import 'dart:convert';
import 'package:crypto/crypto.dart';
import 'package:drift/drift.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../database/app_database.dart';
import '../llm/prompt_builder.dart';
import 'database_provider.dart';
import 'llm_provider.dart';

// ── Insight type enum ─────────────────────────────────────────────────────────

enum InsightType { weekly, monthly, query }

// ── Insight notifier — fetches data, builds prompt, calls LLM, caches result ──

class InsightNotifier extends Notifier<AsyncValue<String?>> {
  @override
  AsyncValue<String?> build() => const AsyncData(null);

  Future<void> generateInsight({
    InsightType type = InsightType.weekly,
    bool forceRefresh = false,
  }) async {
    state = const AsyncLoading();

    try {
      // Ensure model is initialised before generating
      await ref.read(llmReadyProvider.future);
      if (!ref.mounted) return;

      final now = DateTime.now();
      final end = DateTime(now.year, now.month, now.day, 23, 59, 59);
      final start = end.subtract(const Duration(days: 6));

      final dao = ref.read(moodDaoProvider);
      final entries = await dao.getEntriesWithActivitiesInRange(start, end);
      if (!ref.mounted) return;

      if (entries.length < 2) {
        state = const AsyncData(null);
        return;
      }

      final prompt = PromptBuilder.buildWeeklyPrompt(entries);
      final hash = _hashPrompt(prompt);

      if (!forceRefresh) {
        final cached = await ref.read(insightDaoProvider).getCached(hash);
        if (!ref.mounted) return;
        if (cached != null) {
          state = AsyncData(cached.responseText);
          return;
        }
      }

      final llm = ref.read(llmServiceProvider);
      final buffer = StringBuffer();
      await for (final token in llm.generateStream(prompt)) {
        if (!ref.mounted) return;
        buffer.write(token);
        state = AsyncData(buffer.toString());
      }

      if (!ref.mounted) return;
      final result = buffer.toString().trim();
      await ref.read(insightDaoProvider).upsertInsight(
            LlmInsightsCompanion.insert(
              type: type.name,
              promptHash: hash,
              responseText: result,
              rangeStart: Value(start),
              rangeEnd: Value(end),
            ),
          );
      if (!ref.mounted) return;
      state = AsyncData(result);
    } catch (e, st) {
      if (!ref.mounted) return;
      state = AsyncError(e, st);
    }
  }

  void clear() => state = const AsyncData(null);

  static String _hashPrompt(String prompt) =>
      sha256.convert(utf8.encode(prompt)).toString();
}

final insightNotifierProvider =
    NotifierProvider.autoDispose<InsightNotifier, AsyncValue<String?>>(
        InsightNotifier.new);