import 'dart:async';
import 'dart:convert';

// import 'dart:io';

import 'package:computer/computer.dart';
import 'package:dartssh2/dartssh2.dart';
import 'package:fl_lib/fl_lib.dart';
import 'package:flutter_gbk2utf8/flutter_gbk2utf8.dart';
import 'package:server_box/core/extension/ssh_client.dart';
import 'package:server_box/core/sync.dart';
import 'package:server_box/core/utils/server.dart';
import 'package:server_box/core/utils/ssh_auth.dart';
import 'package:server_box/data/helper/system_detector.dart';
import 'package:server_box/data/model/app/error.dart';
import 'package:server_box/data/model/app/scripts/script_consts.dart';
import 'package:server_box/data/model/app/scripts/shell_func.dart';
import 'package:server_box/data/model/server/server.dart';
import 'package:server_box/data/model/server/server_private_info.dart';
import 'package:server_box/data/model/server/server_status_update_req.dart';
import 'package:server_box/data/model/server/system.dart';
import 'package:server_box/data/model/server/try_limiter.dart';
import 'package:server_box/data/res/status.dart';
import 'package:server_box/data/res/store.dart';
import 'package:server_box/data/ssh/session_manager.dart';

class ServerProvider extends Provider {
  const ServerProvider._();
  static const instance = ServerProvider._();

  static final Map<String, VNode<Server>> servers = {};
  static final serverOrder = <String>[].vn;
  static final _tags = <String>{}.vn;
  static VNode<Set<String>> get tags => _tags;

  static Timer? _timer;

  static final _manualDisconnectedIds = <String>{};

  static final _serverIdsUpdating = <String, Future<void>?>{};

  @override
  Future<void> load() async {
    super.load();
    // #147
    // Clear all servers because of restarting app will cause duplicate servers
    final oldServers = Map<String, VNode<Server>>.from(servers);
    servers.clear();
    serverOrder.value.clear();

    final spis = Stores.server.fetch();
    for (int idx = 0; idx < spis.length; idx++) {
      final spi = spis[idx];
      final originServer = oldServers[spi.id];

      /// #258
      /// If not [shouldReconnect], then keep the old state.
      if (originServer != null && !originServer.value.spi.shouldReconnect(spi)) {
        originServer.value.spi = spi;
        servers[spi.id] = originServer;
      } else {
        final newServer = genServer(spi);
        servers[spi.id] = newServer.vn;
      }
    }
    final serverOrder_ = Stores.setting.serverOrder.fetch();
    if (serverOrder_.isNotEmpty) {
      spis.reorder(order: serverOrder_, finder: (n, id) => n.id == id);
      serverOrder.value.addAll(spis.map((e) => e.id));
    } else {
      serverOrder.value.addAll(servers.keys);
    }
    // Must use [equals] to compare [Order] here.
    if (!serverOrder.value.equals(serverOrder_)) {
      Stores.setting.serverOrder.put(serverOrder.value);
    }
    _updateTags();
    // Must notify here, or the UI will not be updated.
    serverOrder.notify();
  }

  /// Get a [Server] by [spi] or [id].
  ///
  /// Priority: [spi] > [id]
  static VNode<Server>? pick({Spi? spi, String? id}) {
    if (spi != null) {
      return servers[spi.id];
    }
    if (id != null) {
      return servers[id];
    }
    return null;
  }

  static void _updateTags() {
    final tags = <String>{};
    for (final s in servers.values) {
      final spiTags = s.value.spi.tags;
      if (spiTags == null) continue;
      for (final t in spiTags) {
        tags.add(t);
      }
    }
    _tags.value = tags;
  }

  static Server genServer(Spi spi) {
    return Server(spi, InitStatus.status, ServerConn.disconnected);
  }

  /// if [spi] is specificed then only refresh this server
  /// [onlyFailed] only refresh failed servers
  static Future<void> refresh({Spi? spi, bool onlyFailed = false}) async {
    if (spi != null) {
      _manualDisconnectedIds.remove(spi.id);
      await _getData(spi);
      return;
    }

    await Future.wait(
      servers.values.map((val) async {
        final s = val.value;
        if (onlyFailed) {
          if (s.conn != ServerConn.failed) return;
          TryLimiter.reset(s.spi.id);
        }

        if (_manualDisconnectedIds.contains(s.spi.id)) return;

        if (s.conn == ServerConn.disconnected && !s.spi.autoConnect) {
          return;
        }

