import CoreDomain
import CoreModel
import Observation

@MainActor
@Observable
public final class PlanViewModel {
    public private(set) var uiState: PlanUiState = .loading
    public var selectedType: PlanType = .weekly

    private let planUseCase: PlanUseCase
    private let sessionUseCase: SessionUseCase
    private var loadTask: Task<Void, Never>?
    private var dataTask: Task<Void, Never>?

    public init(planUseCase: PlanUseCase, sessionUseCase: SessionUseCase) {
        self.planUseCase = planUseCase
        self.sessionUseCase = sessionUseCase
    }

    public func load() {
        loadTask?.cancel()
        loadTask = Task { [weak self] in
            guard let self else { return }
            do {
                for try await isLoggedIn in self.sessionUseCase.observeIsLoggedIn() {
                    self.handleLoginState(isLoggedIn)
                }
            } catch is CancellationError {
            } catch {
                self.uiState = .error(error.localizedDescription)
            }
        }
    }

    public func selectType(_ type: PlanType) {
        guard type != selectedType else { return }
        selectedType = type
        reloadData()
    }

    private func handleLoginState(_ isLoggedIn: Bool) {
        dataTask?.cancel()
        guard isLoggedIn else {
            uiState = .loggedOut
            return
        }
        reloadData()
    }

    private func reloadData() {
        dataTask?.cancel()
        uiState = .loading
        dataTask = Task { [weak self] in
            guard let self else { return }
            do {
                for try await record in self.planUseCase.observePlan(type: self.selectedType) {
                    self.uiState = .success(record)
                }
            } catch is CancellationError {
            } catch {
                self.uiState = .error(error.localizedDescription)
            }
        }
    }
}