Model System

/**
 * Create a new model class
 * @param {string} name - Model name
 * @param {Object} properties - Model properties definition  
 * @param {Object} options - Model configuration options
 * @param {string} options.base - Base model to extend from
 * @param {Object} options.relations - Model relationships
 * @param {Object} options.validations - Validation rules
 * @param {Object} options.settings - Model settings
 * @returns {Function} Model constructor
 */
loopback.createModel(name, properties, options);

/**
 * Alternative config object approach
 * @param {Object} config - Model configuration
 * @param {string} config.name - Model name
 * @param {Object} config.properties - Properties definition
 * @param {Object} config.relations - Relationships
 * @param {Object} config.base - Base model name
 * @returns {Function} Model constructor
 */
loopback.createModel(config);

/**
 * Configure an existing model
 * @param {Function} ModelCtor - Model constructor to configure
 * @param {Object} config - Configuration to apply
 * @param {DataSource} config.dataSource - Data source to attach to
 * @param {Object} config.relations - Relations to add/update
 */
loopback.configureModel(ModelCtor, config);

/**
 * Find a model by name
 * @param {string} modelName - Model name to find
 * @returns {Function|null} Model constructor or null if not found
 */
loopback.findModel(modelName);

/**
 * Get a model by name (throws if not found)
 * @param {string} modelName - Model name to get
 * @returns {Function} Model constructor
 * @throws {Error} If model not found
 */
loopback.getModel(modelName);

/**
 * Find model by base model type
 * @param {Function} modelType - Base model constructor
 * @returns {Function} Subclass if found, or base class
 */
loopback.getModelByType(modelType);

// Create a basic model
const Book = loopback.createModel('Book', {
  title: { type: String, required: true },
  author: String,
  isbn: { type: String, index: true },
  publishedDate: Date,
  price: Number
});

// Create model with relationships and options
const Author = loopback.createModel('Author', {
  name: { type: String, required: true },
  email: { type: String, index: { unique: true } },
  bio: String
}, {
  relations: {
    books: {
      type: 'hasMany',
      model: 'Book',
      foreignKey: 'authorId'
    }
  },
  validations: {
    email: { format: 'email' }
  }
});

// Alternative config approach
const Review = loopback.createModel({
  name: 'Review',
  properties: {
    rating: { type: Number, min: 1, max: 5 },
    comment: String,
    createdAt: { type: Date, default: Date.now }
  },
  relations: {
    book: {
      type: 'belongsTo',
      model: 'Book',
      foreignKey: 'bookId'
    }
  }
});

// Configure existing model
loopback.configureModel(Book, {
  dataSource: loopback.memory(),
  relations: {
    reviews: {
      type: 'hasMany',
      model: 'Review',
      foreignKey: 'bookId'
    }
  }
});

/**
 * Base Model constructor
 * @param {Object} data - Initial model data
 */
function Model(data);

// Static methods
/**
 * Extend the model to create a subclass
 * @param {string} className - Name for the new model class
 * @param {Object} properties - Properties for the new model
 * @param {Object} settings - Settings for the new model
 * @returns {Function} New model constructor
 */
Model.extend(className, properties, settings);

/**
 * Setup the model (called automatically)
 */
Model.setup();

/**
 * Define a remote method on the model
 * @param {string} name - Method name
 * @param {Object} options - Remote method options
 * @param {Object} options.accepts - Input parameters
 * @param {Object} options.returns - Return value description
 * @param {Object} options.http - HTTP configuration
 */
Model.remoteMethod(name, options);

/**
 * Disable a remote method
 * @param {string} name - Method name to disable
 * @param {boolean} isStatic - Whether method is static
 */
Model.disableRemoteMethod(name, isStatic);

/**
 * Register before remote hook
 * @param {string} name - Remote method name or pattern
 * @param {Function} fn - Hook function
 */
Model.beforeRemote(name, fn);

/**
 * Register after remote hook
 * @param {string} name - Remote method name or pattern
 * @param {Function} fn - Hook function
 */
Model.afterRemote(name, fn);

/**
 * Register after remote error hook
 * @param {string} name - Remote method name or pattern
 * @param {Function} fn - Hook function
 */
Model.afterRemoteError(name, fn);

