/**
 * lib/spec-arg.ts — shared `--spec` / `--spec-file` resolution.
 *
 * Every CLI accepts its JSON spec inline (`--spec '<json>'`); the frontend
 * specs routinely exceed what a shell can carry as ONE argument — a pagespec
 * with its `i18nKeys` in four locales blows past the Git Bash argv limit
 * (well below Windows' 32 KB CreateProcess ceiling), making generation
 * impossible without a spawn-based workaround. `--spec-file <path>` reads the
 * same JSON from disk instead. Six backend CLIs carried this pattern
 * individually; this helper is the shared implementation the frontend CLIs
 * adopt (parseArgs is `strict: true` everywhere, so an unknown `--spec-file`
 * used to be a HARD parse error, not a soft ignore).
 */
import { readFileSync } from 'node:fs'

export type SpecArgResult = { raw: string } | { error: string }

/** Resolve the raw spec JSON: `--spec-file` wins, then `--spec`. */
export function readSpecArg(values: { spec?: string; 'spec-file'?: string }): SpecArgResult {
  const file = values['spec-file']
  if (file) {
    try {
      return { raw: readFileSync(file, 'utf-8') }
    } catch (err) {
      return { error: `Failed to read --spec-file ${file}: ${err instanceof Error ? err.message : String(err)}` }
    }
  }
  if (values.spec) return { raw: values.spec }
  return { error: 'Either --spec or --spec-file is required' }
}