/**
* Runtime Type Guards
*
* DESIGN PATTERNS:
* - Type guard pattern: Runtime validation of external data structures
* - Pure function pattern: No side effects, deterministic output
*
* CODING STANDARDS:
* - Use TypeScript 'is' return type for type narrowing
* - Validate at system boundaries (stdin parsing, external data)
* - Use 'in' operator for safe property narrowing (no type assertions)
*
* AVOID:
* - Complex validation logic (use a schema library for that)
* - Side effects in guard functions
* - Type assertions (as) to bypass type checking
*/
import type { Decision, HookResponse, HookContext } from '../types';
/**
* Set of valid decision values for efficient runtime lookup.
* Mirrors the Decision type: 'allow' | 'deny' | 'ask' | 'skip'
*/
const VALID_DECISIONS: ReadonlySet<string> = new Set<Decision>(['allow', 'deny', 'ask', 'skip']);
/**
* Type guard for HookResponse objects.
* Validates that a value conforms to the HookResponse interface at runtime.
*
* @param value - Unknown value to check
* @returns True if value is a valid HookResponse
*/
export function isHookResponse(value: unknown): value is HookResponse {
if (typeof value !== 'object' || value === null) return false;
if (!('decision' in value) || typeof value.decision !== 'string') return false;
if (!VALID_DECISIONS.has(value.decision)) return false;
if (!('message' in value) || typeof value.message !== 'string') return false;
return true;
}
/**
* Type guard for HookContext objects.
* Validates that a value conforms to the HookContext interface at runtime.
* toolInput is shallowly validated because its internal structure varies by tool
* and is not constrained by the interface.
*
* @param value - Unknown value to check
* @returns True if value is a valid HookContext
*/
export function isHookContext(value: unknown): value is HookContext {
if (typeof value !== 'object' || value === null) return false;
if (!('toolName' in value) || typeof value.toolName !== 'string') return false;
if (!('toolInput' in value) || typeof value.toolInput !== 'object' || value.toolInput === null) {
return false;
}
if (!('cwd' in value) || typeof value.cwd !== 'string') return false;
if (!('sessionId' in value) || typeof value.sessionId !== 'string') return false;
return true;
}
