import 'dart:async';
import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import '../../services/call_session.dart';
import '../widgets/status_indicator.dart';
import 'call_screen.dart';
import 'settings_screen.dart';

/// Home screen — pre-call setup and call initiation.
///
/// Responsibilities:
///   1. Request RECORD_AUDIO permission on first launch.
///   2. Show current key status (fingerprint loaded / none).
///   3. Allow user to navigate to Settings to enter passphrase.
///   4. Start / end the secure call.
class HomeScreen extends StatefulWidget {
  final CallSession session;
  const HomeScreen({super.key, required this.session});

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  StreamSubscription<SessionState>? _stateSub;
  SessionState _state = SessionState.noKey;
  String? _fingerprint;
  bool _permGranted = false;

  @override
  void initState() {
    super.initState();
    _state    = widget.session.state;
    _stateSub = widget.session.onStateChange
        .listen((s) { if (mounted) setState(() => _state = s); });
    _init();
  }

  Future<void> _init() async {
    await _checkPermission();
    await _loadFingerprint();
  }

  Future<void> _checkPermission() async {
    final status = await Permission.microphone.status;
    if (status.isGranted) {
      if (mounted) setState(() => _permGranted = true);
      return;
    }
    final result = await Permission.microphone.request();
    if (mounted) setState(() => _permGranted = result.isGranted);
  }

  Future<void> _loadFingerprint() async {
    final fp = await widget.session.getSavedFingerprint();
    if (mounted) setState(() => _fingerprint = fp);
  }

  Future<void> _openSettings() async {
    await Navigator.of(context).push(
      MaterialPageRoute(
        builder: (_) => SettingsScreen(session: widget.session),
      ),
    );
    // Refresh fingerprint after returning from settings.
    await _loadFingerprint();
  }

  Future<void> _startCall() async {
    if (!_permGranted) {
      await _checkPermission();
      if (!_permGranted) {
        if (mounted) {
          ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
            content: Text('Microphone permission is required'),
            backgroundColor: Colors.redAccent,
          ));
        }
        return;
      }
    }

    if (!widget.session.hasKey) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
          content: Text('Set a passphrase in Settings first'),
          backgroundColor: Colors.amber,
        ));
      }
      return;
    }

    await widget.session.startCall();
    if (!mounted) return;
    await Navigator.of(context).push(
      MaterialPageRoute(
        builder: (_) => CallScreen(session: widget.session),
      ),
    );
  }

  @override
  void dispose() {
    _stateSub?.cancel();
    super.dispose();
  }

  // ── Build ──────────────────────────────────────────────────────────

  @override
  Widget build(BuildContext context) {
    final canCall = _permGranted &&
        (_state == SessionState.keyLoaded ||
         _state == SessionState.inCall);

    return Scaffold(
      backgroundColor: const Color(0xFF0D0D1A),
      appBar: AppBar(
        backgroundColor: const Color(0xFF0D0D1A),
        title: const Text('SecureCall',
            style: TextStyle(color: Colors.white, letterSpacing: 2,
                fontWeight: FontWeight.w300)),
        actions: [
          IconButton(
            icon: const Icon(Icons.settings_outlined, color: Colors.white54),
            tooltip: 'Settings',
            onPressed: _openSettings,
          ),
        ],
      ),
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 28, vertical: 12),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              // ── Status bar ────────────────────────────────────────
              Center(child: StatusIndicator(state: _state)),
              const SizedBox(height: 32),

              // ── Key fingerprint card ──────────────────────────────
              _KeyCard(fingerprint: _fingerprint, onTap: _openSettings),
              const SizedBox(height: 20),

              // ── Permission card ───────────────────────────────────
              if (!_permGranted)
                _WarningCard(
                  icon: Icons.mic_off,
                  message:
                      'Microphone permission denied.\nTap to request again.',
                  onTap: _checkPermission,
                ),

              const Spacer(),

              // ── How it works ──────────────────────────────────────
              _HowItWorksSection(),
              const SizedBox(height: 28),

              // ── Start call button ─────────────────────────────────
              ElevatedButton.icon(
                onPressed: canCall ? _startCall : null,
                icon: const Icon(Icons.lock_rounded, size: 20),
                label: const Text('START SECURE CALL',
                    style: TextStyle(
                        fontSize: 16,
                        letterSpacing: 2,
                        fontWeight: FontWeight.bold)),
                style: ElevatedButton.styleFrom(
                  backgroundColor: const Color(0xFF00C853),
                  disabledBackgroundColor: const Color(0xFF1A3020),
                  padding: const EdgeInsets.symmetric(vertical: 18),
                  shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(14)),
                ),
              ),
              const SizedBox(height: 16),
              Center(
                child: Text(
                  canCall
                      ? 'First start a normal phone call, then press the button'
                      : _fingerprint == null
                          ? 'Set a passphrase in ⚙ Settings to enable'
                          : 'Microphone permission required',
                  textAlign: TextAlign.center,
                  style: const TextStyle(
                      color: Colors.white38, fontSize: 12, height: 1.5),
                ),
              ),
              const SizedBox(height: 12),
            ],
          ),
        ),
      ),
    );
  }
}

