JSON and Schema Validation

/**
 * Union type representing all valid JSON values
 */
type JsonValue = boolean | string | number | JsonArray | JsonObject | null;

/**
 * Object with string keys and JsonValue values
 */
interface JsonObject {
  [key: string]: JsonValue;
}

/**
 * Array of JsonValue items
 */
interface JsonArray extends Array<JsonValue> {}

/**
 * Type guard to check if value is a JsonObject
 * @param value - Value to check
 * @returns True if value is JsonObject
 */
function isJsonObject(value: unknown): value is JsonObject;

/**
 * Type guard to check if value is a JsonArray
 * @param value - Value to check
 * @returns True if value is JsonArray
 */
function isJsonArray(value: unknown): value is JsonArray;

/**
 * String type for JSON pointer paths (RFC 6901)
 */
type JsonPointer = string;

/**
 * Result of schema validation operation
 */
interface SchemaValidatorResult {
  /** Whether validation succeeded */
  success: boolean;
  /** Validated data (potentially transformed by smart defaults) */
  data: JsonValue;
  /** Array of validation errors if validation failed */
  errors?: SchemaValidatorError[];
}

/**
 * Schema validation error information
 */
type SchemaValidatorError = Partial<{
  instancePath: string;
  schemaPath: string;
  keyword: string;
  params: Record<string, any>;
  message: string;
}>;

/**
 * Options for schema validation
 */
interface SchemaValidatorOptions {
  /** Whether to apply smart defaults during validation */
  withPrompts?: boolean;
  /** Custom prompt provider for interactive defaults */
  promptProvider?: PromptProvider;
}

/**
 * Function type for validating JSON data against a compiled schema
 */
interface SchemaValidator {
  (data: JsonValue, options?: SchemaValidatorOptions): Observable<SchemaValidatorResult>;
}

/**
 * Format validator function from AJV
 */
type SchemaFormatter = {
  readonly async: boolean;
  validate(data: any): boolean | Promise<boolean>;
};

/**
 * Named format with its validator
 */
interface SchemaFormat {
  name: string;
  formatter: SchemaFormatter;
}

/**
 * Provider function for generating smart default values
 */
interface SmartDefaultProvider<T = JsonValue> {
  (schema: JsonObject): Observable<T>;
}

/**
 * Custom keyword validator function for schema extensions
 */
interface SchemaKeywordValidator {
  (data: any, schema: any, parentSchema: any, currentPath: string): boolean | Observable<boolean>;
}

/**
 * Registry interface for schema compilation and validation
 */
interface SchemaRegistry {
  /**
   * Compile a JSON schema into a validator function
   * @param schema - JSON schema object
   * @returns Observable emitting compiled validator
   */
  compile(schema: JsonObject): Observable<SchemaValidator>;
  
  /**
   * Add a custom format validator to the registry
   * @param name - Format name
   * @param formatter - Format validator implementation
   */
  addFormat(name: string, formatter: SchemaFormatter): void;
  
  /**
   * Add a smart default provider for a specific schema pattern
   * @param pointer - JSON pointer identifying where to apply defaults
   * @param provider - Provider function for generating defaults
   */
  addSmartDefaultProvider<T = JsonValue>(pointer: string, provider: SmartDefaultProvider<T>): void;
  
  /**
   * Register a custom keyword validator
   * @param keyword - Keyword name
   * @param validator - Validator implementation
   */
  registerKeywordValidator(keyword: string, validator: SchemaKeywordValidator): void;
}

/**
 * Main schema registry implementation using AJV
 * Provides JSON schema compilation and validation with extensible format support
 */
class CoreSchemaRegistry implements SchemaRegistry {
  /**
   * Create a new schema registry
   * @param formats - Optional map of initial format validators
   */
  constructor(formats?: { [name: string]: SchemaFormatter });
  
  compile(schema: JsonObject): Observable<SchemaValidator>;
  addFormat(name: string, formatter: SchemaFormatter): void;
  addSmartDefaultProvider<T = JsonValue>(pointer: string, provider: SmartDefaultProvider<T>): void;
  registerKeywordValidator(keyword: string, validator: SchemaKeywordValidator): void;
}

/**
 * Definition for an interactive prompt during validation
 */
interface PromptDefinition {
  /** Unique identifier for the prompt */
  id: string;
  /** Question text to display to user */
  message: string;
  /** Type of prompt (input, confirm, select, etc.) */
  type: string;
  /** Default value if user provides no input */
  default?: JsonValue;
  /** Array of choices for selection prompts */
  choices?: Array<string | { name: string; value: JsonValue }>;
  /** Validation function for user input */
  validate?: (value: JsonValue) => boolean | string;
}

