Flaro/Flixy/Views/SignIn/JellyfinSignInView.swift

import SwiftUI
import FlixyDesign
import JellyfinKit

/// Die Anmeldung an einem Jellyfin-Server.
///
/// Drei Bildschirme in einem, weil es drei Fragen sind und nicht mehr: wo
/// steht der Server, wie heißt du, und — wenn der Server es kann — bestätige
/// diesen Code. Der Weg über den Code steht vorn, weil dabei kein Passwort
/// durch diese App läuft.
struct JellyfinSignInView: View {
    @Environment(FlixySession.self) private var session
    @Environment(\.dismiss) private var dismiss
    @Environment(\.flixyAccent) private var accent

    @State private var model: JellyfinSignInModel?
    @FocusState private var focusedField: Field?

    private enum Field { case address, userName, password }

    var body: some View {
        NavigationStack {
            ScrollView {
                if let model {
                    content(for: model)
                        .padding(.horizontal, FlixySpacing.section)
                        .padding(.vertical, FlixySpacing.section)
                        .frame(maxWidth: 420)
                        .frame(maxWidth: .infinity)
                }
            }
            .scrollDismissesKeyboard(.interactively)
            .background(Color.flixyCanvas)
            .navigationTitle(Text("signIn.jellyfin.title"))
            .flixyInlineTitle()
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("action.cancel") {
                        model?.cancel()
                        dismiss()
                    }
                }
            }
        }
        .tint(accent)
        .task {
            // Erst hier, nicht im Eigenschaftswert: das Modell braucht die
            // Gerätekennung der Sitzung. Baut es sich eine eigene, steht die
            // App nach dem Anmelden ein zweites Mal in der Geräteliste.
            guard model == nil else { return }
            let fresh = JellyfinSignInModel(identity: session.jellyfinDeviceIdentity)
            fresh.onAuthenticated = { client, account, serverName in
                dismiss()
                Task { await session.adoptJellyfin(client: client, account: account, serverName: serverName) }
            }
            model = fresh
        }
        .onDisappear {
            // Wird das Blatt weggewischt, läuft sonst die Abfrageschleife
            // noch minutenlang weiter — unsichtbar und für nichts.
            model?.cancel()
        }
    }

    @ViewBuilder
    private func content(for model: JellyfinSignInModel) -> some View {
        @Bindable var model = model

        VStack(alignment: .leading, spacing: FlixySpacing.section) {
            switch model.step {
            case .address:
                addressStep(model: model)
            case .checking:
                waiting(text: "signIn.jellyfin.searching")
            case .quickConnect(let code):
                quickConnectStep(model: model, code: code)
            case .credentials:
                credentialsStep(model: model)
            case .signingIn:
                waiting(text: "signIn.jellyfin.signingIn")
            }

            if let message = model.errorMessage {
                Label(message, systemImage: "exclamationmark.triangle")
                    .font(.flixyCaption)
                    .foregroundStyle(Color.flixyDestructive)
            }
        }
    }

    // MARK: - Adresse

    @ViewBuilder
    private func addressStep(model: JellyfinSignInModel) -> some View {
        @Bindable var model = model

        VStack(alignment: .leading, spacing: FlixySpacing.regular) {
            Text("signIn.jellyfin.addressPrompt")
                .font(.flixyRowHeader)
                .foregroundStyle(Color.flixyTextPrimary)

            TextField("signIn.jellyfin.addressPlaceholder", text: $model.address)
                .textFieldStyle(.plain)
                .textContentType(.URL)
                .flixyPlainEntry(isAddress: true)
                .submitLabel(.go)
                .focused($focusedField, equals: .address)
                .onSubmit { Task { await model.findServer() } }
                // Hier statt beim Öffnen des Blattes: so bekommt das Feld den
                // Fokus auch dann, wenn man nach einem Vertipper zurückkommt.
                .task { focusedField = .address }
                .padding(FlixySpacing.regular)
                .background(Color.flixyElevated, in: .rect(cornerRadius: FlixyRadius.control))
                .foregroundStyle(Color.flixyTextPrimary)

            // Ein Beispiel statt einer Erklärung: „Schema, Host, Port" sagt
            // niemandem etwas, „192.168.1.50" jedem.
            Text("signIn.jellyfin.addressHint")
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextMuted)

            Button {
                focusedField = nil
                Task { await model.findServer() }
            } label: {
                Text("signIn.jellyfin.connect")
                    .font(.flixyRowHeader)
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, FlixySpacing.regular)
            }
            .buttonStyle(.borderedProminent)
            .tint(accent)
            .disabled(model.address.trimmingCharacters(in: .whitespaces).isEmpty)
        }
    }