// ── Sub-widgets ────────────────────────────────────────────────────────

class _KeyCard extends StatelessWidget {
  final String? fingerprint;
  final VoidCallback onTap;
  const _KeyCard({required this.fingerprint, required this.onTap});

  @override
  Widget build(BuildContext context) {
    final hasKey = fingerprint != null;
    return InkWell(
      onTap: onTap,
      borderRadius: BorderRadius.circular(12),
      child: Container(
        padding: const EdgeInsets.all(16),
        decoration: BoxDecoration(
          color: const Color(0xFF1A1A2E),
          borderRadius: BorderRadius.circular(12),
          border: Border.all(
            color: hasKey
                ? const Color(0xFF00C853).withValues(alpha: 0.5)
                : Colors.white12,
          ),
        ),
        child: Row(
          children: [
            Icon(
              hasKey ? Icons.vpn_key_rounded : Icons.vpn_key_off_outlined,
              color: hasKey ? const Color(0xFF00C853) : Colors.white38,
              size: 28,
            ),
            const SizedBox(width: 14),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    hasKey ? 'Encryption key loaded' : 'No encryption key',
                    style: TextStyle(
                      color: hasKey
                          ? const Color(0xFF00C853)
                          : Colors.white54,
                      fontWeight: FontWeight.w600,
                    ),
                  ),
                  if (hasKey) ...[
                    const SizedBox(height: 4),
                    Text(
                      'Fingerprint: $fingerprint',
                      style: const TextStyle(
                          color: Colors.white38,
                          fontSize: 12,
                          fontFamily: 'monospace',
                          letterSpacing: 2),
                    ),
                  ] else ...[
                    const SizedBox(height: 4),
                    const Text('Tap to open Settings and set passphrase',
                        style: TextStyle(color: Colors.white30, fontSize: 12)),
                  ],
                ],
              ),
            ),
            const Icon(Icons.chevron_right, color: Colors.white24),
          ],
        ),
      ),
    );
  }
}

class _WarningCard extends StatelessWidget {
  final IconData icon;
  final String message;
  final VoidCallback onTap;
  const _WarningCard(
      {required this.icon, required this.message, required this.onTap});

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: onTap,
      borderRadius: BorderRadius.circular(12),
      child: Container(
        padding: const EdgeInsets.all(14),
        decoration: BoxDecoration(
          color: Colors.amber.withValues(alpha: 0.08),
          borderRadius: BorderRadius.circular(12),
          border:
              Border.all(color: Colors.amber.withValues(alpha: 0.4)),
        ),
        child: Row(
          children: [
            Icon(icon, color: Colors.amber, size: 22),
            const SizedBox(width: 12),
            Expanded(
              child: Text(message,
                  style: const TextStyle(
                      color: Colors.amber, fontSize: 13, height: 1.4)),
            ),
          ],
        ),
      ),
    );
  }
}

class _HowItWorksSection extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    const steps = [
      (Icons.phone_in_talk_rounded,
       'Start a normal cellular voice call with your peer'),
      (Icons.vpn_key_rounded,
       'Both devices must have the same passphrase loaded'),
      (Icons.mic,
       'Press PTT to speak — FSK audio transmits over the call'),
      (Icons.hearing,
       'Tap LISTEN to receive and decode incoming voice'),
    ];

    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: const Color(0xFF0F0F1E),
        borderRadius: BorderRadius.circular(12),
        border: Border.all(color: Colors.white10),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Text('HOW TO USE',
              style: TextStyle(
                  color: Colors.white38, fontSize: 11, letterSpacing: 2)),
          const SizedBox(height: 12),
          ...steps.map((s) => Padding(
                padding: const EdgeInsets.only(bottom: 10),
                child: Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Icon(s.$1, color: Colors.white38, size: 16),
                    const SizedBox(width: 10),
                    Expanded(
                        child: Text(s.$2,
                            style: const TextStyle(
                                color: Colors.white54,
                                fontSize: 13,
                                height: 1.4))),
                  ],
                ),
              )),
        ],
      ),
    );
  }
}