import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../data/api/chat_api.dart';
import '../data/models/briefing_conversation.dart';
import '../data/models/message.dart';
import 'api_client_provider.dart';

/// Drives the loading indicator in BriefingScreen's reply area.
final isBriefingStreamingProvider =
    NotifierProvider<_BoolNotifier, bool>(_BoolNotifier.new);

class _BoolNotifier extends Notifier<bool> {
  @override
  bool build() => false;
}

final briefingProvider =
    AsyncNotifierProvider<BriefingNotifier, BriefingConversation>(
        BriefingNotifier.new);

class BriefingNotifier extends AsyncNotifier<BriefingConversation> {
  @override
  Future<BriefingConversation> build() async {
    return ref.read(briefingApiProvider).getToday();
  }

  /// Silently fetch the latest briefing and patch state without triggering
  /// AsyncLoading — existing content stays visible while the fetch is in flight.
  Future<void> silentRefresh() async {
    final current = state.value;
    if (current == null) return;
    try {
      final fresh = await ref.read(briefingApiProvider).getToday();
      final curLast = current.messages.isNotEmpty ? current.messages.last : null;
      final newLast = fresh.messages.isNotEmpty ? fresh.messages.last : null;
      if (fresh.messages.length != current.messages.length ||
          newLast?.content != curLast?.content) {
        state = AsyncData(fresh);
      }
    } catch (_) {
      // Network hiccup — silently ignore, keep existing content
    }
  }

  /// Trigger a briefing slot (e.g. "compilation") then reload.
  Future<void> refresh(String slot) async {
    await ref.read(briefingApiProvider).triggerSlot(slot);
    ref.invalidateSelf();
    await future;
  }

  /// Inject a news article as context and trigger generation.
  ///
  /// Mirrors sendReply() but calls the /discuss endpoint instead of
  /// /messages so the backend injects article content before generating.
  Future<void> discussArticle(int convId, int itemId) async {
    final conv = state.value;
    if (conv == null) return;
    final chatApi = ref.read(chatApiProvider);
    final briefingApi = ref.read(briefingApiProvider);

    final previous = conv.messages;
    final placeholder = Message(
      conversationId: convId,
      role: MessageRole.assistant,
      content: '',
      status: 'generating',
    );
    state = AsyncData(conv.copyWith(messages: [...previous, placeholder]));
    ref.read(isBriefingStreamingProvider.notifier).state = true;

    try {
      await briefingApi.discussArticle(convId, itemId);
    } catch (e) {
      state = AsyncData(conv.copyWith(messages: previous));
      ref.read(isBriefingStreamingProvider.notifier).state = false;
      rethrow;
    }

    // SSE stream (best-effort)
    bool streamedContent = false;
    try {
      await for (final event in chatApi.streamGeneration(convId)) {
        if (event is! ChatTextChunk) continue;
        streamedContent = true;
        final current = state.value;
        if (current == null) break;
        final msgs = current.messages;
        if (msgs.isEmpty) continue;
        final updated =
            msgs.last.copyWith(content: msgs.last.content + event.text);
        state = AsyncData(current.copyWith(
            messages: [...msgs.sublist(0, msgs.length - 1), updated]));
      }
    } catch (_) {
      // Fall through to polling.
    }

    // Poll until complete (max 20 attempts, 2s apart)
    try {
      for (var attempt = 0; attempt < 20; attempt++) {
        if (attempt > 0) await Future.delayed(const Duration(seconds: 2));
        final fresh = await briefingApi.getMessages(convId);
        final done = fresh.any(
          (m) => m.role == MessageRole.assistant && m.status != 'generating',
        );
        final hasContent = fresh.any(
          (m) => m.role == MessageRole.assistant && m.content.isNotEmpty,
        );
        final current = state.value;
        if (current != null && (!streamedContent || done || hasContent)) {
          state = AsyncData(current.copyWith(messages: fresh));
        }
        if (done) break;
      }
    } catch (_) {
      final current = state.value;
      if (current != null) {
        final msgs = current.messages;
        if (msgs.isNotEmpty && msgs.last.status == 'generating') {
          state = AsyncData(current.copyWith(messages: [
            ...msgs.sublist(0, msgs.length - 1),
            msgs.last.copyWith(status: 'complete'),
          ]));
        }
      }
    } finally {
      ref.read(isBriefingStreamingProvider.notifier).state = false;
    }
  }

  /// Send a reply to today's briefing conversation.
  ///
  /// Mirrors MessagesNotifier.sendMessage():
  ///   1. Optimistic UI update
  ///   2. POST message to chat endpoint
  ///   3. SSE stream (best-effort)
  ///   4. Poll until complete
  Future<void> sendReply(String content) async {
    final conv = state.value;
    if (conv == null) return;
    final convId = conv.id;
    final chatApi = ref.read(chatApiProvider);

    final previous = conv.messages;
    final userMsg = Message(
      conversationId: convId,
      role: MessageRole.user,
      content: content,
    );
    final placeholder = Message(
      conversationId: convId,
      role: MessageRole.assistant,
      content: '',
      status: 'generating',
    );
    state = AsyncData(conv.copyWith(messages: [...previous, userMsg, placeholder]));
    ref.read(isBriefingStreamingProvider.notifier).state = true;

    try {
      await chatApi.sendMessage(convId, content);
    } catch (e) {
      state = AsyncData(conv.copyWith(messages: previous));
      ref.read(isBriefingStreamingProvider.notifier).state = false;
      rethrow;
    }

    // SSE stream (best-effort)
    bool streamedContent = false;
    try {
      await for (final event in chatApi.streamGeneration(convId)) {
        if (event is! ChatTextChunk) continue;
        streamedContent = true;
        final current = state.value;
        if (current == null) break;
        final msgs = current.messages;
        if (msgs.isEmpty) continue;
        final updated =
            msgs.last.copyWith(content: msgs.last.content + event.text);
        state = AsyncData(current.copyWith(
            messages: [...msgs.sublist(0, msgs.length - 1), updated]));
      }
    } catch (_) {
      // Fall through to polling.
    }

    // Poll until complete (max 20 attempts, 2s apart)
    try {
      for (var attempt = 0; attempt < 20; attempt++) {
        if (attempt > 0) await Future.delayed(const Duration(seconds: 2));
        final fresh = await ref.read(briefingApiProvider).getMessages(convId);
        final done = fresh.any(
          (m) => m.role == MessageRole.assistant && m.status != 'generating',
        );
        final hasContent = fresh.any(
          (m) => m.role == MessageRole.assistant && m.content.isNotEmpty,
        );
        final current = state.value;
        if (current != null && (!streamedContent || done || hasContent)) {
          state = AsyncData(current.copyWith(messages: fresh));
        }
        if (done) break;
      }
    } catch (_) {
      // Clear the generating placeholder so UI doesn't spin forever.
      final current = state.value;
      if (current != null) {
        final msgs = current.messages;
        if (msgs.isNotEmpty && msgs.last.status == 'generating') {
          state = AsyncData(current.copyWith(messages: [
            ...msgs.sublist(0, msgs.length - 1),
            msgs.last.copyWith(status: 'complete'),
          ]));
        }
      }
    } finally {
      ref.read(isBriefingStreamingProvider.notifier).state = false;
    }
  }
}