import SwiftUI
import TVAnarchyCore

/// The locked front door. Until this Mac has joined an install (via Device Mesh)
/// there's nothing to show, so a fresh install renders ONLY this page: what the
/// app is, plus the two ways in (scan the join QR an already-trusted device
/// displays from Settings → Device Mesh, or paste the same config as text).
/// Joining persists the credentials and flips the shell over to the real UI.
struct IntroView: View {
    let onJoined: () -> Void

    private enum Mode { case welcome, scanning, pasting, joined }
    @State private var mode: Mode = .welcome
    @State private var pasted = ""
    @State private var error: String?
    @State private var joinedConfig: WGQuickConfig?

    private let fleet = FleetState()

    var body: some View {
        VStack(spacing: 18) {
            Spacer(minLength: 24)
            Image(systemName: "antenna.radiowaves.left.and.right.circle.fill")
                .font(.system(size: 64)).foregroundStyle(.tint)
            Text("TVAnarchy").font(.largeTitle).bold()
            Text("Your media install's remote control — browse the library, play anywhere, manage downloads. Everything lives on the devices in your install, so the first step is joining this Mac to it.")
                .font(.callout).foregroundStyle(.secondary)
                .multilineTextAlignment(.center).frame(maxWidth: 420)

            switch mode {
            case .welcome: welcome
            case .scanning: scanner
            case .pasting: paster
            case .joined: done
            }

            if let error {
                Text(error).font(.caption).foregroundStyle(.red)
                    .frame(maxWidth: 420)
            }
            Spacer(minLength: 24)
        }
        .padding(32)
        .frame(minWidth: 560, minHeight: 540)
    }

    private var welcome: some View {
        VStack(spacing: 10) {
            Text("On a Mac that's already part of the install, open Settings → Device Mesh, enroll this Mac by name, and bring the QR here.")
                .font(.caption).foregroundStyle(.secondary)
                .multilineTextAlignment(.center).frame(maxWidth: 420)
            HStack(spacing: 12) {
                Button { error = nil; mode = .scanning } label: {
                    Label("Scan join QR", systemImage: "qrcode.viewfinder")
                }
                .controlSize(.large).buttonStyle(.borderedProminent)
                Button { error = nil; mode = .pasting } label: {
                    Label("Paste config", systemImage: "doc.on.clipboard")
                }
                .controlSize(.large)
            }
        }
    }

    private var scanner: some View {
        VStack(spacing: 10) {
            QRScannerView { payload in join(payload) }
                .frame(width: 360, height: 270)
                .clipShape(RoundedRectangle(cornerRadius: 12))
                .overlay(RoundedRectangle(cornerRadius: 12).strokeBorder(.quaternary))
            Text("Hold the join QR up to this Mac's camera.")
                .font(.caption).foregroundStyle(.secondary)
            Button("Cancel") { error = nil; mode = .welcome }
        }
    }

    private var paster: some View {
        VStack(spacing: 10) {
            TextEditor(text: $pasted)
                .font(.caption.monospaced())
                .frame(width: 420, height: 180)
                .overlay(RoundedRectangle(cornerRadius: 6).strokeBorder(.quaternary))
            Text("Paste the WireGuard config from the enrolling Mac (Copy config under its QR).")
                .font(.caption).foregroundStyle(.secondary)
            HStack {
                Button("Cancel") { error = nil; mode = .welcome }
                Button("Join") { join(pasted) }
                    .buttonStyle(.borderedProminent)
                    .disabled(pasted.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
            }
        }
    }

    private var done: some View {
        VStack(spacing: 10) {
            Image(systemName: "checkmark.seal.fill").font(.system(size: 40)).foregroundStyle(.green)
            Text("Joined as \(joinedConfig?.device ?? "this Mac") · \(joinedConfig?.address ?? "")")
                .font(.headline)
            Text("Credentials are saved. At home the install is reachable over the LAN right away; for anywhere-access, import the same config into the WireGuard app and enable the tunnel.")
                .font(.caption).foregroundStyle(.secondary)
                .multilineTextAlignment(.center).frame(maxWidth: 420)
            HStack(spacing: 12) {
                if let conf = joinedConfig {
                    Button("Copy config for WireGuard") { copyToClipboard(conf.text) }
                }
                Button("Enter TVAnarchy") { onJoined() }
                    .buttonStyle(.borderedProminent).controlSize(.large)
            }
        }
    }

    private func join(_ text: String) {
        let host = Host.current().localizedName?.lowercased()
            .map { $0.isLetter || $0.isNumber ? $0 : "-" } ?? []
        let fallback = String(host).split(separator: "-").joined(separator: "-")
        do {
            joinedConfig = try fleet.join(configText: text,
                                          fallbackDevice: fallback.isEmpty ? "this-mac" : fallback)
            error = nil
            mode = .joined
        } catch {
            // Keep scanning/pasting — a half-read QR or stray clipboard content
            // shouldn't bounce the user back to the start.
            self.error = error.localizedDescription
        }
    }
}