/**
 * Provider function for handling interactive prompts
 * @param definitions - Array of prompt definitions to display
 * @returns Promise resolving to user responses
 */
type PromptProvider = (definitions: PromptDefinition[]) => Promise<{ [id: string]: JsonValue }>;

/**
 * Visitor function for JSON schema traversal
 * @param current - Current schema node being visited
 * @param pointer - JSON pointer to current location
 * @param parentSchema - Parent schema context
 * @param index - Index in parent array (if applicable)
 * @returns Modified schema or void to leave unchanged
 */
interface JsonSchemaVisitor {
  (current: JsonObject, pointer: JsonPointer, parentSchema?: JsonObject, index?: string): JsonObject | void;
}

/**
 * Visitor function for JSON data transformation
 * @param value - Current data value being visited
 * @param pointer - JSON pointer to current location
 * @param schema - Schema context for current value
 * @param root - Root data object
 * @returns Modified value or void to leave unchanged
 */
interface JsonVisitor {
  (value: JsonValue, pointer: JsonPointer, schema?: JsonObject, root?: JsonValue): JsonValue | void;
}

/**
 * Visit and potentially transform a JSON schema using visitor pattern
 * @param schema - Schema to traverse
 * @param visitor - Visitor function to apply
 * @param root - Root schema context
 * @returns Transformed schema
 */
function visitJsonSchema(schema: JsonObject, visitor: JsonSchemaVisitor, root?: JsonObject): JsonObject;

/**
 * Visit and potentially transform JSON data using visitor pattern
 * @param data - Data to traverse
 * @param visitor - Visitor function to apply
 * @param schema - Schema context
 * @param root - Root data context
 * @returns Transformed data
 */
function visitJson(data: JsonValue, visitor: JsonVisitor, schema?: JsonObject, root?: JsonValue): JsonValue;

namespace transforms {
  /**
   * Add smart defaults to a schema based on provided defaults object
   * @param schema - Source schema
   * @param defaults - Default values to merge
   * @returns Schema with smart defaults applied
   */
  function addSmartDefaults(schema: JsonObject, defaults: JsonObject): JsonObject;
  
  /**
   * Add undefined values as valid for all properties (makes all properties optional)
   * @param schema - Source schema  
   * @returns Schema with undefined allowed for all properties
   */
  function addUndefinedDefaults(schema: JsonObject): JsonObject;
}

import { json } from "@angular-devkit/core";

// Create a schema registry
const registry = new json.schema.CoreSchemaRegistry();

// Define a schema
const userSchema = {
  type: 'object',
  properties: {
    name: { type: 'string', minLength: 1 },
    email: { type: 'string', format: 'email' },
    age: { type: 'number', minimum: 0 }
  },
  required: ['name', 'email']
};

// Compile the schema
const validator = await registry.compile(userSchema).toPromise();

// Validate data
const result = await validator({
  name: 'John Doe',
  email: 'john@example.com',
  age: 30
}).toPromise();

if (result.success) {
  console.log('Validation passed:', result.data);
} else {
  console.log('Validation failed:', result.errors);
}

import { json } from "@angular-devkit/core";

const registry = new json.schema.CoreSchemaRegistry();

// Add custom format validator
registry.addFormat('phone', {
  async: false,
  validate: (data: string) => /^\+?[\d\s-()]+$/.test(data)
});

const schema = {
  type: 'object',
  properties: {
    phoneNumber: { type: 'string', format: 'phone' }
  }
};

const validator = await registry.compile(schema).toPromise();
const result = await validator({ phoneNumber: '+1-555-123-4567' }).toPromise();

import { json } from "@angular-devkit/core";

const registry = new json.schema.CoreSchemaRegistry();

// Add smart default provider
registry.addSmartDefaultProvider('/properties/timestamp', (schema) => {
  return of(new Date().toISOString());
});

// Custom prompt provider
const promptProvider: json.schema.PromptProvider = async (definitions) => {
  const responses: { [id: string]: json.JsonValue } = {};
  for (const def of definitions) {
    // Simulate user input (in real usage, this would show actual prompts)
    responses[def.id] = def.default || '';
  }
  return responses;
};

const validator = await registry.compile(schema).toPromise();
const result = await validator(data, { 
  withPrompts: true, 
  promptProvider 
}).toPromise();