{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://x07.io/spec/x07ast.v0.9.0.schema.json",
  "title": "X07 x07AST v0.9.0",
  "description": "Canonical, JSON-based AST carrier for LLM-first X07 program generation and repair. Expressions are encoded as JSON S-expressions (json-sexpr).",
  "type": "object",
  "additionalProperties": false,
  "required": ["schema_version", "kind", "module_id", "imports", "decls"],
  "properties": {
    "schema_version": { "const": "x07.x07ast@0.9.0" },
    "kind": {
      "type": "string",
      "enum": ["entry", "module"],
      "default": "entry"
    },
    "module_id": { "$ref": "#/$defs/module_id" },
    "imports": {
      "type": "array",
      "items": { "$ref": "#/$defs/module_id" },
      "uniqueItems": true,
      "default": []
    },
    "decls": {
      "type": "array",
      "items": { "$ref": "#/$defs/decl" },
      "default": []
    },
    "solve": { "$ref": "#/$defs/sexpr" },
    "meta": {
      "type": "object",
      "description": "Optional tool metadata. Not interpreted by the compiler; may be used for traceability.",
      "additionalProperties": true,
      "default": {}
    }
  },
  "allOf": [
    {
      "if": { "properties": { "kind": { "const": "entry" } } },
      "then": { "required": ["solve"] },
      "else": { "not": { "required": ["solve"] } }
    }
  ],
  "$defs": {
    "module_id": {
      "type": "string",
      "minLength": 1,
      "maxLength": 128,
      "pattern": "^[A-Za-z_][A-Za-z0-9_-]*(\\.[A-Za-z_][A-Za-z0-9_-]*)*$",
      "description": "Dot-separated module identifier."
    },
    "symbol": {
      "type": "string",
      "minLength": 1,
      "maxLength": 256,
      "pattern": "^[A-Za-z_][A-Za-z0-9_-]*(\\.[A-Za-z_][A-Za-z0-9_-]*)*$",
      "description": "Dot-separated symbol name (e.g., main.helper, std.text.utf8.validate_or_empty)."
    },
    "local_name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 64,
      "pattern": "^[A-Za-z_][A-Za-z0-9_]*$",
      "description": "Local identifier (variable/parameter)."
    },
    "type_name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 64,
      "pattern": "^[a-z][a-z0-9_]*$",
      "description": "Type name token (e.g., i32, bytes, bytes_view, vec_u8, iface)."
    },
    "tparam_name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 32,
      "pattern": "^[A-Z][A-Za-z0-9_]*$",
      "description": "Type parameter identifier (e.g., A, K, V)."
    },
    "bound_name": {
      "type": "string",
      "enum": ["any", "bytes_like", "num_like", "value", "hashable", "orderable"],
      "description": "Canonical type parameter bound."
    },
    "type_param": {
      "type": "object",
      "additionalProperties": false,
      "required": ["name"],
      "properties": {
        "name": { "$ref": "#/$defs/tparam_name" },
        "bound": { "$ref": "#/$defs/bound_name" }
      }
    },
    "type_params": {
      "type": "array",
      "items": { "$ref": "#/$defs/type_param" },
      "default": []
    },
    "type_var": {
      "type": "array",
      "minItems": 2,
      "maxItems": 2,
      "prefixItems": [{ "const": "t" }, { "$ref": "#/$defs/tparam_name" }]
    },
    "type_app": {
      "type": "array",
      "minItems": 2,
      "maxItems": 32,
      "prefixItems": [{ "$ref": "#/$defs/type_name" }],
      "items": { "$ref": "#/$defs/type_ref" }
    },
    "type_expr": {
      "description": "Structured type expression list. [\"t\",\"A\"] declares a type variable; other lists are type application: [head, arg1, ...].",
      "oneOf": [{ "$ref": "#/$defs/type_var" }, { "$ref": "#/$defs/type_app" }]
    },
    "type_ref": {
      "description": "Type reference: either legacy concrete type token or structured type expression.",
      "oneOf": [{ "$ref": "#/$defs/type_name" }, { "$ref": "#/$defs/type_expr" }]
    },
    "i32": {
      "type": "integer",
      "minimum": -2147483648,
      "maximum": 2147483647
    },
    "atom": {
      "type": "string",
      "minLength": 1,
      "maxLength": 256,
      "pattern": "^[^\\s]+$",
      "description": "Identifier token (no whitespace). Operators like '+', '<u', '>=u' are represented as atoms."
    },
    "sexpr": {
      "description": "An expression encoded as json-sexpr: either an i32, an atom string, or a list whose head is an atom string.",
      "oneOf": [
        { "$ref": "#/$defs/i32" },
        { "$ref": "#/$defs/atom" },
        { "$ref": "#/$defs/sexpr_list" }
      ]
    },
    "sexpr_list": {
      "description": "A list expression; first element is the head atom (form/callee), rest are arguments/subexpressions.",
      "anyOf": [
        {
          "type": "array",
          "minItems": 2,
          "maxItems": 2,
          "prefixItems": [{ "const": "bytes.lit" }, { "$ref": "#/$defs/text" }]
        },
        {
          "type": "array",
          "minItems": 1,
          "maxItems": 100000,
          "prefixItems": [{ "$ref": "#/$defs/atom" }],
          "items": { "$ref": "#/$defs/sexpr" }
        }
      ]
    },
    "text": {
      "type": "string",
      "maxLength": 1048576,
      "description": "UTF-8 text literal (whitespace allowed)."
