/**
 * @author Ed Spencer
 * @class Ext.data.Field
 * @extends Object
 * 
 * <p>Fields are used to define what a Model is. They aren't instantiated directly - instead, when we create a class 
 * that extends {@link Ext.data.Model}, it will automatically create a Field instance for each field configured in a 
 * {@link Ext.data.Model Model}. For example, we might set up a model like this:</p>
 * 
<pre><code>
Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        'name', 'email',
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'}
    ]
});
</code></pre>
 * 
 * <p>Four fields will have been created for the User Model - name, email, age and gender. Note that we specified a
 * couple of different formats here; if we only pass in the string name of the field (as with name and email), the
 * field is set up with the 'auto' type. It's as if we'd done this instead:</p>
 * 
<pre><code>
Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        {name: 'name', type: 'auto'},
        {name: 'email', type: 'auto'},
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'}
    ]
});
</code></pre>
 * 
 * <p><u>Types and conversion</u></p>
 * 
 * <p>The {@link #type} is important - it's used to automatically convert data passed to the field into the correct
 * format. In our example above, the name and email fields used the 'auto' type and will just accept anything that is
 * passed into them. The 'age' field had an 'int' type however, so if we passed 25.4 this would be rounded to 25.</p>
 * 
 * <p>Sometimes a simple type isn't enough, or we want to perform some processing when we load a Field's data. We can
 * do this using a {@link #convert} function. Here, we're going to create a new field based on another:</p>
 * 
<code><pre>
Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        'name', 'email',
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'},

        {
            name: 'firstName',
            convert: function(value, record) {
                var fullName  = record.get('name'),
                    splits    = fullName.split(" "),
                    firstName = splits[0];

                return firstName;
            }
        }
    ]
});
</code></pre>
 * 
 * <p>Now when we create a new User, the firstName is populated automatically based on the name:</p>
 * 
<code><pre>
var ed = Ext.ModelManager.create({name: 'Ed Spencer'}, 'User');

console.log(ed.get('firstName')); //logs 'Ed', based on our convert function
</code></pre>
 * 
 * <p>In fact, if we log out all of the data inside ed, we'll see this:</p>
 * 
<code><pre>
console.log(ed.data);

//outputs this:
{
    age: 0,
    email: "",
    firstName: "Ed",
    gender: "Unknown",
    name: "Ed Spencer"
}
</code></pre>
 * 
 * <p>The age field has been given a default of zero because we made it an int type. As an auto field, email has
 * defaulted to an empty string. When we registered the User model we set gender's {@link #defaultValue} to 'Unknown'
 * so we see that now. Let's correct that and satisfy ourselves that the types work as we expect:</p>
 * 
<code><pre>
ed.set('gender', 'Male');
ed.get('gender'); //returns 'Male'

ed.set('age', 25.4);
ed.get('age'); //returns 25 - we wanted an int, not a float, so no decimal places allowed
</code></pre>
 * 
 */
Ext.define('Ext.data.Field', {
    requires: ['Ext.data.Types', 'Ext.data.SortTypes'],
    alias: 'data.field',
    
    constructor : function(config) {
        if (Ext.isString(config)) {
            config = {name: config};
        }
        Ext.apply(this, config);
        
        var types = Ext.data.Types,
            st = this.sortType,
            t;

        if (this.type) {
            if (Ext.isString(this.type)) {
                this.type = types[this.type.toUpperCase()] || types.AUTO;
            }
        } else {
            this.type = types.AUTO;
        }

        // named sortTypes are supported, here we look them up
        if (Ext.isString(st)) {
            this.sortType = Ext.data.SortTypes[st];
        } else if(Ext.isEmpty(st)) {
            this.sortType = this.type.sortType;
        }

        if (!this.convert) {
            this.convert = this.type.convert;
        }
    },
    
    /**
     * @cfg {String} name
     * The name by which the field is referenced within the Model. This is referenced by, for example,
     * the <code>dataIndex</code> property in column definition objects passed to {@link Ext.grid.property.HeaderContainer}.
     * <p>Note: In the simplest case, if no properties other than <code>name</code> are required, a field
     * definition may consist of just a String for the field name.</p>
     */
    
    /**
     * @cfg {Mixed} type
     * (Optional) The data type for automatic conversion from received data to the <i>stored</i> value if <code>{@link Ext.data.Field#convert convert}</code>
     * has not been specified. This may be specified as a string value. Possible values are
     * <div class="mdetail-params"><ul>
     * <li>auto (Default, implies no conversion)</li>
     * <li>string</li>
     * <li>int</li>
     * <li>float</li>
     * <li>boolean</li>
     * <li>date</li></ul></div>
     * <p>This may also be specified by referencing a member of the {@link Ext.data.Types} class.</p>
     * <p>Developers may create their own application-specific data types by defining new members of the
     * {@link Ext.data.Types} class.</p>
     */
    
    /**
     * @cfg {Function} convert
     * (Optional) A function which converts the value provided by the Reader into an object that will be stored
     * in the Model. It is passed the following parameters:<div class="mdetail-params"><ul>
     * <li><b>v</b> : Mixed<div class="sub-desc">The data value as read by the Reader, if undefined will use
     * the configured <code>{@link Ext.data.Field#defaultValue defaultValue}</code>.</div></li>
     * <li><b>rec</b> : Ext.data.Model<div class="sub-desc">The data object containing the Model as read so far by the 
     * Reader. Note that the Model may not be fully populated at this point as the fields are read in the order that 
     * they are defined in your {@link #fields} array.</div></li>
     * </ul></div>
     * <pre><code>
// example of convert function
function fullName(v, record){
    return record.name.last + ', ' + record.name.first;
}

function location(v, record){
    return !record.city ? '' : (record.city + ', ' + record.state);
}

