import SwiftUI
import CoreImage.CIFilterBuiltins
import NucleicProtocol
import NucleicTailnet
import UIKit

struct SettingsView: View {
    @EnvironmentObject var store: RemoteStore
    @State private var showScanner = false
    @State private var showManualPair = false
    @State private var showAddDevice = false
    /// Bumped after removing a paired Mac so the "Paired Macs" list re-reads the registry (mesh P3).
    @State private var pairedHostsToken = UUID()
    @AppStorage("nucleic.showRawEvents") private var showRaw = false
    @AppStorage("nucleic.showLockEvents") private var showLockEvents = true
    @AppStorage(HeartbeatSettings.shareAnonymousUsageKey) private var shareAnonymousUsage = true
    @AppStorage(AppAppearance.storageKey) private var appearanceRaw = AppAppearance.system.rawValue
    @AppStorage(AppTextSize.storageKey) private var textSizeRaw = AppTextSize.medium.rawValue
    @AppStorage(ColorVisionMode.storageKey) private var colorVisionRaw = ColorVisionMode.standard.rawValue

    var body: some View {
        NavigationStack {
            Form {
                if store.demoMode {
                    Section {
                        Button(role: .destructive) { store.exitDemo() } label: {
                            Label("Leave demo", systemImage: "arrow.uturn.left")
                        }
                    } header: {
                        Text("Demo")
                    } footer: {
                        Text("")
                    }
                }

                Section {
                    Picker("Theme", selection: $appearanceRaw) {
                        ForEach(AppAppearance.allCases) { appearance in
                            Text(appearance.label).tag(appearance.rawValue)
                        }
                    }
                    Picker("Text size", selection: $textSizeRaw) {
                        ForEach(AppTextSize.allCases) { size in
                            Text(size.label).tag(size.rawValue)
                        }
                    }
                    Picker("Color vision", selection: $colorVisionRaw) {
                        ForEach(ColorVisionMode.allCases) { mode in
                            Text(mode.label).tag(mode.rawValue)
                        }
                    }
                } header: {
                    Text("Appearance")
                } footer: {
                    Text("")
                }

                Section("Connection") {
                    LabeledContent("Status", value: store.connectivity.label)
                    // What this pairing can dial — the live transport is in Status above.
                    if let host = IdentityStore.loadPairedHost() {
                        LabeledContent("Transports", value: Self.transportsLabel(host))
                    }
                    Button("Reconnect") { store.reconnect() }
                        .disabled(!store.isPaired)
                }

                // Mesh P3: every Mac this phone is paired with — all connected at once and shown
                // together in the app (no active-host selector). Removing one forgets just that Mac
                // and drops its connection; the others keep running.
                let pairedHosts = IdentityStore.pairedHosts()
                if !pairedHosts.isEmpty {
                    Section("Mesh") {
                        ForEach(pairedHosts, id: \.fingerprint) { host in
                            HStack(spacing: 10) {
                                Image(systemName: "desktopcomputer").foregroundStyle(.secondary)
                                VStack(alignment: .leading, spacing: 2) {
                                    Text(host.hostName.isEmpty ? "Mac" : host.hostName)
                                    Text(host.fingerprint.prefix(16) + "…")
                                        .font(.footnote.monospaced()).foregroundStyle(.secondary)
                                }
                                Spacer()
                                Button(role: .destructive) {
                                    store.unpair(host.fingerprint)
                                    pairedHostsToken = UUID()
                                } label: {
                                    Image(systemName: "minus.circle")
                                }
                                .buttonStyle(.borderless)
                            }
                        }
                    }
                    .id(pairedHostsToken)
                }

                Section {
                    if TailnetSupport.isBuiltIn {
                        if let status = store.tailnetStatus {
                            LabeledContent("Node", value: status)
                        }
                        if let loginURL = store.tailnetLoginURL {
                            Link(destination: loginURL) {
                                Label("Open Tailscale login", systemImage: "arrow.up.forward.app")
                            }
                        } else {
                            Text("No setup needed — when your Mac shares over Tailscale, this iPhone joins your tailnet on first connect and opens a browser login to approve itself.")
                                .font(.caption).foregroundStyle(.secondary)
                        }
                    } else {
                        Text("This build doesn't include Tailscale support.")
                            .foregroundStyle(.secondary)
                    }
                } header: {
                    Text("Tailscale")
                } footer: {
                    Text("")
                }