/**
 * Check access permission for context
 * @param {Object} token - Access token
 * @param {*} modelId - Model instance ID
 * @param {Object} sharedMethod - Shared method
 * @param {Object} ctx - Access context
 * @param {Function} callback - Callback function
 */
Model.checkAccess(token, modelId, sharedMethod, ctx, callback);

/**
 * Get the attached application
 * @param {Function} callback - Callback function
 */
Model.getApp(callback);

// Instance methods
/**
 * Check if model instance is valid
 * @param {Function} callback - Callback function
 */
model.isValid(callback);

/**
 * Trigger model hooks
 * @param {string} actionName - Action name
 * @param {Function} work - Work function
 * @param {*} data - Hook data
 * @param {Function} callback - Callback function
 */
model.trigger(actionName, work, data, callback);

/**
 * PersistedModel constructor (extends Model)
 * @param {Object} data - Initial model data
 */
function PersistedModel(data);

// Instance methods
/**
 * Save the model instance
 * @param {Object} options - Save options
 * @param {Function} callback - Callback function
 */
instance.save(options, callback);

/**
 * Delete the model instance
 * @param {Function} callback - Callback function
 */
instance.destroy(callback);

/**
 * Update a single attribute
 * @param {string} name - Attribute name
 * @param {*} value - New value
 * @param {Function} callback - Callback function
 */
instance.updateAttribute(name, value, callback);

/**
 * Update multiple attributes
 * @param {Object} data - Attributes to update
 * @param {Function} callback - Callback function
 */
instance.updateAttributes(data, callback);

/**
 * Replace all attributes
 * @param {Object} data - New attribute values
 * @param {Function} callback - Callback function
 */
instance.replaceAttributes(data, callback);

/**
 * Reload instance from database
 * @param {Function} callback - Callback function
 */
instance.reload(callback);

/**
 * Check if instance is new (not saved)
 * @returns {boolean} True if new record
 */
instance.isNewRecord();

/**
 * Set the instance ID
 * @param {*} val - ID value
 */
instance.setId(val);

/**
 * Get the instance ID
 * @returns {*} ID value
 */
instance.getId();

/**
 * Get the ID property name
 * @returns {string} ID property name
 */
instance.getIdName();

/**
 * Create new model instance(s)
 * @param {Object|Object[]} data - Data for new instance(s)
 * @param {Function} callback - Callback function
 */
Model.create(data, callback);

/**
 * Update or insert model instance
 * @param {Object} data - Instance data (must include ID for updates)
 * @param {Function} callback - Callback function
 */
Model.upsert(data, callback);

/**
 * Find existing instance or create new one
 * @param {Object} filter - Filter to find existing instance
 * @param {Object} data - Data for new instance if not found
 * @param {Function} callback - Callback function
 */
Model.findOrCreate(filter, data, callback);

/**
 * Replace existing instance or create new one
 * @param {Object} data - Instance data (must include ID)
 * @param {Function} callback - Callback function
 */
Model.replaceOrCreate(data, callback);

/**
 * Update or insert with where condition
 * @param {Object} where - Where conditions for matching existing instance
 * @param {Object} data - Data for new instance if not found
 * @param {Function} callback - Callback function
 */
Model.upsertWithWhere(where, data, callback);

/**
 * Replace instance by ID
 * @param {*} id - Instance ID
 * @param {Object} data - New instance data
 * @param {Function} callback - Callback function
 */
Model.replaceById(id, data, callback);

/**
 * Find model instances
 * @param {Object} filter - Query filter
 * @param {Object} filter.where - Where conditions
 * @param {Object} filter.include - Relations to include
 * @param {string|string[]} filter.fields - Fields to select
 * @param {number} filter.limit - Limit results
 * @param {number} filter.skip - Skip results
 * @param {string|Object} filter.order - Sort order
 * @param {Function} callback - Callback function
 */
Model.find(filter, callback);

/**
 * Find single model instance
 * @param {Object} filter - Query filter (same as find)
 * @param {Function} callback - Callback function
 */
Model.findOne(filter, callback);

/**
 * Find model instance by ID
 * @param {*} id - Instance ID
 * @param {Object} filter - Additional filter options
 * @param {Function} callback - Callback function
 */
Model.findById(id, filter, callback);

