Sessions and replays

Management endpointsCopy Anchor Link

Engine creates sessions in its studio. The LGS has no studio, so it serves management endpoints under /lgs next to the RGS endpoints. Every response is JSON, and every amount is an integer with six decimals.

@slot-engine/lgs exports a type for the body of every successful response:

A management endpoint that rejects a request answers with an LgsErrorResponse, { "error": "ERR_VAL", "message": "..." }.

import type { LgsSessionResponse } from "@slot-engine/lgs"

const res = await fetch(`http://localhost:7771/lgs/sessions/${sessionId}`)
const { wallet, lastBet } = (await res.json()) as LgsSessionResponse

GET /lgsCopy Anchor Link

Returns the resolved configuration of the LGS.

{
  "name": "Engine",
  "languages": ["ar", "da", "de", "en", "..."],
  "currencies": ["USD", "CAD", "JPY", "EUR", "..."],
  "defaultLanguage": "en",
  "defaultCurrency": "USD",
  "balance": {
    "starting": 10000000000,
    "options": [100000000, 1000000000, 10000000000, 100000000000]
  },
  "bets": {
    "min": 100000,
    "max": 1000000000,
    "step": 10000,
    "default": 1000000,
    "levels": [100000, 200000, "..."]
  },
  "games": [{ "id": "my-game", "name": "My Game" }]
}

GET /lgs/gamesCopy Anchor Link

Returns the registered games and their modes.

{
  "games": [
    {
      "id": "my-game",
      "name": "My Game",
      "modes": [
        {
          "name": "base",
          "cost": 1,
          "rtp": 0.96,
          "isBonusBuy": false,
          "isFeature": false
        },
        {
          "name": "bonus",
          "cost": 70,
          "rtp": 0.96,
          "isBonusBuy": true,
          "isFeature": false
        }
      ]
    }
  ]
}

POST /lgs/sessionsCopy Anchor Link

Creates a session and, unless you pass walletId, a wallet for it.

The response has status 201 and contains the session ID, the wallet ID, the launch parameters and the same parameters as a query string:

{
  "sessionID": "wYv1...",
  "walletId": "Qf8c...",
  "launchParams": {
    "sessionID": "wYv1...",
    "rgs_url": "localhost:7771",
    "lang": "en",
    "currency": "USD",
    "device": "desktop",
    "social": false,
    "demo": false
  },
  "launchQuery": "sessionID=wYv1...&rgs_url=localhost%3A7771&lang=en&currency=USD&device=desktop&social=false&demo=false"
}

rgs_url is the Host header of the request. Under the panel it is localhost:7770, standalone it is localhost:7771, and a request through another host name gets that host name back.

Invalid input, an unknown game, an unknown wallet or a disabled currency or language answer with status 400:

{ "error": "ERR_VAL", "message": "Game \"nope\" is not registered" }

GET /lgs/sessions/:idCopy Anchor Link

Returns the session, its wallet, the active bet and the last bet. activeBet is null when no round is open. lastBet is the newest bet of the session, open or settled, and null before the first bet.

{
  "session": {
    "id": "wYv1...",
    "walletId": "Qf8c...",
    "gameId": "my-game",
    "currency": "USD",
    "language": "en",
    "device": "desktop",
    "social": false,
    "demo": false,
    "authenticated": true,
    "activeBetId": 3,
    "createdAt": 1793216082000,
    "force": { "bookId": 812 }
  },
  "wallet": { "id": "Qf8c...", "currency": "USD", "amount": 9997200000 },
  "activeBet": {
    "id": 3,
    "mode": "base",
    "amount": 1000000,
    "payout": 1200000,
    "active": true,
    "...": "..."
  },
  "lastBet": {
    "id": 3,
    "mode": "base",
    "bookId": 812,
    "payoutMultiplier": 1.2,
    "payout": 1200000,
    "active": true,
    "...": "..."
  }
}

An unknown session answers with status 404 and { "error": "ERR_VAL", "message": "unknown session" }.

