import type { Tx } from "./db";
import { ancestorsOf, loadOrgMaps, subtreeOf, type OrgMaps } from "./org";
import { loadPlacements } from "./placement";
import { deriveStatusAsOf, EVENT_DATE_OPEN, parseStatuses, todayIso, type OrgLookups, type ReportEmployee, type ReportEvent } from "./reports";
import type { EmploymentType, HistoryEventType } from "./supabase/types";

// Shared by the Berichte page and /api/export/* so they can never drift on
// what "the current view" means — same filters, same stichtag/event-window
// rules.
export type ReportFilters = {
  /** Id einer Organisationseinheit; wirkt auf die Einheit *und alles darunter*. */
  division?: string;
  location?: string;
  status?: string;
  employment?: string;
};

export type SnapshotFilters = ReportFilters & { asOf?: string };
export type EventFilters = { eventType?: HistoryEventType; division?: string; location?: string; from?: string; to?: string };

/**
 * Für jede Einheit vorberechnen, welcher Bereich, welche Abteilung und
 * welches Team über ihr liegen. Ein Bericht gruppiert dann über einen
 * Kartenzugriff statt über einen Aufstieg im Baum je Zeile.
 */
export function lookupsFromOrgMaps(orgMaps: OrgMaps, locations: { id: string; name: string }[]): OrgLookups {
  const divisionName = new Map<string, string>();
  const departmentName = new Map<string, string>();
  const teamName = new Map<string, string>();

  for (const unit of orgMaps.unitList) {
    for (const a of ancestorsOf(orgMaps, unit.id)) {
      if (a.unit_type === "Bereich") divisionName.set(unit.id, a.name);
      else if (a.unit_type === "Abteilung") departmentName.set(unit.id, a.name);
      else if (a.unit_type === "Team") teamName.set(unit.id, a.name);
    }
  }

  return { divisionName, departmentName, teamName, locationName: new Map(locations.map((l) => [l.id, l.name])) };
}

export async function loadOrgLookups(tx: Tx): Promise<{
  lookups: OrgLookups;
  orgMaps: OrgMaps;
  divisions: { id: string; name: string }[];
  locations: { id: string; name: string }[];
}> {
  const orgMaps = await loadOrgMaps(tx);
  const locations = orgMaps.locationList.map((l) => ({ id: l.id, name: l.name }));

  return {
    lookups: lookupsFromOrgMaps(orgMaps, locations),
    orgMaps,
    // Als Filter angeboten wird die oberste Ebene unter der Gesellschaft —
    // das, was im Altmodell „Bereich" hiess. Der Filter greift auf den
    // ganzen Teilbaum.
    divisions: orgMaps.unitList.filter((u) => u.unit_type === "Bereich").map((u) => ({ id: u.id, name: u.name })),
    locations,
  };
}

const SNAPSHOT_EMPLOYEE_COLUMNS = [
  "id",
  "first_name",
  "last_name",
  "job_title",
  "location_id",
  "employment_type",
  "contract_type",
  "entry_date",
  "exit_date",
  "weekly_hours",
  "source",
  "paygrade",
  "birth_date",
  "gender",
  "karenz_start_date",
  "karenz_return_date",
  "worker_type",
  "collective_agreement",
  "work_days",
  "is_betriebsrat",
  "has_dienstwagen",
  "is_laterale_fuehrung",
  "is_c_level",
] as const;

// Anzahl der Angehörigen je Person. Nur der Fremdschlüssel wird gelesen —
// für die Berichtsdimensionen zählt die Anzahl, nicht wer es ist.
export async function loadDependentsCounts(tx: Tx): Promise<Map<string, number>> {
  // Am direkten Zugang zählt die Datenbank, statt dass die Anwendung alle
  // Zeilen holt und sie selbst durchgeht.
  const rows = await tx
    .selectFrom("employee_dependents")
    .select(({ fn }) => ["employee_id", fn.countAll<string>().as("anzahl")])
    .groupBy("employee_id")
    .execute();
  return new Map(rows.map((r) => [r.employee_id, Number(r.anzahl)]));
}

// Bestand zum Stichtag: Status *und* Einordnung werden auf `asOf` aufgelöst.
export async function loadSnapshotEmployees(tx: Tx, filters: SnapshotFilters): Promise<ReportEmployee[]> {
  const asOf = filters.asOf || todayIso();

  function snapshotQuery() {
    let q = tx.selectFrom("employees").select([...SNAPSHOT_EMPLOYEE_COLUMNS]).orderBy("id");
    if (filters.location) q = q.where("location_id", "=", filters.location);
    if (filters.employment) q = q.where("employment_type", "=", filters.employment as EmploymentType);
    return q;
  }

  const [data, dependentsCounts, placements, orgMaps] = await Promise.all([
    snapshotQuery().execute(),
    loadDependentsCounts(tx),
    loadPlacements(tx, { asOf }),
    filters.division ? loadOrgMaps(tx) : Promise.resolve(null),
  ]);

