# Yahoo! UI Library

### dataschema 3.0.0

Yahoo! UI Library > dataschema > dataschema-json.js (source view)
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    /**
     * Provides a DataSchema implementation which can be used to work with JSON data.
     *
     * @module dataschema
     * @submodule dataschema-json
     */

    /**
     * JSON subclass for the DataSchema Utility.
     * @class DataSchema.JSON
     * @extends DataSchema.Base
     * @static
     */
    var LANG = Y.Lang,

        SchemaJSON = {

            /////////////////////////////////////////////////////////////////////////////
            //
            // DataSchema.JSON static methods
            //
            /////////////////////////////////////////////////////////////////////////////
            /**
             * Utility function converts JSON locator strings into walkable paths
             *
             * @method DataSchema.JSON.getPath
             * @param locator {String} JSON value locator.
             * @return {String[]} Walkable path to data value.
             * @static
             */
            getPath: function(locator) {
                var path = null,
                    keys = [],
                    i = 0;

                if (locator) {
                    // Strip the ["string keys"] and [1] array indexes
                    locator = locator.
                        replace(/\[(['"])(.*?)\1\]/g,
                        function (x,$1,$2) {keys[i]=$2;return '.@'+(i++);}).
                        replace(/\[(\d+)\]/g,
                        function (x,$1) {keys[i]=parseInt($1,10)|0;return '.@'+(i++);}).
                        replace(/^\./,''); // remove leading dot

                    // Validate against problematic characters.
                    if (!/[^\w\.\$@]/.test(locator)) {
                        path = locator.split('.');
                        for (i=path.length-1; i >= 0; --i) {
                            if (path[i].charAt(0) === '@') {
                                path[i] = keys[parseInt(path[i].substr(1),10)];
                            }
                        }
                    }
                    else {
                        Y.log("Invalid locator: " + locator, "error", "dataschema-json");
                    }
                }
                return path;
            },

            /**
             * Utility function to walk a path and return the value located there.
             *
             * @method DataSchema.JSON.getLocationValue
             * @param path {String[]} Locator path.
             * @param data {String} Data to traverse.
             * @return {Object} Data value at location.
             * @static
             */
            getLocationValue: function (path, data) {
                var i = 0,
                    len = path.length;
                for (;i<len;i++) {
                    if(!LANG.isUndefined(data[path[i]])) {
                        data = data[path[i]];
                    }
                    else {
                        data = undefined;
                        break;
                    }
                }
                return data;
            },

            /**
             * Applies a given schema to given JSON data.
             *
             * @method apply
             * @param schema {Object} Schema to apply.
             * @param data {Object} JSON data.
             * @return {Object} Schema-parsed data.
             * @static
             */
            apply: function(schema, data) {
                var data_in = data,
                    data_out = {results:[],meta:{}};

                // Convert incoming JSON strings
                if(!LANG.isObject(data)) {
                    try {
                        data_in = Y.JSON.parse(data);
                    }
                    catch(e) {
                        data_out.error = e;
                        return data_out;
                    }
                }

                if(LANG.isObject(data_in) && schema) {
                    // Parse results data
                    if(!LANG.isUndefined(schema.resultListLocator)) {
                        data_out = SchemaJSON._parseResults(schema, data_in, data_out);
                    }

                    // Parse meta data
                    if(!LANG.isUndefined(schema.metaFields)) {
                        data_out = SchemaJSON._parseMeta(schema.metaFields, data_in, data_out);
                    }
                }
                else {
                    Y.log("JSON data could not be schema-parsed: " + Y.dump(data) + " " + Y.dump(data), "error", "dataschema-json");
                    data_out.error = new Error("JSON schema parse failure");
                }

                return data_out;
            },

            /**
             * Schema-parsed list of results from full data
             *
             * @method _parseResults
             * @param schema {Object} Schema to parse against.
             * @param json_in {Object} JSON to parse.
             * @param data_out {Object} In-progress parsed data to update.
             * @return {Object} Parsed data object.
             * @static
             * @protected
             */
            _parseResults: function(schema, json_in, data_out) {
                var results = [],
                    path,
                    error;

                if(schema.resultListLocator) {
                    path = SchemaJSON.getPath(schema.resultListLocator);
                    if(path) {
                        results = SchemaJSON.getLocationValue(path, json_in);
                        if (results === undefined) {
                            data_out.results = [];
                            error = new Error("JSON results retrieval failure");
                        }
                        else {
                            if(LANG.isArray(schema.resultFields) && LANG.isArray(results)) {
                                data_out = SchemaJSON._getFieldValues(schema.resultFields, results, data_out);
                            }
                            else {
                                data_out.results = [];
                                error = new Error("JSON Schema fields retrieval failure");
                            }
                        }
                    }
                    else {
                        error = new Error("JSON Schema results locator failure");
                    }

                    if (error) {
                        Y.log("JSON data could not be parsed: " + Y.dump(json_in), "error", "dataschema-json");
                        data_out.error = error;
                    }

