//
//  AccountDeletionViewModels.swift
//  suixinkan
//

import Foundation

/// 注销资产核验页 ViewModel，管理资产快照、确认状态与验证页上下文。
final class AccountDeletionViewModel {
    private let service: any AccountDeletionServing

    let username: String
    private(set) var assets: [AccountDeletionAssetSummary] = []
    private(set) var consequences: [String] = []
    private(set) var isAcknowledged = false
    private(set) var isLoading = false
    private(set) var errorMessage: String?

    var onStateChange: (() -> Void)?

    /// 创建注销核验 ViewModel，默认读取当前登录账号并使用共享 Mock 服务。
    init(
        username: String? = AccountDeletionIdentity.currentUsername(),
        service: any AccountDeletionServing = AccountDeletionMockService.shared
    ) {
        self.username = AccountDeletionIdentity.normalizedUsername(username ?? "")
        self.service = service
    }

    /// 勾选后才允许进入短信验证。
    var isContinueEnabled: Bool {
        !assets.isEmpty && isAcknowledged && !isLoading
    }

    /// 资产加载完成后主按钮保持可点击，未勾选时由业务校验给出明确提示。
    var isContinueButtonEnabled: Bool {
        !assets.isEmpty && !isLoading
    }

    /// 拉取注销前置核验结果。
    func load() async {
        guard !isLoading else { return }
        isLoading = true
        errorMessage = nil
        notifyStateChange()
        defer {
            isLoading = false
            notifyStateChange()
        }

        do {
            let precheck = try await service.loadPrecheck(username: username)
            assets = precheck.assets
            consequences = precheck.consequences
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    /// 切换用户对注销影响的确认状态。
    func toggleAcknowledgement() {
        isAcknowledged.toggle()
        notifyStateChange()
    }

    /// 生成短信验证页上下文。
    func makeVerificationContext() throws -> AccountDeletionVerificationContext {
        guard isContinueEnabled else {
            throw AccountDeletionError.incompleteAcknowledgement
        }
        guard !username.isEmpty else {
            throw AccountDeletionError.missingIdentity
        }
        return AccountDeletionVerificationContext(
            username: username,
            maskedPhone: AccountDeletionIdentity.maskedPhone(username),
            assets: assets
        )
    }

    /// 使用当前服务创建短信验证 ViewModel，保持同一套 Mock 状态。
    func makeVerificationViewModel() throws -> AccountDeletionVerificationViewModel {
        try AccountDeletionVerificationViewModel(
            context: makeVerificationContext(),
            service: service
        )
    }

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

/// 注销短信验证页 ViewModel，负责验证码发送、校验和提交申请。
final class AccountDeletionVerificationViewModel {
    private let service: any AccountDeletionServing
    private let clientRequestID = UUID()

    let context: AccountDeletionVerificationContext
    private(set) var verificationCode = ""
    private(set) var isSendingCode = false
    private(set) var isSubmitting = false
    private(set) var hasSentCode = false
    private(set) var errorMessage: String?

    var onStateChange: (() -> Void)?

    /// 创建短信验证 ViewModel。
    init(
        context: AccountDeletionVerificationContext,
        service: any AccountDeletionServing = AccountDeletionMockService.shared
    ) throws {
        guard !context.username.isEmpty else {
            throw AccountDeletionError.missingIdentity
        }
        self.context = context
        self.service = service
    }

    /// 验证码满足6位数字且当前未提交时允许继续。
    var isSubmitEnabled: Bool {
        verificationCode.count == 6
            && verificationCode.allSatisfy(\.isNumber)
            && !isSubmitting
    }

    /// 更新用户输入的验证码，只保留前6位数字。
    func updateVerificationCode(_ value: String) {
        verificationCode = String(value.filter(\.isNumber).prefix(6))
        errorMessage = nil
        notifyStateChange()
    }

    /// 发送 Mock 短信验证码。
    func sendVerificationCode() async {
        guard !isSendingCode else { return }
        isSendingCode = true
        errorMessage = nil
        notifyStateChange()
        defer {
            isSendingCode = false
            notifyStateChange()
        }

        do {
            try await service.sendVerificationCode(to: context.username)
            hasSentCode = true
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    /// 提交注销申请并返回计划删除时间。
    func submit() async throws -> AccountDeletionRequest {
        guard isSubmitEnabled else {
            throw AccountDeletionError.invalidVerificationCode
        }
        guard !isSubmitting else { throw CancellationError() }

        isSubmitting = true
        errorMessage = nil
        notifyStateChange()
        defer {
            isSubmitting = false
            notifyStateChange()
        }

        do {
            return try await service.submitDeletion(
                username: context.username,
                verificationCode: verificationCode,
                acknowledgedAssetKinds: Set(context.assets.map(\.kind)),
                clientRequestID: clientRequestID
            )
        } catch {
            errorMessage = error.localizedDescription
            throw error
        }
    }

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