import Foundation

/// Builds the "Geräte" tab's LAN device list from a live router — DHCP leases enriched with the
/// physical port each device was learned on (ARP + bridge host table) — grouped into one table
/// per physical port, and drives the two write actions this tab offers: converting a dynamic
/// lease to a permanent static one, and removing a static lease again (RouterOS has no reverse
/// of "make-static", so "back to dynamic" is just removal — see `pendingStaticRemoval`).
@MainActor
final class DevicesViewModel: ObservableObject {
    @Published private(set) var devices: [LanDevice] = []
    @Published private(set) var portGroups: [DevicePortGroup] = []
    @Published private(set) var isLoading = false
    @Published private(set) var loadError: String?

    @Published var pendingStaticAssignment: LanDevice?
    /// The device whose static reservation the user is about to remove — RouterOS has no
    /// "make-dynamic" (confirmed against the official DHCP docs: only check-status, make-static,
    /// send-reconfigure exist for this menu), so "back to dynamic" is genuinely just removing the
    /// static lease; the device gets a fresh dynamic lease on its own next DHCP request, not
    /// immediately or necessarily on the same IP.
    @Published var pendingStaticRemoval: LanDevice?
    @Published private(set) var isApplying = false
    @Published private(set) var applyError: String?

    /// Set once a ping/traceroute/DNS lookup finishes — `.sheet(item:)` in `DevicesView` shows its
    /// raw output. `nil` in between runs and while one is in progress.
    @Published var networkToolResult: NetworkToolResult?
    @Published private(set) var isRunningNetworkTool = false
    @Published var networkToolError: String?
    /// Set once a port scan finishes — separate from `networkToolResult` since it needs a
    /// structured (colored per-port) display, not raw text. Runs directly from this Mac via
    /// `PortScanner`, not through the router — see its own doc comment for why.
    @Published var portScanResult: PortScanResult?

    private let connectionService: ConnectionService
    private let backupService: BackupService
    private let networkToolsService: NetworkToolsService

    init(
        connectionService: ConnectionService,
        backupService: BackupService = BackupService(),
        networkToolsService: NetworkToolsService = NetworkToolsService()
    ) {
        self.connectionService = connectionService
        self.backupService = backupService
        self.networkToolsService = networkToolsService
    }

    func runPing(for device: LanDevice) {
        runNetworkTool(title: "Ping: \(device.ipAddress)") { [networkToolsService] credentials in
            try await networkToolsService.ping(address: device.ipAddress, for: credentials)
        }
    }

    func runTraceroute(for device: LanDevice) {
        runNetworkTool(title: "Traceroute: \(device.ipAddress)") { [networkToolsService] credentials in
            try await networkToolsService.traceroute(address: device.ipAddress, for: credentials)
        }
    }

    func runDnsLookup(for device: LanDevice) {
        guard let hostName = device.hostName, !hostName.isEmpty else { return }
        runNetworkTool(title: "DNS-Auflösung: \(hostName)") { [networkToolsService] credentials in
            try await networkToolsService.resolve(hostname: hostName, for: credentials)
        }
    }

    func dismissNetworkToolError() {
        networkToolError = nil
    }

    /// Runs directly from this Mac (no router credentials involved), so it doesn't go through
    /// `runNetworkTool(title:action:)` — but still respects the same `isRunningNetworkTool` busy
    /// flag so a scan and a ping/traceroute/DNS lookup can't overlap and race on the same overlay.
    func runPortScan(for device: LanDevice) {
        guard !isRunningNetworkTool else { return }
        isRunningNetworkTool = true
        networkToolError = nil
        let label = (device.hostName?.isEmpty == false ? "\(device.hostName!) (\(device.ipAddress))" : device.ipAddress)
        Task {
            let results = await PortScanner.scan(host: device.ipAddress)
            portScanResult = PortScanResult(
                deviceLabel: label,
                entries: results.map { PortScanResult.Entry(port: $0.port.port, serviceName: $0.port.serviceName, status: $0.status) }
            )
            isRunningNetworkTool = false
        }
    }

