import type { RouteSchema } from './config.js'

const BODY_METHODS = new Set(['POST', 'PUT', 'PATCH'])

function issueMessages(error: { issues: { path: (string | number)[]; message: string }[] }): string[] {
  return error.issues.map((i) => (i.path.length ? `${i.path.join('.')} ${i.message}` : i.message))
}

/**
 * Validates a request against a route's schema validators.
 *
 * Returns a 400 Response when validation fails, or null when the request is
 * valid and should proceed to payment enforcement.
 */
export async function validateRequest(req: Request, schema: RouteSchema): Promise<Response | null> {
  if (schema.body && BODY_METHODS.has(req.method.toUpperCase())) {
    let body: unknown
    try {
      body = await req.clone().json()
    } catch {
      return Response.json({ error: 'Request body must be valid JSON' }, { status: 400 })
    }
    const result = schema.body.safeParse(body)
    if (!result.success) {
      return Response.json(
        { error: 'Request validation failed', validation_errors: issueMessages(result.error) },
        { status: 400 },
      )
    }
  }

  if (schema.query) {
    const queryData: Record<string, string> = {}
    for (const [k, v] of new URL(req.url).searchParams.entries()) queryData[k] = v
    const result = schema.query.safeParse(queryData)
    if (!result.success) {
      return Response.json(
        { error: 'Request validation failed', validation_errors: issueMessages(result.error) },
        { status: 400 },
      )
    }
  }

  return null
}