{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://purinzan.github.io/ladder-fabricator/schema/ladder-ast.schema.json",
  "title": "Ladder Fabricator circuit AST",
  "description": "Authoring schema for validated MELSEC iQ-F and KEYENCE KV-X ladder diagrams.",
  "type": "object",
  "additionalProperties": false,
  "required": ["schema_version", "rungs"],
  "properties": {
    "schema_version": {"enum": [1, 2]},
    "target": {"$ref": "#/$defs/target"},
    "title": {"type": "string", "maxLength": 160},
    "comments": {
      "type": "object",
      "maxProperties": 512,
      "propertyNames": {"type": "string", "minLength": 1},
      "additionalProperties": {"type": "string", "maxLength": 2048}
    },
    "rungs": {
      "type": "array",
      "minItems": 1,
      "maxItems": 64,
      "items": {"$ref": "#/$defs/rung"}
    }
  },
  "allOf": [
    {
      "if": {"properties": {"schema_version": {"const": 2}}, "required": ["schema_version"]},
      "then": {"required": ["target"]},
      "else": {"not": {"required": ["target"]}}
    }
  ],
  "$defs": {
    "target": {
      "oneOf": [
        {"type": "object", "additionalProperties": false, "required": ["vendor", "series"], "properties": {"vendor": {"const": "melsec"}, "series": {"const": "iq-f"}}},
        {"type": "object", "additionalProperties": false, "required": ["vendor", "series"], "properties": {"vendor": {"const": "keyence"}, "series": {"const": "kv-x"}}}
      ]
    },
    "rung": {
      "type": "object",
      "additionalProperties": false,
      "required": ["id", "logic", "output"],
      "properties": {
        "id": {"type": "string", "pattern": "^[A-Za-z][A-Za-z0-9_-]{0,47}$"},
        "title": {"type": "string", "maxLength": 160},
        "logic": {"$ref": "#/$defs/logic-root"},
        "output": {"$ref": "#/$defs/output"}
      }
    },
    "contact": {
      "type": "object",
      "additionalProperties": false,
      "required": ["device"],
      "properties": {
        "device": {"type": "string", "minLength": 2},
        "contact": {"enum": ["a", "b", "rising", "falling"]}
      }
    },
    "compare": {
      "type": "object",
      "additionalProperties": false,
      "required": ["compare"],
      "properties": {
        "compare": {
          "type": "object",
          "additionalProperties": false,
          "required": ["operator", "left", "right"],
          "properties": {
            "operator": {"enum": ["=", "<>", "<", "<=", ">", ">="]},
            "left": {"type": "string"},
            "right": {"type": "string"}
          }
        }
      }
    },
    "logic-root": {
      "oneOf": [
        {"$ref": "#/$defs/logic"},
        {"type": "object", "additionalProperties": false, "required": ["inv"], "properties": {"inv": {"$ref": "#/$defs/logic"}}}
      ]
    },
    "logic": {
      "oneOf": [
        {"type": "string", "minLength": 2},
        {"$ref": "#/$defs/contact"},
        {"$ref": "#/$defs/compare"},
        {"type": "object", "additionalProperties": false, "required": ["and"], "properties": {"and": {"type": "array", "minItems": 2, "items": {"$ref": "#/$defs/logic"}}}},
        {"type": "object", "additionalProperties": false, "required": ["or"], "properties": {"or": {"type": "array", "minItems": 2, "items": {"$ref": "#/$defs/logic"}}}},
        {"type": "object", "additionalProperties": false, "required": ["not"], "properties": {"not": {"$ref": "#/$defs/logic"}}}
      ]
    },
    "output": {
      "oneOf": [
        {"type": "object", "additionalProperties": false, "required": ["device"], "properties": {"type": {"enum": ["coil", "set", "rst", "pls", "plf"]}, "device": {"type": "string"}}},
        {"type": "object", "additionalProperties": false, "required": ["type", "setpoint", "process_value", "parameters", "destination"], "properties": {"type": {"const": "pid"}, "setpoint": {"type": "string"}, "process_value": {"type": "string"}, "parameters": {"type": "string"}, "destination": {"type": "string"}}},
        {"type": "object", "additionalProperties": false, "required": ["type", "source", "destination"], "properties": {"type": {"const": "mov"}, "source": {"type": "string"}, "destination": {"type": "string"}}}
      ]
    }
  }
}