/**
 * @class Ext.String
 *
 * A collection of useful static methods to deal with strings
 * @singleton
 */

Ext.String = {
    trimRegex: /^[\x09\x0a\x0b\x0c\x0d\x20\xa0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u202f\u205f\u3000]+|[\x09\x0a\x0b\x0c\x0d\x20\xa0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u202f\u205f\u3000]+$/g,
    escapeRe: /('|\\)/g,
    formatRe: /\{(\d+)\}/g,
    escapeRegexRe: /([-.*+?^${}()|[\]\/\\])/g,

    /**
     * Convert certain characters (&, <, >, and ') to their HTML character equivalents for literal display in web pages.
     * @param {String} value The string to encode
     * @return {String} The encoded text
     * @method
     */
    htmlEncode: (function() {
        var entities = {
            '&': '&amp;',
            '>': '&gt;',
            '<': '&lt;',
            '"': '&quot;'
        }, keys = [], p, regex;
        
        for (p in entities) {
            keys.push(p);
        }
        
        regex = new RegExp('(' + keys.join('|') + ')', 'g');
        
        return function(value) {
            return (!value) ? value : String(value).replace(regex, function(match, capture) {
                return entities[capture];    
            });
        };
    })(),

    /**
     * Convert certain characters (&, <, >, and ') from their HTML character equivalents.
     * @param {String} value The string to decode
     * @return {String} The decoded text
     * @method
     */
    htmlDecode: (function() {
        var entities = {
            '&amp;': '&',
            '&gt;': '>',
            '&lt;': '<',
            '&quot;': '"'
        }, keys = [], p, regex;
        
        for (p in entities) {
            keys.push(p);
        }
        
        regex = new RegExp('(' + keys.join('|') + '|&#[0-9]{1,5};' + ')', 'g');
        
        return function(value) {
            return (!value) ? value : String(value).replace(regex, function(match, capture) {
                if (capture in entities) {
                    return entities[capture];
                } else {
                    return String.fromCharCode(parseInt(capture.substr(2), 10));
                }
            });
        };
    })(),

    /**
     * Appends content to the query string of a URL, handling logic for whether to place
     * a question mark or ampersand.
     * @param {String} url The URL to append to.
     * @param {String} string The content to append to the URL.
     * @return (String) The resulting URL
     */
    urlAppend : function(url, string) {
        if (!Ext.isEmpty(string)) {
            return url + (url.indexOf('?') === -1 ? '?' : '&') + string;
        }

        return url;
    },

    /**
     * Trims whitespace from either end of a string, leaving spaces within the string intact.  Example:
     * @example
var s = '  foo bar  ';
alert('-' + s + '-');         //alerts "- foo bar -"
alert('-' + Ext.String.trim(s) + '-');  //alerts "-foo bar-"

     * @param {String} string The string to escape
     * @return {String} The trimmed string
     */
    trim: function(string) {
        return string.replace(Ext.String.trimRegex, "");
    },

    /**
     * Capitalize the given string
     * @param {String} string
     * @return {String}
     */
    capitalize: function(string) {
        return string.charAt(0).toUpperCase() + string.substr(1);
    },

    /**
     * Truncate a string and add an ellipsis ('...') to the end if it exceeds the specified length
     * @param {String} value The string to truncate
     * @param {Number} length The maximum length to allow before truncating
     * @param {Boolean} word True to try to find a common word break
     * @return {String} The converted text
     */
    ellipsis: function(value, len, word) {
        if (value && value.length > len) {
            if (word) {
                var vs = value.substr(0, len - 2),
                index = Math.max(vs.lastIndexOf(' '), vs.lastIndexOf('.'), vs.lastIndexOf('!'), vs.lastIndexOf('?'));
                if (index !== -1 && index >= (len - 15)) {
                    return vs.substr(0, index) + "...";
                }
            }
            return value.substr(0, len - 3) + "...";
        }
        return value;
    },

    /**
     * Escapes the passed string for use in a regular expression
     * @param {String} string
     * @return {String}
     */
    escapeRegex: function(string) {
        return string.replace(Ext.String.escapeRegexRe, "\\$1");
    },

    /**
     * Escapes the passed string for ' and \
     * @param {String} string The string to escape
     * @return {String} The escaped string
     */
    escape: function(string) {
        return string.replace(Ext.String.escapeRe, "\\$1");
    },

    /**
     * Utility function that allows you to easily switch a string between two alternating values.  The passed value
     * is compared to the current string, and if they are equal, the other value that was passed in is returned.  If
     * they are already different, the first value passed in is returned.  Note that this method returns the new value
     * but does not change the current string.
     * <pre><code>
    // alternate sort directions
    sort = Ext.String.toggle(sort, 'ASC', 'DESC');

    // instead of conditional logic:
    sort = (sort == 'ASC' ? 'DESC' : 'ASC');
       </code></pre>
     * @param {String} string The current string
     * @param {String} value The value to compare to the current string
     * @param {String} other The new value to use if the string already equals the first value passed in
     * @return {String} The new value
     */
    toggle: function(string, value, other) {
        return string === value ? other : value;
    },

    /**
     * Pads the left side of a string with a specified character.  This is especially useful
     * for normalizing number and date strings.  Example usage:
     *
     * <pre><code>
var s = Ext.String.leftPad('123', 5, '0');
// s now contains the string: '00123'
       </code></pre>
     * @param {String} string The original string
     * @param {Number} size The total length of the output string
     * @param {String} character (optional) The character with which to pad the original string (defaults to empty string " ")
     * @return {String} The padded string
     */
    leftPad: function(string, size, character) {
        var result = String(string);
        character = character || " ";
        while (result.length < size) {
            result = character + result;
        }
        return result;
    },

    /**
     * Allows you to define a tokenized string and pass an arbitrary number of arguments to replace the tokens.  Each
     * token must be unique, and must increment in the format {0}, {1}, etc.  Example usage:
     * <pre><code>
var cls = 'my-class', text = 'Some text';
var s = Ext.String.format('&lt;div class="{0}">{1}&lt;/div>', cls, text);
// s now contains the string: '&lt;div class="my-class">Some text&lt;/div>'
       </code></pre>
     * @param {String} string The tokenized string to be formatted
     * @param {String} value1 The value to replace token {0}
     * @param {String} value2 Etc...
     * @return {String} The formatted string
     */
    format: function(format) {
        var args = Ext.Array.toArray(arguments, 1);
        return format.replace(Ext.String.formatRe, function(m, i) {
            return args[i];
        });
    }
};