    // MARK: - Code

    @ViewBuilder
    private func quickConnectStep(model: JellyfinSignInModel, code: String) -> some View {
        VStack(alignment: .leading, spacing: FlixySpacing.regular) {
            foundServerHeader(model: model)

            Text("signIn.jellyfin.quickConnectHint")
                .font(.flixyBody)
                .foregroundStyle(Color.flixyTextSecondary)

            Text(code)
                .font(.system(.largeTitle, design: .monospaced, weight: .semibold))
                .tracking(8)
                .foregroundStyle(Color.flixyTextPrimary)
                .textSelection(.enabled)
                .padding(.vertical, FlixySpacing.regular)
                .frame(maxWidth: .infinity)
                .background(Color.flixyElevated, in: .rect(cornerRadius: FlixyRadius.control))

            HStack(spacing: FlixySpacing.snug) {
                ProgressView().controlSize(.small)
                Text("signIn.jellyfin.waitingForApproval")
                    .font(.flixyCaption)
                    .foregroundStyle(Color.flixyTextMuted)
            }

            Text("signIn.jellyfin.privacy")
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextMuted)

            Divider().overlay(Color.flixySeparator)

            Button("signIn.jellyfin.usePassword") { model.useCredentials() }
                .font(.flixyCaption)
            Button("signIn.jellyfin.otherAddress") { model.startOver() }
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextSecondary)
        }
    }

    // MARK: - Benutzername und Passwort

    @ViewBuilder
    private func credentialsStep(model: JellyfinSignInModel) -> some View {
        @Bindable var model = model

        VStack(alignment: .leading, spacing: FlixySpacing.regular) {
            foundServerHeader(model: model)

            TextField("signIn.jellyfin.userName", text: $model.userName)
                .textContentType(.username)
                .flixyPlainEntry()
                .submitLabel(.next)
                .focused($focusedField, equals: .userName)
                .onSubmit { focusedField = .password }
                .padding(FlixySpacing.regular)
                .background(Color.flixyElevated, in: .rect(cornerRadius: FlixyRadius.control))

            SecureField("signIn.jellyfin.password", text: $model.password)
                .textContentType(.password)
                .submitLabel(.go)
                .focused($focusedField, equals: .password)
                .onSubmit { Task { await model.signInWithPassword() } }
                .padding(FlixySpacing.regular)
                .background(Color.flixyElevated, in: .rect(cornerRadius: FlixyRadius.control))

            Button {
                focusedField = nil
                Task { await model.signInWithPassword() }
            } label: {
                Text("signIn.jellyfin.submit")
                    .font(.flixyRowHeader)
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, FlixySpacing.regular)
            }
            .buttonStyle(.borderedProminent)
            .tint(accent)
            .disabled(model.userName.isEmpty)

            // Das Passwort wird für die eine Anfrage gehalten und danach
            // verworfen. Gespeichert wird nur der Token, und der im
            // Schlüsselbund.
            Text("signIn.jellyfin.passwordNote")
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextMuted)

            Divider().overlay(Color.flixySeparator)

            if model.offersQuickConnect {
                Button("signIn.jellyfin.useCode") { Task { await model.beginQuickConnect() } }
                    .font(.flixyCaption)
            }
            Button("signIn.jellyfin.otherAddress") { model.startOver() }
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextSecondary)
        }
        .foregroundStyle(Color.flixyTextPrimary)
    }

    // MARK: - Bausteine

    @ViewBuilder
    private func foundServerHeader(model: JellyfinSignInModel) -> some View {
        VStack(alignment: .leading, spacing: FlixySpacing.tight) {
            Text("signIn.jellyfin.foundServer")
                .font(.flixyCaption)
                .foregroundStyle(Color.flixyTextMuted)
                .textCase(.uppercase)
            Text(model.serverName ?? model.address)
                .font(.flixyTitle)
                .foregroundStyle(Color.flixyTextPrimary)
        }
    }

    @ViewBuilder
    private func waiting(text: LocalizedStringKey) -> some View {
        HStack(spacing: FlixySpacing.snug) {
            ProgressView().controlSize(.small)
            Text(text)
                .font(.flixyBody)
                .foregroundStyle(Color.flixyTextSecondary)
        }
        .frame(maxWidth: .infinity, alignment: .center)
        .padding(.vertical, FlixySpacing.section)
    }
}