import type { SupabaseClient } from "@supabase/supabase-js";
import type { DbTransaction } from "@/types/database";
import {
  applyTransactionToMutableAccumulator,
  createMutableLedgerAccumulator,
  mutableAccumulatorToIntegrity,
  sortedNonZeroUserNetPairs,
  type LedgerGlobalSummary,
} from "@/lib/ledger-integrity";

const PAGE_SIZE = 5000;

/**
 * Scans every transaction row (paginated) and builds full integrity + user nets.
 * Server-only — call from Server Components / Route Handlers, not from client components.
 */
export async function fetchLedgerGlobalSummary(
  supabase: SupabaseClient,
): Promise<{ ok: true; data: LedgerGlobalSummary } | { ok: false; message: string }> {
  const acc = createMutableLedgerAccumulator();
  let offset = 0;
  for (;;) {
    const { data, error } = await supabase
      .from("transactions")
      .select("id, created_at, from, to, amount, remarks, match_id")
      .order("id", { ascending: true })
      .range(offset, offset + PAGE_SIZE - 1);

    if (error) {
      return { ok: false, message: error.message };
    }
    const rows = (data ?? []) as DbTransaction[];
    if (rows.length === 0) {
      break;
    }
    for (const row of rows) {
      applyTransactionToMutableAccumulator(acc, row);
    }
    offset += rows.length;
    if (rows.length < PAGE_SIZE) {
      break;
    }
  }

  const integrity = mutableAccumulatorToIntegrity(acc);
  const userNetEntries = sortedNonZeroUserNetPairs(acc.net);
  return { ok: true, data: { integrity, userNetEntries } };
}