import type { AppContainer } from './bootstrap.js';
import { withRetry } from './utils/retry.js';
import { isSkip } from './services/processor.js';
import { reportDeliveryResult, reportInvitationCooldown } from './web/event-reporting.js';
import { SessionBoundRuntime } from './services/session-bound-runtime.js';
import { RedditRateLimitError } from './reddit/api.js';

export interface StoppableSchedule {
  stop(): void;
}

/** The limiter increments after a successful send, so its count is already current. */
export function currentHourlySendCount(
  limiter: { getStats(): { messagesThisHour: number } },
): number {
  return limiter.getStats().messagesThisHour;
}

/**
 * Runs a task again only after its previous run has settled. This deliberately
 * replaces setInterval: a slow browser response check must never overlap the
 * next check and contend for the same browser/session resources.
 */
export function startNonOverlappingSchedule(
  task: () => Promise<void>,
  intervalMs: number,
): StoppableSchedule {
  let stopped = false;
  let timer: NodeJS.Timeout | null = null;

  const run = async (): Promise<void> => {
    if (stopped) return;
    try {
      await task();
    } finally {
      if (!stopped) timer = setTimeout(() => void run(), intervalMs);
    }
  };

  void run();
  return {
    stop: () => {
      stopped = true;
      if (timer) clearTimeout(timer);
    },
  };
}

function sleep(ms: number, signal?: AbortSignal): Promise<void> {
  if (signal?.aborted) return Promise.reject(new DOMException('Operation aborted', 'AbortError'));
  return new Promise((resolve, reject) => {
    let timer: NodeJS.Timeout;
    const abort = (): void => {
      clearTimeout(timer);
      cleanup();
      reject(new DOMException('Operation aborted', 'AbortError'));
    };
    const cleanup = (): void => signal?.removeEventListener('abort', abort);
    const done = (): void => {
      cleanup();
      resolve();
    };
    timer = setTimeout(done, ms);
    signal?.addEventListener('abort', abort, { once: true });
  });
}

const PAUSED_LOG_INTERVAL_MS = 60_000;
const PAUSE_POLL_MS = 1_000;
const ERROR_BACKOFF_MS = 60_000;

/**
 * Runs the bot's main polling loop and the background response checker until
 * SIGINT/SIGTERM. Resolves once shutdown completes.
 */
export async function runMainLoop(app: AppContainer): Promise<void> {
  if (app.accountRuntimeManager) {
    await runConcurrentAccountRuntimes(app);
    return;
  }
  const {
    config,
    logger,
    browserClient,
    accountAuth,
    postsRepo,
    messagesRepo,
    recipientDeduplicator,
    redditApi,
    monitorService,
    processorService,
    responseChecker,
    chatService,
    rateLimiter,
    mediaSyncService,
    db,
    webServer,
  } = app;

  let isShuttingDown = false;
  const shutdownController = new AbortController();
  let responseCheckSchedule: StoppableSchedule | null = null;
  let sessionRuntime: SessionBoundRuntime | null = null;

  const shutdown = async (): Promise<void> => {
    if (isShuttingDown) return;
    isShuttingDown = true;
    shutdownController.abort();

    sessionRuntime?.shutdown();

    logger.info('Shutting down gracefully...');
    webServer?.stop();
    await browserClient.close();
    db.close();
    logger.info('Goodbye!');
  };

  process.on('SIGINT', shutdown);
  process.on('SIGTERM', shutdown);

  logger.info('');
  logger.info('Bot is now running!');
  logger.info(`Monitoring subreddits: ${config.reddit.subreddits.map((s) => `${s.name}[${s.type}]`).join(', ')}`);
  logger.info(`Poll interval: ${config.reddit.pollIntervalMs / 1000} seconds`);
  logger.info(`Min delay between messages: ${config.rateLimit.minDelayBetweenMessagesMs / 1000} seconds`);
  logger.info(`Max messages per hour: ${config.rateLimit.maxMessagesPerHour}`);
  logger.info('');

