import SwiftUI

struct LoginRootView: View {
    @ObservedObject var model: AppViewModel

    #if !os(macOS)
    @State private var isNFCSheetPresented = false
    #endif

    var body: some View {
        #if os(macOS)
        MacPairingView(model: model)
        #else
        NavigationStack {
            PairingWelcomeView(
                model: model,
                onScanRequested: {
                    model.isScannerPresented = true
                },
                onNFCRequested: {
                    isNFCSheetPresented = true
                }
            )
            .fullScreenCover(isPresented: $model.isScannerPresented) {
                QRScannerSheet(
                    title: "Scan pairing QR",
                    description: "Open pairing in your idp.global web session, then scan the QR shown there to link this iPhone.",
                    navigationTitle: "Link Passport"
                ) { payload in
                    model.manualPairingPayload = payload
                    Task {
                        await model.signIn(with: payload, transport: .qr)
                    }
                }
            }
        }
        .sheet(isPresented: $isNFCSheetPresented) {
            NFCSheet(
                title: "Hold near pairing tag",
                message: "Use a supported idp.global NFC tag to link this iPhone and attach a signed location proof.",
                actionTitle: "Link device"
            ) { request in
                await model.signIn(with: request)
            }
        }
        #endif
    }
}

#if !os(macOS)
private struct PairingWelcomeView: View {
    @ObservedObject var model: AppViewModel
    let onScanRequested: () -> Void
    let onNFCRequested: () -> Void

    var body: some View {
        AppScrollScreen(compactLayout: true, bottomPadding: 150) {
            AppPanel(compactLayout: true, radius: 30) {
                ShadcnBadge(
                    title: "Passport setup",
                    tone: .accent,
                    leading: Image(systemName: "shield.lefthalf.filled")
                )

                HStack(alignment: .top, spacing: 16) {
                    ZStack {
                        RoundedRectangle(cornerRadius: 20, style: .continuous)
                            .fill(IdP.tint.opacity(0.14))
                            .frame(width: 72, height: 72)

                        Image(systemName: "qrcode.viewfinder")
                            .font(.system(size: 30, weight: .semibold))
                            .foregroundStyle(IdP.tint)
                    }

                    VStack(alignment: .leading, spacing: 8) {
                        Text("Link this iPhone to your idp.global account")
                            .font(.title2.weight(.bold))
                            .fixedSize(horizontal: false, vertical: true)

                        Text("Start pairing in your browser, then scan the fresh QR on the next screen. This device becomes your passport for approvals, alerts, and identity proofs.")
                            .font(.subheadline)
                            .foregroundStyle(Color.idpMutedForeground)
                    }
                }

                Text("No camera? The scanner screen also lets you paste a pairing link manually.")
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
            }

            AppSectionCard(
                title: "How pairing works",
                subtitle: "The QR is created by the web session you want to trust.",
                compactLayout: true
            ) {
                VStack(spacing: 14) {
                    PairingStepRow(
                        number: 1,
                        title: "Start from the web",
                        message: "Open idp.global in your browser and begin a new device pairing flow."
                    )

                    PairingStepRow(
                        number: 2,
                        title: "Scan the QR",
                        message: "Use the camera on the next screen to scan the pairing QR shown by that browser session."
                    )

                    PairingStepRow(
                        number: 3,
                        title: "Approve future sign-ins",
                        message: "Once linked, this iPhone can receive approval requests and security alerts."
                    )
                }
            }

            AppSectionCard(
                title: "Before you scan",
                subtitle: "A few quick checks help the link complete cleanly.",
                compactLayout: true
            ) {
                VStack(alignment: .leading, spacing: 10) {
                    PairingNoteRow(icon: "safari", text: "Keep the pairing page open in your browser until this phone confirms the link.")
                    PairingNoteRow(icon: "camera.fill", text: "Grant camera access when prompted so the QR can be read directly.")
                    PairingNoteRow(icon: "wave.3.right", text: "If your organization uses NFC tags, you can link with NFC instead of QR.")
                }
            }
        }
        .navigationTitle("Welcome")
        .idpInlineNavigationTitle()
        .safeAreaInset(edge: .bottom) {
            VStack(spacing: 10) {
                Button(action: onScanRequested) {
                    HStack(spacing: 10) {
                        if model.isAuthenticating {
                            ProgressView()
                                .progressViewStyle(.circular)
                                .tint(Color.idpPrimaryForeground)
                        } else {
                            Image(systemName: "camera.viewfinder")
                        }

                        Text(model.isAuthenticating ? "Linking device..." : "Scan pairing QR")
                    }
                }
                .buttonStyle(PrimaryActionStyle())
                .disabled(model.isAuthenticating)

                Button(action: onNFCRequested) {
                    Label("Use NFC tag instead", systemImage: "wave.3.right")
                }
                .buttonStyle(SecondaryActionStyle())
                .disabled(model.isAuthenticating)
            }
            .padding(.horizontal, 16)
            .padding(.top, 10)
            .padding(.bottom, 14)
            .background(.regularMaterial)
        }
    }
}

private struct PairingStepRow: View {
    let number: Int
    let title: String
    let message: String

    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            Text("\(number)")
                .font(.subheadline.weight(.bold))
                .frame(width: 28, height: 28)
                .foregroundStyle(IdP.tint)
                .background(IdP.tint.opacity(0.12), in: Circle())

            VStack(alignment: .leading, spacing: 4) {
                Text(title)
                    .font(.subheadline.weight(.semibold))
                Text(message)
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
            }
        }
    }
}

private struct PairingNoteRow: View {
    let icon: String
    let text: String

    var body: some View {
        HStack(alignment: .top, spacing: 10) {
            Image(systemName: icon)
                .foregroundStyle(IdP.tint)
                .frame(width: 18, height: 18)

            Text(text)
                .font(.footnote)
                .foregroundStyle(Color.idpMutedForeground)
                .fixedSize(horizontal: false, vertical: true)
        }
    }
}
#endif

#if os(macOS)
private struct MacPairingView: View {
    @ObservedObject var model: AppViewModel

    var body: some View {
        VStack(alignment: .leading, spacing: 18) {
            HStack(spacing: 12) {
                Image(systemName: "shield.lefthalf.filled")
                    .font(.title2)
                    .foregroundStyle(IdP.tint)

                VStack(alignment: .leading, spacing: 2) {
                    Text("Set up idp.global")
                        .font(.headline)
                    Text("Use the demo payload or paste a pairing link.")
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                }
            }

            TextEditor(text: $model.manualPairingPayload)
                .font(.footnote.monospaced())
                .scrollContentBackground(.hidden)
                .frame(minHeight: 140)
                .padding(10)
                .background(Color.idpSecondaryGroupedBackground, in: RoundedRectangle(cornerRadius: IdP.cardRadius, style: .continuous))

            VStack(spacing: 10) {
                Button("Use demo payload") {
                    Task {
                        await model.signInWithSuggestedPayload()
                    }
                }
                .buttonStyle(PrimaryActionStyle())

                Button("Link with payload") {
                    Task {
                        await model.signInWithManualPayload()
                    }
                }
                .buttonStyle(SecondaryActionStyle())
            }
        }
        .padding(20)
    }
}
#endif