Function validateMapping

apps/sim/lib/table/import.ts:274–360

(params: {
  csvHeaders: string[]
  mapping: CsvHeaderMapping
  tableSchema: TableSchema
})

 * are not covered by the CSV. Returns the normalized header -> column map.
 */
export function validateMapping(params: {
  csvHeaders: string[]
  mapping: CsvHeaderMapping
  tableSchema: TableSchema
}): CsvMappingValidationResult {
  const { csvHeaders, mapping, tableSchema } = params
  const columnByName = new Map(tableSchema.columns.map((c) => [c.name, c]))

  const unknownHeaders = Object.keys(mapping).filter((h) => !csvHeaders.includes(h))
  if (unknownHeaders.length > 0) {
    throw new CsvImportValidationError(
      `Mapping references unknown CSV headers: ${unknownHeaders.join(', ')}`,
      { unknownHeaders }
    )
  }

  const invalidTargets = Object.entries(mapping).filter(
    ([, target]) => target !== null && typeof target !== 'string'
  )
  if (invalidTargets.length > 0) {
    throw new CsvImportValidationError(
      `Mapping values must be a column name (string) or null, got: ${invalidTargets
        .map(([header]) => header)
        .join(', ')}`
    )
  }

  const targetsSeen = new Map<string, string[]>()
  const unknownColumns: string[] = []
  const effectiveMap = new Map<string, string>()
  const skippedHeaders: string[] = []

  for (const header of csvHeaders) {
    const target = header in mapping ? mapping[header] : undefined
    if (target === null || target === undefined) {
      skippedHeaders.push(header)
      continue
    }
    if (!columnByName.has(target)) {
      unknownColumns.push(target)
      continue
    }
    const existing = targetsSeen.get(target) ?? []
    existing.push(header)
    targetsSeen.set(target, existing)
    effectiveMap.set(header, target)
  }

  if (unknownColumns.length > 0) {
    throw new CsvImportValidationError(
      `Mapping references columns that do not exist on the table: ${unknownColumns.join(', ')}`,
      { unknownColumns }
    )
  }

  const duplicateTargets = [...targetsSeen.entries()]
    .filter(([, headers]) => headers.length > 1)
    .map(([col]) => col)