{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://nexus.drevops.com/schema/nexus.schema.json",
  "title": "Nexus diagram",
  "description": "A Nexus diagram document (.nexus.json): a Drupal content model with its annotations and, optionally, its canvas layout and display settings. Nexus opens it with 'Open a saved diagram'.",
  "type": "object",
  "required": ["nexus", "entities"],
  "additionalProperties": false,
  "properties": {
    "$schema": {
      "description": "The URL of this schema, so an editor can validate the document.",
      "type": "string"
    },
    "nexus": {
      "description": "The version of the document format.",
      "const": 1
    },
    "title": {
      "description": "The diagram's title. Defaults to 'Content model'.",
      "type": "string"
    },
    "colors": {
      "description": "Fill colour overrides, keyed by entity type.",
      "type": "object",
      "propertyNames": { "$ref": "#/$defs/machineName" },
      "additionalProperties": { "$ref": "#/$defs/color" }
    },
    "symbols": {
      "description": "Symbol overrides, keyed by entity type.",
      "type": "object",
      "propertyNames": { "$ref": "#/$defs/machineName" },
      "additionalProperties": { "$ref": "#/$defs/symbol" }
    },
    "customTypes": {
      "description": "Entity types beyond the built-in ones (node, taxonomy_term, media, paragraph, block_content, user, external).",
      "type": "array",
      "items": { "$ref": "#/$defs/customType" }
    },
    "entities": {
      "description": "The entity bundles of the model, each with its fields.",
      "type": "array",
      "items": { "$ref": "#/$defs/entity" }
    },
    "annotations": {
      "description": "Event, API, Callback and Note nodes and the edges between any 2 nodes of the diagram.",
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "nodes": {
          "type": "array",
          "items": { "$ref": "#/$defs/annotationNode" }
        },
        "edges": {
          "type": "array",
          "items": { "$ref": "#/$defs/annotationEdge" }
        }
      }
    },
    "layout": {
      "description": "Canvas positions keyed by node id. Leave it out, or empty, and Nexus lays the diagram out when it opens.",
      "type": "object",
      "additionalProperties": { "$ref": "#/$defs/position" }
    },
    "ui": {
      "description": "The panel arrangement Nexus saves with a diagram. Leave it out, or null, to keep the arrangement the browser already has.",
      "type": ["object", "null"]
    }
  },
  "$defs": {
    "machineName": {
      "description": "A Drupal machine name: lowercase letters, digits and underscores.",
      "type": "string",
      "pattern": "^[a-z0-9_]+$"
    },
    "color": {
      "description": "A 6- or 8-digit hex colour.",
      "type": "string",
      "pattern": "^#(?:[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$"
    },
    "symbol": {
      "description": "The shape that draws an entity type.",
      "enum": ["rounded", "rectangle", "ellipse", "diamond", "hexagon", "tag", "barrel", "cut", "rhomboid", "pentagon", "octagon"]
    },
    "customType": {
      "type": "object",
      "required": ["type", "label"],
      "additionalProperties": false,
      "properties": {
        "type": { "$ref": "#/$defs/machineName" },
        "label": { "type": "string", "minLength": 1 }
      }
    },
    "entity": {
      "description": "An entity bundle, such as a content type or a vocabulary. Its id in the diagram is '<entityType>.<bundle>'.",
      "type": "object",
      "required": ["entityType", "bundle", "label"],
      "additionalProperties": false,
      "properties": {
        "entityType": { "$ref": "#/$defs/machineName" },
        "bundle": {
          "description": "The bundle's machine name, or '*' for an entity that stands for every bundle of its type.",
          "anyOf": [{ "$ref": "#/$defs/machineName" }, { "const": "*" }]
        },
        "label": { "type": "string", "minLength": 1 },
        "note": { "description": "Free text shown as a note badge.", "type": "string" },
        "description": { "description": "The bundle's description, as its Drupal config gives it.", "type": "string" },
        "fields": {
          "type": "array",
          "items": { "$ref": "#/$defs/field" }
        }
      }
    },
    "field": {
      "description": "A field on an entity bundle. Its id in the diagram is 'field:<entityType>.<bundle>:<name>'.",
