pelagia-portal/App/lib/leave-clash.ts

import type { Prisma } from "@prisma/client";

// Leave-clash detection (Crewing-Implementation-Spec §5.3, R6). Required strength
// is treated as 1: approving a leave is a clash when it would leave the vessel
// with ZERO active same-rank cover over the leave window — i.e. every other
// not-signed-off crew member of that rank on the vessel is either absent or on an
// approved leave that overlaps the window. A clash auto-raises a LEAVE requisition.

interface ClashInput {
  assignmentId: string;
  rankId: string;
  vesselId: string | null;
  fromDate: Date;
  toDate: Date;
}

export async function leaveLeavesNoCover(
  tx: Prisma.TransactionClient,
  { assignmentId, rankId, vesselId, fromDate, toDate }: ClashInput
): Promise<boolean> {
  // No vessel cost axis → no rank-cover check.
  if (!vesselId) return false;

  const others = await tx.crewAssignment.findMany({
    where: { rankId, vesselId, status: { not: "SIGNED_OFF" }, id: { not: assignmentId } },
    select: { id: true },
  });
  // This crew member was the only same-rank cover on the vessel.
  if (others.length === 0) return true;

  const otherIds = others.map((o) => o.id);
  const overlapping = await tx.leaveRequest.findMany({
    where: {
      assignmentId: { in: otherIds },
      status: "APPROVED",
      fromDate: { lte: toDate },
      toDate: { gte: fromDate },
    },
    select: { assignmentId: true },
  });
  const out = new Set(overlapping.map((l) => l.assignmentId));
  const remainingCover = otherIds.filter((id) => !out.has(id)).length;
  return remainingCover === 0;
}