import Foundation

@MainActor
final class ExpertViewModel: ObservableObject {
    /// One raw, uncurated key=value field — the escape hatch that keeps every RouterOS menu
    /// reachable even where `RouterOSMenuSchema.fields` doesn't (yet) curate every parameter.
    struct ExtraField: Identifiable, Equatable {
        let id = UUID()
        var key: String = ""
        var value: String = ""
    }

    @Published var selectedSchema: RouterOSMenuSchema?
    @Published var customMenuPath: String = ""
    @Published var customRestPath: String = ""

    @Published private(set) var items: [RouterOSMenuItem] = []
    @Published private(set) var isLoading = false
    @Published private(set) var loadError: String?
    /// Options for `.menuItemPick` fields, keyed by that field's referenced `menuPath` — e.g.
    /// existing pool names for a DHCP server's "address-pool" field. Refreshed alongside
    /// `items` so a pool/profile/script created moments earlier already shows up.
    @Published private(set) var crossReferenceOptions: [String: [String]] = [:]
    /// Live interface names for `.interfacePick` fields, refreshed alongside `items` — unlike
    /// `ConnectionService.interfaces` (fetched once at connect time), this picks up interfaces
    /// created after connecting (e.g. a VLAN added minutes earlier in this same Expert tab).
    /// Confirmed live: a DHCP server's "interface" field didn't offer a just-created VLAN until
    /// this was added.
    @Published private(set) var liveInterfaceNames: [String] = []

    /// Non-nil while the add/edit sheet is open. An empty `id` means "new item".
    @Published var editingItem: RouterOSMenuItem?
    @Published var formValues: [String: String] = [:]
    @Published var extraFields: [ExtraField] = []

    @Published private(set) var isApplying = false
    @Published private(set) var applyError: String?
    @Published var pendingRemoval: RouterOSMenuItem?

    /// Same "Port-Konflikt-Prüfung" as the Setup Wizard's LAN step (found.md #1), applied here to
    /// whichever `.interfacePick` field the current schema has — per explicit request ("die
    /// Abfrage vom Einrichten-Assistenten auf Expert anwenden ... mit allen Warnungen"). Unlike
    /// the wizard (one conflict per `LanDhcpConfig.ID` in a list), the edit sheet only ever has
    /// one interface field open at a time, so a single value (not a dictionary) is enough.
    @Published private(set) var interfacePortConflict: PortConflict?
    @Published private(set) var isCheckingInterfacePortConflict = false
    @Published private(set) var acknowledgedInterfacePortConflict = false
    /// Bumped on every `checkInterfacePortConflict()` call, same race-safety reasoning as
    /// `SetupViewModel.portConflictRequestGeneration` (bugs.md #1) — a slower, older in-flight
    /// check discards its own result if a newer one has since started.
    private var interfacePortConflictGeneration = 0

    private let connectionService: ConnectionService
    private let backupService: BackupService

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

    /// Backs up the current config once per connection, right before the Expert tool's first
    /// write — mirrors the Einrichten-Wizard's "always back up before applying" habit, just
    /// once per session here rather than before every single edit (an Expert-tool session can
    /// easily be a dozen small edits in a row).
    private func ensureSessionBackup() async throws {
        guard !connectionService.hasExpertToolBackedUpThisSession, let credentials = connectionService.credentials else { return }
        _ = try await backupService.createBackup(for: credentials)
        connectionService.markExpertToolBackedUpThisSession()
    }

    func open(_ schema: RouterOSMenuSchema) {
        selectedSchema = schema
        items = []
        loadError = nil
        Task { await reloadItems() }
    }

    /// Opens any RouterOS menu path the user types in directly, generic key=value form —
    /// the guarantee that literally any menu is reachable, curated or not.
    func openCustomPath() {
        let menuPath = customMenuPath.trimmingCharacters(in: .whitespaces)
        let restPath = customRestPath.trimmingCharacters(in: .whitespaces)
        guard !menuPath.isEmpty, !restPath.isEmpty else { return }
        open(RouterOSMenuSchema(
            menuPath: menuPath,
            restPath: restPath,
            category: .system,
            displayName: menuPath,
            summary: "Eigener Menüpfad — generischer Zugriff ohne kuratierte Felder.",
            explanation: "Alle Felder, die der Router für diesen Pfad zurückgibt, erscheinen unten als freie Schlüssel/Wert-Paare. Prüfe die RouterOS-Dokumentation für die genaue Bedeutung."
        ))
    }

    func reloadItems() async {
        guard let schema = selectedSchema else { return }
        isLoading = true
        loadError = nil
        do {
            items = try await connectionService.fetchMenuItems(menuPath: schema.menuPath, restPath: schema.restPath)
        } catch {
            loadError = error.localizedDescription
        }
        isLoading = false
        await loadCrossReferenceOptions(for: schema)
        await loadLiveInterfaceNames(for: schema)
    }

