// Discord Fleet Daily Reports
// Purpose: Schedules and delivers completed-day fleet summaries to the existing admin alert channel.
// Scope: Discord owns timing/formatting/delivery; the fleet service owns evidence, analysis, and durable delivery state.
const { DateTime } = require('luxon');
const { EmbedBuilder } = require('discord.js');

function parseSendTime(value) {
  const match = /^(\d{1,2}):(\d{2})$/.exec(String(value || '').trim());
  if (!match) return { hour: 8, minute: 0 };
  return {
    hour: Math.max(0, Math.min(23, Number(match[1]))),
    minute: Math.max(0, Math.min(59, Number(match[2]))),
  };
}

function nextRunAt({ zone, hour, minute }) {
  const now = DateTime.now().setZone(zone);
  let next = now.set({ hour, minute, second: 0, millisecond: 0 });
  if (next <= now) next = next.plus({ days: 1 });
  return next;
}

function formatNumber(value, digits = 1) {
  return Number(value || 0).toLocaleString(undefined, { maximumFractionDigits: digits });
}

function createFleetDailyReports({ logger, discordConfig, fleetConfig, fleetReportService, roverManager, sendToChannel }) {
  let timer = null;
  const reportConfig = fleetConfig?.discord || {};
  const enabled = fleetReportService?.enabled && reportConfig.enabled !== false;
  const channelId = discordConfig?.channels?.adminAlerts;
  const zone = String(reportConfig.timezone || 'America/New_York');
  const { hour, minute } = parseSendTime(reportConfig.sendAt);

  function publicRoverIds() {
    // Discord's shared admin-alert channel does not provide a per-viewer socket
    // against which private-rover grants can be checked. Excluding private
    // rovers here preserves the existing privacy boundary instead of assuming
    // every channel reader has every private grant.
    return roverManager.getRoster()
      .filter((rover) => !rover?.private?.enabled)
      .map((rover) => String(rover.id));
  }

  function completedDayRange() {
    const end = DateTime.now().setZone(zone).startOf('day');
    const start = end.minus({ days: 1 });
    return {
      reportDate: start.toISODate(),
      since: start.toMillis(),
      until: end.toMillis(),
    };
  }

  function buildEmbed(reportDate, report) {
    const totals = report.totals;
    const attention = report.attention
      .filter((item) => item.severity !== 'notice')
      .slice(0, 12)
      .map((item) => `• ${item.roverId}: ${item.title}`)
      .join('\n') || 'No material battery or efficiency changes need attention.';
    const roverLines = report.rovers.map((rover) => {
      const health = rover.batteryHealth || {};
      const efficiency = rover.overallWhPerKm == null
        ? `efficiency pending (${formatNumber(rover.distanceMm / 1000, 0)} m)`
        : `${formatNumber(rover.overallWhPerKm)} Wh/km`;
      const capacity = health.measuredUsableMah == null
        ? `health collecting (${health.confidence || 'low'} confidence)`
        : `${formatNumber(health.measuredUsableMah / 1000, 2)} Ah usable · ${formatNumber(health.capacityRetentionPercent)}% retained · ${health.confidence} confidence`;
      return `• ${rover.name}: ${formatNumber(rover.distanceMm / 1e6, 2)} km · ${formatNumber(rover.dischargedWh, 2)} Wh · ${efficiency}\n  Battery: ${capacity}`;
    }
    ).join('\n') || 'No public rover telemetry.';
    return new EmbedBuilder()
      .setTitle(`Daily fleet report — ${reportDate}`)
      .setColor(totals.attentionCount ? 0xf0b651 : 0x4caf50)
      .addFields(
        {
          name: 'Fleet energy',
          value: `${formatNumber(totals.distanceMm / 1e6, 2)} km · ${formatNumber(totals.dischargedWh, 2)} Wh · ${totals.overallWhPerKm == null ? 'efficiency pending' : `${formatNumber(totals.overallWhPerKm)} Wh/km`} · ${formatNumber(totals.stationaryDischargedWh, 2)} stationary Wh`,
        },
        { name: 'Needs attention', value: attention.slice(0, 1024) },
        { name: 'Rovers', value: roverLines.slice(0, 1024) },
      )
      .setFooter({ text: 'The server reports page contains the complete all-rovers metric table.' });
  }

  async function deliverPreviousDay() {
    if (!enabled || !channelId) return;
    const range = completedDayRange();
    const existing = fleetReportService.storage.getDailyReport(range.reportDate);
    if (existing?.discordDeliveredAt) return;
    const report = fleetReportService.getDailyReport({
      since: range.since,
      until: range.until,
      roverIds: publicRoverIds(),
    });
    if (!report) return;
    /*
      Daily storage retains the exact metric report used for delivery, but the
      Discord message intentionally has no raw JSON attachment. Admins need
      actionable fleet comparisons here; the complete read-only evidence stays
      on the reports page without turning routine events into notification noise.
    */
    fleetReportService.storage.saveDailyReport(range.reportDate, report);
    const sent = await sendToChannel(
      channelId,
      `Daily fleet report for ${range.reportDate}`,
      { embeds: [buildEmbed(range.reportDate, report)] },
      { parse: [] },
    );
    if (sent) {
      fleetReportService.storage.markDailyReportDelivery(range.reportDate, { deliveredAt: Date.now(), error: null });
    } else {
      fleetReportService.storage.markDailyReportDelivery(range.reportDate, { error: 'Discord delivery returned no message' });
    }
  }

  function scheduleNext() {
    if (!enabled || !channelId) return;
    const next = nextRunAt({ zone, hour, minute });
    const delay = Math.max(1000, next.toMillis() - Date.now());
    timer = setTimeout(async () => {
      try {
        await deliverPreviousDay();
      } catch (err) {
        logger.warn('Daily fleet report delivery failed', { error: err.message });
      } finally {
        scheduleNext();
      }
    }, delay);
    timer.unref?.();
    logger.info('Scheduled daily fleet report', { nextRunAt: next.toISO(), channelId });
  }

  function start() {
    scheduleNext();
  }

  function stop() {
    if (timer) clearTimeout(timer);
    timer = null;
  }

  return { start, stop, deliverPreviousDay };
}

module.exports = {
  createFleetDailyReports,
};