import { DECISION_COLUMNS, HIRING_COLUMNS, type DecisionRow, type Grid, type HiringRow } from "./types";

export type ParseResult<T> = { ok: true; rows: T[] } | { ok: false; missing: string[] };

const norm = (s: unknown) => String(s ?? "").trim().toLowerCase();

function headerIndex(header: string[], names: Record<string, string>, lenient: boolean) {
  const idx: Record<string, number> = {};
  const missing: string[] = [];
  const keys = Object.keys(names);
  keys.forEach((key) => {
    const at = header.findIndex((h) => norm(h) === norm(names[key]));
    if (at >= 0) idx[key] = at;
    else if (lenient) idx[key] = -1; // negative control only: a missing column reads as empty, with no error
    else missing.push(names[key]);
  });
  return { idx, missing };
}

/**
 * Reads the hiring sheet by column NAME. Blank rows are skipped. With `schemaCheck`
 * off (tests only) there is no check, which is the
 * failure the check exists to prevent: a renamed column reads as empty cells, and every
 * arrival waits for an address that is in fact there, with no error anywhere.
 */
export function parseHiring(grid: Grid, schemaCheck = true): ParseResult<HiringRow> {
  if (!grid.length) return { ok: false, missing: Object.values(HIRING_COLUMNS) };
  const { idx, missing } = headerIndex(grid[0], HIRING_COLUMNS, !schemaCheck);
  if (missing.length) return { ok: false, missing };
  const cell = (r: string[], k: string) => String(r[idx[k]] ?? "").trim();
  const rows: HiringRow[] = [];
  grid.slice(1).forEach((r, i) => {
    if (r.every((c) => String(c ?? "").trim() === "")) return;
    rows.push({
      rowNumber: i + 2,
      arrivalId: cell(r, "arrivalId"),
      therapist: cell(r, "therapist"),
      status: String(r[idx.status] ?? ""), // kept raw: normalisation is a rule, see rules.ts
      startDate: cell(r, "startDate"),
      welcomeEmail: cell(r, "welcomeEmail"),
      approvedBy: cell(r, "approvedBy"),
    });
  });
  return { ok: true, rows };
}

export function parseDecisions(grid: Grid): ParseResult<DecisionRow> {
  if (!grid.length) return { ok: false, missing: Object.values(DECISION_COLUMNS) };
  const { idx, missing } = headerIndex(grid[0], DECISION_COLUMNS, false);
  if (missing.length) return { ok: false, missing };
  const rows: DecisionRow[] = [];
  for (const r of grid.slice(1)) {
    const arrivalId = String(r[idx.arrivalId] ?? "").trim();
    const decision = String(r[idx.decision] ?? "").trim();
    if (!arrivalId && !decision) continue;
    rows.push({ arrivalId, decision, by: String(r[idx.by] ?? "").trim() });
  }
  return { ok: true, rows };
}