        // Check if already updating, and if so, wait for it to complete
        final existingUpdate = _serverIdsUpdating[s.spi.id];
        if (existingUpdate != null) {
          // Already updating, wait for the existing update to complete
          try {
            await existingUpdate;
          } catch (e) {
            // Ignore errors from the existing update, we'll try our own
          }
          return;
        }

        // Start a new update operation
        final updateFuture = _updateServer(s.spi);
        _serverIdsUpdating[s.spi.id] = updateFuture;

        try {
          await updateFuture;
        } finally {
          _serverIdsUpdating.remove(s.spi.id);
        }
      }),
    );
  }

  static Future<void> _updateServer(Spi spi) async {
    await _getData(spi);
  }

  static Future<void> startAutoRefresh() async {
    var duration = Stores.setting.serverStatusUpdateInterval.fetch();
    stopAutoRefresh();
    if (duration == 0) return;
    if (duration < 0 || duration > 10 || duration == 1) {
      duration = 3;
      Loggers.app.warning('Invalid duration: $duration, use default 3');
    }
    _timer = Timer.periodic(Duration(seconds: duration), (_) async {
      await refresh();
    });
  }

  static void stopAutoRefresh() {
    if (_timer != null) {
      _timer!.cancel();
      _timer = null;
    }
  }

  static bool get isAutoRefreshOn => _timer != null;

  static void setDisconnected() {
    for (final s in servers.values) {
      s.value.conn = ServerConn.disconnected;
      s.notify();

      // Update SSH session status to disconnected
      final sessionId = 'ssh_${s.value.spi.id}';
      TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
    }
    //TryLimiter.clear();
  }

  static void closeServer({String? id}) {
    if (id == null) {
      for (final s in servers.values) {
        _closeOneServer(s.value.spi.id);
      }
      return;
    }
    _closeOneServer(id);
  }

  static void _closeOneServer(String id) {
    final s = servers[id];
    if (s == null) {
      Loggers.app.warning('Server with id $id not found');
      return;
    }
    final item = s.value;
    item.client?.close();
    item.client = null;
    item.conn = ServerConn.disconnected;
    _manualDisconnectedIds.add(id);
    s.notify();

    // Remove SSH session when server is manually closed
    final sessionId = 'ssh_$id';
    TermSessionManager.remove(sessionId);
  }

  static void addServer(Spi spi) {
    servers[spi.id] = genServer(spi).vn;
    Stores.server.put(spi);
    serverOrder.value.add(spi.id);
    serverOrder.notify();
    Stores.setting.serverOrder.put(serverOrder.value);
    _updateTags();
    refresh(spi: spi);
    bakSync.sync(milliDelay: 1000);
  }

  static void delServer(String id) {
    servers.remove(id);
    serverOrder.value.remove(id);
    serverOrder.notify();
    Stores.setting.serverOrder.put(serverOrder.value);
    Stores.server.delete(id);
    _updateTags();

    // Remove SSH session when server is deleted
    final sessionId = 'ssh_$id';
    TermSessionManager.remove(sessionId);

    bakSync.sync(milliDelay: 1000);
  }

  static void deleteAll() {
    // Remove all SSH sessions before clearing servers
    for (final id in servers.keys) {
      final sessionId = 'ssh_$id';
      TermSessionManager.remove(sessionId);
    }

    servers.clear();
    serverOrder.value.clear();
    serverOrder.notify();
    Stores.setting.serverOrder.put(serverOrder.value);
    Stores.server.clear();
    _updateTags();
    bakSync.sync(milliDelay: 1000);
  }

  static Future<void> updateServer(Spi old, Spi newSpi) async {
    if (old != newSpi) {
      Stores.server.update(old, newSpi);
      servers[old.id]?.value.spi = newSpi;

      if (newSpi.id != old.id) {
        servers[newSpi.id] = servers[old.id]!;
        servers.remove(old.id);
        serverOrder.value.update(old.id, newSpi.id);
        Stores.setting.serverOrder.put(serverOrder.value);
        serverOrder.notify();

        // Update SSH session ID when server ID changes
        final oldSessionId = 'ssh_${old.id}';
        TermSessionManager.remove(oldSessionId);
        // Session will be re-added when reconnecting if necessary
      }

