{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "Image Snapshot v1",
  "description": "Canonical image_snapshot v1 request envelope carrying a Base64-encoded JPEG frame and its caller-supplied identifiers. Readers are tolerant: unknown members are accepted and discarded so a later field addition stays non-breaking.",
  "type": "object",
  "additionalProperties": true,
  "required": ["message_type", "schema_version", "camera_id", "timestamp", "image_data", "device_name"],
  "properties": {
    "message_type": {
      "description": "Constant discriminator identifying this envelope shape.",
      "type": "string",
      "const": "image_snapshot"
    },
    "schema_version": {
      "description": "Envelope schema version. Emitted as the string \"1.0\" by the v1 producer.",
      "type": "string",
      "examples": ["1.0"]
    },
    "camera_id": {
      "description": "Opaque caller-supplied camera identifier. No character set or length bound is applied.",
      "type": "string"
    },
    "timestamp": {
      "description": "Capture time as epoch seconds. Integer, not an RFC 3339 string.",
      "type": "integer"
    },
    "image_data": {
      "description": "Standard-alphabet Base64 encoding of the raw JPEG payload. Padded, not URL-safe.",
      "type": "string",
      "contentEncoding": "base64",
      "contentMediaType": "image/jpeg",
      "pattern": "^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/][AQgw]==|[A-Za-z0-9+/]{2}[AEIMQUYcgkosw048]=)?(?![\\s\\S])"
    },
    "device_name": {
      "description": "Opaque caller-supplied device identifier. No character set or length bound is applied.",
      "type": "string"
    },
    "location": {
      "description": "Optional [latitude, longitude] pair. Contract-only: accepted by consumers for compatibility with other producers, and never emitted by this v1 producer.",
      "type": "array",
      "items": {
        "type": "number"
      },
      "minItems": 2,
      "maxItems": 2,
      "examples": [[0, 0]]
    },
    "metadata": {
      "description": "Optional free-form caller-supplied metadata. Defaults to empty and is omitted rather than emitted as null when empty. Carries no sequence_number and no source_topic; this producer derives nothing from a transport topic.",
      "type": "object",
      "additionalProperties": true,
      "default": {}
    },
    "correlation_id": {
      "description": "Optional caller-supplied correlation identifier. Omitted rather than emitted as null when unset.",
      "type": "string"
    }
  },
  "examples": [
    {
      "message_type": "image_snapshot",
      "schema_version": "1.0",
      "camera_id": "camera-01",
      "timestamp": 1700000000,
      "image_data": "/9j/4AAQSkZJRgABAQAAAQABAAD/2Q==",
      "device_name": "device-01"
    },
    {
      "message_type": "image_snapshot",
      "schema_version": "1.0",
      "camera_id": "camera-01",
      "timestamp": 1700000060,
      "image_data": "/9j/4AAQSkZJRgABAQAAAQABAAD/2Q==",
      "device_name": "device-01",
      "metadata": {
        "site": "site-01",
        "asset": "asset-01"
      },
      "correlation_id": "00000000-0000-4000-8000-000000000001"
    }
  ],
  "$comment": "Recommended size bounds are 4 MiB maximum raw JPEG and 8 MiB maximum serialized envelope. Both are caller-configured defaults applied by the producer before and after normalization; neither is enforced by this schema, which declares no maxLength. additionalProperties is intentionally true (tolerant reader): strict rejection of unknown members belongs in tests, not in the runtime parser."
}