const fs = require("fs");

function sendReminder(filePath, userId, channel) {
  const raw = fs.readFileSync(filePath, "utf8");
  const state = JSON.parse(raw);
  const user = state.users.find((item) => item.id === userId);

  if (!user) {
    throw new Error("User not found");
  }

  if (!user.remindersEnabled) {
    return { sent: false, reason: "disabled" };
  }

  const hour = new Date().getHours();

  if (hour < 8 || hour > 20) {
    return { sent: false, reason: "quiet-hours" };
  }

  if (channel === "sms" && !user.phoneNumber) {
    return { sent: false, reason: "missing-phone" };
  }

  user.lastReminderAt = new Date().toISOString();
  fs.writeFileSync(filePath, JSON.stringify(state, null, 2));
  console.log("Sent reminder", userId, channel);

  return { sent: true, channel };
}

module.exports = { sendReminder };