export function kleinIdentityPlan(request) {
 if(request.engine!=='flux' || ['video','extend'].includes(request.mode)) return null
 const sourceId=request.mode==='generate' ? request.identityStillId || request.imageAId || '' : request.imageAId || request.identityStillId || ''
 const mode=['generate','iterate'].includes(request.mode) ? (sourceId?'edit':'generate') : request.mode
 return {sourceId,mode}
}

/** Follow the live conditioning chain, including optional hero/compose references. */
function hasSourceReference(graph, link, referenceId) {
 const seen=new Set()
 while(Array.isArray(link) && !seen.has(String(link[0]))) {
  const id=String(link[0]);seen.add(id)
  const node=graph[id]
  if(id===referenceId) return node?.class_type==='ReferenceLatent' && node.inputs.latent?.[0]==='11' && graph['11']?.class_type==='VAEEncode'
  link=node?.inputs?.conditioning
 }
 return false
}

export function assertKleinSample(graph, sourceId) {
 const sampler=graph['19']?.inputs
 const latent=graph[sampler?.latent_image?.[0]]
 if(latent?.class_type==='EmptyFlux2LatentImage') {
  if(!sourceId) return 'empty'
  const guider=graph[sampler.guider?.[0]]?.inputs
  if(hasSourceReference(graph,guider?.positive,'12') && hasSourceReference(graph,guider?.negative,'13')) return 'empty+reference'
  throw new Error('Klein source reference conditioning is missing from the sampler.')
 }
 // Refine retains its dedicated masked-source workflow.
 if(latent?.class_type==='SetLatentNoiseMask' && latent.inputs.samples?.[0]==='11' && graph['11']?.class_type==='VAEEncode') return 'masked source'
 throw new Error('Klein edit must sample empty latent with source references, not the source image latent.')
}

export function applyKleinIdentity(graph, plan) {
 const sampleLatent=assertKleinSample(graph,plan.sourceId)
 return {sampleLatent,sampleDenoise:sampleLatent==='masked source' ? graph['17']?.inputs.denoise ?? null : null}
}