import { Injectable, Logger } from '@nestjs/common';
import { Cron, CronExpression } from '@nestjs/schedule';
import { InjectDataSource } from '@nestjs/typeorm';
import { DataSource } from 'typeorm';

import { MatrixClient } from './matrix.client';

/** edr-org.seeder.ts's EDR_ORG_KEY / EDR_UNIT_KEY — the org is currently flat
 *  (one org, one unit), so this is the entire scope of what gets provisioned. */
const ORG_KEY = 'edr_freight';
const UNIT_KEY = 'edr_freight_app';

const SPACE_ALIAS = 'edr-freight';
const GENERAL_ALIAS = 'general';

interface PositionHolder {
  positionKey: string;
  positionName: string;
  userId: string;
  userName: string;
}

export interface ReconcileResult {
  rooms: number;
  joined: number;
  kicked: number;
  deactivated: number;
}

/**
 * Keeps Matrix rooms and their membership in sync with IAM's unit/position
 * tree. There is no local hook on "employee position changed" — IAM writes
 * happen inside the vendored @tria-plc/iamapi-common package — so this is a
 * reconcile loop, not an event handler: nightly, plus on-demand via
 * POST /chat/sync.
 *
 * Room identity is a deterministic alias (#dept-<positionKey>), not a stored
 * mapping table — resolved via the directory API, created on first miss.
 * Room membership is diffed against Matrix's own joined_members, not a local
 * snapshot — so a user removed from IAM disappears from chat on the very
 * next reconcile, with no extra state for this service to own.
 */
@Injectable()
export class ChatProvisioningService {
  private readonly logger = new Logger(ChatProvisioningService.name);

  constructor(
    @InjectDataSource() private readonly dataSource: DataSource,
    private readonly matrix: MatrixClient,
  ) {}

  @Cron(CronExpression.EVERY_DAY_AT_3AM, { name: 'chat-provisioning-reconcile' })
  async scheduledReconcile(): Promise<void> {
    try {
      const result = await this.reconcile();
      this.logger.log(
        `Chat reconcile: ${result.rooms} room(s), ${result.joined} joined, ` +
          `${result.kicked} kicked, ${result.deactivated} deactivated`,
      );
    } catch (err) {
      // Never throws into the scheduler — chat provisioning must not be able
      // to take down anything else on the cron registry.
      this.logger.error(
        `Chat reconcile failed: ${(err as Error).message}`,
        (err as Error).stack,
      );
    }
  }

  private async currentHolders(): Promise<PositionHolder[]> {
    return this.dataSource.query(
      `SELECT p.key AS "positionKey",
              COALESCE(p.name->>'en', p.key) AS "positionName",
              e.user_id AS "userId",
              COALESCE(iu.name->>'en', iu.username, iu.email) AS "userName"
         FROM iam.employee_positions ep
         JOIN iam.employees e ON e.id = ep.employee_id
         JOIN iam.positions p ON p.id = ep.position_id
         JOIN iam.units u ON u.id = p.unit_id
         JOIN iam.organizations o ON o.id = u.organization_id
         JOIN iam.users iu ON iu.id = e.user_id
        WHERE ep.is_current = true
          AND e.is_current = true
          AND o.key = $1
          AND u.key = $2`,
      [ORG_KEY, UNIT_KEY],
    );
  }

  /** Force-joins additions, kicks+deactivates users no longer entitled anywhere. */
  private async syncMembership(
    roomId: string,
    desiredUserIds: Set<string>,
    botMxid: string,
  ): Promise<{ joined: number; kicked: string[] }> {
    const current = await this.matrix.joinedMembers(roomId);
    const currentSet = new Set(current.filter((id) => id !== botMxid));

    let joined = 0;
    for (const userId of desiredUserIds) {
      if (!currentSet.has(userId)) {
        await this.matrix.forceJoin(roomId, userId);
        joined += 1;
      }
    }

    const kicked: string[] = [];
    for (const userId of currentSet) {
      if (!desiredUserIds.has(userId)) {
        await this.matrix.kick(roomId, userId, 'No longer assigned to this room');
        kicked.push(userId);
      }
    }

    return { joined, kicked };
  }

  async reconcile(): Promise<ReconcileResult> {
    const holders = await this.currentHolders();
    const botMxid = await this.matrix.whoami();

    const spaceId = await this.matrix.ensureRoom(SPACE_ALIAS, 'EDR Freight', {
      isSpace: true,
    });
    const generalRoomId = await this.matrix.ensureRoom(GENERAL_ALIAS, 'General', {
      parentSpaceId: spaceId,
    });

    const allUserIds = new Set(holders.map((h) => this.matrix.mxid(h.userId)));

    // Accounts are otherwise only created lazily on first JWT login (see
    // ChatSsoService) — force-joining someone who has never clicked "Chat"
    // yet 404s ("User not found") without this.
    const seenUserIds = new Set<string>();
    for (const h of holders) {
      const mxid = this.matrix.mxid(h.userId);
      if (seenUserIds.has(mxid)) continue;
      seenUserIds.add(mxid);
      await this.matrix.ensureUser(mxid, h.userName);
    }

    let rooms = 2; // space + general
    let joined = 0;
    let kicked = 0;
    // A user kicked from anything while holding zero current positions
    // anywhere in the unit (allUserIds spans every position) is a full
    // leaver, not just moved between positions — deactivate their account.
    const kickedUserIds = new Set<string>();

    const generalDiff = await this.syncMembership(generalRoomId, allUserIds, botMxid);
    joined += generalDiff.joined;
    kicked += generalDiff.kicked.length;
    generalDiff.kicked.forEach((uid) => kickedUserIds.add(uid));

    const byPosition = new Map<string, { name: string; userIds: Set<string> }>();
    for (const h of holders) {
      const entry = byPosition.get(h.positionKey) ?? {
        name: h.positionName,
        userIds: new Set<string>(),
      };
      entry.userIds.add(this.matrix.mxid(h.userId));
      byPosition.set(h.positionKey, entry);
    }

    for (const [positionKey, { name, userIds }] of byPosition) {
      const roomId = await this.matrix.ensureRoom(`dept-${positionKey}`, name, {
        parentSpaceId: spaceId,
      });
      rooms += 1;

      const diff = await this.syncMembership(roomId, userIds, botMxid);
      joined += diff.joined;
      kicked += diff.kicked.length;
      diff.kicked.forEach((uid) => kickedUserIds.add(uid));
    }

    let deactivated = 0;
    for (const userId of kickedUserIds) {
      if (allUserIds.has(userId)) continue; // moved position, still current elsewhere
      try {
        await this.matrix.deactivateUser(userId);
        deactivated += 1;
      } catch (err) {
        this.logger.warn(
          `Failed to deactivate departed user ${userId}: ${(err as Error).message}`,
        );
      }
    }

    return { rooms, joined, kicked, deactivated };
  }
}