import Foundation

/// AI 修图任务列表状态，负责筛选、游标分页、去重和静默刷新。
final class TravelAlbumAIJobListViewModel {
    private(set) var items: [TravelAlbumAIJobSummary] = []
    private(set) var selectedFilter: TravelAlbumAIJobFilter = .all
    private(set) var isLoading = false
    private(set) var isRefreshing = false
    private(set) var isLoadingMore = false
    private(set) var errorMessage: String?
    private var nextCursor: String?
    private var hasMore = false

    var onStateChange: (() -> Void)?
    var onShowMessage: ((String) -> Void)?

    var containsInProgressJobs: Bool { items.contains { $0.status.isInProgress } }
    var canLoadMore: Bool { hasMore && !isLoadingMore }

    /// 选择筛选项并重新加载第一页。
    func selectFilter(_ filter: TravelAlbumAIJobFilter, api: any TravelAlbumServing) async {
        guard selectedFilter != filter else { return }
        selectedFilter = filter
        items = []
        notify()
        await loadFirstPage(api: api)
    }

    /// 首次加载或下拉刷新第一页。
    func loadFirstPage(api: any TravelAlbumServing, refreshing: Bool = false, silent: Bool = false) async {
        guard !isLoading && !isRefreshing else { return }
        if refreshing { isRefreshing = true } else if !silent { isLoading = true }
        errorMessage = nil
        notify()
        defer {
            isLoading = false
            isRefreshing = false
            notify()
        }
        await request(cursor: nil, reset: true, api: api, allowCursorRecovery: false, silent: silent)
    }

    /// 加载下一页。
    func loadMore(api: any TravelAlbumServing) async {
        guard canLoadMore, let cursor = nextCursor else { return }
        isLoadingMore = true
        notify()
        defer { isLoadingMore = false; notify() }
        await request(cursor: cursor, reset: false, api: api, allowCursorRecovery: true, silent: false)
    }

    private func request(
        cursor: String?,
        reset: Bool,
        api: any TravelAlbumServing,
        allowCursorRecovery: Bool,
        silent: Bool
    ) async {
        do {
            let response = try await api.aiRetouchJobList(
                statusGroup: selectedFilter,
                limit: 20,
                cursor: cursor
            )
            if reset {
                items = response.items
            } else {
                var known = Set(items.map(\.id))
                items += response.items.filter { known.insert($0.id).inserted }
            }
            nextCursor = response.nextCursor
            hasMore = response.hasMore && response.nextCursor?.isEmpty == false
            errorMessage = nil
        } catch is CancellationError {
            return
        } catch {
            let message = error.localizedDescription
            if allowCursorRecovery && message.localizedCaseInsensitiveContains("cursor") {
                nextCursor = nil
                hasMore = false
                await request(cursor: nil, reset: true, api: api, allowCursorRecovery: false, silent: silent)
                return
            }
            if items.isEmpty { errorMessage = message.isEmpty ? "任务加载失败" : message }
            if !silent { onShowMessage?(message.isEmpty ? "任务加载失败" : message) }
        }
    }

    private func notify() { onStateChange?() }
}

/// AI 修图任务详情状态，负责刷新、404 识别和终态判断。
final class TravelAlbumAIJobDetailViewModel {
    private(set) var detail: TravelAlbumAIJobDetail?
    private(set) var isLoading = false
    private(set) var isRefreshing = false
    private(set) var errorMessage: String?
    private(set) var isNotFound = false

    let batchId: Int
    var onStateChange: (() -> Void)?
    var onShowMessage: ((String) -> Void)?
    var onNotFound: (() -> Void)?

    init(batchId: Int) { self.batchId = batchId }

    var shouldPoll: Bool { detail?.status.isInProgress == true }

    /// 拉取任务详情；静默刷新失败时保留现有内容。
    func load(api: any TravelAlbumServing, refreshing: Bool = false, silent: Bool = false) async {
        guard batchId > 0, !isLoading && !isRefreshing else {
            if batchId <= 0 { markNotFound() }
            return
        }
        if refreshing { isRefreshing = true } else if detail == nil && !silent { isLoading = true }
        errorMessage = nil
        notify()
        defer {
            isLoading = false
            isRefreshing = false
            notify()
        }
        do {
            detail = try await api.aiRetouchJobInfo(batchId: batchId)
            isNotFound = false
        } catch is CancellationError {
            return
        } catch APIError.httpStatus(let status, _) where status == 404 {
            markNotFound()
        } catch {
            let message = error.localizedDescription.isEmpty ? "任务详情加载失败" : error.localizedDescription
            if detail == nil { errorMessage = message }
            if !silent { onShowMessage?(message) }
        }
    }

    private func markNotFound() {
        guard !isNotFound else { return }
        isNotFound = true
        onNotFound?()
    }

    private func notify() { onStateChange?() }
}