      "type": "object",
      "required": ["name", "label", "fieldType", "kind"],
      "additionalProperties": false,
      "properties": {
        "name": { "$ref": "#/$defs/machineName" },
        "label": { "type": "string", "minLength": 1 },
        "fieldType": {
          "description": "The Drupal field type, such as 'string' or 'entity_reference'.",
          "$ref": "#/$defs/machineName"
        },
        "kind": {
          "description": "'single' or 'multi' for a configured field, by its cardinality; 'system' for a base field; 'calculated' for a computed one.",
          "enum": ["single", "multi", "system", "calculated"]
        },
        "cardinality": {
          "description": "How many values the field holds: 1, a limit above 1, or -1 for unlimited. Defaults to -1 for a 'multi' field and 1 for any other.",
          "type": "integer",
          "anyOf": [{ "const": -1 }, { "minimum": 1 }]
        },
        "required": { "type": "boolean" },
        "note": { "description": "Free text shown as a note badge.", "type": "string" },
        "targetType": {
          "description": "The entity type a reference field points to, or null for a field that references nothing.",
          "anyOf": [{ "$ref": "#/$defs/machineName" }, { "type": "null" }]
        },
        "targetBundles": {
          "description": "The bundles a reference field points to. Empty points it to the '<targetType>.*' entity.",
          "type": "array",
          "items": { "$ref": "#/$defs/machineName" }
        },
        "hidden": { "description": "True keeps the field off the canvas.", "type": "boolean" },
        "description": { "description": "The help text editors see under the field.", "type": "string" },
        "defaultValue": { "description": "The value a new item starts with, as text.", "type": "string" },
        "allowedValues": {
          "description": "The values a list field offers, in order.",
          "type": "array",
          "items": { "$ref": "#/$defs/allowedValue" }
        },
        "allowedValuesFunction": {
          "description": "The PHP function that returns a list field's allowed values in place of a fixed list.",
          "type": "string"
        },
        "translatable": { "description": "Whether the field's value can differ per language. Leave it out when the source doesn't say.", "type": "boolean" }
      },
      "allOf": [
        {
          "if": { "properties": { "kind": { "const": "single" } } },
          "then": { "properties": { "cardinality": { "const": 1 } } }
        },
        {
          "if": { "properties": { "kind": { "const": "multi" } } },
          "then": { "properties": { "cardinality": { "not": { "const": 1 } } } }
        }
      ]
    },
    "allowedValue": {
      "description": "1 value a list field offers.",
      "type": "object",
      "required": ["value"],
      "additionalProperties": false,
      "properties": {
        "value": { "description": "The value Drupal stores.", "type": "string", "minLength": 1 },
        "label": { "description": "The label editors pick. Defaults to the value.", "type": "string" }
      }
    },
    "annotationNode": {
      "description": "An Event, API, Callback or Note node. Its id is the id it's given here.",
      "type": "object",
      "required": ["id", "kind", "label"],
      "additionalProperties": false,
      "properties": {
        "id": { "type": "string", "minLength": 1 },
        "kind": { "enum": ["event", "api", "callback", "note"] },
        "label": { "type": "string" },
        "method": { "description": "A second line of text, such as an HTTP verb.", "type": "string" },
        "note": { "description": "Free text shown as a note badge. A Note node draws it on the canvas as Markdown instead.", "type": "string" }
      }
    },
    "annotationEdge": {
      "description": "An edge between 2 nodes of the diagram, named by their ids.",
      "type": "object",
      "required": ["from", "to"],
      "additionalProperties": false,
      "properties": {
        "from": { "type": "string", "minLength": 1 },
        "to": { "type": "string", "minLength": 1 },
        "label": { "type": "string" }
      }
    },
    "position": {
      "type": "object",
      "required": ["x", "y"],
      "additionalProperties": false,
      "properties": {
        "x": { "type": "number" },
        "y": { "type": "number" }
      }
    }
  }
}