/**
 * Message Handler - 텔레그램 메시지 처리의 핵심 모듈
 *
 * 메시지 수신 -> 사용자 등록/확인 -> 에이전트 라우팅 -> AI 응답 -> 피드백 수집
 */

import { sendMessage, sendMessageWithKeyboard, sendChatAction } from '../../telegram';
import { checkRateLimit } from '../../security';
import { registerAgent, routeToActiveAgent, type RegisterableAgent } from '../../agents/agent-registry';
import { OnboardingAgent } from '../../agents/onboarding-agent';
import { TroubleshootAgent } from '../../agents/troubleshoot-agent';
import { AssetAgent } from '../../agents/asset-agent';
import { BillingAgent } from '../../agents/billing-agent';
import { getMessage } from '../../i18n';
import { selectToolsForMessage, executeTool } from '../../tools';
import { createLogger } from '../../utils/logger';
import { getOpenAIUrl } from '../../utils/api-urls';
import { AI_CONFIG } from '../../constants/agent-config';
import { escalateToAdmin, shouldEscalate } from '../../services/human-handoff';
import type { Env, TelegramUpdate, User, OpenAIAPIResponse, OpenAIMessage } from '../../types';

const logger = createLogger('message-handler');

// Register agent singletons with priorities (lower = checked first)
const onboardingAgent = new OnboardingAgent();
const troubleshootAgent = new TroubleshootAgent();
const assetAgent = new AssetAgent();
const billingAgent = new BillingAgent();

registerAgent('onboarding', onboardingAgent, 10);
registerAgent('troubleshoot', troubleshootAgent, 20);
registerAgent('asset', assetAgent, 30);
registerAgent('billing', billingAgent, 40);

export async function handleMessage(
  env: Env,
  update: TelegramUpdate
): Promise<void> {
  if (!update.message?.text) return;

  const message = update.message;
  const chatId = message.chat.id;
  const text = message.text!;
  const telegramUserId = message.from.id.toString();
  const lang = message.from.language_code ?? 'ko';
  const requestId = crypto.randomUUID();

  // 1. Check if user is blocked & register/update user
  const user = await getOrCreateUser(env.DB, telegramUserId, message.from.first_name ?? '', message.from.username);
  if (!user) {
    await sendMessage(env.BOT_TOKEN, chatId, getMessage(lang, 'error_general'));
    return;
  }
  if (user.is_blocked) {
    await sendMessage(env.BOT_TOKEN, chatId, getMessage(lang, 'error_blocked'));
    return;
  }

  // 2. Rate limiting
  if (!(await checkRateLimit(env.RATE_LIMIT_KV, telegramUserId))) {
    await sendMessage(env.BOT_TOKEN, chatId, getMessage(lang, 'error_rate_limit'));
    return;
  }

  // 3. Send typing action
  await sendChatAction(env.BOT_TOKEN, chatId).catch(() => {});

  try {
    // 4. Route to active agent session first
    const meta = { chatId, messageId: message.message_id };
    const agentResult = await routeToActiveAgent(env.DB, telegramUserId, text, env, meta);
    if (agentResult) {
      const { cleanText, sessionEnded } = cleanSessionMarkers(agentResult.response);

      // Handle escalation marker
      if (agentResult.response.includes('__ESCALATE__')) {
        const cleaned = cleanText.replace('__ESCALATE__', '').trim();
        await storeConversation(env.DB, user.id, text, cleaned, requestId);
        await sendMessage(env.BOT_TOKEN, chatId, cleaned);
        await escalateToAdmin(env, telegramUserId, text, 'agent');
        return;
      }

      await storeConversation(env.DB, user.id, text, cleanText, requestId);
      await sendMessage(env.BOT_TOKEN, chatId, cleanText);

      // Prompt feedback only after multi-round agents
      const isMultiRound = agentResult.agentName === 'troubleshoot' || agentResult.agentName === 'onboarding';
      if (sessionEnded && isMultiRound) {
        await promptFeedback(env, chatId, lang, agentResult.agentName);
      }
      return;
    }

    // 5. AI-based intent classification → agent routing
    const intent = await classifyIntent(env, text);
    logger.info('의도 분류 결과', { intent, telegramUserId });

    const agentMap: Record<string, { agent: RegisterableAgent; type: string }> = {
      onboarding: { agent: onboardingAgent, type: 'onboarding' },
      troubleshoot: { agent: troubleshootAgent, type: 'troubleshoot' },
      billing: { agent: billingAgent, type: 'billing' },
      asset: { agent: assetAgent, type: 'asset' },
    };

    if (intent && intent in agentMap) {
      const { agent, type: sessionType } = agentMap[intent];
      const response = await agent.processConsultation(env.DB, telegramUserId, text, env, meta);
      const { cleanText, sessionEnded } = cleanSessionMarkers(response);
      await storeConversation(env.DB, user.id, text, cleanText, requestId);
      await sendMessage(env.BOT_TOKEN, chatId, cleanText);

      const isMultiRound = sessionType === 'troubleshoot' || sessionType === 'onboarding';
      if (sessionEnded && isMultiRound) {
        await promptFeedback(env, chatId, lang, sessionType);
      }
      return;
    }

