{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://railiance.dev/schemas/rail.schema.json",
  "title": "Railiance rail declaration",
  "description": "Normative shape for declarations/rail.yaml in every rail-* repo. Authored by railiance-master under RMASTER-WP-0021-T04 from the two live rails and docs/rail-composition-contract.md. Codifies current practice; it does not tighten the rail family beyond what both live declarations already carry.",
  "type": "object",
  "additionalProperties": false,
  "required": [
    "kind",
    "rail_id",
    "repo",
    "ownership_repo",
    "contract_version",
    "composition_kind",
    "execution_architecture",
    "readiness_state",
    "required_substrate_capabilities",
    "supported_rollout_modes"
  ],
  "properties": {
    "kind": {
      "const": "execution-rail",
      "description": "Fixed discriminator. Both live rails already agree on this value."
    },
    "rail_id": {
      "$ref": "#/$defs/railSlug",
      "description": "Canonical identifier for the rail. Must equal the repo slug."
    },
    "repo": {
      "$ref": "#/$defs/repoSlug",
      "description": "The rail-* repo holding this declaration."
    },
    "ownership_repo": {
      "$ref": "#/$defs/repoSlug",
      "description": "The ownership-axis repo accountable for this execution contract. Both live rails name railiance-cluster."
    },
    "contract_version": {
      "$ref": "#/$defs/semver",
      "description": "Version of this rail contract. A derived rail pins the base contract with base_rail_contract, which is a separate field."
    },
    "composition_kind": {
      "enum": ["base", "derived"],
      "description": "base owns a complete workload execution contract for a substrate class. derived inherits a versioned base-rail contract and owns only its specialization. See docs/rail-composition-contract.md and ADR-0005."
    },
    "execution_architecture": {
      "type": "string",
      "minLength": 3,
      "description": "The operations architecture this rail names, e.g. kubernetes, knative-serving-on-kubernetes. Free-form on purpose: a new rail is justified by new semantics, not by an enum update."
    },
    "readiness_state": {
      "enum": ["declared", "installed", "verified", "production-approved", "deprecated"],
      "description": "Readiness of the rail contract itself, matching docs/rail-composition-contract.md. Distinct from rapp readiness_state (draft/declared/deployed/verified/retired) and from reef lifecycle_state. Do not unify the three vocabularies without a separate decision."
    },
    "required_substrate_capabilities": {
      "type": "array",
      "minItems": 1,
      "uniqueItems": true,
      "items": { "type": "string", "minLength": 1 },
      "description": "Capabilities the substrate must publish before this rail is usable. This is the live name; the bootstrap contract's older substrate_prerequisites label is retired in favour of this field."
    },
    "supported_rollout_modes": {
      "type": "array",
      "minItems": 1,
      "uniqueItems": true,
      "items": { "type": "string", "minLength": 1 },
      "description": "Rollout modes this rail supports, e.g. stage1-run, revision-canary."
    },
    "default_for": {
      "type": "array",
      "minItems": 1,
      "uniqueItems": true,
      "items": { "type": "string", "minLength": 1 },
      "description": "Workload classes this rail is the default for. Present on the base rail today; optional so a derived rail is not forced to claim default status."
    },
    "compatibility_notes": {
      "$ref": "#/$defs/notes",
      "description": "Human-readable caveats. Never load-bearing."
    },
    "base_rail": {
      "$ref": "#/$defs/railSlug",
      "description": "Required on derived rails. The rail whose contract is inherited."
    },
    "base_rail_contract": {
      "$ref": "#/$defs/semver",
      "description": "Required on derived rails. Exact contract_version of the base rail this derivation is written against. Ranges are not pins."
    },
    "inherited_semantics": {
      "type": "array",
      "minItems": 1,
      "uniqueItems": true,
      "items": { "type": "string", "minLength": 1 },
      "description": "Required on derived rails. Semantics taken from the base contract rather than restated."
    },
    "overridden_semantics": {
      "type": "array",
      "minItems": 1,
      "uniqueItems": true,
      "items": { "type": "string", "minLength": 1 },
      "description": "Required on derived rails. The only semantics this rail owns. If this list is empty the derived rail has no reason to exist."
    },
    "compatibility_constraints": {
      "type": "array",
      "minItems": 1,
      "items": { "type": "string", "minLength": 1 },
      "description": "Required on derived rails. Constraints a substrate or binding must satisfy to use this derivation."
    },
    "source_documents": {
      "type": "array",
      "minItems": 1,
      "items": { "$ref": "#/$defs/sourceDocument" }
    }
  },
  "allOf": [
    {
      "description": "A derived rail must name its base contract and the semantics it inherits or overrides.",
      "if": {
        "properties": { "composition_kind": { "const": "derived" } },
        "required": ["composition_kind"]
      },
      "then": {
        "required": [
          "base_rail",
          "base_rail_contract",
          "inherited_semantics",
          "overridden_semantics",
          "compatibility_constraints"
        ]
      }
    },
    {
      "description": "A base rail must not carry derived-only fields. Those fields would imply an inheritance it does not have.",
      "if": {
        "properties": { "composition_kind": { "const": "base" } },
        "required": ["composition_kind"]
      },
      "then": {
        "not": {
          "anyOf": [
            { "required": ["base_rail"] },
            { "required": ["base_rail_contract"] },
            { "required": ["inherited_semantics"] },
            { "required": ["overridden_semantics"] },
            { "required": ["compatibility_constraints"] }
          ]
        }
      }
    }
  ],
  "$defs": {
    "repoSlug": {
      "type": "string",
      "pattern": "^[a-z0-9]+(-[a-z0-9]+)*$",
      "minLength": 2
    },
    "railSlug": {
      "type": "string",
      "pattern": "^rail-[a-z0-9]+(-[a-z0-9]+)*$"
    },
    "semver": {
      "type": "string",
      "pattern": "^(0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)$"
    },
    "notes": {
      "type": "array",
      "items": { "type": "string", "minLength": 1 },
      "description": "Human-readable caveats. Never load-bearing: nothing may depend on parsing a note."
    },
    "sourceDocument": {
      "type": "object",
      "additionalProperties": false,
      "required": ["repo", "path"],
      "properties": {
        "repo": { "$ref": "#/$defs/repoSlug" },
        "path": { "type": "string", "minLength": 1 }
      }
    }
  }
}