/**
 * Check if instance exists
 * @param {*} id - Instance ID
 * @param {Function} callback - Callback function
 */
Model.exists(id, callback);

/**
 * Count model instances
 * @param {Object} where - Where conditions
 * @param {Function} callback - Callback function
 */
Model.count(where, callback);

/**
 * Update model instances
 * @param {Object} where - Where conditions
 * @param {Object} data - Data to update
 * @param {Function} callback - Callback function
 */
Model.update(where, data, callback);

/**
 * Update all matching instances (alias for update)
 * @param {Object} where - Where conditions
 * @param {Object} data - Data to update
 * @param {Function} callback - Callback function
 */
Model.updateAll(where, data, callback);

/**
 * Delete instance by ID
 * @param {*} id - Instance ID
 * @param {Function} callback - Callback function  
 */
Model.destroyById(id, callback);

/**
 * Delete all matching instances
 * @param {Object} where - Where conditions
 * @param {Function} callback - Callback function
 */
Model.destroyAll(where, callback);

// Create instances
Book.create({
  title: 'The Great Gatsby',
  author: 'F. Scott Fitzgerald',
  isbn: '978-0-7432-7356-5'
}, (err, book) => {
  console.log('Created:', book.id);
});

// Find with filter
Book.find({
  where: { author: { like: '%Fitzgerald%' } },
  include: 'reviews',
  limit: 10,
  order: 'publishedDate DESC'
}, (err, books) => {
  console.log('Found books:', books.length);
});

// Update instances
Book.updateAll(
  { author: 'F. Scott Fitzgerald' },
  { author: 'Francis Scott Fitzgerald' }, 
  (err, info) => {
    console.log('Updated:', info.count);
  }
);

/**
 * Create a change stream for real-time updates
 * @param {Object} options - Stream options
 * @param {Function} callback - Callback function
 */
Model.createChangeStream(options, callback);

/**
 * Get changes since a checkpoint
 * @param {number} since - Checkpoint ID
 * @param {Object} filter - Optional filter
 * @param {Function} callback - Callback function
 */
Model.changes(since, filter, callback);

/**
 * Replicate changes to another model
 * @param {number} since - Checkpoint ID  
 * @param {Function} targetModel - Target model constructor
 * @param {Object} options - Replication options
 * @param {Function} callback - Callback function
 */
Model.replicate(since, targetModel, options, callback);

/**
 * Get the Change model for this model
 * @returns {Function} Change model constructor
 */
Model.getChangeModel();

/**
 * Get source ID for replication
 * @param {Function} callback - Callback function
 */
Model.getSourceId(callback);

/**
 * Model registry for managing models and data sources
 */
class Registry {
  /**
   * Create new registry instance
   */
  constructor();

  /**
   * Registry methods (same as loopback static methods)
   */
  createModel(name, properties, options);
  configureModel(ModelCtor, config);
  findModel(modelName);
  getModel(modelName);
  getModelByType(modelType);
  createDataSource(name, options);
  memory(name);
}

/**
 * Model property definition
 */
interface PropertyDefinition {
  type: Function;              // Property type (String, Number, Date, etc.)
  required?: boolean;          // Whether property is required
  default?: any;              // Default value
  index?: boolean | Object;   // Index configuration
  unique?: boolean;           // Unique constraint
  min?: number;               // Minimum value (numbers)
  max?: number;               // Maximum value (numbers)
  length?: number;            // String length
  format?: string;            // Validation format
}

/**
 * Model relationship definition
 */
interface RelationDefinition {
  type: string;               // Relationship type: hasMany, belongsTo, hasOne, etc.
  model: string;              // Related model name
  foreignKey?: string;        // Foreign key property
  through?: string;           // Through model for many-to-many
  as?: string;               // Relationship alias
  options?: Object;          // Additional relationship options
}

/**
 * Model validation definition
 */
interface ValidationDefinition {
  [propertyName: string]: {
    presence?: boolean;
    length?: { min?: number; max?: number };
    format?: string | RegExp;
    inclusion?: { in: any[] };
    exclusion?: { in: any[] };
    uniqueness?: boolean;
    custom?: Function;
  };
}