/**
 * cli:derive-related-tabs — validate.ts
 *
 * Stage 1: Zod structural validation (strict — unknown keys rejected).
 * Stage 2: existence checks (baRoot dir, app dir), with `baRoot` resolved
 *          against `--workdir` (or cwd). A missing MODULE dir is only a
 *          warning — the run then legitimately reports zero screens/tabs.
 */
import { existsSync, statSync } from 'node:fs'
import { join, resolve } from 'node:path'
import { DeriveRelatedTabsInputSchema } from './types.js'
import type { ValidationResult } from './types.js'

export function validateSpec(raw: unknown, workdir?: string): ValidationResult {
  const parsed = DeriveRelatedTabsInputSchema.safeParse(raw)
  if (!parsed.success) {
    return {
      valid: false,
      errors: parsed.error.issues.map((i) => `${i.path.join('.') || '(root)'}: ${i.message}`),
      warnings: [],
    }
  }
  const spec = parsed.data
  const warnings: string[] = []

  const resolvedBaRoot = resolve(workdir ?? process.cwd(), spec.baRoot)
  if (!isDirectory(resolvedBaRoot)) {
    return {
      valid: false,
      errors: [`BA root directory not found: ${resolvedBaRoot}`],
      warnings,
    }
  }

  const appDir = join(resolvedBaRoot, spec.app)
  if (!isDirectory(appDir)) {
    return {
      valid: false,
      errors: [`Application directory not found: ${appDir} (app code: ${spec.app})`],
      warnings,
    }
  }

  if (!isDirectory(join(appDir, spec.module))) {
    warnings.push(
      `Module directory not found: ${spec.app}/${spec.module} — the run will report zero screens`,
    )
  }

  if (spec.pagespecs && spec.mode !== 'validate') {
    warnings.push('pagespecs: true is only honored in mode "validate" — ignored in derive mode')
  }

  return { valid: true, errors: [], warnings, spec, resolvedBaRoot }
}

function isDirectory(p: string): boolean {
  try {
    return existsSync(p) && statSync(p).isDirectory()
  } catch {
    return false
  }
}