import SwiftUI
import Observation
import DSKit
import AIFabric

/// The single app-state store driving the 3-pane shell. @MainActor @Observable: mutations are
/// main-isolated; the DSClient returns Sendable models; AIService is an actor.
@MainActor
@Observable
public final class AppModel {
    public enum Section: String, CaseIterable, Identifiable, Hashable {
        case dashboard, documents, search, ask, memos, digest
        public var id: String { rawValue }
        public var title: String {
            switch self {
            case .dashboard: return "대시보드"
            case .documents: return "문서"
            case .search: return "검색"
            case .ask: return "질문"
            case .memos: return "메모"
            case .digest: return "뉴스"
            }
        }
    }

    /// 인증 단계: 시작 시 refresh 쿠키로 무로그인 복귀 시도(checking) → 실패 시 로그인 화면(loggedOut)
    /// → 성공 시 셸(ready). Fixture 클라이언트는 refresh 가 fixture 토큰을 돌려줘 곧장 ready.
    public enum AuthPhase: Equatable { case checking, loggedOut, ready }

    public var section: Section = .dashboard
    public var selectedDocumentID: Int?
    public var selectedMemoID: Int?

    public var tree: [DomainTreeNode] = []
    public var stats: CategoryCounts?
    public var documentList: [DocumentResponse] = []
    public var documentDetail: DocumentDetailResponse?
    public var searchQuery: String = ""
    public var searchResponse: SearchResponse?
    public var askQuery: String = ""
    public var askResult: AIResult?
    public var askMeta: DSKit.AskResponse? // qualified: AIFabric also defines an AskResponse
    public var memoList: [MemoResponse] = []
    public var memoDetail: MemoResponse?
    public var digest: DigestResponse?
    public var errorText: String?

    public private(set) var authPhase: AuthPhase = .checking
    /// 로그인 화면에 노출되는 실패 사유 (재시도 시 소거).
    public var loginError: String?
    /// bootstrap single-shot 가드 (취소 시에만 되돌림).
    private var didBootstrap = false

    let client: any DSClient
    let ai: AIService
    /// DS base — 다운로드 등 파생 URL 의 단일 기준 (live()/preview 가 주입).
    let base: DSBaseURL
    /// 현재 access 토큰 (다운로드 ?token= 용). bootstrap/login 시 갱신.
    public private(set) var accessToken: String = ""

    public init(client: any DSClient, ai: AIService, base: DSBaseURL = .publicTLS) {
        self.client = client
        self.ai = ai
        self.base = base
    }

    @MainActor
    public static var preview: AppModel {
        AppModel(client: FixtureDSClient(), ai: AIService(router: AppAIComposition.mockRouter()))
    }

    /// 본 서버(GPU DS) 라이브 결선: LiveDSClient + 실 AIFabric 라우터(realRouter). ask 토큰 closure 는
    /// client 의 TokenProvider 단일 소스(401 refresh 회전 반영). 토큰 영속화 기본 = InMemory —
    /// access 토큰은 15분 수명이라 영속 가치가 없고, 재시작 복귀는 HttpOnly refresh 쿠키(7일,
    /// HTTPCookieStorage 자동 보관)가 담당. Keychain 은 서명 배포 빌드에서 주입.
    @MainActor
    public static func live(
        base: DSBaseURL = .publicTLS,
        persistence: TokenPersistence = InMemoryTokenStore()
    ) -> AppModel {
        let client = LiveDSClient(base: base, persistence: persistence)
        let router = AppAIComposition.realRouter(base: base) { await client.currentAccessToken() }
        return AppModel(client: client, ai: AIService(router: router), base: base)
    }