    // 6. General AI fallback (intent = 'general' or classification failed)
    const aiResponse = await handleGeneralAI(env, user, text, telegramUserId);
    await storeConversation(env.DB, user.id, text, aiResponse, requestId);
    await sendMessage(env.BOT_TOKEN, chatId, aiResponse);

    // 7. Check frustration for potential escalation
    if (shouldEscalate(text, 0)) {
      logger.warn('Frustration detected in general AI flow', { telegramUserId });
    }
  } catch (error) {
    logger.error('Message handling error', error as Error, { telegramUserId, requestId });
    await sendMessage(env.BOT_TOKEN, chatId, getMessage(lang, 'error_general'));
  }
}

function cleanSessionMarkers(text: string): { cleanText: string; sessionEnded: boolean } {
  const sessionEnded = text.includes('[세션 종료]') || text.includes('__SESSION_END__');
  const cleanText = text
    .replace('[세션 종료]', '')
    .replace('__SESSION_END__', '')
    .trim();
  return { cleanText, sessionEnded };
}

async function getOrCreateUser(
  db: D1Database,
  telegramId: string,
  firstName: string,
  username?: string
): Promise<(User & { id: number }) | null> {
  try {
    await db
      .prepare(
        `INSERT INTO users (telegram_id, username, first_name, last_active_at)
         VALUES (?, ?, ?, CURRENT_TIMESTAMP)
         ON CONFLICT (telegram_id) DO UPDATE SET
           username = COALESCE(excluded.username, users.username),
           first_name = COALESCE(excluded.first_name, users.first_name),
           last_active_at = CURRENT_TIMESTAMP,
           updated_at = CURRENT_TIMESTAMP`
      )
      .bind(telegramId, username ?? null, firstName)
      .run();

    const user = await db
      .prepare('SELECT * FROM users WHERE telegram_id = ?')
      .bind(telegramId)
      .first<User>();

    return user ?? null;
  } catch (error) {
    logger.error('User upsert failed', error as Error, { telegramId });
    return null;
  }
}

const VALID_INTENTS = ['troubleshoot', 'onboarding', 'billing', 'asset', 'general'] as const;

async function classifyIntent(env: Env, text: string): Promise<string | null> {
  if (!env.OPENAI_API_KEY) return null;

  try {
    const controller = new AbortController();
    const timeoutId = setTimeout(() => controller.abort(), 5000);

    try {
      const response = await fetch(getOpenAIUrl(env), {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          Authorization: `Bearer ${env.OPENAI_API_KEY}`,
        },
        signal: controller.signal,
        body: JSON.stringify({
          model: AI_CONFIG.model,
          messages: [
            {
              role: 'system',
              content: `사용자 메시지의 의도를 분류하세요. 반드시 아래 중 하나만 응답하세요:
- troubleshoot: 기술 문제, 접속 불가, 오류, 장애, 느림, 차단, 네트워크 문제, 도메인/서버/서비스 문제 해결
- onboarding: 신규 가입, 서비스 소개, 요금/플랜 문의, 처음 이용
- billing: 입금, 충전, 잔액, 결제, 환불, 요금 관련
- asset: 자산 현황, 내 서버/도메인 목록, 보유 서비스 조회
- general: 위 어느 것에도 해당하지 않는 일반 질문이나 인사

한 단어만 응답하세요.`,
            },
            { role: 'user', content: text },
          ],
          max_tokens: 10,
          temperature: 0,
        }),
      });

      if (!response.ok) return null;

      const data = (await response.json()) as OpenAIAPIResponse;
      const raw = data.choices[0]?.message?.content?.trim().toLowerCase();
      if (raw && VALID_INTENTS.includes(raw as typeof VALID_INTENTS[number])) {
        return raw === 'general' ? null : raw;
      }
      return null;
    } finally {
      clearTimeout(timeoutId);
    }
  } catch (error) {
    logger.error('Intent classification failed', error as Error);
    return null;
  }
}

async function handleGeneralAI(
  env: Env,
  user: User,
  userMessage: string,
  telegramUserId: string
): Promise<string> {
  if (!env.OPENAI_API_KEY) {
    return await handleWorkersAIFallback(env, userMessage);
  }

  try {
    // Load recent conversation context
    const history = await env.DB
      .prepare(
        `SELECT role, content FROM conversations
         WHERE user_id = ? ORDER BY created_at DESC LIMIT ?`
      )
      .bind(user.id, user.context_limit)
      .all<{ role: string; content: string }>();

    const conversationHistory = history.results.reverse();
    const tools = selectToolsForMessage(userMessage);