  // Background response checker
  const RESPONSE_CHECK_INTERVAL_MS = Math.max(config.reddit.pollIntervalMs * 5, 60_000);

  const checkResponses = async (): Promise<void> => {
    if (isShuttingDown) return;
    try {
      logger.debug('Checking for responses to sent messages (Background Thread)...');
      const responses = await responseChecker.checkForResponses();
      for (const r of responses) {
        if (!r.gotResponse) continue;
        const snippet = r.responseSnippet ? `: ${r.responseSnippet.slice(0, 200)}` : '';
        webServer?.logActivity(
          'response',
          `Reply from u/${r.recipient}${snippet}`,
          r.recipient,
        );
        webServer?.pushLog('info', `💬 Reply from u/${r.recipient}`);
      }
      if (responses.some((r) => r.gotResponse)) {
        const updatedExamples = responseChecker.getSuccessfulExamples(3);
        processorService.setSuccessfulExamples(updatedExamples);
      }
    } catch (error) {
      logger.error('Error in background response checker:', error);
    }
  };

  let startupSyncStarted = false;
  sessionRuntime = new SessionBoundRuntime(
    () => {
      responseCheckSchedule = startNonOverlappingSchedule(checkResponses, RESPONSE_CHECK_INTERVAL_MS);
      if (config.media.syncEnabled) mediaSyncService.start();
      if (!startupSyncStarted) {
        startupSyncStarted = true;
        chatService
          .runStartupSync()
          .then(async ({ kind, chats }) => {
            logger.info(`[chat] startup sync (${kind}) complete: ${chats} chats`);
            await chatService.enrichUsernames();
          })
          .catch((err) => logger.error('[chat] startup sync failed:', err));
      }
    },
    () => {
      responseCheckSchedule?.stop();
      responseCheckSchedule = null;
      mediaSyncService.stop();
    },
  );

  let lastPausedLog = 0;
  let lastCooldownLog = 0;
  let reportedCooldownUntil: number | null = null;
  const COOLDOWN_LOG_INTERVAL_MS = 5 * 60_000;

  while (!isShuttingDown) {
    try {
      const authenticated = accountAuth.isFullyAuthenticated()
        || await accountAuth.ensureFullyAuthenticated();
      if (!sessionRuntime.reconcile(authenticated)) {
        if (Date.now() - lastPausedLog > PAUSED_LOG_INTERVAL_MS) {
          logger.info('Reddit is logged out. Waiting for a session dump from the extension.');
          lastPausedLog = Date.now();
        }
        await sleep(PAUSE_POLL_MS, shutdownController.signal);
        continue;
      }

      if (webServer && !webServer.isRunning()) {
        if (Date.now() - lastPausedLog > PAUSED_LOG_INTERVAL_MS) {
          logger.info('Bot is paused. Use the web dashboard to start.');
          lastPausedLog = Date.now();
        }
        await sleep(PAUSE_POLL_MS, shutdownController.signal);
        continue;
      }

      // If Reddit told us to take a break on creating new chats, don't even
      // pull new posts — they'd just queue up and skip. Wait the cooldown out.
      const cooldown = chatService.getInvitationCooldown();
      if (cooldown) {
        if (webServer && reportedCooldownUntil !== cooldown.until) {
          reportInvitationCooldown(webServer.dashboardEvents, cooldown);
          reportedCooldownUntil = cooldown.until;
        }
        const minutesLeft = Math.ceil((cooldown.until - Date.now()) / 60_000);
        if (Date.now() - lastCooldownLog > COOLDOWN_LOG_INTERVAL_MS) {
          logger.warn(`Chat invitation cooldown active — ~${minutesLeft}m left. ${cooldown.reason}`);
          webServer?.pushLog(
            'warn',
            `⏸️ Chat throttle: ${cooldown.reason} (~${minutesLeft}m remaining)`,
          );
          lastCooldownLog = Date.now();
        }
        await sleep(config.reddit.pollIntervalMs, shutdownController.signal);
        continue;
      }
      if (webServer && reportedCooldownUntil !== null) {
        reportInvitationCooldown(webServer.dashboardEvents, null);
        reportedCooldownUntil = null;
      }
      lastCooldownLog = 0;

      const posts = await monitorService.getUnprocessedPosts();

      if (posts.length > 0) {
        logger.info(`Found ${posts.length} unprocessed posts`);
        webServer?.pushLog('info', `Found ${posts.length} unprocessed posts`);
      } else {
        logger.info('No new posts found. Monitoring...');
      }

      for (const post of posts) {
        if (isShuttingDown) break;

        try {
          const subredditEntry = config.reddit.subreddits.find(
            (s) => s.name.toLowerCase() === post.subreddit.toLowerCase(),
          );
          const isChatSub = subredditEntry?.type === 'chat';
          const postImageUrl = isChatSub ? null : redditApi.getImageUrl(post);
          const postUrl = redditApi.getPostUrl(post);
          postsRepo.insert({
            id: post.id,
            subreddit: post.subreddit,
            author: post.author,
            title: post.title,
            postUrl,
            imageUrl: postImageUrl,
            postCreatedAt: post.created_utc * 1000,
            processedAt: Date.now(),
          });

