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 {
        GeometryReader { proxy in
            let topInset = proxy.safeAreaInsets.top

            ZStack(alignment: .bottom) {
                AppScrollScreen(compactLayout: true, bottomPadding: 220) {
                    Color.clear.frame(height: topInset + 8)
                        .padding(.top, -AppLayout.compactVerticalPadding)

                    PairingHero()

                    PairingStepsCard()

                    PairingChecklistCard()
                }
                .ignoresSafeArea(.container, edges: .vertical)

                EdgeFade(edge: .top, height: topInset)
                    .frame(maxHeight: .infinity, alignment: .top)
                    .ignoresSafeArea()
                    .allowsHitTesting(false)

                EdgeFade(edge: .bottom, height: 200)
                    .frame(maxHeight: .infinity, alignment: .bottom)
                    .ignoresSafeArea()
                    .allowsHitTesting(false)

                PairingActionDock(
                    isAuthenticating: model.isAuthenticating,
                    onScanRequested: onScanRequested,
                    onNFCRequested: onNFCRequested
                )
            }
        }
        .navigationTitle("")
        .toolbar(.hidden, for: .navigationBar)
    }
}

private struct EdgeFade: View {
    enum Edge { case top, bottom }
    let edge: Edge
    let height: CGFloat

    var body: some View {
        LinearGradient(
            stops: edge == .top ? [
                .init(color: Color.idpGroupedBackground, location: 0.0),
                .init(color: Color.idpGroupedBackground.opacity(0.95), location: 0.4),
                .init(color: Color.idpGroupedBackground.opacity(0.0), location: 1.0)
            ] : [
                .init(color: Color.idpGroupedBackground.opacity(0.0), location: 0.0),
                .init(color: Color.idpGroupedBackground.opacity(0.95), location: 0.6),
                .init(color: Color.idpGroupedBackground, location: 1.0)
            ],
            startPoint: .top,
            endPoint: .bottom
        )
        .frame(height: height)
    }
}

private struct PairingHero: View {
    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            HStack(spacing: 10) {
                HeroGlyph()
                ShadcnBadge(
                    title: "Passport setup",
                    tone: .accent,
                    leading: Image(systemName: "lock.shield")
                )
            }

            VStack(alignment: .leading, spacing: 8) {
                Text("Your passport, in your pocket")
                    .font(.title2.weight(.bold))
                    .fixedSize(horizontal: false, vertical: true)

                Text("Link this iPhone to your idp.global web session to approve sign-ins, receive security alerts, and prove your identity with NFC.")
                    .font(.subheadline)
                    .foregroundStyle(Color.idpMutedForeground)
                    .fixedSize(horizontal: false, vertical: true)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(.top, 4)
    }
}

private struct HeroGlyph: View {
    var body: some View {
        ZStack {
            RoundedRectangle(cornerRadius: IdP.controlRadius, style: .continuous)
                .fill(IdP.tint)

            Image(systemName: "shield.lefthalf.filled")
                .font(.system(size: 20, weight: .semibold))
                .foregroundStyle(Color.idpPrimaryForeground)
        }
        .frame(width: 40, height: 40)
    }
}

private struct PairingStepsCard: View {
    var body: some View {
        AppSectionCard(
            title: "How pairing works",
            subtitle: "Three quick steps to finish setup.",
            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."
                )

                PairingStepRow(
                    number: 2,
                    title: "Scan the pairing QR",
                    message: "Point this iPhone at the QR shown by that browser session."
                )

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

private struct PairingChecklistCard: View {
    var body: some View {
        AppSectionCard(
            title: "Before you scan",
            subtitle: "A few quick checks help the link complete cleanly.",
            compactLayout: true
        ) {
            VStack(alignment: .leading, spacing: 12) {
                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: "doc.on.clipboard",
                    text: "No camera? The scanner also accepts a pasted pairing link."
                )
                PairingNoteRow(
                    icon: "wave.3.right",
                    text: "Organizations using NFC tags can link with NFC instead of QR."
                )
            }
        }
    }
}

private struct PairingActionDock: View {
    let isAuthenticating: Bool
    let onScanRequested: () -> Void
    let onNFCRequested: () -> Void

    var body: some View {
        VStack(spacing: 10) {
            Button(action: onScanRequested) {
                HStack(spacing: 10) {
                    if isAuthenticating {
                        ProgressView()
                            .progressViewStyle(.circular)
                            .tint(Color.idpPrimaryForeground)
                    } else {
                        Image(systemName: "qrcode.viewfinder")
                    }

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

            Button(action: onNFCRequested) {
                Label("Use NFC tag instead", systemImage: "wave.3.right")
            }
            .buttonStyle(SecondaryActionStyle())
            .disabled(isAuthenticating)
        }
        .padding(16)
        .glassEffect(.regular, in: RoundedRectangle(cornerRadius: 20, style: .continuous))
        .padding(.horizontal, 16)
        .padding(.bottom, 12)
    }
}


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

    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            ZStack {
                RoundedRectangle(cornerRadius: 6, style: .continuous)
                    .fill(IdP.tint.opacity(0.12))
                Text("\(number)")
                    .font(.caption.weight(.bold))
                    .foregroundStyle(IdP.tint)
            }
            .frame(width: 24, height: 24)

            VStack(alignment: .leading, spacing: 2) {
                Text(title)
                    .font(.subheadline.weight(.semibold))
                Text(message)
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
                    .fixedSize(horizontal: false, vertical: true)
            }

            Spacer(minLength: 0)
        }
    }
}

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

    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            Image(systemName: icon)
                .font(.caption.weight(.semibold))
                .foregroundStyle(IdP.tint)
                .frame(width: 24, height: 24)
                .background(IdP.tint.opacity(0.12), in: RoundedRectangle(cornerRadius: 6, style: .continuous))

            Text(text)
                .font(.footnote)
                .foregroundStyle(Color.idpForeground)
                .fixedSize(horizontal: false, vertical: true)

            Spacer(minLength: 0)
        }
    }
}
#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