PUT /lgs/sessions/:id/forceCopy Anchor Link

Sets or clears the forced outcome of a session. Every following play of the session, in every mode, returns the forced outcome until you clear it. A round that is already open keeps its outcome.

The body has one field, force, with a ForcedOutcome or null. @slot-engine/lgs exports the type:

type ForcedOutcome = { bookId: number } | { payoutMultiplier: number }

curl -X PUT http://localhost:7771/lgs/sessions/wYv1.../force \
  -H "content-type: application/json" \
  -d '{"force":{"payoutMultiplier":2.5}}'

The response has status 200 and contains the stored force:

{ "force": { "payoutMultiplier": 2.5 } }

A body outside these three shapes answers with status 400 and ERR_VAL, for example a force with both keys, with an unknown key, or with a negative value. An unknown session answers with status 404 and { "error": "ERR_VAL", "message": "unknown session" }.

POST /lgs/sessions takes the same force field, so a session can start with a force. Game Math describes how the LGS finds the forced book.

Launch parametersCopy Anchor Link

The launch parameters use the names of Engine's launch URL, so a front end reads them the same way in both environments.

Append launchQuery to the URL of your front end:

http://localhost:3000/?sessionID=wYv1...&rgs_url=localhost%3A7771&lang=en&currency=USD&device=desktop&social=false&demo=false

The official Engine client builds https:// + rgs_url unless you set the protocol. The LGS serves plain HTTP:

const client = RGSClient({ url: window.location.href, protocol: "http" })

ReplaysCopy Anchor Link

A replay opens a front end in replay mode. The front end plays one book without a session. The LGS stores nothing for a replay. POST /lgs/replays checks the replay and builds its launch parameters.

POST /lgs/replaysCopy Anchor Link

curl -X POST http://localhost:7771/lgs/replays \
  -H "content-type: application/json" \
  -d '{"gameId":"my-game","mode":"bonus","event":812}'

The response has status 200 and contains the launch parameters and the same parameters as a query string:

{
  "launchParams": {
    "replay": true,
    "game": "my-game",
    "version": 1,
    "mode": "bonus",
    "event": 812,
    "rgs_url": "localhost:7771",
    "currency": "USD",
    "amount": 1000000,
    "lang": "en",
    "device": "desktop",
    "social": false,
    "demo": false
  },
  "launchQuery": "replay=true&game=my-game&version=1&mode=bonus&event=812&rgs_url=localhost%3A7771&currency=USD&amount=1000000&lang=en&device=desktop&social=false&demo=false"
}

rgs_url is the Host header of the request, as for sessions.

Invalid input answers with status 400. So do an unknown game, an unknown mode, a book that the lookup table of the mode does not list, a disabled currency or language, and an amount that breaks the bet rules:

{ "error": "ERR_VAL", "message": "Book 99 is not in the lookup table of mode \"bonus\"" }

Replay launch parametersCopy Anchor Link

The replay launch parameters use the names of Engine's replay URL.

The front end fetches the book from GET /bet/replay/{game}/{version}/{mode}/{event} on rgs_url.

Share a wallet between sessionsCopy Anchor Link

A reload of the front end keeps the session ID in the URL, so the same session continues and an open round resumes on authenticate.

To test two front ends on one balance, create a second session with the walletId of the first:

curl -X POST http://localhost:7771/lgs/sessions \
  -H "content-type: application/json" \
  -d '{"gameId":"my-game","walletId":"Qf8c..."}'

The LGS runs the operations of one wallet one after another, so two sessions cannot both spend the same balance.

CORSCopy Anchor Link

The LGS allows every origin on /lgs/* and on the RGS routes, /wallet/* and /bet/* for EngineLgs. A front end served from another port, like a Vite dev server on 3000 or 5173, can call the LGS directly. Under the panel, the panel's own /api routes stay without CORS headers.