                }
                return data_out;
            },

            /**
             * Get field data values out of list of full results
             *
             * @method _getFieldValues
             * @param fields {Array} Fields to find.
             * @param array_in {Array} Results to parse.
             * @param data_out {Object} In-progress parsed data to update.
             * @return {Object} Parsed data object.
             * @static
             * @protected
             */
            _getFieldValues: function(fields, array_in, data_out) {
                var results = [],
                    len = fields.length,
                    i, j,
                    field, key, path, parser,
                    simplePaths = [], complexPaths = [], fieldParsers = [],
                    result, record;

                // First collect hashes of simple paths, complex paths, and parsers
                for (i=0; i<len; i++) {
                    field = fields[i]; // A field can be a simple string or a hash
                    key = field.key || field; // Find the key

                    // Validate and store locators for later
                    path = SchemaJSON.getPath(key);
                    if (path) {
                        if (path.length === 1) {
                            simplePaths[simplePaths.length] = {key:key, path:path[0]};
                        } else {
                            complexPaths[complexPaths.length] = {key:key, path:path};
                        }
                    } else {
                        Y.log("Invalid key syntax: " + key, "warn", "dataschema-json");
                    }

                    // Validate and store parsers for later
                    //TODO: use Y.DataSchema.parse?
                    parser = (LANG.isFunction(field.parser)) ? field.parser : Y.Parsers[field.parser+''];
                    if (parser) {
                        fieldParsers[fieldParsers.length] = {key:key, parser:parser};
                    }
                }

                // Traverse list of array_in, creating records of simple fields,
                // complex fields, and applying parsers as necessary
                for (i=array_in.length-1; i>=0; --i) {
                    record = {};
                    result = array_in[i];
                    if(result) {
                        // Cycle through simpleLocators
                        for (j=simplePaths.length-1; j>=0; --j) {
                            // Bug 1777850: The result might be an array instead of object
                            record[simplePaths[j].key] = Y.DataSchema.Base.parse(
                                    (LANG.isUndefined(result[simplePaths[j].path]) ?
                                    result[j] : result[simplePaths[j].path]), simplePaths[j]);
                        }

                        // Cycle through complexLocators
                        for (j=complexPaths.length - 1; j>=0; --j) {
                            record[complexPaths[j].key] = Y.DataSchema.Base.parse(
                                (SchemaJSON.getLocationValue(complexPaths[j].path, result)), complexPaths[j] );
                        }

                        // Cycle through fieldParsers
                        for (j=fieldParsers.length-1; j>=0; --j) {
                            key = fieldParsers[j].key;
                            record[key] = fieldParsers[j].parser(record[key]);
                            // Safety net
                            if (LANG.isUndefined(record[key])) {
                                record[key] = null;
                            }
                        }
                        results[i] = record;
                    }
                }
                data_out.results = results;
                return data_out;
            },

            /**
             * Parses results data according to schema
             *
             * @method _parseMeta
             * @param metaFields {Object} Metafields definitions.
             * @param json_in {Object} JSON to parse.
             * @param data_out {Object} In-progress parsed data to update.
             * @return {Object} Schema-parsed meta data.
             * @static
             * @protected
             */
            _parseMeta: function(metaFields, json_in, data_out) {
                if(LANG.isObject(metaFields)) {
                    var key, path;
                    for(key in metaFields) {
                        if (metaFields.hasOwnProperty(key)) {
                            path = SchemaJSON.getPath(metaFields[key]);
                            if (path && json_in) {
                                data_out.meta[key] = SchemaJSON.getLocationValue(path, json_in);
                            }
                        }
                    }
                }
                else {
                    data_out.error = new Error("JSON meta data retrieval failure");
                }
                return data_out;
            }
        };

    Y.DataSchema.JSON = Y.mix(SchemaJSON, Y.DataSchema.Base);

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