import { type Client, EmbedBuilder } from "discord.js";
import type { Payload } from "payload";
import type { Mission } from "@/payload-types";
import { botConfig } from "@/bot/config";
import { computeEvaluationReminderPlan, type ReminderLink } from "@/lib/evaluations/reminders";
import { isMissionEvaluable } from "@/lib/evaluations";

/**
 * Evaluation reminder service: after a mission becomes evaluable (completed, or
 * its scheduled start has passed), every participant with a linked Discord
 * account gets a one-shot DM asking them to rate their leadership — and every
 * leader additionally gets a section asking them to rate the subordinates who
 * participated. Each DM links to the relevant profile pages, where the rating
 * dialog lives.
 *
 * The DM deliberately ignores `preferences.discord.enabled` (the notification
 * bridge opt-in): that toggle defaults to false and is not yet exposed in the
 * web UI, so honoring it here would silently DM nobody. This is a dedicated
 * unit-admin flow, not a forwarding of the generic notification stream.
 */

const EMBED_COLOR = 0xf59e0b;
const MISSIONS_PER_TICK = 3;
const MAX_DMS_PER_TICK = 40;
const SEND_DELAY_MS = 300;

let reconcileRunning = false;

const errorMessage = (error: unknown): string =>
  error instanceof Error ? error.message : "Unknown error";

const missionTitle = (mission: Mission): string =>
  mission.codeName ? `${mission.name} (${mission.codeName})` : mission.name;

const getReminderMissions = async (payload: Payload): Promise<Mission[]> => {
  const now = new Date().toISOString();
  const res = await payload.find({
    collection: "missions",
    overrideAccess: true,
    depth: 0,
    sort: "-classification.startDateTime",
    limit: MISSIONS_PER_TICK,
    where: {
      and: [
        { evaluationRemindersSentAt: { exists: false } },
        {
          or: [
            { "ownershipAndStatus.status": { equals: "Completed" } },
            {
              and: [
                { "ownershipAndStatus.status": { in: ["Scheduled", "Active"] } },
                { "classification.startDateTime": { less_than: now } },
              ],
            },
          ],
        },
      ],
    },
  });
  return res.docs as unknown as Mission[];
};

const formatLinks = (links: ReminderLink[], appUrl: string): string => {
  const lines = links.map(
    (link) => `• [${link.displayName}](${appUrl}${link.profilePath})`,
  );
  // Discord embed field values cap at 1024 chars.
  return (lines.join("\n").slice(0, 1024) || "—");
};

const renderReminderEmbed = (
  mission: Mission,
  rateLeaders: ReminderLink[],
  rateSubordinates: ReminderLink[],
  appUrl: string,
): EmbedBuilder => {
  const embed = new EmbedBuilder()
    .setTitle(`Leadership feedback requested — ${missionTitle(mission)}`)
    .setColor(EMBED_COLOR)
    .setFooter({
      text: "Ratings are private and anonymous in aggregate. A leader's results become visible once 3+ members have rated them.",
    });

  if (rateLeaders.length > 0) {
    embed.addFields({
      name: "⭐ Rate your leadership",
      value: formatLinks(rateLeaders, appUrl),
    });
  }
  if (rateSubordinates.length > 0) {
    embed.addFields({
      name: "🪖 Rate your subordinates' performance",
      value: formatLinks(rateSubordinates, appUrl),
    });
  }
  return embed;
};

const sendReminderDms = async (
  client: Client,
  payload: Payload,
  mission: Mission,
): Promise<{ sent: number; capped: boolean }> => {
  const plan = await computeEvaluationReminderPlan(payload, mission.id);
  const targets = plan.recipients.filter((r) => r.discordId);
  const skipped = plan.recipients.length - targets.length;
  if (skipped > 0) {
    payload.logger.warn(
      `[Bot] Evaluation reminders for mission #${mission.id}: skipping ${skipped} user(s) without a linked Discord account.`,
    );
  }

  let sent = 0;
  for (const target of targets) {
    if (sent >= MAX_DMS_PER_TICK) {
      payload.logger.warn(
        `[Bot] Evaluation reminder DM cap (${MAX_DMS_PER_TICK}) reached for mission #${mission.id}; remaining users will be sent next tick.`,
      );
      return { sent, capped: true };
    }
    try {
      const user = await client.users.fetch(target.discordId as string);
      await user.send({
        embeds: [
          renderReminderEmbed(mission, target.rateLeaders, target.rateSubordinates, botConfig.appUrl),
        ],
      });
      sent += 1;
    } catch (error) {
      payload.logger.warn(
        `[Bot] Evaluation reminder DM failed for user #${target.userId} (mission #${mission.id}): ${errorMessage(error)}`,
      );
    }
    await new Promise((resolve) => setTimeout(resolve, SEND_DELAY_MS));
  }
  return { sent, capped: false };
};

/**
 * Sends reminder DMs for one mission, then stamps the one-shot marker —
 * unless the per-tick DM cap was hit, in which case the marker is left unset
 * so the remaining users are sent on a later pass. Exported for the
 * /remind-evaluations command's manual trigger.
 *
 * @returns the number of DMs actually sent.
 */
export const processMission = async (
  client: Client,
  payload: Payload,
  mission: Mission,
): Promise<number> => {
  const { sent, capped } = await sendReminderDms(client, payload, mission);
  if (capped) {
    payload.logger.warn(
      `[Bot] Evaluation reminders for mission #${mission.id}: DM cap hit — marker not set, will retry next tick.`,
    );
    return sent;
  }
  await payload.update({
    collection: "missions",
    id: mission.id,
    data: { evaluationRemindersSentAt: new Date().toISOString() },
    overrideAccess: true,
  });
  payload.logger.info(
    `[Bot] Sent ${sent} evaluation reminder DM(s) for mission #${mission.id} (${mission.name}).`,
  );
  return sent;
};

export interface ReconcileSummary {
  processed: number;
  sent: number;
}

export const reconcile = async (
  client: Client,
  payload: Payload,
): Promise<ReconcileSummary> => {
  if (reconcileRunning) return { processed: 0, sent: 0 };
  reconcileRunning = true;
  let processed = 0;
  let sent = 0;
  try {
    const missions = (await getReminderMissions(payload)).filter((mission) =>
      isMissionEvaluable(
        mission.ownershipAndStatus?.status ?? "",
        mission.classification?.startDateTime ?? null,
      ),
    );
    for (const mission of missions) {
      try {
        sent += await processMission(client, payload, mission);
        processed += 1;
      } catch (error) {
        payload.logger.error(
          `[Bot] Evaluation reminder reconcile failed for mission #${mission.id}: ${errorMessage(error)}`,
        );
      }
    }
  } catch (error) {
    payload.logger.error(`[Bot] Evaluation reminder reconcile failed: ${errorMessage(error)}`);
  } finally {
    reconcileRunning = false;
  }
  return { processed, sent };
};

export const start = (client: Client, payload: Payload): void => {
  payload.logger.info("[Bot] Evaluation reminder service started");
  void reconcile(client, payload);
  setInterval(() => {
    void reconcile(client, payload);
  }, botConfig.evaluationPollMs);
};