to hold positions."
        ]

        for (index, note) in notes.enumerated() {
            let date = calendar.date(byAdding: .month, value: -index, to: Date()) ?? Date()
            MonthlyCheckInStore.setNote(note, for: date)
        }
    }
}