import Foundation

/// 进入业务页面前的核验结果，不将非空未知记录解释为任何已知注销状态。
enum StoreAccountDeregistrationAccessDecision: Equatable {
    case notChecked
    case checking
    case allowed
    case cooling
    case unresolved
    case failed(String)
    case obsolete
}

/// 进入业务前核验当前身份；冷静期只能查询或由用户明确撤销，不自动重新登录。
final class StoreAccountDeregistrationAccessViewModel {
    /// 未核验与查询失败都不能创建普通业务根页面。
    private(set) var decision: StoreAccountDeregistrationAccessDecision = .notChecked
    /// 防止同一页面重复发起查询。
    private(set) var isChecking = false
    /// 最近一次通过身份核验的服务端状态，用于冷静期展示和撤销前比对。
    private(set) var status: StoreAccountDeregistrationStatus?
    private var restrictionRevision = 0
    private var requiresSubmissionReconciliation: Bool
    private let submissionStore: (any StoreAccountDeregistrationSubmissionTracking)?
    private var observedCooling = false

    /// 本机存在待核实提交意图时，即使暂时返回 null 也不直接恢复普通业务。
    init(requiresSubmissionReconciliation: Bool = false,
         submissionStore: (any StoreAccountDeregistrationSubmissionTracking)? = nil) {
        self.submissionStore = submissionStore
        self.requiresSubmissionReconciliation = requiresSubmissionReconciliation
            || submissionStore?.hasUnresolvedSubmission == true
    }

    /// 新的限制信号优先于此前已发出的状态查询，防止旧正常响应覆盖新限制。
    func recordRestriction() {
        restrictionRevision += 1
        status = nil
        decision = .unresolved
    }

    /// 查询前后核对身份；旧身份响应和错误均不能决定新会话是否进入业务页。
    func verify(api: any StoreAccountDeregistrationStatusServing,
                isCurrentIdentity: @escaping @MainActor () -> Bool) async {
        guard !isChecking else { return }
        isChecking = true
        let revision = restrictionRevision
        decision = .checking
        status = nil
        defer { isChecking = false }
        guard await isCurrentIdentity() else { decision = .obsolete; return }
        do {
            let result = try await api.status()
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            apply(result)
        } catch {
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            if case APIError.serverCode(150015, _) = error {
                decision = .unresolved
            } else if case StoreAccountDeregistrationError.sessionChanged = error {
                decision = .obsolete
            } else {
                decision = .failed(error.localizedDescription)
            }
        }
    }

    /// 用户确认后先重查同一申请再撤销，结果丢失时保留限制，禁止自动重发 POST。
    func cancel(api: any StoreAccountDeregistrationServing,
                isCurrentIdentity: @escaping @MainActor () -> Bool) async {
        guard !isChecking, decision == .cooling, let recordID = status?.recordID else { return }
        isChecking = true
        let revision = restrictionRevision
        defer { isChecking = false }
        guard await isCurrentIdentity() else { decision = .obsolete; return }
        do {
            let current = try await api.status()
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            guard current.isCooling, current.recordID == recordID else { applyCancellationCheck(current); return }
            try await api.cancel()
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            let confirmed = try await api.status()
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            applyCancellationCheck(confirmed)
        } catch {
            guard await isCurrentIdentity() else { decision = .obsolete; return }
            guard restrictionRevision == revision else { return }
            status = nil
            decision = .failed("撤销结果尚未确认，请重新查询状态。\n" + error.localizedDescription)
        }
    }

    private func applyCancellationCheck(_ result: StoreAccountDeregistrationStatus) {
        // 曾查到冷静期后，旧 null/草稿不能证明撤销完成；须重新核实完整状态。
        guard result.isCooling || result.isCancelled else {
            status = result
            decision = .unresolved
            return
        }
        apply(result)
    }

    private func apply(_ result: StoreAccountDeregistrationStatus) {
        status = result
        if submissionStore?.hasUnresolvedSubmission == true { requiresSubmissionReconciliation = true }
        if result.isCancelled, submissionStore?.clearCancelledSubmission(matching: result) == true {
            requiresSubmissionReconciliation = false
        }
        if result.isCooling {
            observedCooling = true
            decision = .cooling
        } else {
            decision = result.permitsPreparation && !requiresSubmissionReconciliation
                && (!observedCooling || result.isCancelled) ? .allowed : .unresolved
        }
    }

    /// 150015 只影响发出请求时的同一门店身份凭证，不能按手机号传播限制。
    static func restrictionApplies(requestToken: String?, session: AppSessionStore) -> Bool {
        guard session.accountType == .storeUser,
              let requestToken, !requestToken.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else { return false }
        return requestToken == session.token
    }
}