{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://rulegraph.org/schema/rg-ast/v1.2/rg-ast-v1.2.schema.json",
  "title": "RuleGraph AST v1.2",
  "type": "object",

  "oneOf": [
    { "required": ["sym"] },
    { "required": ["const"] },
    { "required": ["neg"] },
    { "required": ["add"] },
    { "required": ["sub"] },
    { "required": ["mul"] },
    { "required": ["div"] },
    { "required": ["pow"] },
    { "required": ["vec"] },
    { "required": ["call"] },
    { "required": ["let"] },
    { "required": ["piecewise"] }
  ],

  "properties": {
    "sym": { "type": "string", "minLength": 1 },

    "const": {
      "oneOf": [
        { "type": "number" },
        { "type": "integer" },
        {
          "type": "object",
          "required": ["rat"],
          "properties": {
            "rat": {
              "type": "object",
              "required": ["p", "q"],
              "properties": {
                "p": { "type": "integer" },
                "q": { "type": "integer", "minimum": 1 }
              },
              "additionalProperties": false
            }
          },
          "additionalProperties": false
        }
      ]
    },

    "neg": { "$ref": "#/$defs/Node" },

    "add": {
      "type": "array",
      "minItems": 2,
      "items": { "$ref": "#/$defs/Node" }
    },
    
    "sub": {
      "type": "array",
      "minItems": 2,
      "items": { "$ref": "#/$defs/Node" }
    },

    "mul": {
      "type": "array",
      "minItems": 2,
      "items": { "$ref": "#/$defs/Node" }
    },

    "div": {
      "type": "array",
      "minItems": 2,
      "maxItems": 2,
      "prefixItems": [
        { "$ref": "#/$defs/Node" },
        { "$ref": "#/$defs/Node" }
      ],
      "items": false
    },

    "pow": {
      "type": "array",
      "minItems": 2,
      "maxItems": 2,
      "prefixItems": [
        { "$ref": "#/$defs/Node" },
        { "$ref": "#/$defs/Node" }
      ],
      "items": false
    },

    "vec": {
      "type": "array",
      "minItems": 2,
      "items": { "$ref": "#/$defs/Node" }
    },

    "call": {
      "type": "object",
      "required": ["fn", "args"],
      "properties": {
        "fn": {
          "type": "string",
          "enum": [
            "norm","dot","cross",
            "abs","sign","min","max","clamp","saturate","step","mix",
            "exp","log","sqrt","sin","cos","tan","sinh","cosh","tanh",
            "lt","le","gt","ge","eq","ne",
            "and","or","not"
          ]
        },
        "args": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/Node" }
        }
      },
      "additionalProperties": false
    },

    "let": {
      "type": "array",
      "minItems": 2,
      "maxItems": 2,
      "prefixItems": [
        { "type": "object", "required": ["sym"], "properties": { "sym": { "type": "string" } }, "additionalProperties": false },
        { "$ref": "#/$defs/Node" }
      ],
      "items": false
    },

    "piecewise": {
      "type": "object",
      "required": ["cases"],
      "properties": {
        "cases": {
          "type": "array",
          "minItems": 1,
          "items": {
            "type": "object",
            "required": ["if", "then"],
            "properties": {
              "if":   { "$ref": "#/$defs/Node" },
              "then": { "$ref": "#/$defs/Node" }
            },
            "additionalProperties": false
          }
        },
        "otherwise": { "$ref": "#/$defs/Node" }
      },
      "additionalProperties": false
    }
  },

  "$defs": {
    "Node": {
      "type": "object",
      "oneOf": [
        { "required": ["sym"] },
        { "required": ["const"] },
        { "required": ["neg"] },
        { "required": ["add"] },
        { "required": ["sub"] },
        { "required": ["mul"] },
        { "required": ["div"] },
        { "required": ["pow"] },
        { "required": ["vec"] },
        { "required": ["call"] },
        { "required": ["let"] },
        { "required": ["piecewise"] }
      ]
    }
  },

  "additionalProperties": false
}