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: 170) {
            PairingHero()

            PairingStepsCard()

            PairingChecklistCard()
        }
        .navigationTitle("")
        .toolbar(.hidden, for: .navigationBar)
        .safeAreaInset(edge: .bottom) {
            PairingActionDock(
                isAuthenticating: model.isAuthenticating,
                onScanRequested: onScanRequested,
                onNFCRequested: onNFCRequested
            )
        }
    }
}

private struct PairingHero: View {
    var body: some View {
        VStack(alignment: .leading, spacing: 18) {
            HeroGlyph()

            VStack(alignment: .leading, spacing: 10) {
                Text("Your passport, in your pocket")
                    .font(.system(size: 30, weight: .bold, design: .default))
                    .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, 8)
    }
}

private struct HeroGlyph: View {
    var body: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 26, style: .continuous)
                .fill(
                    LinearGradient(
                        colors: [
                            IdP.tint,
                            IdP.tint.opacity(0.78)
                        ],
                        startPoint: .topLeading,
                        endPoint: .bottomTrailing
                    )
                )
                .frame(width: 76, height: 76)
                .shadow(color: IdP.tint.opacity(0.35), radius: 18, x: 0, y: 10)

            RoundedRectangle(cornerRadius: 26, style: .continuous)
                .stroke(Color.white.opacity(0.22), lineWidth: 1)
                .frame(width: 76, height: 76)

            Image(systemName: "shield.lefthalf.filled")
                .font(.system(size: 34, weight: .semibold))
                .foregroundStyle(.white)
        }
    }
}

private struct PairingStepsCard: View {
    var body: some View {
        AppPanel(compactLayout: true, radius: 22) {
            VStack(alignment: .leading, spacing: 4) {
                Text("How pairing works")
                    .font(.headline)
                Text("Three quick steps to finish setup.")
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
            }

            VStack(spacing: 0) {
                PairingStepRow(
                    number: 1,
                    title: "Start from the web",
                    message: "Open idp.global in your browser and begin a new device pairing."
                )

                StepDivider()

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

                StepDivider()

                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 {
        AppPanel(compactLayout: true, radius: 22) {
            VStack(alignment: .leading, spacing: 4) {
                Text("Before you scan")
                    .font(.headline)
                Text("A few quick checks help the link complete cleanly.")
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
            }

            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(.horizontal, 16)
        .padding(.top, 12)
        .padding(.bottom, 14)
        .background(
            Rectangle()
                .fill(.regularMaterial)
                .ignoresSafeArea()
                .overlay(alignment: .top) {
                    Rectangle()
                        .fill(Color.idpSeparator.opacity(0.5))
                        .frame(height: 0.5)
                }
        )
    }
}

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

    var body: some View {
        HStack(alignment: .top, spacing: 14) {
            ZStack {
                Circle()
                    .fill(IdP.tint.opacity(0.14))
                Text("\(number)")
                    .font(.subheadline.weight(.bold))
                    .foregroundStyle(IdP.tint)
            }
            .frame(width: 30, height: 30)

            VStack(alignment: .leading, spacing: 3) {
                Text(title)
                    .font(.subheadline.weight(.semibold))
                Text(message)
                    .font(.footnote)
                    .foregroundStyle(Color.idpMutedForeground)
                    .fixedSize(horizontal: false, vertical: true)
            }

            Spacer(minLength: 0)
        }
        .padding(.vertical, 10)
    }
}

private struct StepDivider: View {
    var body: some View {
        HStack(spacing: 14) {
            Rectangle()
                .fill(Color.idpSeparator.opacity(0.6))
                .frame(width: 1, height: 10)
                .padding(.leading, 14)
            Spacer()
        }
    }
}

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

    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            Image(systemName: icon)
                .font(.system(size: 13, weight: .semibold))
                .foregroundStyle(IdP.tint)
                .frame(width: 26, height: 26)
                .background(IdP.tint.opacity(0.12), in: RoundedRectangle(cornerRadius: 8, style: .continuous))

            Text(text)
                .font(.footnote)
                .foregroundStyle(Color.idpForeground.opacity(0.82))
                .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