// The app-level client: the same flows the screens have always called —
// connect with pinning, fetch with verification and acknowledgment, send
// with sent copies, contacts and rotation — now as one thin layer over
// fumi-core through the native binding. Every network operation runs on an
// isolate; the reads the UI makes per frame stay synchronous.

import "dart:io";
import "dart:math";
import "dart:typed_data";

import "package:smol_mail/native/client.dart";
import "package:smol_mail/native/ffi.dart";

import "package:smol_mail/smol/address.dart";
import "package:smol_mail/smol/errors.dart";
import "package:smol_mail/smol/store.dart";

class RefreshOutcome {
  final String message;
  final bool warn;

  const RefreshOutcome(this.message, this.warn);
}

class FetchSummary {
  final int stored;
  final List<String> rejected;

  const FetchSummary(this.stored, this.rejected);
}

class OpenedRecord {
  final String id;
  final String? sender; // base32
  final int? time;
  final Map<String, String> fields;
  final String body;
  final String? error;

  const OpenedRecord(this.id,
      {this.sender, this.time, this.fields = const {}, this.body = "", this.error});

  String get subject => error == null ? (fields["subject"] ?? "") : "";
}

class SmolClient {
  final SmolStore store;

  /// Trust warnings (§4/§8) the UI must not let the user miss; the app wires
  /// this to a persistent banner in app_widget.dart.
  void Function(String message)? onWarning;

  SmolClient(this.store);

  void _warn(String message) => onWarning?.call(message);

  FumiNative get _native => store.native;

  SmolFfi get _ffi => SmolFfi.open();

  /// Resolves the host the way that works everywhere this app runs: the
  /// platform resolver. On Android the native getaddrinfo that fumi-core's
  /// connect would use can be dead for app processes while this path works,
  /// so the facade resolves here and hands the IP across as a dial hint —
  /// the hostname keeps every identity role. IP literals dial themselves.
  Future<String> _dial(String host) async {
    final parsed = InternetAddress.tryParse(host);
    if (parsed != null) return parsed.address;
    try {
      final addresses = await InternetAddress.lookup(host);
      if (addresses.isEmpty) {
        throw SmolError("could not resolve $host");
      }
      return addresses.first.address;
    } on SocketException catch (err) {
      throw SmolError("could not resolve $host: ${err.message}");
    } catch (err) {
      if (err is SmolError) rethrow;
      throw SmolError("could not resolve $host");
    }
  }

  /// The account host's dial hint, for the ops that connect home.
  Future<String> _accountDial() async {
    final addr = accountAddress();
    if (addr == null) return "";
    return _dial(addr.host);
  }

  // Opening an envelope is microseconds native; the results never change, so
  // they are kept like the Dart core kept them. Failures cache too.
  final _openedCache = <String, OpenedRecord>{};

  SmolIdentity? get identity => store.identity();

  Uint8List? get master => store.master();

  SmolAddress? accountAddress() {
    final text = _ffi.accountAddress(_native.store!);
    if (text == null) return null;
    return parseAddress(text);
  }

  // --- identity setup ------------------------------------------------------------

  /// A fresh master secret at rotation index 0. Only this local step;
  /// nothing is sent until [registerAccount].
  Future<Uint8List> createIdentity() async {
    final fresh = _randomMaster();
    store.setMaster(fresh);
    return fresh;
  }

  Uint8List _randomMaster() {
    // The platform CSPRNG: 32 random bytes are the whole identity.
    final rng = Random.secure();
    return Uint8List.fromList(
        List.generate(32, (_) => rng.nextInt(256)));
  }

  /// §2: a master alone does not say which rotation index a server has bound,
  /// so restoring resolves the address and walks indices until one derives
  /// the key RESOLVE returned, then binds the account locally.
  Future<SmolAddress> restoreAndRecall(String masterHex, String addressText) async {
    Uint8List master;
    try {
      master = _unhex(masterHex.trim());
    } on Exception {
      throw const SmolError("master must be 64 hex characters");
    }
    if (master.length != 32) {
      throw SmolError("master is ${master.length} bytes, expected 32");
    }
    final addr = parseAddress(addressText);
    store.restoreMaster(master, 0);
    await _restore(addr);
    master.fillRange(0, master.length, 0);
    return addr;
  }

