classic-models-agent-flows/workflows/supply-stock-watch.json

{
  "name": "Supply \u2014 stock watch",
  "nodes": [
    {
      "parameters": {
        "topic": "classic-models.catalog",
        "groupId": "supply-stock-watch",
        "resolveOffset": "onCompletion",
        "allowedStatuses": [
          "success"
        ],
        "options": {
          "jsonParseMessage": true,
          "onlyMessage": true,
          "fromBeginning": false
        }
      },
      "type": "n8n-nodes-base.kafkaTrigger",
      "typeVersion": 2,
      "position": [
        0,
        0
      ],
      "id": "kafka-trigger-stock-watch",
      "name": "Catalog events",
      "credentials": {
        "kafka": {
          "id": "8qNZXLzvdx5rWQ0V",
          "name": "kafka-classic-models"
        }
      }
    },
    {
      "parameters": {
        "jsCode": "// A stock movement, judged the moment it happens.\n//\n// This is the reactive half of Supply. The 06:00 run proposes\n// purchase orders on a buying cycle, which is genuinely periodic; noticing that\n// a reference is about to run out is not, and a nightly sweep would report at\n// 06:00 what was true at 14:32 the previous afternoon.\n//\n// What it reacts to is a fact the API published, not a row it went looking for.\nconst THRESHOLD = 50;\nconst COVER = 3;          // a proposal covers three times the threshold\nconst STOCK_CHANGED = 'com.sttlab.classicmodels.product.stock_changed.v1';\n\nconst event = $json ?? {};\n\n// The topic carries every catalog event, so most messages are not ours. Saying\n// so explicitly keeps the offset moving: a workflow that threw on an\n// uninteresting event would replay it forever.\nif (event.type !== STOCK_CHANGED) {\n  return [{ json: { considered: false, type: event.type ?? 'unreadable' } }];\n}\n\nconst data = event.data ?? {};\nconst before = Number(data.before?.quantityinstock);\nconst after = Number(data.after?.quantityinstock);\nif (!Number.isFinite(before) || !Number.isFinite(after)) {\n  return [{ json: {\n    considered: false,\n    escalate: true,\n    reason: `${event.subject}: the movement carried no readable quantities.`,\n  }}];\n}\n\n// Only a *crossing* is news. Without this, every further order line on an\n// already-low reference raises the same alarm again, and an agent that repeats\n// itself is one a human learns to ignore.\nconst crossed = before >= THRESHOLD && after < THRESHOLD;\n// A stock-out is a different fact from a low stock, even when the reference was\n// already below the threshold \u2014 nothing can be promised at all.\nconst emptied = after === 0 && before > 0;\n\n// `order:` means demand; anything else is someone correcting the books. Both\n// justify a purchase order, but only demand is a signal about the future.\nconst fromDemand = String(data.reason ?? '').startsWith('order:');\n\nconst store = $getWorkflowStaticData('global');\nstore.watchlist = store.watchlist ?? {};\n\nif (!crossed && !emptied) {\n  // Not news, but if this reference is already being watched its figures have\n  // just moved. Refresh them rather than leaving a human reading the number it\n  // held at the moment of detection, which is the number least likely to still\n  // be true.\n  const watched = store.watchlist[event.subject];\n  if (watched) {\n    watched.on_hand = after;\n    watched.propose_order = THRESHOLD * COVER - after;\n    watched.last_movement_at = event.time ?? new Date().toISOString();\n  }\n  return [{ json: {\n    considered: true,\n    detected: false,\n    watching: Boolean(watched),\n    productcode: event.subject,\n    on_hand: after,\n  }}];\n}\n\nconst state = { detected: true, escalate: true,\n  productcode: event.subject,\n  on_hand: after,\n  was: before,\n  threshold: THRESHOLD,\n  stock_out: after === 0,\n  driver: fromDemand ? 'demand' : 'correction',\n  movement: data.reason ?? null,\n  propose_order: THRESHOLD * COVER - after,\n  observed_at: event.time ?? new Date().toISOString(),\n  // Kept so this detection can be joined to the request that caused it. It is\n  // the only link back \u2014 the event deliberately names no actor.\n  traceparent: event.traceparent ?? null,\n};\n\nstate.reason = state.stock_out\n  ? `${state.productcode} is out of stock (was ${before}). Nothing can be promised.`\n  : `${state.productcode} fell from ${before} to ${after}, below the threshold of ${THRESHOLD}.`;\n\n// The watchlist is the destination, and it is a real one: the proposal still\n// has nowhere to be written \u2014 the domain has no purchase order and no supplier\n// entity \u2014 so a detection that only logged would be lost between two nightly\n// runs. Here it survives, keyed by reference so a reference cannot appear twice.\nstore.watchlist[state.productcode] = state;\n\nreturn [{ json: state }];\n"
      },
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [
        220,
        0
      ],
      "id": "detect-crossing",
      "name": "Judge the movement"
    },
    {
      "parameters": {
        "httpMethod": [
          "GET",
          "POST"
        ],
        "path": "stock-watchlist",
        "responseMode": "lastNode",
        "options": {},
        "multipleMethods": true
      },
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 2,
      "position": [
        0,
        200
      ],
      "id": "watchlist-read",
      "name": "Watchlist",
      "webhookId": "stock-watchlist-get"
    },
    {
      "parameters": {
        "jsCode": "// What has been detected and not yet dealt with.\n//\n// A detection that goes only into an execution log is one nobody reads. This\n// makes the watchlist readable \u2014 by the periodic run, which can start from what\n// was already noticed rather than rediscovering it, and by a human.\n//\n// GET  /webhook/stock-watchlist        \u2192 the current list\n// POST /webhook/stock-watchlist        {\"clear\": [\"S24_2000\"]} \u2192 drop entries\nconst store = $getWorkflowStaticData('global');\nstore.watchlist = store.watchlist ?? {};\n\n// GET carries no body; the node still runs, and clear is then empty.\nconst body = $json.body ?? {};\nconst clear = Array.isArray(body.clear) ? body.clear : [];\nfor (const code of clear) delete store.watchlist[code];\n\nconst entries = Object.values(store.watchlist);\nreturn [{ json: {\n  watching: entries.length,\n  cleared: clear,\n  // Worst first: an out-of-stock reference is not the same problem as one that\n  // merely crossed the threshold.\n  entries: entries.sort((a, b) => a.on_hand - b.on_hand),\n}}];\n"
      },
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [
        220,
        200
      ],
      "id": "watchlist-render",
      "name": "Render the watchlist"
    }
  ],
  "connections": {
    "Catalog events": {
      "main": [
        [
          {
            "node": "Judge the movement",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Watchlist": {
      "main": [
        [
          {
            "node": "Render the watchlist",
            "type": "main",
            "index": 0
          }
        ],
        [
          {
            "node": "Render the watchlist",
            "type": "main",
            "index": 0
          }
        ]
      ]
    }
  },
  "settings": {
    "executionOrder": "v1"
  }
}