/**
 * @author Ed Spencer
 *
 * WebStorageProxy is simply a superclass for the {@link Ext.data.proxy.LocalStorage LocalStorage} and {@link
 * Ext.data.proxy.SessionStorage SessionStorage} proxies. It uses the new HTML5 key/value client-side storage objects to
 * save {@link Ext.data.Model model instances} for offline use.
 * @private
 */
Ext.define('Ext.data.proxy.WebStorage', {
    extend: 'Ext.data.proxy.Client',
    alternateClassName: 'Ext.data.WebStorageProxy',
    requires: [
        'Ext.data.SequentialIdGenerator'
    ],

    /**
     * @cfg {String} id
     * The unique ID used as the key in which all record data are stored in the local storage object.
     */
    id: undefined,

    /**
     * Creates the proxy, throws an error if local storage is not supported in the current browser.
     * @param {Object} config (optional) Config object.
     */
    constructor: function(config) {
        this.callParent(arguments);

        /**
         * @property {Object} cache
         * Cached map of records already retrieved by this Proxy. Ensures that the same instance is always retrieved.
         */
        this.cache = {};

        //<debug>
        if (this.getStorageObject() === undefined) {
            Ext.Error.raise("Local Storage is not supported in this browser, please use another type of data proxy");
        }
        //</debug>

        //if an id is not given, try to use the store's id instead
        this.id = this.id || (this.store ? this.store.storeId : undefined);

        //<debug>
        if (this.id === undefined) {
            Ext.Error.raise("No unique id was provided to the local storage proxy. See Ext.data.proxy.LocalStorage documentation for details");
        }
        //</debug>

        this.initialize();
    },

    //inherit docs
    create: function(operation, callback, scope) {
        var me = this,
            records = operation.records,
            length = records.length,
            ids = me.getIds(),
            id, record, i;

        operation.setStarted();

        if(me.isHierarchical === undefined) {
            // if the storage object does not yet contain any data, this is the first point at which we can determine whether or not this proxy deals with hierarchical data.
            // it cannot be determined during initialization because the Model is not decorated with NodeInterface until it is used in a TreeStore
            me.isHierarchical = !!records[0].isNode;
            if(me.isHierarchical) {
                me.getStorageObject().setItem(me.getTreeKey(), true);
            }
        }

        for (i = 0; i < length; i++) {
            record = records[i];

            if (record.phantom) {
                record.phantom = false;
                id = me.getNextId();
            } else {
                id = record.getId();
            }

            me.setRecord(record, id);
            record.commit();
            ids.push(id);
        }

        me.setIds(ids);

        operation.setCompleted();
        operation.setSuccessful();

        if (typeof callback == 'function') {
            callback.call(scope || me, operation);
        }
    },

    //inherit docs
    read: function(operation, callback, scope) {
        //TODO: respect sorters, filters, start and limit options on the Operation

        var me = this,
            records = [],
            i = 0,
            success = true,
            Model = me.model,
            ids, length, record, data, id;

        operation.setStarted();

        if(me.isHierarchical) {
            records = me.getTreeData();
        } else {
            ids = me.getIds();
            length = ids.length;
            id = operation.id;
            //read a single record
            if (id) {
                data = me.getRecord(id);
                if (data !== null) {
                    record = new Model(data, id, data);
                }

                if (record) {
                    records.push(record);
                } else {
                    success = false;
                }
            } else {
                for (; i < length; i++) {
                    id = ids[i];
                    data = me.getRecord(id);
                    records.push(new Model(data, id, data));
                }
            }

        }

        if(success) {
            operation.setSuccessful();
        }
        operation.setCompleted();

        operation.resultSet = Ext.create('Ext.data.ResultSet', {
            records: records,
            total  : records.length,
            loaded : true
        });

        if (typeof callback == 'function') {
            callback.call(scope || me, operation);
        }
    },

    //inherit docs
    update: function(operation, callback, scope) {
        var records = operation.records,
            length  = records.length,
            ids     = this.getIds(),
            record, id, i;

        operation.setStarted();

        for (i = 0; i < length; i++) {
            record = records[i];
            this.setRecord(record);
            record.commit();

            //we need to update the set of ids here because it's possible that a non-phantom record was added
            //to this proxy - in which case the record's id would never have been added via the normal 'create' call
            id = record.getId();
            if (id !== undefined && Ext.Array.indexOf(ids, id) == -1) {
                ids.push(id);
            }
        }
        this.setIds(ids);

        operation.setCompleted();
        operation.setSuccessful();

        if (typeof callback == 'function') {
            callback.call(scope || this, operation);
        }
    },