                Section("This device") {
                    LabeledContent("Scope", value: store.grantedScope.rawValue.capitalized)
                    LabeledContent("Key fingerprint", value: store.deviceFingerprint)
                        .font(.footnote.monospaced())
                }

                Section {
                    Toggle("Show lock events", isOn: $showLockEvents)
                    Toggle("Show raw events", isOn: $showRaw)
                } header: {
                    Text("Transcript")
                } footer: {
                    Text("")
                }

                Section {
                    Toggle("Share anonymous usage", isOn: $shareAnonymousUsage)
                } header: {
                    Text("Privacy")
                } footer: {
                    Text("")
                }

                Section {
                    // Grow the mesh: ask a connected Mac to mint a join code this phone shows —
                    // scan it from a new iPhone/iPad, or copy the link to a new Mac. Only when a
                    // live Mac can mint one (the phone can't originate a join code on its own).
                    if store.canAddDeviceToMesh {
                        Button {
                            showAddDevice = true
                        } label: {
                            Label("Add a device to this mesh", systemImage: "plus.circle")
                        }
                    }
                    Button {
                        showScanner = true
                    } label: {
                        Label("Join an Orbital mesh", systemImage: "qrcode.viewfinder")
                    }
                    Button {
                        showManualPair = true
                    } label: {
                        Label("Enter code manually", systemImage: "keyboard")
                    }
                    if store.isPaired {
                        Button(role: .destructive) { store.unpair() } label: {
                            Label("Unpair this device", systemImage: "minus.circle")
                        }
                    }
                } footer: {
                    Text("")
                }
            }
            .navigationTitle("Settings")
            .compactTabBarInset()
            .sheet(isPresented: $showScanner) {
                PairingScannerView { payload in
                    showScanner = false
                    store.pair(with: payload)
                }
            }
            .sheet(isPresented: $showManualPair) {
                ManualPairingView { payload in
                    showManualPair = false
                    store.pair(with: payload)
                }
            }
        }
    }

    /// Every path this pairing can dial: LAN always, plus what the host advertised — a
    /// tailnet hint from the QR and/or a relay membership (QR or the host's later push).
    private static func transportsLabel(_ host: PairedHost) -> String {
        var parts = ["LAN"]
        if host.tailnetHost != nil { parts.append("Tailnet") }
        if host.relayMembershipToken?.isEmpty == false { parts.append("Relay") }
        return parts.joined(separator: " + ")
    }
}

/// Shown before pairing (UX_IOS §7): explain the flow and launch the scanner.
struct PairingIntroView: View {
    @EnvironmentObject var store: RemoteStore
    @State private var showScanner = false
    @State private var showManualPair = false

    var body: some View {
        VStack(spacing: 24) {
            Image(systemName: "qrcode.viewfinder").font(.system(size: 72)).foregroundStyle(.tint)
            Text("Join your Mac's group").font(.title2.weight(.semibold))
            Text("On your Mac, open Nucleic ▸ Settings ▸ Add device to show a QR code, then scan it here — or enter the join code beneath it manually. Scanning any Mac in the group connects you to all of them.")
                .multilineTextAlignment(.center)
                .foregroundStyle(.secondary)
                .padding(.horizontal, 32)
            Button {
                showScanner = true
            } label: {
                Label("Scan QR code", systemImage: "camera").font(.headline).padding(.horizontal)
            }
            .buttonStyle(.borderedProminent)

            // A camera-free path — the iPad's scanner can't run while the app is mirrored to an
            // external display or in some Stage Manager states; pasting the code always works.
            Button {
                showManualPair = true
            } label: {
                Label("Enter code manually", systemImage: "keyboard")
            }
            .buttonStyle(.bordered)

            // Feedback after a scan: the whole UI is still the intro until pairing completes, so
            // without this a failed or in-flight pair looks like "nothing happened."
            pairingStatus

            VStack(spacing: 6) {
                Button { store.enterDemo() } label: {
                    Label("Explore a demo — no Mac needed", systemImage: "play.circle")
                }
                .buttonStyle(.bordered)
                Text("Sample data and a simulated agent — no Mac or account required.")
                    .font(.footnote)
                    .foregroundStyle(.secondary)
                    .multilineTextAlignment(.center)
                    .padding(.horizontal, 32)
            }
            .padding(.top, 8)
        }
        .padding()
        // Fill the available height so the enclosing VStack reaches full screen and the
        // BuildBanner/DemoBanner strips stay pinned at the top. Without this the intro only
        // claims its intrinsic height, so the stack gets centered and the banner drifts down.
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .sheet(isPresented: $showScanner) {
            PairingScannerView { payload in
                showScanner = false
                store.pair(with: payload)
            }
        }
        .sheet(isPresented: $showManualPair) {
            ManualPairingView { payload in
                showManualPair = false
                store.pair(with: payload)
            }
        }
    }