    /// 앱 시작 1회 (single-shot — 새 창/뷰 재생성의 .task 재발화에도 중복 실행 안 함):
    /// refresh 쿠키로 토큰 복귀 시도. 401(쿠키 없음/만료) = 조용히 loggedOut(정상 신규 로그인 흐름) /
    /// 그 외(서버 도달 불가 등) = loggedOut + 사유를 loginError 로 노출(no-silent-fallback) /
    /// task 취소(창 닫힘) = 미시도로 복원해 다음 appear 에서 재시도.
    public func bootstrap() async {
        guard !didBootstrap else { return }
        didBootstrap = true
        // authPhase 는 초기값 .checking 그대로 사용 — 여기서 리셋하지 않아 ready 세션의 UI 플립 방지.
        do {
            let token = try await client.refresh().accessToken
            accessToken = token
            authPhase = .ready
            await loadInitial()
        } catch let e as DSError where e.isAuthExpired {
            authPhase = .loggedOut
        } catch {
            if Task.isCancelled {
                didBootstrap = false
                return
            }
            authPhase = .loggedOut
            loginError = (error as? LocalizedError)?.errorDescription ?? "\(error)"
        }
    }

    /// 정식 로그인 (POST /auth/login → JWT). totp 는 개행/내부 공백 제거 후 비어 있으면 미전송.
    public func login(username: String, password: String, totp: String?) async {
        loginError = nil
        do {
            let code = totp.map {
                $0.replacingOccurrences(of: " ", with: "").trimmingCharacters(in: .whitespacesAndNewlines)
            }
            let response = try await client.login(
                username: username,
                password: password,
                totpCode: (code?.isEmpty ?? true) ? nil : code
            )
            accessToken = response.accessToken
            authPhase = .ready
            await loadInitial()
        } catch {
            loginError = (error as? LocalizedError)?.errorDescription ?? "\(error)"
        }
    }

    public func loadInitial() async {
        await guarded { self.tree = try await self.client.documentTree() }
        await guarded { self.stats = try await self.client.categoryCounts() }
        await guarded { self.documentList = try await self.client.documents(DocumentListQuery()).items }
        await guarded { self.memoList = try await self.client.memos(MemoListQuery()).items }
        await guarded { self.digest = try await self.client.digest(date: nil, country: nil) }
    }

    public func openDocument(_ id: Int) async {
        selectedDocumentID = id
        await guarded { self.documentDetail = try await self.client.document(id: id) }
    }

    public func runSearch() async {
        guard !searchQuery.isEmpty else { return }
        await guarded { self.searchResponse = try await self.client.search(q: self.searchQuery, mode: .hybrid, page: 1, debug: false) }
    }

    public func runAsk(backend: AIProviderID?) async {
        guard !askQuery.isEmpty else { return }
        askResult = await ai.corpusAsk(question: askQuery, explicit: backend)
        await guarded { self.askMeta = try await self.client.ask(q: self.askQuery, limit: nil, backend: nil, debug: false) }
    }

    public func openMemo(_ id: Int) async {
        selectedMemoID = id
        await guarded { self.memoDetail = try await self.client.memo(id: id) }
    }

    public func downloadURL(for doc: DocumentResponse) -> URL? {
        guard doc.hasDownloadableOriginal, !accessToken.isEmpty else { return nil }
        return DSDownload.fileURL(base: base, documentID: doc.id, accessToken: accessToken)
    }

    private func guarded(_ work: () async throws -> Void) async {
        do {
            try await work()
        } catch let e as DSError where e.isAuthExpired {
            // LiveDSClient 내부 refresh+재시도까지 실패(refresh 쿠키 만료/폐기) — 세션 종료로 강등.
            authPhase = .loggedOut
            loginError = "세션이 만료되었습니다. 다시 로그인하세요."
        } catch {
            errorText = (error as? LocalizedError)?.errorDescription ?? "\(error)"
        }
        await syncAccessToken()
    }

    /// 401 회전(LiveDSClient 내부 refresh) 후 다운로드 ?token= 사본 재동기화 — guarded 가 모든
    /// 데이터 호출의 깔때기이므로 회전 발생 지점 직후 항상 거친다. 토큰 단일 소스 = TokenProvider.
    private func syncAccessToken() async {
        guard let live = client as? LiveDSClient, let t = await live.currentAccessToken() else { return }
        if t != accessToken { accessToken = t }
    }
}