import "package:auto_route/auto_route.dart";
import "package:flutter/material.dart";
import "package:flutter/services.dart";
import "package:flutter_riverpod/flutter_riverpod.dart";

import "package:smol_mail/data/providers/providers.dart";
import "package:smol_mail/presentation/routes/app_router.gr.dart";
import "package:smol_mail/presentation/widgets/primary_button.dart";
import "package:smol_mail/presentation/widgets/secondary_button.dart";
import "package:smol_mail/presentation/widgets/small_loading_spinner.dart";
import "package:smol_mail/smol/crypto.dart";
import "package:smol_mail/smol/errors.dart";
import "package:smol_mail/smol/proto.dart";
import "package:smol_mail/presentation/theme/app_colors.dart";
import "package:smol_mail/shared/utils/snackbar.dart";

/// First-run flow: create or restore an identity, back the seed up, pin the
/// home server's key and register an address (SPEC.md §4: registration against
/// an unpinned server is not permitted).
@RoutePage()
class OnboardingScreen extends ConsumerStatefulWidget {
  const OnboardingScreen({super.key});

  @override
  ConsumerState<OnboardingScreen> createState() => _OnboardingScreenState();
}

enum _Step { welcome, backup, restore, register }

class _OnboardingScreenState extends ConsumerState<OnboardingScreen> {
  _Step step = _Step.welcome;
  Uint8List? createdSeed;
  bool busy = false;
  // The register step doubles as "pin a key to finish recalling" when a
  // restore's recall can't proceed without one yet — same fields, different
  // framing and default action, not the generic "register a new address" copy.
  bool recallIntent = false;

  final seedController = TextEditingController();
  final restoreAddressController = TextEditingController();
  final addressController = TextEditingController();
  final serverKeyController = TextEditingController();
  final tokenController = TextEditingController();

  @override
  void dispose() {
    seedController.dispose();
    restoreAddressController.dispose();
    addressController.dispose();
    serverKeyController.dispose();
    tokenController.dispose();
    super.dispose();
  }

  void _showError(Object error) {
    if (!mounted) return;
    // Replace rather than queue: a fresh error must not wait behind a stale
    // one — a queued SnackBar is indistinguishable from "nothing happened".
    ScaffoldMessenger.of(context).hideCurrentSnackBar();
    showErrorSnackBar(
        context, error is SmolError ? error.message : error.toString());
  }

  // Reaching onboarding at all means HomeGuard already found no complete
  // identity+account, so a seed still sitting in the store here can only be
  // an abandoned attempt from earlier in this same flow (wrong seed, failed
  // recall, "Back") — safe to replace rather than reject.
  // wipe() is fire-and-forget here, like every other store write in this
  // screen (setIdentity, pinServer, ...) — Hive updates its in-memory state
  // synchronously and persists to disk in the background, so the identity
  // check right after is already consistent without awaiting the write.
  void _clearAbandonedIdentity() {
    final client = ref.read(clientProvider);
    if (client.identity != null && client.accountAddress() == null) {
      ref.read(storeProvider).wipe();
    }
  }

  void _createIdentity() {
    _clearAbandonedIdentity();
    final client = ref.read(clientProvider);
    try {
      final fresh = client.createIdentity();
      setState(() {
        createdSeed = fresh.seed;
        step = _Step.backup;
      });
    } on Exception catch (err) {
      _showError(err);
    }
  }

  void _restoreIdentity() {
    setState(() => step = _Step.restore);
  }

  // Restoring must succeed on its own even if recall fails (server not
  // pinned yet, offline, typo) — recall can always be retried from the
  // register step or settings afterward.
  void _submitRestore() {
    _clearAbandonedIdentity();
    final client = ref.read(clientProvider);
    try {
      client.restoreIdentity(seedController.text);
    } on Exception catch (err) {
      _showError(err);
      return;
    }
    final addressText = restoreAddressController.text.trim();
    if (addressText.isEmpty) {
      setState(() => step = _Step.register);
      return;
    }
    // The register step has its own address field (it also needs a server
    // key, which restore doesn't collect) — carry over what was already
    // typed rather than making the user re-enter it.
    addressController.text = addressText;
    final SmolAddress addr;
    try {
      addr = parseAddress(addressText);
    } on Exception catch (err) {
      // A genuine typo, distinct from the merely-unpinned case below — still
      // worth an error, but land on the same recall-oriented step to fix it.
      _showError(err);
      setState(() {
        recallIntent = true;
        step = _Step.register;
      });
      return;
    }
    // Recall needs the host pinned first (SPEC.md §4). That's the expected,
    // common state right after a restore — not an error — so check for it
    // up front instead of letting recallAccount fail and surfacing that as
    // one: this address just needs a key before its first recall can proceed.
    if (ref.read(storeProvider).serverPin(addr.host) == null) {
      setState(() {
        recallIntent = true;
        step = _Step.register;
      });
      return;
    }
    () async {
      try {
        await client.recallAccount(addressText);
        if (!mounted) return;
        ref.read(revisionProvider.notifier).bump();
        AutoRouter.of(context).replace(InboxRoute());
      } on Exception catch (err) {
        if (!mounted) return;
        _showError(err);
        setState(() {
          recallIntent = true;
          step = _Step.register;
        });
      }
    }();
  }

  Future<void> _submitRegistration() async {
    await _submit(recall: false);
  }

  // Restoring a seed on a new device knows the identity but not the address it
  // was registered under; recall binds it without re-REGISTER.
  Future<void> _submitRecall() async {
    await _submit(recall: true);
  }

