{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://kiosk.tech/spec/schemas/envelope.schema.json",
  "title": "Kiosk response envelope",
  "description": "Every schema/query/run/pay response -- success or error -- is one of these two shapes.",
  "oneOf": [
    { "$ref": "#/$defs/success" },
    { "$ref": "#/$defs/error" }
  ],
  "$defs": {
    "success": {
      "type": "object",
      "required": ["ok", "kind"],
      "properties": {
        "ok": { "const": true },
        "kind": {
          "enum": ["rows", "value", "events"],
          "description": "Payload discriminator: rows (array), value (single object), events (reserved)."
        },
        "rows": { "type": "array" },
        "value": {},
        "events": { "type": "array" }
      },
      "allOf": [
        { "if": { "properties": { "kind": { "const": "rows" } } }, "then": { "required": ["rows"] } },
        { "if": { "properties": { "kind": { "const": "value" } } }, "then": { "required": ["value"] } },
        { "if": { "properties": { "kind": { "const": "events" } } }, "then": { "required": ["events"] } }
      ]
    },
    "error": {
      "type": "object",
      "required": ["ok", "error"],
      "properties": {
        "ok": { "const": false },
        "error": { "$ref": "https://kiosk.tech/spec/schemas/error.schema.json" }
      }
    }
  }
}