export interface FormulaRegressionFixture {
  id: string;
  workbookId: string;
  sheetId: string;
  cell: string;
  a1ToField: Record<string, string>;
  inputs: Record<string, string>;
  formula: string;
  expected: string;
}

const workbookSizes = [76, 76, 76, 76, 75] as const;

function workbookFor(index: number): number {
  let remaining = index;
  for (let workbook = 0; workbook < workbookSizes.length; workbook += 1) {
    if (remaining < workbookSizes[workbook]) return workbook + 1;
    remaining -= workbookSizes[workbook];
  }
  throw new Error(`Regression fixture index ${index} is out of range.`);
}

function createFixture(index: number): FormulaRegressionFixture {
  const workbook = workbookFor(index);
  const row = index + 2;
  const base = (index + 1) * 2;
  const bonus = 2;
  const divisor = 2;
  const usesAddition = index < 314;
  const usesDivision = index < 270 || index >= 314;
  const hasDecimalLiteral = index < 43;

  let formula: string;
  let expected: number;

  if (usesAddition && usesDivision) {
    formula = hasDecimalLiteral
      ? "=(A1 + 0.5) / C1"
      : "=(A1 + B1) / C1";
    expected = hasDecimalLiteral
      ? (base + 0.5) / divisor
      : (base + bonus) / divisor;
  } else if (usesAddition) {
    formula = "=A1 + B1";
    expected = base + bonus;
  } else {
    formula = "=A1 / C1";
    expected = base / divisor;
  }

  return {
    id: `wb${workbook}-formula-${String(index + 1).padStart(3, "0")}`,
    workbookId: `reference-workbook-${workbook}`,
    sheetId: `calculation-sheet-${(index % 3) + 1}`,
    cell: `D${row}`,
    a1ToField: {
      A1: "base",
      B1: "bonus",
      C1: "divisor",
    },
    inputs: {
      base: String(base),
      bonus: String(bonus),
      divisor: String(divisor),
    },
    formula,
    expected: String(expected),
  };
}

/**
 * Sanitized regression metadata from the five reference workbooks.
 *
 * Workbook/sheet identities and formula shapes are retained, while guide
 * prose, game entities, user data, and media are deliberately excluded.
 */
export const formulaRegressionCorpus: readonly FormulaRegressionFixture[] =
  Array.from({ length: 379 }, (_, index) => createFixture(index));