import Foundation
import HelperShared
import Localization
import Metrics
import Observation

/// 刷新 DNS、释放内存、设置 DNS 服务器：已安装辅助工具时直接执行，否则弹出系统管理员授权
@MainActor
@Observable
public final class MaintenanceController {
    public struct Outcome: Equatable {
        let text: String
        let isError: Bool
    }

    public private(set) var running: MaintenanceCommand?
    public private(set) var outcomes: [MaintenanceCommand: Outcome] = [:]
    public private(set) var isApplyingDNS = false
    public private(set) var dnsOutcome: Outcome?

    @ObservationIgnored private let helper: HelperClient
    @ObservationIgnored private let tally: CleanupTally

    init(helper: HelperClient, tally: CleanupTally) {
        self.helper = helper
        self.tally = tally
    }

    func run(_ command: MaintenanceCommand) async {
        guard running == nil else { return }
        running = command
        defer { running = nil }

        let before = MemorySampler().sample()
        helper.refreshStatus()
        let prompt = command == .flushDNS ? tr("OpenStats 需要管理员权限来刷新 DNS 缓存。") : tr("OpenStats 需要管理员权限来释放内存。")
        let error = helper.isReady
            ? await helper.run(command)
            : await Self.runWithAdministratorPrompt(shell: command.shellCommand, prompt: prompt)

        if let error {
            Log.app.error("\(command.rawValue, privacy: .public) 失败：\(error, privacy: .public)")
            outcomes[command] = Outcome(text: error, isError: error != Self.cancelled)
            return
        }
        tally.recordOptimization()
        switch command {
        case .flushDNS:
            outcomes[command] = Outcome(text: tr("DNS 缓存已刷新"), isError: false)
        case .purgeMemory:
            let after = MemorySampler().sample()
            let freed = (before?.cached ?? 0) > (after?.cached ?? 0) ? before!.cached - after!.cached : 0
            outcomes[command] = Outcome(text: freed > 0 ? tr("已释放 \(Format.bytes(freed)) 缓存内存") : tr("内存已整理"), isError: false)
        }
    }

    /// 为网络服务设置 DNS（空数组为恢复自动），完成后刷新 DNS 缓存
    func setDNSServers(_ servers: [String], service: String) async {
        guard !isApplyingDNS else { return }
        guard DNSConfiguration.isValidServiceName(service), servers.count <= DNSConfiguration.maxServers,
              servers.allSatisfy(DNSConfiguration.isValidAddress) else {
            dnsOutcome = Outcome(text: tr("DNS 地址格式不正确"), isError: true)
            return
        }
        isApplyingDNS = true
        dnsOutcome = nil
        defer { isApplyingDNS = false }

        let error: String?
        if let version = await helper.remoteProtocolVersion(), version >= 3 {
            error = await helper.setDNSServers(service: service, servers: servers)
        } else {
            // killall 在 mDNSResponder 恰好重启时可能返回非 0，不视为失败
            let shell = DNSConfiguration.shellCommand(service: service, servers: servers)
                + " && /usr/bin/dscacheutil -flushcache && (/usr/bin/killall -HUP mDNSResponder || true)"
            error = await Self.runWithAdministratorPrompt(shell: shell, prompt: tr("OpenStats 需要管理员权限来修改“\(service)”的 DNS。"))
        }
        if let error {
            Log.network.error("设置 DNS 失败：\(error, privacy: .public)")
            dnsOutcome = Outcome(text: error, isError: error != Self.cancelled)
        } else {
            dnsOutcome = Outcome(text: servers.isEmpty ? tr("已恢复自动获取 DNS") : tr("DNS 已设置为 \(servers.joined(separator: tr("、")))"), isError: false)
        }
    }

    nonisolated static var cancelled: String { tr("已取消") }

    /// 未安装辅助工具时的回退：通过 AppleScript 请求一次性管理员授权执行命令。
    /// 命令只由固定路径与已校验的参数拼成，这里再做 AppleScript 字符串转义
    static func runWithAdministratorPrompt(shell: String, prompt: String) async -> String? {
        let escape = { (text: String) in text.replacingOccurrences(of: "\\", with: "\\\\").replacingOccurrences(of: "\"", with: "\\\"") }
        let script = "do shell script \"\(escape(shell))\" with administrator privileges with prompt \"\(escape(prompt))\""
        return await Task.detached {
            let process = Process()
            process.executableURL = URL(fileURLWithPath: "/usr/bin/osascript")
            process.arguments = ["-e", script]
            let errorPipe = Pipe()
            process.standardError = errorPipe
            process.standardOutput = Pipe()
            do {
                try process.run()
            } catch {
                return error.localizedDescription
            }
            let data = errorPipe.fileHandleForReading.readDataToEndOfFile()
            process.waitUntilExit()
            guard process.terminationStatus != 0 else { return nil }
            let message = String(decoding: data, as: UTF8.self)
            // -128：用户在授权对话框中点了取消
            return message.contains("-128") ? cancelled : message.trimmingCharacters(in: .whitespacesAndNewlines)
        }.value
    }
}