import { ParseMode } from "../appstore/"

function mergeSkuQuantities(
  rows: { sku: string; qty: number }[]
): { sku: string; qty: number }[] {
  if (!rows || rows.length === 0) return [];

  const seen = new Map<string, number>()

  return rows.reduce<{ sku: string; qty: number }[]>((acc, { sku, qty }) => {
    if (seen.has(sku)) {
      // update existing entry’s qty
      const idx = seen.get(sku)!
      acc[idx].qty += qty
    } else {
      // push new entry, remember its index
      acc.push({ sku, qty });
      seen.set(sku, acc.length - 1);
    }
    return acc
  }, [])
}

/**
 * Parse CSV/TSV content into SKU-quantity pairs
 * Detects delimiter automatically (comma or tab)
 */
export function parseCSVOrTSV(input: string, mode: ParseMode): { sku: string; qty: number }[] {
  const trimmed = input.trim();

  // Auto-detect delimiter: check first line
  const firstLine = trimmed.split(/\r?\n/)[0];
  const delimiter = firstLine.includes('\t') ? '\t' : ',';

  return parseWithDelimiter(trimmed, delimiter, mode);
}

function parseWithDelimiter(input: string, delimiter: string, mode: ParseMode): { sku: string; qty: number }[] {
  let rows = input
    .trim()
    .split(/\r?\n/)
    .map(line => line.trim())
    .filter(Boolean) // skip empty rows
    .map(r => r.split(delimiter))
    .map(([sku, qty]) => [sku?.trim(), qty?.trim()])
    .filter(
      r =>
        r.length === 2
          && r[0].trim().length > 0
    ); // only two-columns with non-empty

  if (rows.length === 0) return [];

  switch (mode) {
    case "full":
      // Drop first row (headers), keep the rest
      rows = rows.slice(1);
      break;

    case "selection":
      // Use all rows as-is (assume no headers)
      break;

    case "auto":
      const [, firstQty] = rows[0];
      if (isNaN(Number(firstQty))) {
        rows = rows.slice(1) ;// drop header
      }
      break;
  }

  return mergeSkuQuantities(rows
    .map(([sku, qty]) => {
      const parsedQty = Number(qty);
      return {
        sku: sku.trim(),
        qty: isNaN(parsedQty) ? 0 : parsedQty,
      }
    }))
}