  // Der Bereichsfilter meint den ganzen Teilbaum: „Produktion" schliesst
  // deren Abteilungen und Teams ein, sonst käme null heraus, weil unter dem
  // Bereich selbst nur die Bereichsleitung sitzt.
  const allowedUnits = orgMaps && filters.division ? new Set(subtreeOf(orgMaps, filters.division)) : null;

  const withDerivedStatus: ReportEmployee[] = [];
  for (const e of data) {
    const placement = placements.get(e.id);
    // Zum Stichtag laufend? Sonst zählt die Person zwar noch im Bestand,
    // sitzt aber auf keiner Planstelle mehr.
    const orgUnitId = placement?.current ? placement.orgUnitId : null;
    if (allowedUnits && (!orgUnitId || !allowedUnits.has(orgUnitId))) continue;

    withDerivedStatus.push({
      id: e.id,
      first_name: e.first_name,
      last_name: e.last_name,
      job_title: placement?.jobTitle ?? e.job_title,
      org_unit_id: orgUnitId,
      location_id: e.location_id,
      status: deriveStatusAsOf(e, asOf),
      employment_type: e.employment_type,
      contract_type: e.contract_type,
      entry_date: e.entry_date,
      exit_date: e.exit_date,
      weekly_hours: e.weekly_hours,
      source: e.source,
      paygrade: e.paygrade,
      birth_date: e.birth_date,
      gender: e.gender,
      worker_type: e.worker_type,
      collective_agreement: e.collective_agreement,
      work_days: e.work_days,
      is_betriebsrat: e.is_betriebsrat,
      has_dienstwagen: e.has_dienstwagen,
      is_laterale_fuehrung: e.is_laterale_fuehrung,
      is_c_level: e.is_c_level,
      dependents_count: dependentsCounts.get(e.id) ?? 0,
    });
  }

  const statuses = parseStatuses(filters.status);
  return withDerivedStatus.filter((e) => statuses.includes(e.status as (typeof statuses)[number]));
}

// Ereignisse: employee_history trägt selbst keine Organisationszuordnung, sie
// kommt über die Planstelle, die die Person *am Tag des Ereignisses* innehatte.
// Vorher war es die heutige — womit ein Austritt von vor zwei Jahren unter dem
// Team stand, in das die Person nie versetzt worden war.
//
// from/to: "" (unset) falls back to the current calendar year; the literal
// sentinel EVENT_DATE_OPEN means that side of the interval is intentionally
// unbounded (e.g. "alle Ereignisse bis heute", no start date).
export async function loadEventHistory(tx: Tx, filters: EventFilters): Promise<ReportEvent[]> {
  const currentYear = new Date().getFullYear();
  const from = filters.from === EVENT_DATE_OPEN ? undefined : filters.from || `${currentYear}-01-01`;
  const to = filters.to === EVENT_DATE_OPEN ? undefined : filters.to || `${currentYear}-12-31`;

  function historyQuery() {
    let q = tx
      .selectFrom("employee_history")
      .select(["employee_id", "event_date", "event_type", "description"])
      .orderBy("id");
    if (from) q = q.where("event_date", ">=", from);
    if (to) q = q.where("event_date", "<=", to);
    if (filters.eventType) q = q.where("event_type", "=", filters.eventType);
    return q;
  }

  const [history, employees, assignments, orgMaps] = await Promise.all([
    historyQuery().execute(),
    tx.selectFrom("employees").select(["id", "first_name", "last_name", "job_title", "location_id"]).orderBy("id").execute(),
    tx
      .selectFrom("position_assignments as a")
      .innerJoin("om_positions as p", "p.id", "a.position_id")
      .select(["a.employee_id", "a.valid_from", "a.valid_to", "p.org_unit_id"])
      .orderBy("a.employee_id")
      .execute(),
    filters.division ? loadOrgMaps(tx) : Promise.resolve(null),
  ]);

  const spans = new Map<string, { from: string; to: string | null; unitId: string }[]>();
  for (const a of assignments) {
    const list = spans.get(a.employee_id) ?? [];
    list.push({ from: a.valid_from, to: a.valid_to, unitId: a.org_unit_id });
    spans.set(a.employee_id, list);
  }

  const allowedUnits = orgMaps && filters.division ? new Set(subtreeOf(orgMaps, filters.division)) : null;
  const employeeById = new Map(employees.map((e) => [e.id, e]));

  const events: ReportEvent[] = [];
  for (const h of history) {
    const emp = employeeById.get(h.employee_id);
    if (!emp) continue;
    if (filters.location && emp.location_id !== filters.location) continue;

    const unitId =
      spans.get(h.employee_id)?.find((s2) => s2.from <= h.event_date && (s2.to === null || s2.to > h.event_date))?.unitId ?? null;
    if (allowedUnits && (!unitId || !allowedUnits.has(unitId))) continue;

    events.push({
      employee_id: emp.id,
      first_name: emp.first_name,
      last_name: emp.last_name,
      job_title: emp.job_title,
      org_unit_id: unitId,
      location_id: emp.location_id,
      event_date: h.event_date,
      event_type: h.event_type,
      description: h.description,
    });
  }
  return events;
}