    /// A status line reflecting an in-flight or failed pairing attempt. Silent in the resting
    /// `.unpaired` state (the intro copy already covers that).
    @ViewBuilder
    private var pairingStatus: some View {
        switch store.connectivity {
        case .connecting, .reconnecting:
            // A first tailnet pairing with no auth key detours through a browser login
            // that can take minutes — and this intro is the ONLY screen an unpaired phone
            // has (no Settings tab yet), so the way back to the login page must live here.
            if let loginURL = store.tailnetLoginURL {
                VStack(spacing: 6) {
                    Label("Approve this iPhone in your browser to join your tailnet.",
                          systemImage: "person.crop.circle.badge.checkmark")
                        .font(.footnote).foregroundStyle(.secondary)
                        .multilineTextAlignment(.center).padding(.horizontal, 32)
                    Link("Open the Tailscale login page", destination: loginURL)
                        .font(.footnote.weight(.medium))
                }
            } else {
                Label("Connecting to your Mac…", systemImage: "arrow.triangle.2.circlepath")
                    .font(.footnote).foregroundStyle(.secondary)
            }
        case .hostOffline:
            Label("Can't reach your Mac. Make sure it's on the same Wi‑Fi and remote access is on.",
                  systemImage: "wifi.exclamationmark")
                .font(.footnote).foregroundStyle(.orange)
                .multilineTextAlignment(.center).padding(.horizontal, 32)
        case .failed(let message):
            Label(message, systemImage: "exclamationmark.triangle.fill")
                .font(.footnote).foregroundStyle(.red)
                .multilineTextAlignment(.center).padding(.horizontal, 32)
        case .connected, .unpaired:
            EmptyView()
        }
    }
}

/// A camera-free pairing path (UX_IOS §7): paste the Mac's `nucleic://pair?d=…` code instead of
/// scanning its QR. The iPad's camera can be blocked while mirrored to an external display or in
/// some Stage Manager states, where the scanner's `couldNotStart` path leaves you stuck — this
/// always works. Parses with the same `PairingPayload(qrString:)` the scanner uses.
struct ManualPairingView: View {
    let onEntered: (PairingPayload) -> Void
    @Environment(\.dismiss) private var dismiss
    @State private var code = ""
    @State private var error: String?
    @FocusState private var fieldFocused: Bool

    var body: some View {
        NavigationStack {
            Form {
                Section {
                    TextField("nucleic://pair?d=…", text: $code, axis: .vertical)
                        .textInputAutocapitalization(.never)
                        .autocorrectionDisabled()
                        .keyboardType(.URL)
                        .font(.callout.monospaced())
                        .lineLimit(2...6)
                        .focused($fieldFocused)
                        .onChange(of: code) { error = nil }
                } header: {
                    Text("Join code")
                } footer: {
                    Text("On your Mac, open Nucleic ▸ Settings ▸ Add device and copy the join link shown beneath the QR code, then paste it here.")
                }
                if let error {
                    Label(error, systemImage: "exclamationmark.triangle.fill")
                        .font(.callout).foregroundStyle(.red)
                }
                Button {
                    submit()
                } label: {
                    Label("Join", systemImage: "link").frame(maxWidth: .infinity)
                }
                .buttonStyle(.borderedProminent)
                .disabled(code.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
                .keyboardShortcut(.defaultAction)
            }
            .navigationTitle("Enter pairing code")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) { Button("Cancel") { dismiss() } }
                ToolbarItem(placement: .primaryAction) {
                    Button {
                        if let pasted = UIPasteboard.general.string { code = pasted }
                    } label: {
                        Label("Paste", systemImage: "doc.on.clipboard")
                    }
                    .disabled(!UIPasteboard.general.hasStrings)
                }
            }
            .onAppear { fieldFocused = true }
        }
    }

    private func submit() {
        let trimmed = code.trimmingCharacters(in: .whitespacesAndNewlines)
        guard let payload = try? PairingPayload(qrString: trimmed) else {
            error = "That isn't a valid Nucleic pairing code. Copy the link beneath the QR on your Mac."
            return
        }
        onEntered(payload)
        dismiss()
    }
}