import { prisma } from "@capakraken/db";
import { logger } from "./logger.js";
import { emitReminderDue, emitNotificationCreated } from "../sse/event-bus.js";

const POLL_INTERVAL_MS = 60_000; // 60 seconds
let isProcessing = false;

function computeNextRemindAt(current: Date, recurrence: string): Date {
  const next = new Date(current);
  switch (recurrence) {
    case "daily":
      next.setDate(next.getDate() + 1);
      break;
    case "weekly":
      next.setDate(next.getDate() + 7);
      break;
    case "monthly":
      next.setMonth(next.getMonth() + 1);
      break;
    default:
      return current;
  }
  return next;
}

function computeNextRemindAtAfter(current: Date, recurrence: string, now: Date): Date {
  let next = computeNextRemindAt(current, recurrence);
  if (next.getTime() <= current.getTime()) {
    return current;
  }

  while (next.getTime() <= now.getTime()) {
    const advanced = computeNextRemindAt(next, recurrence);
    if (advanced.getTime() <= next.getTime()) {
      return next;
    }
    next = advanced;
  }

  return next;
}

async function processReminders() {
  if (isProcessing) {
    logger.warn("Skipping reminder scheduler tick while previous run is still processing");
    return;
  }

  isProcessing = true;
  const now = new Date();

  try {
    // Find all due reminders
    const dueReminders = await prisma.notification.findMany({
      where: {
        category: "REMINDER",
        nextRemindAt: { lte: now },
      },
      take: 100, // process in batches
    });

    for (const reminder of dueReminders) {
      try {
        if (reminder.recurrence) {
          // Recurring: create a new notification for this occurrence, advance nextRemindAt
          const notification = await prisma.notification.create({
            data: {
              userId: reminder.userId,
              category: "NOTIFICATION",
              type: "REMINDER_DUE",
              priority: reminder.priority,
              title: reminder.title,
              body: reminder.body,
              entityId: reminder.entityId,
              entityType: reminder.entityType,
              link: reminder.link,
              sourceId: reminder.id,
              channel: "in_app",
            },
          });

          // Advance to next occurrence
          await prisma.notification.update({
            where: { id: reminder.id },
            data: {
              nextRemindAt: computeNextRemindAtAfter(
                reminder.nextRemindAt!,
                reminder.recurrence,
                now,
              ),
            },
          });

          emitNotificationCreated(reminder.userId, notification.id);
          emitReminderDue(reminder.userId, notification.id);
        } else {
          // One-shot: mark the reminder as "fired" by clearing nextRemindAt
          await prisma.notification.update({
            where: { id: reminder.id },
            data: { nextRemindAt: null },
          });

          emitReminderDue(reminder.userId, reminder.id);
          emitNotificationCreated(reminder.userId, reminder.id);
        }
      } catch (err) {
        logger.error(
          { err, reminderId: reminder.id, userId: reminder.userId },
          "Failed to process reminder",
        );
      }
    }
  } finally {
    isProcessing = false;
  }
}

let intervalId: ReturnType<typeof setInterval> | null = null;

export function startReminderScheduler(): void {
  if (intervalId) return; // already running
  logger.info({ pollIntervalMs: POLL_INTERVAL_MS }, "Starting reminder scheduler");
  // Run immediately to catch up on overdue reminders
  void processReminders();
  intervalId = setInterval(() => void processReminders(), POLL_INTERVAL_MS);
}

export function stopReminderScheduler(): void {
  if (intervalId) {
    clearInterval(intervalId);
    intervalId = null;
    isProcessing = false;
    logger.info("Stopped reminder scheduler");
  }
}