import 'dart:convert';

enum Intent { createEvent, searchEvent, unknown }

/// 意图匹配规则（顺序敏感：searchEvent 优先级高于 createEvent）
final _orderedPatterns = <(RegExp, Intent)>[
  (RegExp(r'^查看|^有什么|^今天.*日程|^明天.*安排|^查询'), Intent.searchEvent),
  (RegExp(r'提醒|开会|预约|安排.*时间|创建.*日程'), Intent.createEvent),
  (RegExp(r'明天.*\d|今天.*\d|后天.*\d|\d{1,2}点|\d{1,2}:\d{2}'), Intent.createEvent),
];

/// 时区常量
const _defaultTimezone = 'Asia/Shanghai';
const _dayToday = '今天';
const _dayTomorrow = '明天';
const _dayAfterTomorrow = '后天';
const _tomorrowOffset = 1;
const _dayAfterTomorrowOffset = 2;
const _defaultMinute = 0;

class AiDecisionEngine {
  Intent matchIntent(String text) {
    for (final (pattern, intent) in _orderedPatterns) {
      if (pattern.hasMatch(text)) return intent;
    }
    return Intent.unknown;
  }

  Map<String, dynamic>? tryExtractEventArgs(String text) {
    if (matchIntent(text) != Intent.createEvent) return null;

    final args = <String, dynamic>{};

    final titleMatch = RegExp(r'提醒(.+?)(?:明天|今天|几点|$)').firstMatch(text);
    if (titleMatch != null) {
      args['title'] = titleMatch.group(1)?.trim() ?? text;
    } else if (RegExp(r'\d{1,2}[:点]|\d{1,2}点').hasMatch(text)) {
      args['title'] = text
          .replaceAll(RegExp(r'\d{1,2}[:点]\d{0,2}|明天|今天|后天'), '')
          .trim();
    }

    final title = args['title'];
    if (title == null || (title as String).isEmpty) return null;

    final timeMatch = RegExp(
      r'(明天|今天|后天)?\s*(\d{1,2})[:点](\d{2})?',
    ).firstMatch(text);
    if (timeMatch != null) {
      final dayStr = timeMatch.group(1) ?? _dayToday;
      final hour = int.parse(timeMatch.group(2)!);
      final minute = int.parse(timeMatch.group(3) ?? '$_defaultMinute');

      final now = DateTime.now();
      final dayOffset = switch (dayStr) {
        _dayTomorrow => _tomorrowOffset,
        _dayAfterTomorrow => _dayAfterTomorrowOffset,
        _ => 0,
      };
      final startAt = DateTime(
        now.year,
        now.month,
        now.day + dayOffset,
        hour,
        minute,
      );

      args['startAt'] = startAt.toIso8601String();
      args['timezone'] = _defaultTimezone;
    }

    if (!args.containsKey('startAt')) return null;
    return args;
  }

  bool shouldTriggerToolCall(String text) =>
      matchIntent(text) == Intent.createEvent;

  Map<String, dynamic>? getToolCallArgs(String text) {
    if (!shouldTriggerToolCall(text)) return null;
    return tryExtractEventArgs(text);
  }

  ForceTriggerResult? tryForceTrigger(String text) {
    final match = RegExp(
      r'#tool:([A-Za-z0-9_.-]+)\s*(\{.*\})?',
    ).firstMatch(text);
    if (match == null) return null;

    final toolName = match.group(1)!;
    final argsJson = match.group(2);

    Map<String, dynamic>? args;
    if (argsJson != null) {
      try {
        args = jsonDecode(argsJson) as Map<String, dynamic>;
      } catch (_) {
        args = {};
      }
    }

    return ForceTriggerResult(toolName: toolName, args: args ?? {});
  }
}

class ForceTriggerResult {
  final String toolName;
  final Map<String, dynamic> args;
  ForceTriggerResult({required this.toolName, required this.args});
}