import Foundation

/// Pre-existing configuration on a physical port that the Setup wizard's LAN step would silently
/// override if the user picks that port for a new LAN/DHCP network — surfaced instead so the user
/// can either choose a different, actually-free port or explicitly (twice-confirmed) opt in to
/// clearing it. `DhcpServerCommandBuilder` already unconditionally detaches a port from any bridge
/// as a safety net (see its own doc comment) — this check runs *before* that, to make the same
/// fact visible up front instead of only implicitly, and additionally covers cases that builder
/// doesn't touch at all (an existing IP address, or the port already being used as a WAN dial-up).
struct PortConflict: Equatable {
    enum Reason: Equatable {
        case bridgeMember(bridgeName: String)
        case hasAddresses([String])
        case dhcpClient
        case pppoeClient

        var description: String {
            switch self {
            case .bridgeMember(let bridgeName):
                return "Ist Mitglied der Bridge \"\(bridgeName)\""
            case .hasAddresses(let addresses):
                return "Trägt bereits die IP-Adresse\(addresses.count == 1 ? "" : "n") \(addresses.joined(separator: ", "))"
            case .dhcpClient:
                return "Ist als WAN-DHCP-Client konfiguriert (bezieht selbst eine Adresse aus dem Internet)"
            case .pppoeClient:
                return "Wird von einer PPPoE-Einwahl verwendet"
            }
        }
    }

    let interfaceName: String
    let reasons: [Reason]

    /// Commands that clear each found conflict so the port is actually free before
    /// `DhcpServerCommandBuilder`'s own commands run. Bridge membership is deliberately excluded
    /// here — `DhcpServerCommandBuilder` already removes it unconditionally regardless of whether
    /// this check ran or was acknowledged, so repeating it would just be a harmless duplicate
    /// `.remove` at best; excluding it keeps this list to exactly what wouldn't otherwise happen.
    func resolutionCommands() -> [RouterOSCommand] {
        reasons.flatMap { reason -> [RouterOSCommand] in
            switch reason {
            case .bridgeMember:
                return []
            case .hasAddresses:
                return [RouterOSCommand.remove(
                    menuPath: "/ip address", restPath: "ip/address",
                    matchField: "interface", matchValue: interfaceName,
                    summary: "Bestehende IP-Adresse(n) auf \(interfaceName) entfernen"
                )]
            case .dhcpClient:
                return [RouterOSCommand.remove(
                    menuPath: "/ip dhcp-client", restPath: "ip/dhcp-client",
                    matchField: "interface", matchValue: interfaceName,
                    summary: "WAN-DHCP-Client auf \(interfaceName) entfernen"
                )]
            case .pppoeClient:
                return [RouterOSCommand.remove(
                    menuPath: "/interface pppoe-client", restPath: "interface/pppoe-client",
                    matchField: "interface", matchValue: interfaceName,
                    summary: "PPPoE-Einwahl auf \(interfaceName) entfernen"
                )]
            }
        }
    }

    /// `resolutionCommands()` alone for the Setup-Wizard context, where `DhcpServerCommandBuilder`
    /// already unconditionally detaches the port from any bridge as its own separate safety net —
    /// see that method's doc comment. Contexts without that separate detach (the Experte tab's
    /// generic "Port freimachen?" flow, applied to whatever menu the user is actually editing, not
    /// specifically the LAN/DHCP command set) need the bridge-membership removal included here
    /// instead, or acknowledging a bridge-member conflict there would silently do nothing for
    /// that specific reason.
    func resolutionCommandsIncludingBridgeDetach() -> [RouterOSCommand] {
        let bridgeDetach: [RouterOSCommand] = reasons.contains(where: { if case .bridgeMember = $0 { return true } else { return false } })
            ? [RouterOSCommand.remove(
                menuPath: "/interface bridge port", restPath: "interface/bridge/port",
                matchField: "interface", matchValue: interfaceName,
                summary: "\(interfaceName) aus Bridge lösen"
            )]
            : []
        return bridgeDetach + resolutionCommands()
    }
}