{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://buildchain.libkungfu.dev/schemas/v4-host-contract-v1.schema.json",
  "title": "Buildchain v4 Host Contract",
  "oneOf": [{ "$ref": "#/$defs/request" }, { "$ref": "#/$defs/response" }],
  "$defs": {
    "encodedBytes": {
      "type": "object",
      "required": ["encoding", "bytes"],
      "additionalProperties": false,
      "properties": {
        "encoding": { "const": "base64" },
        "bytes": { "type": "string", "contentEncoding": "base64" }
      }
    },
    "command": {
      "type": "object",
      "required": ["id", "arguments"],
      "additionalProperties": false,
      "properties": {
        "id": { "type": "string", "minLength": 1 },
        "arguments": {
          "type": "array",
          "items": { "type": "string" }
        }
      }
    },
    "request": {
      "type": "object",
      "required": [
        "schemaVersion",
        "contract",
        "protocolVersion",
        "requestId",
        "command",
        "input",
        "requiredCapabilities",
        "timeoutMs"
      ],
      "additionalProperties": false,
      "properties": {
        "schemaVersion": { "const": 1 },
        "contract": { "const": "kungfu-buildchain-v4-host-request" },
        "protocolVersion": { "const": "1.0" },
        "requestId": { "type": "string", "minLength": 1 },
        "command": { "$ref": "#/$defs/command" },
        "input": { "$ref": "#/$defs/encodedBytes" },
        "requiredCapabilities": {
          "type": "array",
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1 }
        },
        "timeoutMs": {
          "type": "integer",
          "minimum": 1,
          "maximum": 30000
        }
      }
    },
    "diagnostic": {
      "type": "object",
      "required": ["code", "message", "retryable"],
      "additionalProperties": false,
      "properties": {
        "code": { "type": "string", "minLength": 1 },
        "message": { "type": "string" },
        "retryable": { "type": "boolean" }
      }
    },
    "response": {
      "type": "object",
      "required": [
        "schemaVersion",
        "contract",
        "protocolVersion",
        "requestId",
        "status",
        "host",
        "command",
        "output",
        "structuredResult",
        "diagnostics",
        "exit"
      ],
      "additionalProperties": false,
      "properties": {
        "schemaVersion": { "const": 1 },
        "contract": { "const": "kungfu-buildchain-v4-host-response" },
        "protocolVersion": { "const": "1.0" },
        "requestId": { "type": "string", "minLength": 1 },
        "status": {
          "enum": ["ok", "unsupported", "failed", "cancelled"]
        },
        "host": {
          "type": "object",
          "required": ["kind", "implementation", "capabilities"],
          "additionalProperties": false,
          "properties": {
            "kind": { "type": "string", "minLength": 1 },
            "implementation": { "type": "string", "minLength": 1 },
            "capabilities": {
              "type": "array",
              "uniqueItems": true,
              "items": { "type": "string", "minLength": 1 }
            }
          }
        },
        "command": { "$ref": "#/$defs/command" },
        "output": {
          "type": "object",
          "required": ["stdout", "stderr"],
          "additionalProperties": false,
          "properties": {
            "stdout": { "$ref": "#/$defs/encodedBytes" },
            "stderr": { "$ref": "#/$defs/encodedBytes" }
          }
        },
        "structuredResult": true,
        "diagnostics": {
          "type": "array",
          "items": { "$ref": "#/$defs/diagnostic" }
        },
        "exit": {
          "type": "object",
          "required": ["code", "signal"],
          "additionalProperties": false,
          "properties": {
            "code": { "type": "integer", "minimum": 0, "maximum": 255 },
            "signal": { "type": ["string", "null"] }
          }
        }
      }
    }
  }
}