/**
 * cli:derive-external-api-spec — validate.ts
 */
import { existsSync } from 'node:fs'
import { join } from 'node:path'
import { DeriveExternalApiSpecInputSchema, type ValidationResult } from './types.js'

export function validate(raw: unknown): ValidationResult {
  const parsed = DeriveExternalApiSpecInputSchema.safeParse(raw)
  if (!parsed.success) {
    return {
      valid: false,
      errors: parsed.error.issues.map(i => `[${i.path.join('.')}] ${i.message}`),
      warnings: [],
    }
  }

  const spec = parsed.data
  const errors: string[] = []
  const warnings: string[] = []

  if (!existsSync(spec.baRoot)) {
    errors.push(`baRoot does not exist: ${spec.baRoot}`)
  } else if (!existsSync(join(spec.baRoot, spec.applicationCode))) {
    errors.push(`No application "${spec.applicationCode}" under ${spec.baRoot} — check the BA menu tree.`)
  }

  if (spec.mode === 'write' && spec.declarations.length === 0) {
    errors.push('mode "write" with no declarations[] — nothing to record. Recording an empty decision would silently retire a published API.')
  }
  if (spec.mode === 'check' && spec.declarations.length > 0) {
    warnings.push('declarations[] are ignored in mode "check" — nothing was written.')
  }

  for (const d of spec.declarations) {
    if (d.operations.length > 0 && !d.operations.includes('read')) {
      errors.push(`${d.entity}: a write-only declaration leaves the third party unable to read back what it wrote, and with no id to address.`)
    }
  }

  return { valid: errors.length === 0, errors, warnings }
}