import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../core/exceptions.dart';
import 'api_client_provider.dart';
import 'capture_queue_provider.dart';
import 'chat_provider.dart';

/// Outcome of a single capture attempt — consumed by the UI for snackbars.
class CaptureResult {
  final String message;
  final bool isError;
  const CaptureResult(this.message, {this.isError = false});
}

/// The most recent capture result. UI watches this to show snackbars.
/// Reset to null by the notifier before each new item so listeners always fire.
final captureResultProvider =
    NotifierProvider<_CaptureResultNotifier, CaptureResult?>(
        _CaptureResultNotifier.new);

class _CaptureResultNotifier extends Notifier<CaptureResult?> {
  @override
  CaptureResult? build() => null;
}

/// In-memory sequential work queue for quick captures.
final captureWorkQueueProvider =
    NotifierProvider<CaptureWorkQueueNotifier, List<String>>(
  CaptureWorkQueueNotifier.new,
);

class CaptureWorkQueueNotifier extends Notifier<List<String>> {
  bool _running = false;

  @override
  List<String> build() => [];

  /// Add text to the queue and start the drain loop if not already running.
  void enqueue(String text) {
    state = [...state, text];
    _drain();
  }

  Future<void> _drain() async {
    if (_running) return;
    _running = true;
    try {
      while (state.isNotEmpty) {
        final text = state.first;
        // Signal "no result yet" so the same result value can re-trigger watch.
        ref.read(captureResultProvider.notifier).state = null;
        try {
          // Create a new conversation, add it to the conversations list, then
          // send the message and kick off generation in the background.
          final conv =
              await ref.read(conversationsProvider.notifier).create('');
          final chatRepo = ref.read(chatRepositoryProvider);
          await chatRepo.sendMessage(conv.id, text);
          // Fire-and-forget: drain the SSE stream so the server generates a
          // response (creating notes/tasks/etc.) without blocking the UI.
          chatRepo.streamGeneration(conv.id).drain<void>().ignore();

          state = state.length > 1 ? state.sublist(1) : [];
          ref.read(captureResultProvider.notifier).state =
              const CaptureResult('Sent to Fabled.');
        } on NetworkException catch (_) {
          // Persist to offline queue and stop draining — still offline.
          await ref.read(captureQueueProvider.notifier).enqueue(text);
          state = state.length > 1 ? state.sublist(1) : [];
          ref.read(captureResultProvider.notifier).state = const CaptureResult(
            "You're offline — capture saved and will retry automatically.",
          );
          break;
        } on AppException catch (e) {
          state = state.length > 1 ? state.sublist(1) : [];
          ref.read(captureResultProvider.notifier).state =
              CaptureResult(e.message, isError: true);
        } catch (_) {
          state = state.length > 1 ? state.sublist(1) : [];
          ref.read(captureResultProvider.notifier).state = const CaptureResult(
              'Failed to send. Please try again.',
              isError: true);
        }
      }
    } finally {
      _running = false;
    }
  }
}