    const messages: OpenAIMessage[] = [
      {
        role: 'system',
        content: `당신은 클라우드 호스팅/도메인/서버 관리 서비스의 AI 고객 지원 상담사입니다.
한국어로 친절하고 전문적으로 답변하세요.
기술 용어는 쉽게 풀어 설명하세요.
답변을 모르면 솔직히 모른다고 하고, 관리자 연결을 제안하세요.`,
      },
      ...conversationHistory.map((m) => ({
        role: m.role as 'user' | 'assistant',
        content: m.content,
      })),
      { role: 'user', content: userMessage },
    ];

    const body: Record<string, unknown> = {
      model: AI_CONFIG.model,
      messages,
      max_tokens: 1024,
      temperature: AI_CONFIG.defaultTemperature,
    };

    if (tools.length > 0) {
      body.tools = tools;
      body.tool_choice = 'auto';
    }

    const controller = new AbortController();
    const timeoutId = setTimeout(() => controller.abort(), 25000);

    try {
      const response = await fetch(getOpenAIUrl(env), {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          Authorization: `Bearer ${env.OPENAI_API_KEY}`,
        },
        signal: controller.signal,
        body: JSON.stringify(body),
      });

      if (!response.ok) {
        logger.error('OpenAI API error', new Error(`HTTP ${response.status}`));
        return await handleWorkersAIFallback(env, userMessage);
      }

      const data = (await response.json()) as OpenAIAPIResponse;
      const assistantMessage = data.choices[0].message;

      // Handle tool calls (single round for general AI)
      if (assistantMessage.tool_calls && assistantMessage.tool_calls.length > 0) {
        // Add assistant message with tool calls
        messages.push({
          role: 'assistant',
          content: assistantMessage.content,
          tool_calls: assistantMessage.tool_calls,
        });

        for (const tc of assistantMessage.tool_calls) {
          let args: Record<string, unknown>;
          try {
            args = JSON.parse(tc.function.arguments) as Record<string, unknown>;
          } catch {
            continue;
          }
          const result = await executeTool(tc.function.name, args, env, telegramUserId, env.DB);
          messages.push({
            role: 'tool',
            content: result,
            tool_call_id: tc.id,
            name: tc.function.name,
          });
        }

        // Second call to synthesize tool results
        const followUp = await fetch(getOpenAIUrl(env), {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
            Authorization: `Bearer ${env.OPENAI_API_KEY}`,
          },
          body: JSON.stringify({
            model: AI_CONFIG.model,
            messages,
            max_tokens: 1024,
            temperature: AI_CONFIG.defaultTemperature,
          }),
        });

        if (followUp.ok) {
          const followUpData = (await followUp.json()) as OpenAIAPIResponse;
          return followUpData.choices[0].message.content ?? getMessage('ko', 'error_ai_unavailable');
        }

        // Fallback: return AI text
        return assistantMessage.content ?? getMessage('ko', 'error_ai_unavailable');
      }

      return assistantMessage.content ?? getMessage('ko', 'error_ai_unavailable');
    } finally {
      clearTimeout(timeoutId);
    }
  } catch (error) {
    logger.error('General AI error', error as Error);
    return await handleWorkersAIFallback(env, userMessage);
  }
}

async function handleWorkersAIFallback(env: Env, userMessage: string): Promise<string> {
  try {
    const result = await env.AI.run('@cf/meta/llama-3.1-8b-instruct-fp8', {
      messages: [
        {
          role: 'system',
          content: '당신은 클라우드 호스팅 서비스의 AI 고객 지원 상담사입니다. 한국어로 친절하게 답변하세요.',
        },
        { role: 'user', content: userMessage },
      ],
    });

    if (result && typeof result === 'object' && 'response' in result) {
      return (result as { response: string }).response;
    }

    return getMessage('ko', 'error_ai_unavailable');
  } catch (error) {
    logger.error('Workers AI fallback error', error as Error);
    return getMessage('ko', 'error_ai_unavailable');
  }
}

async function storeConversation(
  db: D1Database,
  userId: number,
  userMessage: string,
  assistantResponse: string,
  requestId: string
): Promise<void> {
  try {
    await db.batch([
      db.prepare(
        `INSERT INTO conversations (user_id, role, content, request_id) VALUES (?, 'user', ?, ?)`
      ).bind(userId, userMessage, requestId),
      db.prepare(
        `INSERT INTO conversations (user_id, role, content, request_id) VALUES (?, 'assistant', ?, ?)`
      ).bind(userId, assistantResponse, requestId),
    ]);
  } catch (error) {
    logger.error('Conversation storage failed', error as Error, { userId, requestId });
  }
}

async function promptFeedback(
  env: Env,
  chatId: number,
  lang: string,
  sessionType: string
): Promise<void> {
  try {
    const text = getMessage(lang, 'feedback_prompt');
    const keyboard = [
      [1, 2, 3, 4, 5].map((rating) => ({
        text: '⭐'.repeat(rating),
        callback_data: `fb:${sessionType}:${rating}`,
      })),
    ];
    await sendMessageWithKeyboard(env.BOT_TOKEN, chatId, text, keyboard);
  } catch (error) {
    logger.error('Failed to send feedback prompt', error as Error);
  }
}