  Future<void> _restore(SmolAddress addr) async {
    // fumi's restore would tolerate an unpinned server (sec 8 trust on
    // first use), but this app's onboarding teaches the pin up front:
    // registration and fetching demand it anyway (sec 4), so restoring is
    // stopped at the pin step rather than letting the account bind to a
    // server whose key nobody verified.
    if (store.serverPin(addr.host, addr.port) == null) {
      throw SmolError("no pinned key for ${addr.host}. Obtain it from the "
          "operator through a trusted channel, then pin it in settings.");
    }
    try {
      // restore resolves, walks the rotation indices and writes the account
      // state; the account handle is rebuilt inside the binding.
      await _native.restore(addr.short, dial: await _dial(addr.host));
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
  }

  void pinServer(String host, String keyB32, int port) =>
      store.pinServer(host, keyB32, port);

  Future<void> registerAccount(String addressText, {String token = ""}) async {
    final addr = parseAddress(addressText);
    try {
      await _native.register(addr.short,
          invite: token.isEmpty ? null : token, dial: await _dial(addr.host));
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
  }

  /// Recall binds the identity to its registered address without
  /// re-REGISTER — the same resolve-and-walk a restore does (§2).
  Future<SmolAddress> recallAccount(String addressText) async {
    final addr = parseAddress(addressText);
    await _restore(addr);
    return addr;
  }

  // --- fetch -----------------------------------------------------------------

  Future<FetchSummary> fetch({bool reset = false}) async {
    if (master == null) throw const SmolError("no identity yet");
    if (accountAddress() == null) {
      throw const SmolError("not registered; register an address first");
    }
    final Map<String, dynamic> summary;
    try {
      summary = await _native.fetch(
          keep: store.leaveOnServer(), reset: reset, dial: await _accountDial());
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
    _openedCache.clear();
    if (summary["cancelled"] == true) {
      _warn("fetch cancelled; partial results kept");
    }
    return FetchSummary(
      summary["stored"] as int,
      [
        for (final r in (summary["rejected"] as List).cast<List<dynamic>>())
          "${r[0]}: ${r[1]}",
      ],
    );
  }

  /// Raises the cancellation flag; a running fetch stops between envelopes
  /// and returns a partial summary.
  void cancelFetch() => _native.cancelFetch();

  // --- delete ------------------------------------------------------------------

  /// Deletes a message locally, and from the server too if it might still be
  /// sitting there (only possible when "leave mail on server" was on when it
  /// was fetched — §10). Sent copies are local-only (§5.6).
  Future<void> deleteMessage(String folder, MailRecord record) async {
    if (folder != "sent" && record.keptOnServer) {
      if (accountAddress() == null) {
        throw const SmolError(
            "not registered; cannot reach the server to delete this message");
      }
      try {
        await _native.delete([record.id], dial: await _accountDial());
      } on NativeSmolException catch (err) {
        throw SmolError(err.message);
      }
    }
    await store.deleteMessage(folder, record.id);
    _openedCache.remove(record.id);
  }

  // --- accept tokens (§5.8) --------------------------------------------------------

  /// Admit a contact to the main tier; their token travels in our next
  /// message to them. Pushes the changed set to the server right away.
  Future<int> acceptContact(String address) async {
    try {
      return await _native.accept(address, dial: await _accountDial());
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
  }

  /// Withdraw a contact's accept token; their mail lands in requests from
  /// their next message on.
  Future<int> blockContact(String address) async {
    try {
      await _native.block(address, dial: await _accountDial());
      return 0;
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
  }

  // --- compose and send -----------------------------------------------------------

  /// Sends one message (§5, §6.1): recipient selection prefers a key we
  /// already trust, then RESOLVE with trust on first use; an accepted
  /// correspondent gets our token and a §5.6 sent copy is kept.
  Future<String> send(String toText, String subject, String body,
      {String? replyTo, bool anonymous = false}) async {
    if (master == null) throw const SmolError("no identity yet");
    final addr = parseAddress(toText);
    final Map<String, dynamic> sent;
    try {
      sent = await _native.send(addr.short, body,
          subject: subject.isEmpty ? null : subject,
          replyTo: replyTo,
          dial: await _dial(addr.host));
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
    if (sent["warning"] != null) {
      _warn(sent["warning"] as String);
    }
    return addr.short;
  }

  // --- reading -----------------------------------------------------------------

  /// Opens one sealed message: the described view the reader shows. Sync —
  /// one unseal is microseconds native, and the old Dart core did the same
  /// work at fifty times the cost.
  OpenedRecord describe(MailRecord row) {
    var entry = _openedCache[row.id];
    if (entry == null) {
      if (_native.account == null) {
        // No account handle: no identity to unseal with.
        entry = OpenedRecord(row.id, error: "no identity yet");
        _openedCache[row.id] = entry;
        return entry;
      }
      try {
        final described =
            _ffi.describe(_native.store!, _native.account!, row.id);
        entry = OpenedRecord(
          row.id,
          sender: described["sender"] as String,
          time: described["time"] as int,
          fields: (described["fields"] as Map).cast<String, String>(),
          body: described["text"] as String,
        );
      } on NativeSmolException catch (err) {
        entry = OpenedRecord(row.id, error: err.message);
      }
      _openedCache[row.id] = entry;
    }
    return entry;
  }