    //inherit
    destroy: function(operation, callback, scope) {
        var me = this,
            records = operation.records,
            ids = me.getIds(),
            idLength = ids.length,
            newIds = [],
            removedHash = {},
            i = records.length,
            id;

        operation.setStarted();

        for (; i--;) {
            Ext.apply(removedHash, me.removeRecord(records[i]));
        }

        for(i = 0; i < idLength; i++) {
            id = ids[i];
            if(!removedHash[id]) {
                newIds.push(id);
            }
        }

        me.setIds(newIds);

        operation.setCompleted();
        operation.setSuccessful();

        if (typeof callback == 'function') {
            callback.call(scope || me, operation);
        }
    },

    /**
     * @private
     * Fetches record data from the Proxy by ID.
     * @param {String} id The record's unique ID
     * @return {Object} The record data
     */
    getRecord: function(id) {
        var me = this,
            cache = me.cache,
            data = !cache[id] ? Ext.decode(me.getStorageObject().getItem(me.getRecordKey(id))) : cache[id];

        if(!data) {
            return null;
        }

        cache[id] = data;
        data[me.model.prototype.idProperty] = id;

        return data;
    },

    /**
     * Saves the given record in the Proxy.
     * @param {Ext.data.Model} record The model instance
     * @param {String} [id] The id to save the record under (defaults to the value of the record's getId() function)
     */
    setRecord: function(record, id) {
        if (id) {
            record.setId(id);
        } else {
            id = record.getId();
        }

        var me = this,
            rawData = record.data,
            data    = {},
            model   = me.model,
            fields  = model.prototype.fields.items,
            length  = fields.length,
            i = 0,
            field, name, obj, key;

        for (; i < length; i++) {
            field = fields[i];
            name  = field.name;

            if(field.persist) {
                data[name] = rawData[name];
            }
        }

        // no need to store the id in the data, since it is already stored in the record key
        delete data[me.model.prototype.idProperty];

        // if the record is a tree node and it's a direct child of the root node, do not store the parentId
        if(record.isNode && record.get('depth') === 1) {
            delete data.parentId;
        }

        obj = me.getStorageObject();
        key = me.getRecordKey(id);

        //keep the cache up to date
        me.cache[id] = data;

        //iPad bug requires that we remove the item before setting it
        obj.removeItem(key);
        obj.setItem(key, Ext.encode(data));
    },

    /**
     * @private
     * Physically removes a given record from the local storage and recursively removes children if the record is a tree node. Used internally by {@link #destroy}.
     * @param {Ext.data.Model} record The record to remove
     * @return {Object} a hash with the ids of the records that were removed as keys and the records that were removed as values
     */
    removeRecord: function(record) {
        var me = this,
            id = record.getId(),
            records = {},
            i, childNodes;

        records[id] = record;
        me.getStorageObject().removeItem(me.getRecordKey(id));
        delete me.cache[id];

        if(record.childNodes) {
            childNodes = record.childNodes;
            for(i = childNodes.length; i--;) {
                Ext.apply(records, me.removeRecord(childNodes[i]));
            }
        }

        return records;
    },

    /**
     * @private
     * Given the id of a record, returns a unique string based on that id and the id of this proxy. This is used when
     * storing data in the local storage object and should prevent naming collisions.
     * @param {String/Number/Ext.data.Model} id The record id, or a Model instance
     * @return {String} The unique key for this record
     */
    getRecordKey: function(id) {
        if (id.isModel) {
            id = id.getId();
        }

        return Ext.String.format("{0}-{1}", this.id, id);
    },

    /**
     * @private
     * Returns the unique key used to store the current record counter for this proxy. This is used internally when
     * realizing models (creating them when they used to be phantoms), in order to give each model instance a unique id.
     * @return {String} The counter key
     */
    getRecordCounterKey: function() {
        return Ext.String.format("{0}-counter", this.id);
    },

    /**
     * @private
     * Returns the unique key used to store the tree indicator. This is used internally to determine if the stored data is hierarchical
     * @return {String} The counter key
     */
    getTreeKey: function() {
        return Ext.String.format("{0}-tree", this.id);
    },

