{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://alxprotocol.com/protocol/1/extensions/signing/schemas/signed-block.schema.json",
  "title": "ALX Signed Block Extension",
  "description": "Optional signing extension profile for ALX Blocks. Signing metadata is excluded from Block identity.",
  "$comment": "This schema validates structural shape only. It does not verify contentHash, blockHash derivation, parent hash ordering, attestation binding, or signature validity.",
  "type": "object",
  "properties": {
    "block": {
      "$ref": "../../../schemas/block.schema.json",
      "description": "The ALX Block being attested."
    },
    "attestation": {
      "$ref": "#/$defs/portableAttestation",
      "description": "A single cryptographic attestation over this Block's blockHash."
    },
    "attestations": {
      "type": "array",
      "minItems": 1,
      "items": {
        "$ref": "#/$defs/portableAttestation"
      },
      "description": "Multiple cryptographic attestations over this Block's blockHash."
    }
  },
  "required": [
    "block"
  ],
  "anyOf": [
    {
      "required": [
        "attestation"
      ]
    },
    {
      "required": [
        "attestations"
      ]
    }
  ],
  "additionalProperties": false,
  "$defs": {
    "portableAttestation": {
      "allOf": [
        { "$ref": "../../../schemas/defs.schema.json#/$defs/attestation" },
        {
          "oneOf": [
            {
              "properties": {
                "algorithm": { "const": "ed25519" },
                "attester": { "pattern": "^0x[a-f0-9]{64}$" },
                "signature": { "pattern": "^0x[a-f0-9]{128}$" }
              },
              "required": ["algorithm", "attester", "signature"]
            },
            {
              "properties": {
                "algorithm": { "const": "p256" },
                "attester": { "pattern": "^0x04[a-f0-9]{128}$" },
                "signature": { "pattern": "^0x[a-f0-9]{128}$" }
              },
              "required": ["algorithm", "attester", "signature"]
            },
            {
              "properties": {
                "algorithm": { "not": { "enum": ["ed25519", "p256"] } }
              },
              "required": ["algorithm"]
            }
          ]
        }
      ]
    }
  }
}