import CoreDomain
import CoreModel
import Observation

@MainActor
@Observable
public final class HomeViewModel {
    public private(set) var uiState: HomeUiState = .loading

    private let homeUseCase: HomeUseCase
    private var loadTask: Task<Void, Never>?

    public init(homeUseCase: HomeUseCase) {
        self.homeUseCase = homeUseCase
    }

    public func load() {
        // flatMapLatest 的等价：新 load 前先取消旧的观察。
        loadTask?.cancel()
        loadTask = Task { [weak self] in
            guard let self else { return }
            self.uiState = .loading
            do {
                for try await data in self.homeUseCase.observeHome() {
                    self.uiState = data.habits.isEmpty ? .empty : .success(data)
                }
            } catch is CancellationError {
                // 被更新的 load() 取代，保持当前状态即可。
            } catch {
                self.uiState = .error(error.localizedDescription)
            }
        }
    }
}