import type { Employee, NormalizedOrgChartDataset, OrganizationTreeNode, OrgChartDataset } from './types.js';

/** Pure derivation for validated datasets. Multiple roots remain a forest. */
export function normalizeOrgChartDataset(data: OrgChartDataset): NormalizedOrgChartDataset {
  const organizationsById = new Map(data.organizations.map(org => [org.id, org]));
  const employeesByOrganization = new Map<string, Employee[]>(data.organizations.map(org => [org.id, []]));
  for (const employee of data.employees) employeesByOrganization.get(employee.organizationId)?.push(employee);
  const nodes = new Map<string, OrganizationTreeNode>(data.organizations.map(org => [org.id, { organization: org, children: [] }]));
  const roots: OrganizationTreeNode[] = [];
  for (const node of nodes.values()) {
    if (node.organization.parentId === null) roots.push(node);
    else nodes.get(node.organization.parentId)?.children.push(node);
  }
  const order = new Map((data.presentation?.organizationOrder ?? []).map((id, index) => [id, index]));
  const compare = (a: OrganizationTreeNode, b: OrganizationTreeNode) => {
    const aOrder = order.get(a.organization.id) ?? Infinity;
    const bOrder = order.get(b.organization.id) ?? Infinity;
    if (aOrder !== bOrder) return aOrder < bOrder ? -1 : 1;
    const difference = a.organization.displayOrder - b.organization.displayOrder;
    if (difference) return difference;
    // Code-unit order is deterministic across environments and independent of locale.
    return a.organization.id < b.organization.id ? -1 : a.organization.id > b.organization.id ? 1 : 0;
  };
  roots.sort(compare);
  for (const node of nodes.values()) node.children.sort(compare);
  return { roots, organizationsById, employeesByOrganization };
}