      // Only reconnect if neccessary
      if (newSpi.shouldReconnect(old)) {
        // Use [newSpi.id] instead of [old.id] because [old.id] may be changed
        TryLimiter.reset(newSpi.id);
        refresh(spi: newSpi);
      }
    }
    _updateTags();
    bakSync.sync(milliDelay: 1000);
  }

  static void _setServerState(VNode<Server> s, ServerConn ss) {
    s.value.conn = ss;
    s.notify();
  }

  static Future<void> _getData(Spi spi) async {
    final sid = spi.id;
    final s = servers[sid];

    if (s == null) return;

    final sv = s.value;
    if (!TryLimiter.canTry(sid)) {
      if (sv.conn != ServerConn.failed) {
        _setServerState(s, ServerConn.failed);
      }
      return;
    }

    sv.status.err = null;

    if (sv.needGenClient || (sv.client?.isClosed ?? true)) {
      _setServerState(s, ServerConn.connecting);

      final wol = spi.wolCfg;
      if (wol != null) {
        try {
          await wol.wake();
        } catch (e) {
          // TryLimiter.inc(sid);
          // s.status.err = SSHErr(
          //   type: SSHErrType.connect,
          //   message: 'Wake on lan failed: $e',
          // );
          // _setServerState(s, ServerConn.failed);
          Loggers.app.warning('Wake on lan failed', e);
          // return;
        }
      }

      try {
        final time1 = DateTime.now();
        sv.client = await genClient(
          spi,
          timeout: Duration(seconds: Stores.setting.timeout.fetch()),
          onKeyboardInteractive: (_) => KeybordInteractive.defaultHandle(spi),
        );
        final time2 = DateTime.now();
        final spentTime = time2.difference(time1).inMilliseconds;
        if (spi.jumpId == null) {
          Loggers.app.info('Connected to ${spi.name} in $spentTime ms.');
        } else {
          Loggers.app.info('Jump to ${spi.name} in $spentTime ms.');
        }

        // Add SSH session to TermSessionManager
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.add(
          id: sessionId,
          spi: spi,
          startTimeMs: time1.millisecondsSinceEpoch,
          disconnect: () => _closeOneServer(spi.id),
          status: TermSessionStatus.connecting,
        );
        TermSessionManager.setActive(sessionId, hasTerminal: false);
      } catch (e) {
        TryLimiter.inc(sid);
        sv.status.err = SSHErr(type: SSHErrType.connect, message: e.toString());
        _setServerState(s, ServerConn.failed);

        // Remove SSH session on connection failure
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.remove(sessionId);

        /// In order to keep privacy, print [spi.name] instead of [spi.id]
        Loggers.app.warning('Connect to ${spi.name} failed', e);
        return;
      }

      _setServerState(s, ServerConn.connected);

      // Update SSH session status to connected
      final sessionId = 'ssh_${spi.id}';
      TermSessionManager.updateStatus(sessionId, TermSessionStatus.connected);

      try {
        // Detect system type using helper
        final detectedSystemType = await SystemDetector.detect(sv.client!, spi);
        sv.status.system = detectedSystemType;

        final (_, writeScriptResult) = await sv.client!.exec((session) async {
          final scriptRaw = ShellFuncManager.allScript(
            spi.custom?.cmds,
            systemType: detectedSystemType,
            disabledCmdTypes: spi.disabledCmdTypes,
          ).uint8List;
          session.stdin.add(scriptRaw);
          session.stdin.close();
        }, entry: ShellFuncManager.getInstallShellCmd(spi.id, systemType: detectedSystemType));
        if (writeScriptResult.isNotEmpty && detectedSystemType != SystemType.windows) {
          ShellFuncManager.switchScriptDir(spi.id, systemType: detectedSystemType);
          throw writeScriptResult;
        }
      } on SSHAuthAbortError catch (e) {
        TryLimiter.inc(sid);
        final err = SSHErr(type: SSHErrType.auth, message: e.toString());
        sv.status.err = err;
        Loggers.app.warning(err);
        _setServerState(s, ServerConn.failed);

        // Update SSH session status to disconnected
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
        return;
      } on SSHAuthFailError catch (e) {
        TryLimiter.inc(sid);
        final err = SSHErr(type: SSHErrType.auth, message: e.toString());
        sv.status.err = err;
        Loggers.app.warning(err);
        _setServerState(s, ServerConn.failed);