    },
    "param": {
      "type": "object",
      "additionalProperties": false,
      "required": ["name", "ty"],
      "properties": {
        "name": { "$ref": "#/$defs/local_name" },
        "ty": { "$ref": "#/$defs/type_ref" },
        "brand": { "$ref": "#/$defs/symbol" }
      }
    },
    "contract_clause": {
      "type": "object",
      "additionalProperties": false,
      "required": ["expr"],
      "properties": {
        "id": { "type": "string", "maxLength": 4096 },
        "expr": { "$ref": "#/$defs/sexpr" },
        "witness": { "type": "array", "items": { "$ref": "#/$defs/sexpr" } }
      }
    },
    "loop_contract": {
      "type": "object",
      "additionalProperties": false,
      "required": ["ptr"],
      "properties": {
        "ptr": {
          "type": "string",
          "minLength": 1,
          "maxLength": 2048,
          "pattern": "^/decls/\\d+/body(?:/.*)?$"
        },
        "invariant": {
          "type": "array",
          "items": { "$ref": "#/$defs/contract_clause" },
          "default": []
        },
        "decreases": {
          "type": "array",
          "items": { "$ref": "#/$defs/contract_clause" },
          "default": []
        }
      }
    },
    "async_protocol": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "await_invariant": {
          "type": "array",
          "items": { "$ref": "#/$defs/contract_clause" },
          "default": []
        },
        "scope_invariant": {
          "type": "array",
          "items": { "$ref": "#/$defs/contract_clause" },
          "default": []
        },
        "cancellation_ensures": {
          "type": "array",
          "items": { "$ref": "#/$defs/contract_clause" },
          "default": []
        }
      }
    },
    "decl_defn": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "name", "params", "result", "body"],
      "properties": {
        "kind": { "const": "defn" },
        "name": { "$ref": "#/$defs/symbol" },
        "doc": { "type": "string", "minLength": 1, "maxLength": 4096 },
        "type_params": { "$ref": "#/$defs/type_params" },
        "requires": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "ensures": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "invariant": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "decreases": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "loop_contracts": { "type": "array", "items": { "$ref": "#/$defs/loop_contract" } },
        "params": {
          "type": "array",
          "items": { "$ref": "#/$defs/param" },
          "default": []
        },
        "result": { "$ref": "#/$defs/type_ref" },
        "result_brand": { "$ref": "#/$defs/symbol" },
        "body": { "$ref": "#/$defs/sexpr" }
      }
    },
    "decl_defasync": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "name", "params", "result", "body"],
      "properties": {
        "kind": { "const": "defasync" },
        "name": { "$ref": "#/$defs/symbol" },
        "doc": { "type": "string", "minLength": 1, "maxLength": 4096 },
        "type_params": { "$ref": "#/$defs/type_params" },
        "requires": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "ensures": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "invariant": { "type": "array", "items": { "$ref": "#/$defs/contract_clause" } },
        "protocol": { "$ref": "#/$defs/async_protocol" },
        "loop_contracts": { "type": "array", "items": { "$ref": "#/$defs/loop_contract" } },
        "params": {
          "type": "array",
          "items": { "$ref": "#/$defs/param" },
          "default": []
        },
        "result": { "$ref": "#/$defs/type_ref" },
        "result_brand": { "$ref": "#/$defs/symbol" },
        "body": { "$ref": "#/$defs/sexpr" }
      }
    },
    "decl_export": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "names"],
      "properties": {
        "kind": { "const": "export" },
        "names": {
          "type": "array",
          "items": { "$ref": "#/$defs/symbol" },
          "minItems": 1,
          "uniqueItems": true
        }
      }
    },
    "decl_extern": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "abi", "name", "params", "result"],
      "properties": {
        "kind": { "const": "extern" },
        "abi": { "type": "string", "enum": ["C"], "default": "C" },
        "name": { "$ref": "#/$defs/symbol" },
        "link_name": {
          "$ref": "#/$defs/local_name",
          "description": "Optional C symbol name to link against; if omitted, defaults to the last segment of /name."
        },
        "params": {
          "type": "array",
          "items": { "$ref": "#/$defs/param" },
          "default": []
        },
        "result": { "$ref": "#/$defs/type_ref" }
      }
    },
    "decl_defrecord": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "name", "fields"],
      "properties": {
        "kind": { "const": "defrecord" },
        "name": { "$ref": "#/$defs/symbol" },
        "doc": { "type": "string", "minLength": 1, "maxLength": 4096 },
        "fields": {
          "type": "array",
          "minItems": 1,
          "uniqueItems": true,
          "items": {
            "type": "object",
            "additionalProperties": false,
            "required": ["name", "ty"],
            "properties": {
              "name": { "$ref": "#/$defs/local_name" },
              "ty": { "$ref": "#/$defs/type_name" }
            }
          }
        }
      }
    },
    "decl_defenum": {
      "type": "object",
      "additionalProperties": false,
      "required": ["kind", "name", "variants"],
      "properties": {
        "kind": { "const": "defenum" },
        "name": { "$ref": "#/$defs/symbol" },
        "doc": { "type": "string", "minLength": 1, "maxLength": 4096 },
        "variants": {
          "type": "array",
          "minItems": 1,
          "uniqueItems": true,
          "items": {
            "type": "object",
            "additionalProperties": false,
            "required": ["name"],
            "properties": {
              "name": { "$ref": "#/$defs/local_name" },
              "payload": { "$ref": "#/$defs/type_name" }
            }
          }
        }
      }
    },
    "decl": {
      "oneOf": [
        { "$ref": "#/$defs/decl_defn" },
        { "$ref": "#/$defs/decl_defasync" },
        { "$ref": "#/$defs/decl_export" },
        { "$ref": "#/$defs/decl_extern" },
        { "$ref": "#/$defs/decl_defrecord" },
        { "$ref": "#/$defs/decl_defenum" }
      ]
    }
  }
}