    private func loadLiveInterfaceNames(for schema: RouterOSMenuSchema) async {
        guard schema.fields.contains(where: {
            if case .interfacePick = $0.kind { return true } else { return false }
        }) else { return }
        do {
            let interfaceItems = try await connectionService.fetchMenuItems(menuPath: "/interface", restPath: "interface")
            liveInterfaceNames = interfaceItems.compactMap { $0.fields["name"] }.sorted()
        } catch {
            liveInterfaceNames = []
        }
    }

    private func loadCrossReferenceOptions(for schema: RouterOSMenuSchema) async {
        for field in schema.fields {
            guard case .menuItemPick(let menuPath, let restPath, let valueField) = field.kind else { continue }
            do {
                let referencedItems = try await connectionService.fetchMenuItems(menuPath: menuPath, restPath: restPath)
                let values = Set(referencedItems.compactMap { $0.fields[valueField] }).sorted()
                crossReferenceOptions[menuPath] = values
            } catch {
                crossReferenceOptions[menuPath] = []
            }
        }
    }

    func startNewItem() {
        guard let schema = selectedSchema else { return }
        editingItem = RouterOSMenuItem(id: "", fields: [:])
        formValues = Dictionary(uniqueKeysWithValues: schema.fields.compactMap { field in
            field.defaultValue.map { (field.key, $0) }
        })
        extraFields = []
        applyError = nil
        resetInterfacePortConflictState()
    }

    func startEditing(_ item: RouterOSMenuItem) {
        guard let schema = selectedSchema else { return }
        editingItem = item
        let curatedKeys = Set(schema.fields.map(\.key))
        formValues = item.fields.filter { curatedKeys.contains($0.key) }
        extraFields = item.fields
            .filter { !curatedKeys.contains($0.key) }
            .sorted { $0.key < $1.key }
            .map { ExtraField(key: $0.key, value: $0.value) }
        applyError = nil
        resetInterfacePortConflictState()
    }

    /// The key of the current schema's `.interfacePick` field, if it has one — a schema only
    /// ever has at most one (matches the one physical/logical port the whole menu item applies
    /// to, e.g. `/ip address`'s "interface").
    private var interfaceFieldKey: String? {
        selectedSchema?.fields.first { if case .interfacePick = $0.kind { return true } else { return false } }?.key
    }

    private func resetInterfacePortConflictState() {
        interfacePortConflict = nil
        isCheckingInterfacePortConflict = false
        acknowledgedInterfacePortConflict = false
        interfacePortConflictGeneration += 1
    }

    /// Mirrors `SetupViewModel.checkPortConflict(for:)` — called whenever the `.interfacePick`
    /// field's value changes (`ExpertMenuDetailView`'s `.onChange`). Best-effort, same as the
    /// wizard's version: a failed check just means no warning shown for that attempt, never
    /// blocks the sheet outright.
    func checkInterfacePortConflict() {
        guard let key = interfaceFieldKey else { return }
        let interfaceName = formValues[key] ?? ""
        acknowledgedInterfacePortConflict = false
        interfacePortConflict = nil
        guard !interfaceName.isEmpty else { return }
        isCheckingInterfacePortConflict = true
        interfacePortConflictGeneration += 1
        let generation = interfacePortConflictGeneration
        Task {
            let result = try? await connectionService.checkPortConflict(interfaceName: interfaceName)
            guard generation == interfacePortConflictGeneration else { return }
            interfacePortConflict = result
            isCheckingInterfacePortConflict = false
        }
    }

    /// The user has been shown what's on this port and, after two explicit confirmations
    /// (`PortConflictWarningView`), chose to have the app clear it immediately as part of this
    /// save — unlike the wizard (deferred to "Jetzt anwenden"), the Experte tab has no separate
    /// review step, so acknowledging here takes effect on the very next "Anlegen"/"Speichern".
    func acknowledgeInterfacePortConflict() {
        acknowledgedInterfacePortConflict = true
    }

    /// Blocks "Anlegen"/"Speichern" until a found conflict is either acknowledged or the
    /// interface field is changed to something actually free.
    var hasUnresolvedInterfacePortConflict: Bool {
        interfacePortConflict != nil && !acknowledgedInterfacePortConflict
    }

    func cancelEditing() {
        editingItem = nil
        formValues = [:]
        extraFields = []
        applyError = nil
        resetInterfacePortConflictState()
    }

    /// The command that saving the current edit sheet would run — shown to the user before it
    /// actually executes, consistent with the rest of the app never applying silently.
    var pendingCommand: RouterOSCommand? {
        guard let schema = selectedSchema, let editingItem else { return nil }
        let isNew = editingItem.id.isEmpty

