/**
 * cli:derive-rule-links — validate.ts
 *
 * Spec validation + prerequisites: the module folder must exist and carry at
 * least one `règles-métier.md` (module or section level) AND a `pagespecs/`
 * dir — an empty report must mean "nothing to link", never "inputs absent".
 */
import { existsSync, readdirSync } from 'node:fs'
import { isAbsolute, join } from 'node:path'
import { DeriveRuleLinksInputSchema, type ValidationResult } from './types.js'

export function validateSpec(raw: unknown, workdir?: string): ValidationResult {
  const parsed = DeriveRuleLinksInputSchema.safeParse(raw)
  if (!parsed.success) {
    return {
      valid: false,
      errors: parsed.error.issues.map((i) => `[${i.path.join('.')}] ${i.message}`),
    }
  }
  const spec = parsed.data
  const resolvedBaRoot = isAbsolute(spec.baRoot) ? spec.baRoot : join(workdir ?? process.cwd(), spec.baRoot)
  const errors: string[] = []
  const moduleDir = join(resolvedBaRoot, spec.app, spec.module)
  if (!existsSync(moduleDir)) {
    errors.push(`Module folder not found: ${moduleDir}`)
    return { valid: false, errors, spec, resolvedBaRoot }
  }

  let anyRules = existsSync(join(moduleDir, 'règles-métier.md'))
  if (!anyRules) {
    try {
      anyRules = readdirSync(moduleDir, { withFileTypes: true }).some(
        (e) =>
          e.isDirectory() &&
          /^[a-z]/.test(e.name) &&
          existsSync(join(moduleDir, e.name, 'règles-métier.md')),
      )
    } catch {
      /* fallthrough to the error below */
    }
  }
  if (!anyRules) {
    errors.push(
      `${spec.app}/${spec.module} has no règles-métier.md (module or section) — run /ba-create-business-rules (phase 4) first.`,
    )
  }
  if (!existsSync(join(moduleDir, 'pagespecs'))) {
    errors.push(`${moduleDir}/pagespecs not found — run /ba-create-prd before deriving the rule links.`)
  }
  return { valid: errors.length === 0, errors, spec, resolvedBaRoot }
}