Ext.define('Dude', {
    extend: 'Ext.data.Model',
    fields: [
        {name: 'fullname',  convert: fullName},
        {name: 'firstname', mapping: 'name.first'},
        {name: 'lastname',  mapping: 'name.last'},
        {name: 'city', defaultValue: 'homeless'},
        'state',
        {name: 'location',  convert: location}
    ]
});

// create the data store
var store = new Ext.data.Store({
    reader: {
        type: 'json',
        model: 'Dude',
        idProperty: 'key',
        root: 'daRoot',
        totalProperty: 'total'
    }
});

var myData = [
    { key: 1,
      name: { first: 'Fat',    last:  'Albert' }
      // notice no city, state provided in data object
    },
    { key: 2,
      name: { first: 'Barney', last:  'Rubble' },
      city: 'Bedrock', state: 'Stoneridge'
    },
    { key: 3,
      name: { first: 'Cliff',  last:  'Claven' },
      city: 'Boston',  state: 'MA'
    }
];
     * </code></pre>
     */
    /**
     * @cfg {String} dateFormat
     * <p>(Optional) Used when converting received data into a Date when the {@link #type} is specified as <code>"date"</code>.</p>
     * <p>A format string for the {@link Ext.Date#parse Ext.Date.parse} function, or "timestamp" if the
     * value provided by the Reader is a UNIX timestamp, or "time" if the value provided by the Reader is a
     * javascript millisecond timestamp. See {@link Date}</p>
     */
    dateFormat: null,
    
    /**
     * @cfg {Boolean} useNull
     * <p>(Optional) Use when converting received data into a Number type (either int or float). If the value cannot be parsed,
     * null will be used if useNull is true, otherwise the value will be 0. Defaults to <tt>false</tt>
     */
    useNull: false,
    
    /**
     * @cfg {Mixed} defaultValue
     * (Optional) The default value used <b>when a Model is being created by a {@link Ext.data.reader.Reader Reader}</b>
     * when the item referenced by the <code>{@link Ext.data.Field#mapping mapping}</code> does not exist in the data
     * object (i.e. undefined). (defaults to "")
     */
    defaultValue: "",
    /**
     * @cfg {String/Number} mapping
     * <p>(Optional) A path expression for use by the {@link Ext.data.reader.Reader} implementation
     * that is creating the {@link Ext.data.Model Model} to extract the Field value from the data object.
     * If the path expression is the same as the field name, the mapping may be omitted.</p>
     * <p>The form of the mapping expression depends on the Reader being used.</p>
     * <div class="mdetail-params"><ul>
     * <li>{@link Ext.data.reader.Json}<div class="sub-desc">The mapping is a string containing the javascript
     * expression to reference the data from an element of the data item's {@link Ext.data.reader.Json#root root} Array. Defaults to the field name.</div></li>
     * <li>{@link Ext.data.reader.Xml}<div class="sub-desc">The mapping is an {@link Ext.DomQuery} path to the data
     * item relative to the DOM element that represents the {@link Ext.data.reader.Xml#record record}. Defaults to the field name.</div></li>
     * <li>{@link Ext.data.reader.Array}<div class="sub-desc">The mapping is a number indicating the Array index
     * of the field's value. Defaults to the field specification's Array position.</div></li>
     * </ul></div>
     * <p>If a more complex value extraction strategy is required, then configure the Field with a {@link #convert}
     * function. This is passed the whole row object, and may interrogate it in whatever way is necessary in order to
     * return the desired data.</p>
     */
    mapping: null,
    /**
     * @cfg {Function} sortType
     * (Optional) A function which converts a Field's value to a comparable value in order to ensure
     * correct sort ordering. Predefined functions are provided in {@link Ext.data.SortTypes}. A custom
     * sort example:<pre><code>
// current sort     after sort we want
// +-+------+          +-+------+
// |1|First |          |1|First |
// |2|Last  |          |3|Second|
// |3|Second|          |2|Last  |
// +-+------+          +-+------+

sortType: function(value) {
   switch (value.toLowerCase()) // native toLowerCase():
   {
      case 'first': return 1;
      case 'second': return 2;
      default: return 3;
   }
}
     * </code></pre>
     */
    sortType : null,
    /**
     * @cfg {String} sortDir
     * (Optional) Initial direction to sort (<code>"ASC"</code> or  <code>"DESC"</code>).  Defaults to
     * <code>"ASC"</code>.
     */
    sortDir : "ASC",
    /**
     * @cfg {Boolean} allowBlank
     * @private
     * (Optional) Used for validating a {@link Ext.data.Model model}, defaults to <code>true</code>.
     * An empty value here will cause {@link Ext.data.Model}.{@link Ext.data.Model#isValid isValid}
     * to evaluate to <code>false</code>.
     */
    allowBlank : true,
    
    /**
     * @cfg {Boolean} persist
     * False to exclude this field from the {@link Ext.data.Model#modified} fields in a model. This 
     * will also exclude the field from being written using a {@link Ext.data.writer.Writer}. This option
     * is useful when model fields are used to keep state on the client but do not need to be persisted
     * to the server. Defaults to <tt>true</tt>.
     */
    persist: true
});