/**
 * Formatting helpers for the SequenceViewer component.
 * Extracted for testability and reuse.
 */

/**
 * Determines the CSS arrow direction class based on message direction.
 * "CPE→ACS" messages point left-to-right (arrow-right).
 * "ACS→CPE" messages point right-to-left (arrow-left).
 */
export function getArrowClass(direction: 'CPE→ACS' | 'ACS→CPE'): 'arrow-right' | 'arrow-left' {
  return direction === 'CPE→ACS' ? 'arrow-right' : 'arrow-left'
}

/**
 * Formats an ISO 8601 timestamp into HH:mm:ss.SSS display format.
 * Uses UTC time to ensure consistent formatting regardless of timezone.
 */
export function formatTimestamp(isoTimestamp: string): string {
  const date = new Date(isoTimestamp)
  const hours = String(date.getUTCHours()).padStart(2, '0')
  const minutes = String(date.getUTCMinutes()).padStart(2, '0')
  const seconds = String(date.getUTCSeconds()).padStart(2, '0')
  const millis = String(date.getUTCMilliseconds()).padStart(3, '0')
  return `${hours}:${minutes}:${seconds}.${millis}`
}

/**
 * Truncates a CWMP method name to 40 characters if it exceeds that length.
 * Appends an ellipsis character (…) when truncated.
 */
export function truncateMethod(method: string): string {
  if (method.length > 40) {
    return method.substring(0, 40) + '…'
  }
  return method
}

/**
 * Returns true if the method name exceeds 40 characters and needs truncation.
 */
export function needsTruncation(method: string): boolean {
  return method.length > 40
}

/**
 * Formats a trace start time ISO string into a localized display string.
 */
export function formatTraceStartTime(iso: string): string {
  return new Date(iso).toLocaleString()
}