  /// The Reply-To address carried inside the message, but only when it is a
  /// full smol:// URI whose key matches the signer (§5.7); anything else is
  /// ordinary text.
  SmolAddress? replyAddress(OpenedRecord opened) {
    final claim = opened.fields["reply-to"];
    if (claim == null || opened.sender == null) return null;
    try {
      final parsed = parseAddress(claim);
      if (parsed.identity != null && parsed.identity == opened.sender) {
        return parsed;
      }
    } on SmolError {
      // malformed claim: display, never bind
    }
    return null;
  }

  /// Bind a user-supplied address to the key that signed a message. A smol://
  /// address carries its own key (verified); a short address is resolved and
  /// the result kept on first use. Anything that binds a different key is
  /// refused.
  Future<void> nameSender(String text, String senderKey) async {
    final addr = parseAddress(text.trim());
    if (addr.identity == null) {
      await refreshContact(addr.short);
      final known = store.contact(addr.short);
      if (known == null) {
        throw const SmolError("could not resolve that address");
      }
      if (known.key != senderKey) {
        throw const SmolError(
            "that address carries a different key than this message's sender");
      }
      return;
    }
    if (addr.identity != senderKey) {
      throw const SmolError(
          "that address carries a different key than this message's sender");
    }
    await store.saveContact(addr.short, senderKey, verified: true);
  }

  /// A signed Reply-To is the sender's own claim, so it saves as verified —
  /// but never over an address already pinned to a different key (§8).
  Future<void> saveReplyAddress(SmolAddress addr, String senderKey) async {
    final existing = store.contact(addr.short);
    if (existing != null && existing.key != senderKey) {
      throw SmolError("${addr.short} is already known with a different key — "
          "verify out of band before replying");
    }
    await store.saveContact(addr.short, senderKey, verified: true);
  }

  // Re-resolve a contact and apply §8: a valid rotation chain is accepted and
  // surfaced; anything else requires out-of-band verification.
  Future<RefreshOutcome> refreshContact(String address) async {
    final addr = parseAddress(address);
    if (addr.identity != null) {
      throw const SmolError(
          "that address already carries a key; use import instead");
    }
    final known = store.contact(addr.short);
    final Map<String, dynamic> resolved;
    try {
      resolved = await _native.resolve(addr.short, dial: await _dial(addr.host));
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
    final change = resolved["change"] as String;
    if (known == null) {
      return RefreshOutcome(
          "${addr.short} pinned (trust on first use)", change == "newUnverified");
    }
    switch (change) {
      case "none":
        return RefreshOutcome("${addr.short}: key unchanged", false);
      case "rotated":
        _warn("${addr.short} rotated its key; a signed chain confirms it.\n"
            "now ${resolved["key"]}");
        return RefreshOutcome(
            "${addr.short} rotated its key; a signed chain confirms it.\n"
            "now ${resolved["key"]}",
            true);
      default:
        return RefreshOutcome(
            "${addr.short} presents a different key with no valid rotation chain.\n"
            "Verify out of band, then import the new smol:// address.",
            true);
    }
  }

  // Bind a smol:// address to the key it carries (§8's strong path).
  Future<void> importContact(String text) async {
    final addr = parseAddress(text.trim());
    if (addr.identity == null) {
      throw const SmolError("import needs a smol:// address carrying a key");
    }
    await store.saveContact(addr.short, addr.identity!, verified: true);
  }

  // --- rotation -----------------------------------------------------------------

  /// §7: rotate to the next index's derived key and rebind the account with
  /// a signed certificate. The superseded key stays derivable from the
  /// master, since mail sealed to it stays readable with nothing else.
  Future<SmolIdentity> rotateIdentity() async {
    if (identity == null || master == null || accountAddress() == null) {
      throw const SmolError("rotate needs a registered account");
    }
    try {
      await _native.rotate(dial: await _accountDial());
    } on NativeSmolException catch (err) {
      throw SmolError(err.message);
    }
    _openedCache.clear();
    return identity!;
  }

  // A full wipe: every secret and every stored envelope. The UI must confirm.
  Future<void> wipe() async {
    await store.wipe();
    _openedCache.clear();
  }

  Uint8List _unhex(String text) {
    if (text.length % 2 != 0) {
      throw const SmolError("odd-length hex string");
    }
    return Uint8List.fromList([
      for (var i = 0; i < text.length; i += 2)
        int.parse(text.substring(i, i + 2), radix: 16),
    ]);
  }
}