        // Update SSH session status to disconnected
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
        return;
      } catch (e) {
        // If max try times < 2 and can't write script, this will stop the status getting and etc.
        // TryLimiter.inc(sid);
        final err = SSHErr(type: SSHErrType.writeScript, message: e.toString());
        sv.status.err = err;
        Loggers.app.warning(err);
        _setServerState(s, ServerConn.failed);

        // Update SSH session status to disconnected
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
      }
    }

    if (sv.conn == ServerConn.connecting) return;

    /// Keep [finished] state, or the UI will be refreshed to [loading] state
    /// instead of the '$Temp | $Uptime'.
    /// eg: '32C | 7 days'
    if (sv.conn != ServerConn.finished) {
      _setServerState(s, ServerConn.loading);
    }

    List<String>? segments;
    String? raw;

    try {
        final execResult = await sv.client?.run(ShellFunc.status.exec(spi.id, systemType: sv.status.system));
        if (execResult != null) {
          String? rawStr;
          bool needGbk = false;
          try {
            rawStr = utf8.decode(execResult, allowMalformed: true);
            // If there are characters that cannot be parsed, try to fallback to gbk decoding
            if (rawStr.contains('�')) {
              Loggers.app.warning('UTF8 decoding failed, use GBK decoding');
              needGbk = true;
            }
          } catch (e) {
            Loggers.app.warning('UTF8 decoding failed, use GBK decoding', e);
            needGbk = true;
          }if (needGbk) {
            try {
              rawStr = gbk.decode(execResult);
            } catch (e2) {
              Loggers.app.warning('GBK decoding failed', e2);
              rawStr = null;
            }
          }
          if (rawStr == null) {
            Loggers.app.warning('Decoding failed, execResult: $execResult');
          }
          raw = rawStr;
        } else {
          raw = execResult.toString();
        }

      if (raw == null || raw.isEmpty) {
        TryLimiter.inc(sid);
        sv.status.err = SSHErr(
          type: SSHErrType.segements,
          message: 'decode or split failed, raw:\n$raw',
        );
        _setServerState(s, ServerConn.failed);

        // Update SSH session status to disconnected on segments error
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
        return;
      }

      //dprint('Get status from ${spi.name}:\n$raw');
      segments = raw.split(ScriptConstants.separator).map((e) => e.trim()).toList();
      if (raw.isEmpty || segments.isEmpty) {
        if (Stores.setting.keepStatusWhenErr.fetch()) {
          // Keep previous server status when err occurs
          if (sv.conn != ServerConn.failed && sv.status.more.isNotEmpty) {
            return;
          }
        }
        TryLimiter.inc(sid);
        sv.status.err = SSHErr(type: SSHErrType.segements, message: 'Seperate segments failed, raw:\n$raw');
        _setServerState(s, ServerConn.failed);

        // Update SSH session status to disconnected on segments error
        final sessionId = 'ssh_${spi.id}';
        TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
        return;
      }
    } catch (e) {
      TryLimiter.inc(sid);
      sv.status.err = SSHErr(type: SSHErrType.getStatus, message: e.toString());
      _setServerState(s, ServerConn.failed);
      Loggers.app.warning('Get status from ${spi.name} failed', e);

      // Update SSH session status to disconnected on status error
      final sessionId = 'ssh_${spi.id}';
      TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
      return;
    }

    try {
      // Parse script output into command-specific map
      final parsedOutput = ScriptConstants.parseScriptOutput(raw);

      final req = ServerStatusUpdateReq(
        ss: sv.status,
        parsedOutput: parsedOutput,
        system: sv.status.system,
        customCmds: spi.custom?.cmds ?? {},
      );
      sv.status = await Computer.shared.start(getStatus, req, taskName: 'StatusUpdateReq<${sv.id}>');
    } catch (e, trace) {
      TryLimiter.inc(sid);
      sv.status.err = SSHErr(type: SSHErrType.getStatus, message: 'Parse failed: $e\n\n$raw');
      _setServerState(s, ServerConn.failed);
      Loggers.app.warning('Server status', e, trace);

      // Update SSH session status to disconnected on parse error
      final sessionId = 'ssh_${spi.id}';
      TermSessionManager.updateStatus(sessionId, TermSessionStatus.disconnected);
      return;
    }

    /// Call this every time for setting [Server.isBusy] to false
    _setServerState(s, ServerConn.finished);
    // reset try times only after prepared successfully
    TryLimiter.reset(sid);
  }
}