//
//  OperatingAreaViewModel.swift
//  suixinkan
//
//  Created by Codex on 2026/6/25.
//

import Foundation

@MainActor
/// 运营区域 ViewModel，负责角色分流、围栏加载、解析和错误状态管理。
final class OperatingAreaViewModel {
    var onChange: (() -> Void)?
    private(set) var mode: OperatingAreaEntryMode? { didSet { onChange?() } }
    private(set) var loading = false { didSet { onChange?() } }
    private(set) var items: [OperatingAreaItem] = [] { didSet { onChange?() } }
    private(set) var fenceRings: [OperatingFenceRing] = [] { didSet { onChange?() } }
    private(set) var blockReason: OperatingAreaBlockReason? { didSet { onChange?() } }
    private(set) var errorMessage: String? { didSet { onChange?() } }

    /// 按当前账号和角色刷新运营区域。
    func reload(
        api: any OperatingAreaServing,
        accountContext: AccountContext,
        permissionContext: PermissionContext
    ) async {
        guard !loading else { return }
        guard let nextMode = resolveMode(accountContext: accountContext, permissionContext: permissionContext) else {
            return
        }

        mode = nextMode
        loading = true
        errorMessage = nil
        blockReason = nil
        defer { loading = false }

        do {
            let response: ListPayload<OperatingAreaItem>
            switch nextMode {
            case .storeAdmin(let storeId):
                response = try await api.storeBusinessArea(storeId: storeId)
            case .scenicAdmin(let scenicId):
                response = try await api.scenicAdminBusinessArea(scenicId: scenicId)
            }
            apply(items: response.list, mode: nextMode)
        } catch {
            resetLoadedData()
            let message = error.localizedDescription
            errorMessage = message
            blockReason = .backendMessage(message)
        }
    }

    /// 根据当前上下文解析运营区域入口模式。
    @discardableResult
    func resolveMode(accountContext: AccountContext, permissionContext: PermissionContext) -> OperatingAreaEntryMode? {
        let roleName = permissionContext.currentRole?.name.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
        let lowercaseRoleName = roleName.lowercased()
        let isStoreRole = roleName.contains("店铺") || roleName.contains("门店") || lowercaseRoleName.contains("store")
        let isScenicRole = roleName.contains("景区") || lowercaseRoleName.contains("scenic")

        if isStoreRole {
            guard let storeId = accountContext.currentStore?.id, storeId > 0 else {
                setBlocked(.missingStore)
                return nil
            }
            mode = .storeAdmin(storeId: storeId)
            blockReason = nil
            return mode
        }

        if isScenicRole {
            guard let scenicId = accountContext.currentScenic?.id, scenicId > 0 else {
                setBlocked(.missingScenic)
                return nil
            }
            mode = .scenicAdmin(scenicId: scenicId)
            blockReason = nil
            return mode
        }

        if let storeId = accountContext.currentStore?.id, storeId > 0 {
            mode = .storeAdmin(storeId: storeId)
            blockReason = nil
            return mode
        }

        if let scenicId = accountContext.currentScenic?.id, scenicId > 0 {
            mode = .scenicAdmin(scenicId: scenicId)
            blockReason = nil
            return mode
        }

        setBlocked(.unsupportedRole)
        return nil
    }

    /// 根据状态生成统计展示。
    var summary: (areaCount: Int, fenceCount: Int, currentStoreFenceCount: Int) {
        (
            areaCount: items.count,
            fenceCount: fenceRings.count,
            currentStoreFenceCount: fenceRings.filter(\.isCurrentStore).count
        )
    }

    /// 当前页面标题。
    var title: String {
        mode?.title ?? "运营区域"
    }

    /// apply 业务逻辑。
    private func apply(items: [OperatingAreaItem], mode: OperatingAreaEntryMode) {
        self.items = items
        if items.isEmpty {
            fenceRings = []
            blockReason = .emptyAreaList
            return
        }

        let currentStoreId: Int? = {
            guard case .storeAdmin(let storeId) = mode else { return nil }
            return storeId
        }()

        let parsed = items.flatMap { item -> [OperatingFenceRing] in
            OperatingAreaParser.parseToRings(item.businessMapArea).enumerated().compactMap { index, points in
                guard points.count >= 3 else { return nil }
                return OperatingFenceRing(
                    itemId: item.id,
                    regionName: item.name,
                    points: points,
                    isCurrentStore: currentStoreId == item.id,
                    ringIndex: index
                )
            }
        }
        fenceRings = parsed
        blockReason = parsed.isEmpty ? .noParsableFenceData : nil
    }

    /// setBlocked相关逻辑。
    private func setBlocked(_ reason: OperatingAreaBlockReason) {
        resetLoadedData()
        blockReason = reason
        errorMessage = nil
        loading = false
    }

    /// 重置LoadedData状态。
    private func resetLoadedData() {
        items = []
        fenceRings = []
    }
}