    private func runNetworkTool(title: String, action: @escaping (RouterOSCredentials) async throws -> String) {
        guard let credentials = connectionService.credentials, !isRunningNetworkTool else { return }
        isRunningNetworkTool = true
        networkToolError = nil
        Task {
            do {
                let output = try await action(credentials)
                networkToolResult = NetworkToolResult(title: title, output: output)
            } catch {
                networkToolError = error.localizedDescription
            }
            isRunningNetworkTool = false
        }
    }

    func load() async {
        isLoading = true
        loadError = nil
        do {
            async let leasesTask = connectionService.fetchMenuItems(menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease")
            async let arpTask = connectionService.fetchMenuItems(menuPath: "/ip arp", restPath: "ip/arp")
            async let bridgeHostsTask = connectionService.fetchMenuItems(menuPath: "/interface bridge host", restPath: "interface/bridge/host")
            async let interfacesTask = connectionService.fetchMenuItems(menuPath: "/interface", restPath: "interface")
            async let dhcpServersTask = connectionService.fetchMenuItems(menuPath: "/ip dhcp-server", restPath: "ip/dhcp-server")

            let leases = try await leasesTask
            let arpEntries = try await arpTask
            let bridgeHosts = try await bridgeHostsTask
            let interfaces = try await interfacesTask
            let dhcpServers = try await dhcpServersTask
            // Best-effort: if this specific lookup fails (e.g. an older RouterOS version that
            // doesn't support filtering "find" on this property), fall back to "nothing known
            // static yet" rather than failing the whole tab — matches the safe default already
            // used when a lease is entirely unmatched. Returns MAC addresses, not `.id`s — see
            // `RouterOSTransport.fetchFieldValues`'s doc comment for why `.id` isn't trustworthy
            // for this menu.
            let staticMacs = Set((try? await connectionService.fetchFieldValues(
                menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease",
                whereField: "dynamic", whereValue: "no", returnField: "mac-address"
            ))?.map { $0.lowercased() } ?? [])

            let builtDevices = Self.buildDevices(
                leases: leases, arpEntries: arpEntries, bridgeHosts: bridgeHosts,
                interfaces: interfaces, dhcpServers: dhcpServers, staticMacAddresses: staticMacs
            )
            devices = builtDevices
            portGroups = Self.buildPortGroups(devices: builtDevices, interfaces: interfaces)
        } catch {
            loadError = error.localizedDescription
        }
        isLoading = false
    }

    /// The command "Feste IP zuweisen" would run — shown to the user before it executes, same
    /// convention as the rest of the app (Wizard review screen, Expert tool's confirmation
    /// dialog).
    var pendingCommand: RouterOSCommand? {
        guard let device = pendingStaticAssignment, device.hasLease else { return nil }
        // Matched by MAC address, not `.id` — deliberately, see `RouterOSTransport.
        // fetchFieldValues`'s doc comment for why the `.id` this app would otherwise have on
        // hand (`device.leaseID`) isn't trustworthy for this menu.
        return .action(
            menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease",
            name: "make-static", matchField: "mac-address", matchValue: device.macAddress,
            summary: "Feste IP \(device.ipAddress) für \(device.macAddress)"
        )
    }

    /// The command "Feste Zuweisung entfernen" would run — matched by MAC, same reasoning as
    /// `pendingCommand`.
    var pendingRemovalCommand: RouterOSCommand? {
        guard let device = pendingStaticRemoval, device.hasLease else { return nil }
        return .remove(
            menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease",
            matchField: "mac-address", matchValue: device.macAddress,
            summary: "Feste Zuweisung entfernen für \(device.macAddress)"
        )
    }

