{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "urn:orbiplex:schema:middleware-channel-frame:v1",
  "title": "Middleware Channel Frame v1",
  "description": "Strict outer application frame for one accepted middleware channel session.",
  "type": "object",
  "additionalProperties": false,
  "required": [
    "schema",
    "schema/v",
    "session/id",
    "session/epoch",
    "frame/seq",
    "message/kind",
    "operation",
    "payload/schema",
    "payload"
  ],
  "properties": {
    "schema": {"const": "middleware-channel-frame.v1"},
    "schema/v": {"const": 1},
    "session/id": {"$ref": "#/$defs/id"},
    "session/epoch": {"type": "integer", "minimum": 1, "maximum": 4294967295},
    "frame/seq": {"type": "integer", "minimum": 1, "maximum": 9007199254740991},
    "message/kind": {
      "type": "string",
      "enum": ["request", "response", "event", "control"]
    },
    "operation": {
      "type": "string",
      "enum": [
        "middleware.init",
        "middleware.invoke",
        "middleware.observe",
        "module-http.invoke",
        "request.cancel",
        "host-capability.invoke",
        "heartbeat",
        "session.shutdown"
      ]
    },
    "request/id": {"$ref": "#/$defs/id"},
    "reply/to": {"$ref": "#/$defs/id"},
    "deadline/at": {"type": "string", "format": "date-time", "maxLength": 64},
    "trace/correlation-id": {"$ref": "#/$defs/id"},
    "payload/schema": {"$ref": "#/$defs/schemaName"},
    "payload": {"type": "object"}
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  "allOf": [
    {
      "if": {"properties": {"message/kind": {"const": "request"}}, "required": ["message/kind"]},
      "then": {
        "required": ["request/id", "deadline/at"],
        "not": {"required": ["reply/to"]},
        "properties": {
          "operation": {
            "enum": ["middleware.init", "middleware.invoke", "module-http.invoke", "host-capability.invoke"]
          }
        }
      }
    },
    {
      "if": {"properties": {"message/kind": {"const": "response"}}, "required": ["message/kind"]},
      "then": {
        "required": ["reply/to"],
        "not": {"anyOf": [{"required": ["request/id"]}, {"required": ["deadline/at"]}]},
        "properties": {
          "operation": {
            "enum": ["middleware.init", "middleware.invoke", "module-http.invoke", "host-capability.invoke"]
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        }
      }
    },
    {
      "if": {"properties": {"message/kind": {"const": "event"}}, "required": ["message/kind"]},
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          "anyOf": [
            {"required": ["request/id"]},
            {"required": ["reply/to"]},
            {"required": ["deadline/at"]}
          ]
        },
        "properties": {"operation": {"const": "middleware.observe"}}
      }
    },
    {
      "if": {"properties": {"message/kind": {"const": "control"}}, "required": ["message/kind"]},
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        "properties": {
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    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "request"},
          "operation": {"const": "host-capability.invoke"}
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        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-channel-host-capability-call.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "response"},
          "operation": {"const": "host-capability.invoke"}
        },
        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-channel-call-result.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "request"},
          "operation": {"const": "module-http.invoke"}
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        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-module-http-request.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "response"},
          "operation": {"const": "module-http.invoke"}
        },
        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-module-http-response.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "control"},
          "operation": {"const": "request.cancel"}
        },
        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-channel-request-cancel.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "control"},
          "operation": {"const": "heartbeat"}
        },
        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-channel-heartbeat.v1"}}}
    },
    {
      "if": {
        "properties": {
          "message/kind": {"const": "control"},
          "operation": {"const": "session.shutdown"}
        },
        "required": ["message/kind", "operation"]
      },
      "then": {"properties": {"payload/schema": {"const": "middleware-channel-session-shutdown.v1"}}}
    }
  ],
  "$defs": {
    "id": {
      "type": "string",
      "minLength": 1,
      "maxLength": 256,
      "pattern": "^[A-Za-z0-9][A-Za-z0-9._:/-]*$"
    },
    "schemaName": {
      "type": "string",
      "minLength": 1,
      "maxLength": 128,
      "pattern": "^[a-z0-9][a-z0-9._-]*$"
    }
  },
  "x-dia-basis": [
    "orbidocs:doc/project/40-proposals/080-multiplexed-middleware-channel-executor.md"
  ]
}