/**
 * @author Ed Spencer
 * @class Ext.data.Operation
 * @extends Object
 * 
 * <p>Represents a single read or write operation performed by a {@link Ext.data.proxy.Proxy Proxy}.
 * Operation objects are used to enable communication between Stores and Proxies. Application
 * developers should rarely need to interact with Operation objects directly.</p>
 * 
 * <p>Several Operations can be batched together in a {@link Ext.data.Batch batch}.</p>
 * 
 * @constructor
 * @param {Object} config Optional config object
 */
Ext.define('Ext.data.Operation', {
    /**
     * @cfg {Boolean} synchronous True if this Operation is to be executed synchronously (defaults to true). This
     * property is inspected by a {@link Ext.data.Batch Batch} to see if a series of Operations can be executed in
     * parallel or not.
     */
    synchronous: true,
    
    /**
     * @cfg {String} action The action being performed by this Operation. Should be one of 'create', 'read', 'update' or 'destroy'
     */
    action: undefined,
    
    /**
     * @cfg {Array} filters Optional array of filter objects. Only applies to 'read' actions.
     */
    filters: undefined,
    
    /**
     * @cfg {Array} sorters Optional array of sorter objects. Only applies to 'read' actions.
     */
    sorters: undefined,
    
    /**
     * @cfg {Object} group Optional grouping configuration. Only applies to 'read' actions where grouping is desired.
     */
    group: undefined,
    
    /**
     * @cfg {Number} start The start index (offset), used in paging when running a 'read' action.
     */
    start: undefined,
    
    /**
     * @cfg {Number} limit The number of records to load. Used on 'read' actions when paging is being used.
     */
    limit: undefined,
    
    /**
     * @cfg {Ext.data.Batch} batch The batch that this Operation is a part of (optional)
     */
    batch: undefined,
        
    /**
     * Read-only property tracking the start status of this Operation. Use {@link #isStarted}.
     * @property started
     * @type Boolean
     * @private
     */
    started: false,
    
    /**
     * Read-only property tracking the run status of this Operation. Use {@link #isRunning}.
     * @property running
     * @type Boolean
     * @private
     */
    running: false,
    
    /**
     * Read-only property tracking the completion status of this Operation. Use {@link #isComplete}.
     * @property complete
     * @type Boolean
     * @private
     */
    complete: false,
    
    /**
     * Read-only property tracking whether the Operation was successful or not. This starts as undefined and is set to true
     * or false by the Proxy that is executing the Operation. It is also set to false by {@link #setException}. Use
     * {@link #wasSuccessful} to query success status.
     * @property success
     * @type Boolean
     * @private
     */
    success: undefined,
    
    /**
     * Read-only property tracking the exception status of this Operation. Use {@link #hasException} and see {@link #getError}.
     * @property exception
     * @type Boolean
     * @private
     */
    exception: false,
    
    /**
     * The error object passed when {@link #setException} was called. This could be any object or primitive.
     * @property error
     * @type Mixed
     * @private
     */
    error: undefined,
    
    constructor: function(config) {
        Ext.apply(this, config || {});
    },
    
    /**
     * Marks the Operation as started
     */
    setStarted: function() {
        this.started = true;
        this.running = true;
    },
    
    /**
     * Marks the Operation as completed
     */
    setCompleted: function() {
        this.complete = true;
        this.running  = false;
    },
    
    /**
     * Marks the Operation as successful
     */
    setSuccessful: function() {
        this.success = true;
    },
    
    /**
     * Marks the Operation as having experienced an exception. Can be supplied with an option error message/object.
     * @param {Mixed} error Optional error string/object
     */
    setException: function(error) {
        this.exception = true;
        this.success = false;
        this.running = false;
        this.error = error;
    },
    
    /**
     * Returns true if this Operation encountered an exception (see also {@link #getError})
     * @return {Boolean} True if there was an exception
     */
    hasException: function() {
        return this.exception === true;
    },
    
    /**
     * Returns the error string or object that was set using {@link #setException}
     * @return {Mixed} The error object
     */
    getError: function() {
        return this.error;
    },
    
    /**
     * Returns an array of Ext.data.Model instances as set by the Proxy.
     * @return {Array} Any loaded Records
     */
    getRecords: function() {
        var resultSet = this.getResultSet();
        
        return (resultSet === undefined ? this.records : resultSet.records);
    },
    
    /**
     * Returns the ResultSet object (if set by the Proxy). This object will contain the {@link Ext.data.Model model} instances
     * as well as meta data such as number of instances fetched, number available etc
     * @return {Ext.data.ResultSet} The ResultSet object
     */
    getResultSet: function() {
        return this.resultSet;
    },
    
    /**
     * Returns true if the Operation has been started. Note that the Operation may have started AND completed,
     * see {@link #isRunning} to test if the Operation is currently running.
     * @return {Boolean} True if the Operation has started
     */
    isStarted: function() {
        return this.started === true;
    },
    
    /**
     * Returns true if the Operation has been started but has not yet completed.
     * @return {Boolean} True if the Operation is currently running
     */
    isRunning: function() {
        return this.running === true;
    },
    
    /**
     * Returns true if the Operation has been completed
     * @return {Boolean} True if the Operation is complete
     */
    isComplete: function() {
        return this.complete === true;
    },
    
    /**
     * Returns true if the Operation has completed and was successful
     * @return {Boolean} True if successful
     */
    wasSuccessful: function() {
        return this.isComplete() && this.success === true;
    },
    
    /**
     * @private
     * Associates this Operation with a Batch
     * @param {Ext.data.Batch} batch The batch
     */
    setBatch: function(batch) {
        this.batch = batch;
    },
    
    /**
     * Checks whether this operation should cause writing to occur.
     * @return {Boolean} Whether the operation should cause a write to occur.
     */
    allowWrite: function() {
        return this.action != 'read';
    }
});