  Future<void> _submit({required bool recall}) async {
    final client = ref.read(clientProvider);
    setState(() => busy = true);
    try {
      final address = parseAddress(addressController.text);
      // Recall needs a pin too (SPEC.md §4), and the key for it is right
      // here in the form — pin it before either path. An empty field means
      // "already pinned, e.g. by a previous attempt or a preset server".
      final serverKey = serverKeyController.text.trim();
      if (serverKey.isNotEmpty) {
        client.pinServer(address.host, serverKey);
      }
      if (recall) {
        await client.recallAccount(address.short);
      } else {
        await client.registerAccount(address.short,
            token: tokenController.text.trim());
      }
      if (mounted) {
        ref.read(revisionProvider.notifier).bump();
        AutoRouter.of(context).replace(InboxRoute());
      }
    } catch (err) {
      _showError(err);
    } finally {
      if (mounted) setState(() => busy = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SingleChildScrollView(
        padding: const EdgeInsets.symmetric(horizontal: 25),
        child: switch (step) {
          _Step.welcome => _welcome(context),
          _Step.backup => _backup(context),
          _Step.restore => _restore(context),
          _Step.register => _register(context),
        },
      ),
    );
  }

  Widget _header(BuildContext context, String title) => Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const SizedBox(height: 60),
          Row(
            children: [
              const Image(image: AssetImage("assets/images/logo-small.png")),
              const SizedBox(width: 10),
              Text("kirakira", style: Theme.of(context).textTheme.titleLarge),
            ],
          ),
          const SizedBox(height: 40),
          Text(title, style: Theme.of(context).textTheme.titleMedium),
        ],
      );

  Widget _welcome(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        _header(context,
            "One keypair is the whole identity: an address, a key and a message."),
        const SizedBox(height: 40),
        PrimaryButton(
          onPressed: _createIdentity,
          child: const Text("Create Identity"),
        ),
        const SizedBox(height: 5),
        SecondaryButton(
          text: "Restore From Seed",
          onPressed: _restoreIdentity,
        ),
        const SizedBox(height: 80),
      ],
    );
  }

  Widget _backup(BuildContext context) {
    final seed = createdSeed!;
    final seedHex = hex(seed);
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        _header(context, "Back up this seed; it is the only secret."),
        const SizedBox(height: 20),
        Text(
          "fingerprint:\n${fingerprint(ed25519PublicKey(seed))}",
          style: Theme.of(context).textTheme.bodySmall,
        ),
        const SizedBox(height: 20),
        SelectableText(
          seedHex,
          style: Theme.of(context)
              .textTheme
              .bodySmall!
              .copyWith(color: Theme.of(context).colorScheme.primary),
        ),
        TextButton(
          onPressed: () async {
            await Clipboard.setData(ClipboardData(text: seedHex));
            if (mounted) {
              ScaffoldMessenger.of(this.context).showSnackBar(
                const SnackBar(content: Text("Seed copied to clipboard")),
              );
            }
          },
          child: const Text("Copy seed"),
        ),
        const SizedBox(height: 40),
        PrimaryButton(
          onPressed: () => setState(() => step = _Step.register),
          child: const Text("I have backed it up"),
        ),
        const SizedBox(height: 80),
      ],
    );
  }

  Widget _restore(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        _header(context, "Enter the 32-byte seed as 64 hex characters."),
        const SizedBox(height: 20),
        TextField(
          controller: seedController,
          decoration: InputDecoration(
            hintText: "64 hex characters",
            filled: true,
            fillColor: Theme.of(context).extension<AppColors>()!.cardFill,
          ),
        ),
        const SizedBox(height: 15),
        TextField(
          controller: restoreAddressController,
          decoration: InputDecoration(
            labelText: "Address (if already registered)",
            hintText: "alice@example.org",
            filled: true,
            fillColor: Theme.of(context).extension<AppColors>()!.cardFill,
          ),
        ),
        const SizedBox(height: 30),
        PrimaryButton(
          onPressed: _submitRestore,
          child: const Text("Restore"),
        ),
        const SizedBox(height: 5),
        SecondaryButton(
          text: "Back",
          onPressed: () => setState(() => step = _Step.welcome),
        ),
        const SizedBox(height: 40),
      ],
    );
  }

  Widget _register(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        _header(
          context,
          recallIntent
              ? "Pin this server's public key to finish restoring your address."
              : "Register an address. Pin the server's public key first — obtain it from the operator through a trusted channel.",
        ),
        const SizedBox(height: 30),
        TextField(
          controller: addressController,
          decoration: InputDecoration(
            labelText: "Address",
            hintText: "you@example.org[:1961]",
            filled: true,
            fillColor: Theme.of(context).extension<AppColors>()!.cardFill,
          ),
        ),
        const SizedBox(height: 15),
        TextField(
          controller: serverKeyController,
          decoration: InputDecoration(
            labelText: "Server public key",
            hintText: "base32, 52 characters",
            filled: true,
            fillColor: Theme.of(context).extension<AppColors>()!.cardFill,
          ),
        ),
        if (!recallIntent) ...[
          const SizedBox(height: 15),
          TextField(
            controller: tokenController,
            decoration: InputDecoration(
              labelText: "Invite token (optional)",
              filled: true,
              fillColor: Theme.of(context).extension<AppColors>()!.cardFill,
            ),
          ),
        ],
        const SizedBox(height: 40),
        PrimaryButton(
          onPressed: busy
              ? () {}
              : (recallIntent ? _submitRecall : _submitRegistration),
          child: busy
              ? const SmallLoadingSpinner()
              : Text(recallIntent ? "Pin and Recall" : "Pin and Register"),
        ),
        TextButton(
          onPressed: busy
              ? () {}
              : (recallIntent ? _submitRegistration : _submitRecall),
          child: Text(recallIntent
              ? "Register a new address instead"
              : "Already registered? Recall"),
        ),
        const SizedBox(height: 80),
      ],
    );
  }
}