    /// Backs up once per connection before this tab's first write — same shared flag the Expert
    /// tool uses (`ConnectionService.hasExpertToolBackedUpThisSession`), so a session that already
    /// backed up via one "power tool" doesn't back up again via the other.
    private func ensureSessionBackup() async throws {
        guard !connectionService.hasExpertToolBackedUpThisSession, let credentials = connectionService.credentials else { return }
        _ = try await backupService.createBackup(for: credentials)
        connectionService.markExpertToolBackedUpThisSession()
    }

    func confirmStaticAssignment() async {
        guard let command = pendingCommand, let device = pendingStaticAssignment else { return }
        isApplying = true
        applyError = nil
        do {
            try await ensureSessionBackup()
            try await connectionService.apply(command)
            // Confirmed live: RouterOS' SSH CLI can run "make-static [find ...]" without any
            // error output while genuinely not converting anything (a mismatched selector) — "no
            // error" alone isn't proof it worked (same lesson as Bug 10 in HANDOFF.md, one level
            // deeper: even a real, syntactically valid, silently-successful-looking command can
            // still not have the intended effect). Verify the lease is now actually in the static
            // set before declaring success — by MAC, same reasoning as `pendingCommand`.
            let staticMacs = Set((try await connectionService.fetchFieldValues(
                menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease",
                whereField: "dynamic", whereValue: "no", returnField: "mac-address"
            )).map { $0.lowercased() })
            guard staticMacs.contains(device.macAddress.lowercased()) else {
                throw RouterOSError.invalidResponse(
                    "Befehl lief ohne Fehlermeldung, aber der Router zeigt den Eintrag weiterhin als dynamisch (geprüft über \"find dynamic=no\"). Bitte manuell mit \"/ip dhcp-server lease print\" kontrollieren."
                )
            }
            pendingStaticAssignment = nil
            await load()
        } catch {
            // Clear this on failure too, not just success — otherwise the confirmationDialog's
            // `isPresented` binding (tied to `pendingStaticAssignment != nil`) stays "open" while
            // SwiftUI also tries to present the error `.alert`, and the two presentations can
            // conflict enough that the alert never actually becomes visible — a silent failure
            // that looked like nothing happened at all.
            pendingStaticAssignment = nil
            applyError = error.localizedDescription
        }
        isApplying = false
    }

    func cancelStaticAssignment() {
        pendingStaticAssignment = nil
    }

    func confirmStaticRemoval() async {
        guard let command = pendingRemovalCommand, let device = pendingStaticRemoval else { return }
        isApplying = true
        applyError = nil
        do {
            try await ensureSessionBackup()
            try await connectionService.apply(command)
            // Same lesson as `confirmStaticAssignment` (Bug 10/17 in HANDOFF.md): empty output
            // isn't proof it worked. Verify the lease for this MAC is actually gone — a lingering
            // "no error" success is worth less than an honest check.
            let remainingLeases = try await connectionService.fetchMenuItems(
                menuPath: "/ip dhcp-server lease", restPath: "ip/dhcp-server/lease"
            )
            let stillPresent = remainingLeases.contains { $0.fields["mac-address"]?.lowercased() == device.macAddress.lowercased() }
            guard !stillPresent else {
                throw RouterOSError.invalidResponse(
                    "Befehl lief ohne Fehlermeldung, aber der Lease-Eintrag ist weiterhin vorhanden. Bitte manuell mit \"/ip dhcp-server lease print\" kontrollieren."
                )
            }
            pendingStaticRemoval = nil
            await load()
        } catch {
            pendingStaticRemoval = nil
            applyError = error.localizedDescription
        }
        isApplying = false
    }

    func cancelStaticRemoval() {
        pendingStaticRemoval = nil
    }

    func dismissApplyError() {
        applyError = nil
    }

    // MARK: - Pure device list construction (testable without a live router)

    nonisolated static func buildDevices(
        leases: [RouterOSMenuItem],
        arpEntries: [RouterOSMenuItem],
        bridgeHosts: [RouterOSMenuItem],
        interfaces: [RouterOSMenuItem],
        dhcpServers: [RouterOSMenuItem],
        staticMacAddresses: Set<String> = []
    ) -> [LanDevice] {
        var bridgeNames = Set<String>()
        for item in interfaces where item.fields["type"] == "bridge" {
            if let name = item.fields["name"] { bridgeNames.insert(name) }
        }

