import { errorToString } from "../utils/errors.ts";

export type ItemResult<T = void> = {
  success: boolean;
  error?: string;
  data?: T;
};

export type BatchSummary<T = void> = {
  total: number;
  successes: number;
  failures: number;
  firstError?: string;
  results: ItemResult<T>[];
};

export async function runSequentialBatch<I, T = void>(
  items: I[],
  run: (item: I) => Promise<ItemResult<T>>,
): Promise<BatchSummary<T>> {
  const results: ItemResult<T>[] = [];
  let successes = 0;
  let failures = 0;
  let firstError: string | undefined;

  for (const item of items) {
    let result: ItemResult<T>;
    try {
      result = await run(item);
    } catch (e) {
      result = { success: false, error: errorToString(e) };
    }
    results.push(result);
    if (result.success) {
      successes++;
    } else {
      failures++;
      if (firstError === undefined && result.error) {
        firstError = result.error;
      }
    }
  }

  return {
    total: items.length,
    successes,
    failures,
    firstError,
    results,
  };
}