        // When editing an existing item, only send a field if its value actually differs from
        // what the router originally reported — RouterOS' `set` only touches parameters it's
        // given, so an unchanged field doesn't need resending, and for some fields resending the
        // existing value verbatim is actively rejected: a dynamic/connected route's `distance=0`
        // ("value of distance out of range (1...255)") and a route's read-only `immediate-gw`
        // ("bad parameter immediate-gw") both failed this way when saving an edit to a completely
        // different field like the comment (confirmed live, 2026-09-15). Diffing against the
        // original also naturally covers *clearing* a field (new value "" differs from the old
        // non-empty one, so it's still sent — explicitly, as "" — unlike a field that was already
        // empty and stays empty, which is correctly left out). New items have no "original" to
        // diff against, so every non-empty curated value is sent as before.
        var arguments: [String: String] = isNew
            ? formValues.filter { !$0.value.isEmpty }
            : formValues.filter { $0.value != (editingItem.fields[$0.key] ?? "") }
        // A non-`clearable` field (see `RouterOSFieldSchema.clearable`'s doc comment) never sends
        // an explicit empty value, even if the diff above decided to "clear" it — RouterOS can
        // reject or even 500 an empty string for a property whose type isn't plain text (confirmed
        // live: `/system routerboard mode-button`'s "hold-time", a time-interval-range field,
        // 500'd on `hold-time=""`).
        for field in schema.fields where !field.clearable {
            if arguments[field.key]?.isEmpty == true {
                arguments.removeValue(forKey: field.key)
            }
        }
        // RouterOS' CLI parser rejects "true"/"false" for boolean parameters — it only accepts
        // "yes"/"no" (confirmed live: "disabled=false" on "/interface vlan add" produced
        // "syntax error (line 1 column 30)"; "disabled=no" succeeded). Schema defaults are
        // occasionally written as "true"/"false" for readability, so normalize here regardless
        // of where the value came from rather than trust every call site to get it right.
        for field in schema.fields {
            guard case .bool = field.kind, let value = arguments[field.key] else { continue }
            if value == "true" { arguments[field.key] = "yes" }
            else if value == "false" { arguments[field.key] = "no" }
        }
        // Same "only if changed" rule for uncurated ("Weitere Parameter") fields — these are
        // pre-filled from the live item for visibility by `startEditing`, so without this every
        // save would resend all of them, including computed/read-only ones RouterOS refuses.
        for extra in extraFields where !extra.key.isEmpty {
            if extra.value != editingItem.fields[extra.key] {
                arguments[extra.key] = extra.value
            }
        }
        let summary = "\(isNew ? "Neu anlegen" : "Ändern") unter \(schema.menuPath)"
        if isNew {
            return .add(menuPath: schema.menuPath, restPath: schema.restPath, arguments: arguments, summary: summary)
        } else if schema.isSingleton {
            // No "[find ...]" for a singleton menu — see RouterOSCommand.cliLine.
            return .set(
                menuPath: schema.menuPath, restPath: schema.restPath,
                matchField: "", matchValue: "",
                arguments: arguments, summary: summary
            )
        } else {
            return .set(
                menuPath: schema.menuPath, restPath: schema.restPath,
                matchField: ".id", matchValue: editingItem.id,
                arguments: arguments, summary: summary
            )
        }
    }

    func saveEditingItem() async {
        guard let command = pendingCommand else { return }
        isApplying = true
        applyError = nil
        connectionService.beginWrite()
        defer { connectionService.endWrite() }
        do {
            try await ensureSessionBackup()
            // Port-Konflikt-Auflösung (found.md #1-style, siehe `PortConflictWarningView`) läuft
            // hier sofort vor dem eigentlichen Befehl — anders als im Wizard gibt es im Experte-
            // Tab keinen separaten Review-Schritt, an dem das gebündelt würde.
            if let conflict = interfacePortConflict, acknowledgedInterfacePortConflict {
                for resolutionCommand in conflict.resolutionCommandsIncludingBridgeDetach() {
                    try await connectionService.apply(resolutionCommand)
                }
            }
            if selectedSchema?.writesRequireSSH == true {
                try await connectionService.applyViaSSH(command)
            } else {
                try await connectionService.apply(command)
            }
            cancelEditing()
            await reloadItems()
        } catch {
            if case RouterOSError.untrustedSSHHostKey(let fingerprint) = error {
                connectionService.noteUntrustedSSHHostKey(fingerprint)
            }
            applyError = error.localizedDescription
        }
        isApplying = false
    }

    func confirmRemoval(_ item: RouterOSMenuItem) async {
        guard let schema = selectedSchema else { return }
        isApplying = true
        applyError = nil
        connectionService.beginWrite()
        defer { connectionService.endWrite() }
        do {
            let command = RouterOSCommand.remove(
                menuPath: schema.menuPath, restPath: schema.restPath,
                matchField: ".id", matchValue: item.id,
                summary: "Löschen unter \(schema.menuPath)"
            )
            try await ensureSessionBackup()
            try await connectionService.apply(command)
            pendingRemoval = nil
            await reloadItems()
        } catch {
            if case RouterOSError.untrustedSSHHostKey(let fingerprint) = error {
                connectionService.noteUntrustedSSHHostKey(fingerprint)
            }
            applyError = error.localizedDescription
        }
        isApplying = false
    }
}