        // Exact: the bridge host table names the actual physical port a MAC was learned on
        // behind a bridge (RouterOS field "on-interface" — confirmed against MikroTik's
        // Bridging and Switching docs, not guessed).
        var exactPortByMAC: [String: String] = [:]
        for item in bridgeHosts {
            guard let mac = item.fields["mac-address"]?.lowercased(), let onInterface = item.fields["on-interface"] else { continue }
            exactPortByMAC[mac] = onInterface
        }

        // Fallback: ARP's "interface" field — exact if that interface isn't a bridge, otherwise
        // only "somewhere on this bridge" (resolved further by the bridge host table above when
        // available).
        var arpInterfaceByMAC: [String: String] = [:]
        for item in arpEntries {
            guard let mac = item.fields["mac-address"]?.lowercased(), let iface = item.fields["interface"] else { continue }
            arpInterfaceByMAC[mac] = iface
        }

        // Last resort: the DHCP server's own configured interface — network-level only, since a
        // server can sit on a bridge shared by several physical ports.
        var interfaceByDHCPServer: [String: String] = [:]
        for item in dhcpServers {
            guard let name = item.fields["name"], let iface = item.fields["interface"] else { continue }
            interfaceByDHCPServer[name] = iface
        }

        func resolvePort(mac: String, fallbackServer: String?) -> (port: String?, network: String?) {
            if let exact = exactPortByMAC[mac] {
                return (exact, nil)
            }
            if let iface = arpInterfaceByMAC[mac] {
                return bridgeNames.contains(iface) ? (nil, iface) : (iface, nil)
            }
            if let server = fallbackServer, let iface = interfaceByDHCPServer[server] {
                return bridgeNames.contains(iface) ? (nil, iface) : (iface, nil)
            }
            return (nil, nil)
        }

        var devices: [LanDevice] = []
        var seenMACs = Set<String>()

        for (index, item) in leases.enumerated() {
            guard let address = item.fields["address"], let macRaw = item.fields["mac-address"] else { continue }
            let mac = macRaw.lowercased()
            seenMACs.insert(mac)
            // Confirmed live on a real hEX (two independent checks, "/ip dhcp-server lease
            // print"'s flags column before and after converting a lease to static): "dynamic" is
            // never emitted by "print terse" for this menu, in EITHER state — not omitted only
            // for the common case, genuinely absent from the parseable output entirely. Reading
            // the field at all (this app's first two attempts) can't work. Static/dynamic here
            // instead comes from `staticMacAddresses`, fetched via RouterOS' `find dynamic=no` —
            // matched by MAC, not `.id`, because `.id` from `fetchMenuItems`' positional overlay
            // was confirmed live to mis-pair with the wrong lease for this exact menu (a static
            // lease's `.id` got attached to a different, still-dynamic lease's row, making it
            // wrongly show "Fest" too).
            let isStaticLease = staticMacAddresses.contains(mac)
            let server = item.fields["server"]
            let (port, network) = resolvePort(mac: mac, fallbackServer: server)
            devices.append(LanDevice(
                // Unique per row, not just the MAC — if RouterOS ever reports two lease entries
                // for the same MAC (observed: a device that should be static still showing
                // dynamic after conversion, plausibly because RouterOS created a fresh dynamic
                // lease alongside the newly-static one), both must render, not silently collapse
                // to one via a SwiftUI List/ForEach duplicate-id collision.
                id: "lease-\(index)-\(mac)",
                ipAddress: address,
                macAddress: macRaw,
                hostName: item.fields["host-name"],
                isStatic: isStaticLease,
                hasLease: true,
                leaseID: item.id,
                dhcpServerName: server,
                resolvedPort: port,
                networkHint: network,
                comment: item.fields["comment"],
                rawFields: [(key: ".id", value: item.id)] + item.fields.sorted { $0.key < $1.key }.map { (key: $0.key, value: $0.value) }
            ))
        }

