{
  "$schema": "http://json-schema.org/draft-07/schema",
  "$id": "https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json",

  "oneOf": [{ "$ref": "#/$defs/message" }, { "$ref": "#/$defs/select" }],

  "$defs": {
    "literal": {
      "type": "object",
      "properties": {
        "type": { "const": "literal" },
        "value": { "type": "string" }
      },
      "required": ["type", "value"]
    },
    "variable": {
      "type": "object",
      "properties": {
        "type": { "const": "variable" },
        "name": { "type": "string" }
      },
      "required": ["type", "name"]
    },
    "literal-or-variable": {
      "oneOf": [{ "$ref": "#/$defs/literal" }, { "$ref": "#/$defs/variable" }]
    },

    "options": {
      "type": "object",
      "additionalProperties": { "$ref": "#/$defs/literal-or-variable" }
    },
    "attributes": {
      "type": "object",
      "additionalProperties": {
        "oneOf": [{ "$ref": "#/$defs/literal" }, { "const": true }]
      }
    },

    "function": {
      "type": "object",
      "properties": {
        "type": { "const": "function" },
        "name": { "type": "string" },
        "options": { "$ref": "#/$defs/options" }
      },
      "required": ["type", "name"]
    },
    "expression": {
      "type": "object",
      "properties": {
        "type": { "const": "expression" },
        "arg": { "$ref": "#/$defs/literal-or-variable" },
        "function": { "$ref": "#/$defs/function" },
        "attributes": { "$ref": "#/$defs/attributes" }
      },
      "anyOf": [
        { "required": ["type", "arg"] },
        { "required": ["type", "function"] }
      ]
    },

    "markup": {
      "type": "object",
      "properties": {
        "type": { "const": "markup" },
        "kind": { "enum": ["open", "standalone", "close"] },
        "name": { "type": "string" },
        "options": { "$ref": "#/$defs/options" },
        "attributes": { "$ref": "#/$defs/attributes" }
      },
      "required": ["type", "kind", "name"]
    },

    "pattern": {
      "type": "array",
      "items": {
        "oneOf": [
          { "type": "string" },
          { "$ref": "#/$defs/expression" },
          { "$ref": "#/$defs/markup" }
        ]
      }
    },

    "input-declaration": {
      "type": "object",
      "properties": {
        "type": { "const": "input" },
        "name": { "type": "string" },
        "value": {
          "allOf": [
            { "$ref": "#/$defs/expression" },
            {
              "properties": {
                "arg": { "$ref": "#/$defs/variable" }
              },
              "required": ["arg"]
            }
          ]
        }
      },
      "required": ["type", "name", "value"]
    },
    "local-declaration": {
      "type": "object",
      "properties": {
        "type": { "const": "local" },
        "name": { "type": "string" },
        "value": { "$ref": "#/$defs/expression" }
      },
      "required": ["type", "name", "value"]
    },
    "declarations": {
      "type": "array",
      "items": {
        "oneOf": [
          { "$ref": "#/$defs/input-declaration" },
          { "$ref": "#/$defs/local-declaration" }
        ]
      }
    },

    "variant-key": {
      "oneOf": [
        { "$ref": "#/$defs/literal" },
        {
          "type": "object",
          "properties": {
            "type": { "const": "*" },
            "value": { "type": "string" }
          },
          "required": ["type"]
        }
      ]
    },
    "message": {
      "type": "object",
      "properties": {
        "type": { "const": "message" },
        "declarations": { "$ref": "#/$defs/declarations" },
        "pattern": { "$ref": "#/$defs/pattern" }
      },
      "required": ["type", "declarations", "pattern"]
    },
    "select": {
      "type": "object",
      "properties": {
        "type": { "const": "select" },
        "declarations": { "$ref": "#/$defs/declarations" },
        "selectors": {
          "type": "array",
          "items": { "$ref": "#/$defs/variable" }
        },
        "variants": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "keys": {
                "type": "array",
                "items": { "$ref": "#/$defs/variant-key" }
              },
              "value": { "$ref": "#/$defs/pattern" }
            },
            "required": ["keys", "value"]
          }
        }
      },
      "required": ["type", "declarations", "selectors", "variants"]
    }
  }
}