          // Refresh examples weighted toward this post's subreddit.
          const subredditExamples = responseChecker.getSuccessfulExamples(3, post.subreddit);
          processorService.setSuccessfulExamples(subredditExamples);

          const processed = await withRetry(
            () => processorService.processPost(post),
            { logger, retries: 2, operationName: 'Post processing' },
          );

          if (isSkip(processed)) {
            logger.debug(`Skipping post ${post.id} - ${processed.skipReason}`);
            webServer?.logActivity(
              'skipped',
              `Skipped post by u/${post.author} (${processed.skipReason})`,
              post.author,
            );
            webServer?.pushLog('info', `⏭️ Skipped u/${post.author} — ${processed.skipReason}`);
            continue;
          }

          postsRepo.updateAnalysis(post.id, processed.imageAnalysis, processed.generatedMessage);

          webServer?.pushLog(
            'info',
            `${isChatSub ? '💬' : '🖼️'} ${isChatSub ? 'Chat post' : 'Image analysis'} for u/${post.author}: ${processed.imageAnalysis}`,
          );
          if (processed.strategyId) {
            webServer?.pushLog('info', `🎯 Strategy: ${processed.strategyId}`);
          }

          await rateLimiter.throttle(
            async () => {
              if (config.browser.dryRun) {
                const reason = 'Dry run: message prepared but not sent';
                logger.info(`${reason} for u/${post.author}`);
                postsRepo.setError(post.id, reason);
                webServer?.logActivity('skipped', `${reason} to u/${post.author}`, post.author);
                webServer?.pushLog('info', `🧪 ${reason} to u/${post.author}`);
                return false;
              }
              if (!recipientDeduplicator.tryReserve(post.author)) {
                const reason = 'User already contacted across accounts';
                logger.info(`Skipping u/${post.author} - ${reason.toLowerCase()}`);
                postsRepo.setError(post.id, reason);
                webServer?.logActivity(
                  'skipped',
                  `Skipped u/${post.author} (already contacted across accounts)`,
                  post.author,
                );
                return false;
              }

              logger.info(`Sending message to u/${post.author}...`);
              webServer?.pushLog('info', `Sending message to u/${post.author}...`);

              let chat;
              try {
                chat = await chatService.startConversation(
                  post.author,
                  processed.generatedMessage,
                  post.author_fullname,
                );
              } catch (error) {
                recipientDeduplicator.release(post.author);
                throw error;
              }
              const success = chat !== null;

              if (chat) {
                postsRepo.markMessageSent(post.id);

                // Refresh top chats in background so dashboard is up-to-date.
                chatService
                  .refreshTopChats(5)
                  .catch((err) => logger.error('Failed to trigger chat refresh:', err));

                messagesRepo.insert({
                  postId: post.id,
                  recipient: post.author,
                  subject: post.author,
                  message: processed.generatedMessage,
                  sentAt: Date.now(),
                  strategyId: processed.strategyId,
                  chatRoomId: chat.roomId,
                  experimentId: processed.experimentId,
                  promptVersion: processed.promptVersion,
                  modelId: processed.modelId,
                  selectionReason: processed.selectionReason,
                  sourceType: processed.sourceType,
                });
                recipientDeduplicator.commit(post.author);

                const currentCount = currentHourlySendCount(rateLimiter);
                logger.info(
                  `Message sent successfully! (${currentCount}/${config.rateLimit.maxMessagesPerHour} this hour)`,
                );
                webServer?.logActivity(
                  'sent',
                  `Sent message to u/${post.author} (r/${post.subreddit})`,
                  post.author,
                  postImageUrl ?? undefined,
                  { postTitle: post.title, postUrl },
                );
                webServer?.pushLog('info', `✅ Message sent to u/${post.author} (${currentCount}/${config.rateLimit.maxMessagesPerHour} this hour)`);
                webServer?.updateStats(currentCount);
                if (webServer) {
                  reportDeliveryResult(webServer.dashboardEvents, {
                    success: true,
                    messageId: post.id,
                    username: post.author,
                    conversationId: chat.roomId,
                  });
                }
              } else {
                recipientDeduplicator.release(post.author);
                postsRepo.setError(post.id, 'Failed to send message');
                webServer?.logActivity(
                  'error',
                  `Failed to send to u/${post.author} (r/${post.subreddit})`,
                  post.author,
                  postImageUrl ?? undefined,
                );
                webServer?.pushLog('error', `❌ Failed to send message to u/${post.author}`);
                if (webServer) {
                  reportDeliveryResult(webServer.dashboardEvents, {
                    success: false,
                    messageId: post.id,
                    username: post.author,
                    error: 'Chat service did not create a conversation',
                  });
                }
              }