        // ARP-only devices: seen on the network but with no matching DHCP lease (statically
        // configured outside DHCP, or a stray/foreign device). Shown read-only — there's no
        // lease item to convert, and guessing which DHCP server's network a static-IP device
        // "belongs to" isn't something this app will do.
        for (index, item) in arpEntries.enumerated() {
            guard let address = item.fields["address"], let macRaw = item.fields["mac-address"] else { continue }
            let mac = macRaw.lowercased()
            guard !seenMACs.contains(mac) else { continue }
            seenMACs.insert(mac)
            let (port, network) = resolvePort(mac: mac, fallbackServer: nil)
            devices.append(LanDevice(
                id: "arp-\(index)-\(mac)",
                ipAddress: address,
                macAddress: macRaw,
                hostName: nil,
                // No lease at all here — "isStatic" (a DHCP *static reservation*) simply doesn't
                // apply, so this must not read as "Fest" (a prior version wrongly hardcoded
                // `true`, which mislabeled every ARP-only device — including ordinary DHCP
                // clients whose lease didn't get matched — as statically assigned). The Geräte
                // view branches on `hasLease` first precisely to keep this case visually distinct
                // from both "Fest" and "Dynamisch".
                isStatic: false,
                hasLease: false,
                leaseID: nil,
                dhcpServerName: nil,
                resolvedPort: port,
                networkHint: network,
                comment: nil,
                rawFields: item.fields.sorted { $0.key < $1.key }.map { (key: $0.key, value: $0.value) }
            ))
        }

        return devices.sorted { isIPLess(ipSortKey($0.ipAddress), ipSortKey($1.ipAddress)) }
    }

    /// Groups devices by physical port for the per-port tables, including physical ports with
    /// zero devices (so unused ports are visible too) and a catch-all group for devices whose
    /// port isn't known exactly (only a bridge/network — see `LanDevice.networkHint`).
    nonisolated static func buildPortGroups(devices: [LanDevice], interfaces: [RouterOSMenuItem]) -> [DevicePortGroup] {
        let physicalTypes: Set<String> = ["ether", "wlan", "wifi", "wireless", "sfp", "sfp-sfpplus", "sfp28", "combo"]
        var physicalPortNames = interfaces
            .filter { physicalTypes.contains($0.fields["type"] ?? "") }
            .compactMap { $0.fields["name"] }
        physicalPortNames.sort(by: naturalPortOrder)

        var devicesByPort: [String: [LanDevice]] = [:]
        var otherDevices: [LanDevice] = []
        for device in devices {
            if let port = device.resolvedPort {
                devicesByPort[port, default: []].append(device)
            } else {
                otherDevices.append(device)
            }
        }

        var groups = physicalPortNames.map { port in
            DevicePortGroup(id: port, title: port, devices: devicesByPort[port] ?? [])
        }
        // A resolved port RouterOS reported that isn't in the physical-interface snapshot
        // (shouldn't normally happen) still gets its own group, so no device silently vanishes.
        let knownPortNames = Set(physicalPortNames)
        for (port, portDevices) in devicesByPort.sorted(by: { $0.key < $1.key }) where !knownPortNames.contains(port) {
            groups.append(DevicePortGroup(id: port, title: port, devices: portDevices))
        }
        if !otherDevices.isEmpty {
            groups.append(DevicePortGroup(id: "unbekannt", title: "Unbekannter Port", devices: otherDevices))
        }
        return groups
    }

    private nonisolated static func naturalPortOrder(_ lhs: String, _ rhs: String) -> Bool {
        func split(_ value: String) -> (prefix: String, number: Int) {
            let digits = value.reversed().prefix(while: \.isNumber)
            let numberPart = String(digits.reversed())
            let prefix = String(value.dropLast(numberPart.count))
            return (prefix, Int(numberPart) ?? 0)
        }
        let left = split(lhs)
        let right = split(rhs)
        return left.prefix == right.prefix ? left.number < right.number : left.prefix < right.prefix
    }

    private nonisolated static func ipSortKey(_ address: String) -> [Int] {
        address.split(separator: ".").compactMap { Int($0) }
    }

    private nonisolated static func isIPLess(_ lhs: [Int], _ rhs: [Int]) -> Bool {
        for (left, right) in zip(lhs, rhs) where left != right {
            return left < right
        }
        return lhs.count < rhs.count
    }
}