    /**
     * @private
     * Returns the array of record IDs stored in this Proxy
     * @return {Number[]} The record IDs. Each is cast as a Number
     */
    getIds: function() {
        var me = this,
            ids = (me.getStorageObject().getItem(me.id) || "").split(","),
            model = me.model,
            length = ids.length,
            isString = model.prototype.fields.get(model.prototype.idProperty).type.type === 'string',
            i;

        if (length == 1 && ids[0] === "") {
            ids = [];
        } else {
            for (i = 0; i < length; i++) {
                ids[i] = isString ? ids[i] : +ids[i];
            }
        }

        return ids;
    },

    /**
     * @private
     * Saves the array of ids representing the set of all records in the Proxy
     * @param {Number[]} ids The ids to set
     */
    setIds: function(ids) {
        var obj = this.getStorageObject(),
            str = ids.join(",");

        obj.removeItem(this.id);

        if (!Ext.isEmpty(str)) {
            obj.setItem(this.id, str);
        }
    },

    /**
     * @private
     * Returns the next numerical ID that can be used when realizing a model instance (see getRecordCounterKey).
     * Increments the counter.
     * @return {Number} The id
     */
    getNextId: function() {
        var me = this,
            obj = me.getStorageObject(),
            key = me.getRecordCounterKey(),
            model = me.model,
            isString = model.prototype.fields.get(model.prototype.idProperty).type.type === 'string',
            id;

        id = me.idGenerator.generate();

        obj.setItem(key, id);

        if(!isString) {
            id = +id;
        }

        return id;
    },

    /**
     * Gets tree data and transforms it from key value pairs into a hierarchical structure.
     * @private
     * @return {Ext.data.NodeInterface[]}
     */
    getTreeData: function() {
        var me = this,
            ids = me.getIds(),
            length = ids.length,
            records = [],
            recordHash = {},
            root = [],
            i = 0,
            Model = me.model,
            idProperty = Model.prototype.idProperty,
            rootLength, record, parent, parentId, children, id;

        for(; i < length; i++) {
            id = ids[i];
            // get the record for each id
            record = me.getRecord(id);
            // push the record into the records array
            records.push(record);
            // add the record to the record hash so it can be easily retrieved by id later
            recordHash[id] = record;
            if(!record.parentId) {
                // push records that are at the root level (those with no parent id) into the "root" array
                root.push(record);
            }
        }

        rootLength = root.length;

        // sort the records by parent id for greater efficiency, so that each parent record only has to be found once for all of its children
        Ext.Array.sort(records, me.sortByParentId);

        // append each record to its parent, starting after the root node(s), since root nodes do not need to be attached to a parent
        for(i = rootLength; i < length; i++) {
            record = records[i];
            parentId = record.parentId;
            if(!parent || parent[idProperty] !== parentId) {
                // if this record has a different parent id from the previous record, we need to look up the parent by id.
                parent = recordHash[parentId];
                parent.children = children = [];
            }

            // push the record onto its parent's children array
            children.push(record);
        }

        for(i = length; i--;) {
            record = records[i];
            if(!record.children && !record.leaf) {
                // set non-leaf nodes with no children to loaded so the proxy won't try to dynamically load their contents when they are expanded
                record.loaded = true;
            }
        }

        // Create model instances out of all the "root-level" nodes.
        for(i = rootLength; i--;) {
            record = root[i];
            root[i] = new Model(record, record[idProperty], record);
        }

        return root;
    },

    /**
     * Sorter function for sorting records by parentId
     * @private
     * @param {Object} node1
     * @param {Object} node2
     * @return {Number}
     */
    sortByParentId: function(node1, node2) {
        return (node1.parentId || 0) - (node2.parentId || 0);
    },

    /**
     * @private
     * Sets up the Proxy by claiming the key in the storage object that corresponds to the unique id of this Proxy. Called
     * automatically by the constructor, this should not need to be called again unless {@link #clear} has been called.
     */
    initialize: function() {
        var me = this,
            storageObject = me.getStorageObject(),
            lastId = +storageObject.getItem(me.getRecordCounterKey());

        storageObject.setItem(me.id, storageObject.getItem(me.id) || "");
        if(storageObject.getItem(me.getTreeKey())) {
            me.isHierarchical = true;
        }

        me.idGenerator = new Ext.data.SequentialIdGenerator({
            seed: lastId ? lastId + 1 : 1
        });
    },

    /**
     * Destroys all records stored in the proxy and removes all keys and values used to support the proxy from the
     * storage object.
     */
    clear: function() {
        var me = this,
            obj = me.getStorageObject(),
            ids = me.getIds(),
            len = ids.length,
            i;

        //remove all the records
        for (i = 0; i < len; i++) {
            obj.removeItem(me.getRecordKey(ids[i]));
        }

        //remove the supporting objects
        obj.removeItem(me.getRecordCounterKey());
        obj.removeItem(me.getTreeKey());
        obj.removeItem(me.id);

        // clear the cache
        me.cache = {};
    },

    /**
     * @private
     * Abstract function which should return the storage object that data will be saved to. This must be implemented
     * in each subclass.
     * @return {Object} The storage object
     */
    getStorageObject: function() {
        //<debug>
        Ext.Error.raise("The getStorageObject function has not been defined in your Ext.data.proxy.WebStorage subclass");
        //</debug>
    }
});