export type ErrorCategory =
  | 'auth'
  | 'rate_limit'
  | 'context_exhausted'
  | 'timeout'
  | 'network'
  | 'tool_error'
  | 'user_abort'
  | 'unknown'

const CATEGORY_PATTERNS: Array<[RegExp, ErrorCategory]> = [
  [/401|unauthori[sz]ed|forbidden|invalid.*(api|token|key)/i, 'auth'],
  [/429|rate.?limit|too many requests|quota/i, 'rate_limit'],
  [/context.*(length|window|exhaust)|max.*tokens|input too long/i, 'context_exhausted'],
  [/timeout|ETIMEDOUT|ETIMEOUT|timed out/i, 'timeout'],
  [/ECONNRESET|ECONNREFUSED|ENOTFOUND|EAI_AGAIN|network|fetch failed|socket hang up/i, 'network'],
  [/tool.*(error|failed)|bad tool input/i, 'tool_error'],
  // SDK result failure subtypes are terminal for this run; don't retry.
  [/error_during_execution|error_max_turns|error_max_budget/i, 'tool_error'],
  [/abort|cancelled|canceled/i, 'user_abort'],
]

export function classifyError(err: unknown): ErrorCategory {
  const msg = err instanceof Error ? err.message : String(err)
  for (const [re, cat] of CATEGORY_PATTERNS) {
    if (re.test(msg)) return cat
  }
  return 'unknown'
}

export function isRetryable(cat: ErrorCategory): boolean {
  return cat === 'rate_limit' || cat === 'timeout' || cat === 'network'
}

export function describeError(err: unknown): { category: ErrorCategory; message: string } {
  const msg = err instanceof Error ? err.message : String(err)
  return { category: classifyError(err), message: msg }
}