              return success;
            },
            (success) => success === true,
            shutdownController.signal,
          );
        } catch (error) {
          if (isShuttingDown && error instanceof DOMException && error.name === 'AbortError') break;
          const errorMessage = error instanceof Error ? error.message : String(error);
          logger.error(`Error processing post ${post.id}:`, error);
          postsRepo.setError(post.id, errorMessage);
        }
      }

      if (!isShuttingDown) {
        logger.debug(`Waiting ${config.reddit.pollIntervalMs / 1000} seconds before next poll...`);
        await sleep(config.reddit.pollIntervalMs, shutdownController.signal);
      }
    } catch (error) {
      if (isShuttingDown && error instanceof DOMException && error.name === 'AbortError') break;
      if (error instanceof RedditRateLimitError) {
        await sleep(Math.max(ERROR_BACKOFF_MS, error.retryAfterMs + 1_000), shutdownController.signal);
        continue;
      }

      const errorMessage = error instanceof Error ? error.message : String(error);
      logger.error(`Error in main loop: ${errorMessage}`);
      await sleep(ERROR_BACKOFF_MS, shutdownController.signal);
    }
  }
}

async function runConcurrentAccountRuntimes(app: AppContainer): Promise<void> {
  const { config, logger, accountRuntimeManager, browserClient, db, webServer } = app;
  logger.info(`Running ${accountRuntimeManager.list().length} account runtime(s) with shared post discovery`);
  await new Promise<void>((resolve) => {
    let shuttingDown = false;
    const controller = new AbortController();
    let nextScannerIndex = 0;

    const discoverAndDispatch = async (): Promise<void> => {
      const runtimes = accountRuntimeManager.list()
        .filter((snapshot) => snapshot.state === 'running')
        .map((snapshot) => accountRuntimeManager.get(snapshot.accountId))
        .filter((runtime): runtime is NonNullable<typeof runtime> => runtime !== null);
      if (runtimes.length === 0) return;

      // Rotate the authenticated browser used to read Reddit, while keeping
      // selection and delivery centralised. A subreddit is therefore fetched
      // once per cycle, never once per account.
      const scanner = runtimes[nextScannerIndex % runtimes.length];
      nextScannerIndex += 1;
      if (!(await scanner.canAcceptPost())) return;

      const posts = await scanner.resources.monitorService.getUnprocessedPosts();
      const post = posts[0];
      if (!post) return;

      const recipients = (await Promise.all(runtimes.map(async (runtime) => ({
        runtime,
        available: await runtime.canAcceptPost(),
      })))).filter((candidate) => candidate.available)
        .map((candidate) => candidate.runtime)
        .sort((left, right) => (
          left.resources.rateLimiter.getStats().messagesThisHour
          - right.resources.rateLimiter.getStats().messagesThisHour
        ));
      const recipient = recipients[0];
      if (!recipient) {
        logger.debug(`Eligible post ${post.id} found, but no account is currently available`);
        return;
      }

      logger.info(`Assigning eligible post ${post.id} (r/${post.subreddit}) to u/${recipient.session.redditUsername}`);
      await recipient.dispatchPost(post, controller.signal);
    };

    const discoveryLoop = (async (): Promise<void> => {
      while (!controller.signal.aborted) {
        try {
          if (webServer?.isRunning() ?? true) await discoverAndDispatch();
        } catch (error) {
          if (controller.signal.aborted) return;
          if (error instanceof RedditRateLimitError) {
            await sleep(error.retryAfterMs + 1_000, controller.signal).catch(() => undefined);
            continue;
          }
          logger.error('Shared post discovery failed:', error);
        }
        await sleep(config.reddit.pollIntervalMs, controller.signal).catch(() => undefined);
      }
    })();

    const shutdown = async (): Promise<void> => {
      if (shuttingDown) return;
      shuttingDown = true;
      controller.abort();
      logger.info('Stopping all Reddit account runtimes...');
      await discoveryLoop;
      await accountRuntimeManager.stopAll();
      webServer?.stop();
      await browserClient.close();
      db.close();
      process.off('SIGINT', onSignal);
      process.off('SIGTERM', onSignal);
      logger.info('Goodbye!');
      resolve();
    };
    const onSignal = (): void => { void shutdown(); };
    process.on('SIGINT', onSignal);
    process.on('SIGTERM', onSignal);
  });
}