import 'dart:async';
import 'dart:ffi';
import 'dart:isolate';

import 'package:ffi/ffi.dart';

import '../../core/hwp_source.dart';

/// 관리자 지시 (10/20): Android 의 HWP · HWPX → PDF - APK 에 든 libjj_rhwp.so (rhwp v0.8.7, MIT - tool/build_rhwp_android.sh ·
/// tool/rhwp_ffi) 를 dart:ffi 로 부른다. 여는 것 · 바꾸는 것은 다른 isolate 에서 (화면을 막지 않게), 한 문서는 한 번에 하나씩.
class RhwpEngine implements HwpPdfEngine {
  static const libName = 'libjj_rhwp.so';

  /// 글꼴을 찾을 폴더 (Android 는 rhwp 가 시스템 글꼴을 스스로 찾지 않는다 - 한글은 Noto Sans/Serif CJK KR 로 대신 그림).
  /// 관리자 판단 (10/20): 한글 글꼴 컴포넌트를 받으면 그 폴더를 앞에 더한다 (아직 없음)
  static const fontDirs = ['/system/fonts'];

  /// 라이브러리를 읽을 수 있는지 (없으면 다른 앱으로 연다)
  static bool get available {
    try {
      DynamicLibrary.open(libName);
      return true;
    } catch (_) {
      return false;
    }
  }

  @override
  Future<HwpPdfDoc> open(String path, {String? password}) async {
    final (handle, err) = await Isolate.run(() => _open(path, password ?? ''));
    if (handle == 0) throw HwpPdfException(err ?? 'rhwp');
    final pages = await Isolate.run(() => _pageCount(handle));
    return _RhwpDoc(handle, pages);
  }
}

class _RhwpDoc implements HwpPdfDoc {
  final int _handle;
  @override
  final int pageCount;
  var _closed = false;

  /// 한 번에 하나씩 (rhwp 문서는 여러 스레드에서 함께 쓰지 않는다)
  Future<void> _queue = Future.value();

  _RhwpDoc(this._handle, this.pageCount);

  Future<T> _serial<T>(Future<T> Function() f) {
    final run = _queue.then((_) => f());
    _queue = run.then((_) {}, onError: (Object _) {});
    return run;
  }

  @override
  Future<void> exportPdf(int from, int to, String out, {List<String> fontDirs = const []}) => _serial(() async {
        if (_closed) throw const HwpPdfException('closed');
        final h = _handle, dirs = fontDirs.join('\n');
        final err = await Isolate.run(() => _export(h, from, to, dirs, out));
        if (err != null) throw HwpPdfException(err);
      });

  @override
  Future<void> close() => _serial(() async {
        if (_closed) return;
        _closed = true;
        _close(_handle);
      });
}

// ───────── C 함수 (isolate 안에서 부른다 - 핸들은 주소 숫자로 넘긴다) ─────────

typedef _OpenC = Pointer<Void> Function(Pointer<Utf8>, Pointer<Utf8>, Pointer<Pointer<Utf8>>);
typedef _CountC = Int32 Function(Pointer<Void>);
typedef _CountD = int Function(Pointer<Void>);
typedef _ExportC = Int32 Function(Pointer<Void>, Int32, Int32, Pointer<Utf8>, Pointer<Utf8>, Pointer<Pointer<Utf8>>);
typedef _ExportD = int Function(Pointer<Void>, int, int, Pointer<Utf8>, Pointer<Utf8>, Pointer<Pointer<Utf8>>);
typedef _CloseC = Void Function(Pointer<Void>);
typedef _CloseD = void Function(Pointer<Void>);
typedef _FreeC = Void Function(Pointer<Utf8>);
typedef _FreeD = void Function(Pointer<Utf8>);

DynamicLibrary _lib() => DynamicLibrary.open(RhwpEngine.libName);

/// 돌려받은 오류 글을 읽고 푼다
String? _takeError(DynamicLibrary lib, Pointer<Pointer<Utf8>> err) {
  final p = err.value;
  if (p == nullptr) return null;
  final s = p.toDartString();
  lib.lookupFunction<_FreeC, _FreeD>('jj_rhwp_free')(p);
  return s;
}

(int, String?) _open(String path, String password) {
  final lib = _lib();
  final open = lib.lookupFunction<_OpenC, _OpenC>('jj_rhwp_open');
  final a = path.toNativeUtf8(), b = password.toNativeUtf8();
  final err = calloc<Pointer<Utf8>>();
  try {
    final doc = open(a, b, err);
    return (doc.address, _takeError(lib, err));
  } finally {
    calloc.free(a);
    calloc.free(b);
    calloc.free(err);
  }
}

int _pageCount(int handle) => _lib().lookupFunction<_CountC, _CountD>('jj_rhwp_page_count')(Pointer<Void>.fromAddress(handle));

String? _export(int handle, int from, int to, String fontDirs, String out) {
  final lib = _lib();
  final export = lib.lookupFunction<_ExportC, _ExportD>('jj_rhwp_export_pdf');
  final d = fontDirs.toNativeUtf8(), o = out.toNativeUtf8();
  final err = calloc<Pointer<Utf8>>();
  try {
    final r = export(Pointer<Void>.fromAddress(handle), from, to, d, o, err);
    final e = _takeError(lib, err);
    return r == 0 ? null : (e ?? 'rhwp');
  } finally {
    calloc.free(d);
    calloc.free(o);
    calloc.free(err);
  }
}

void _close(int handle) => _lib().lookupFunction<_CloseC, _CloseD>('jj_rhwp_close')(Pointer<Void>.fromAddress(handle));