'use strict';

app.crypto.Util = function(window, uuid) {
	
	/**
	 * Generates a new RFC 4122 version 4 compliant random UUID
	 */
	this.UUID = function() {
		return uuid.v4();
	};
	
	/**
	 * Generates a cryptographically secure random base64-encoded key or IV
	 * @param keySize [Number] The size of the key in bits (e.g. 128, 256)
	 * @return [String] The base64 encoded key/IV
	 */
	this.random = function(keySize) {
		var keyBase64, keyBuf;
		
		if (window.crypto && window.crypto.getRandomValues) {
			keyBuf = new Uint8Array(keySize / 8);
			window.crypto.getRandomValues(keyBuf);
			keyBase64 = window.btoa(this.uint8Arr2BinStr(keyBuf));
		} else {
			sjcl.random.addEntropy((new Date()).valueOf(), 2, "calltime");
			keyBuf = sjcl.random.randomWords(keySize / 32, 0);
			keyBase64 = sjcl.codec.base64.fromBits(keyBuf);
		}
		
		return keyBase64;
	};
	
	/**
	 * Encrypt a list of items
	 * @param aes [Object] The object implementing the aes mode
	 * @list list [Array] The list of items to encrypt
	 */
	this.encryptList = function(aes, list) {
		var i, json, ct, outList = [];
		
		for (i = 0; i < list.length; i++) {
			// stringify to JSON before encryption
			json = JSON.stringify(list[i].plaintext);
			ct = aes.encrypt(json, list[i].key, list[i].iv);
			outList.push({ id:list[i].id, ciphertext:ct, key:list[i].key, iv:list[i].iv });
		}
		
		return outList;
	};
	
	/**
	 * Decrypt a list of items
	 * @param aes [Object] The object implementing the aes mode
	 * @list list [Array] The list of items to decrypt
	 */
	this.decryptList = function(aes, list) {
		var i, json, pt, outList = [];

		for (i = 0; i < list.length; i++) {
			// decrypt JSON and parse to object literal
			json = aes.decrypt(list[i].ciphertext, list[i].key, list[i].iv);
			pt = JSON.parse(json);
			outList.push({ id:list[i].id, plaintext:pt, key:list[i].key, iv:list[i].iv });
		}

		return outList;
	};
	
	/**
	 * Parse a date string with the following format "1900-01-31 18:17:53"
	 */
	this.parseDate = function(str) {
		var parts = str.match(/(\d+)/g);
		return new Date(parts[0], parts[1] - 1, parts[2], parts[3], parts[4], parts[5]);
	};
	
	/**
	 * Converts a binary String (e.g. from the FileReader Api) to an ArrayBuffer
	 * @param str [String] a binary string with integer values (0..255) per character
	 * @return [ArrayBuffer]
	 */
	this.binStr2ArrBuf = function(str) {
		var b = new ArrayBuffer(str.length);
		var buf = new Uint8Array(b);
		
		for(var i = 0; i < b.byteLength; i++){
			buf[i] = str.charCodeAt(i);
		}

		return b;
	};
	
	/**
	 * Creates a Blob from an ArrayBuffer using the BlobBuilder Api
	 * @param str [String] a binary string with integer values (0..255) per character
	 * @return [ArrayBuffer] either a data url or a filesystem url
	 */
	this.arrBuf2Blob = function(buf, mimeType) {
        var b = new Uint8Array(buf);
        var blob = new Blob([b], {type: mimeType});
		
		return blob;
	};
	
	/**
	 * Creates a binary String from a Blob using the FileReader Api
	 * @param blob [Blob/File] a blob containing the the binary data
	 * @return [String] a binary string with integer values (0..255) per character
	 */
	this.blob2BinStr = function(blob, callback) {
		var reader = new FileReader();

		reader.onload = function(event) {
			callback(event.target.result);
		};

		reader.readAsBinaryString(blob);
	};
	
	/**
	 * Converts an ArrayBuffer to a binary String. This is a slower alternative to
	 * conversion with arrBuf2Blob -> blob2BinStr, since these use native apis,
	 * but it can be used on browsers without the BlodBuilder Api
	 * @param buf [ArrayBuffer]
	 * @return [String] a binary string with integer values (0..255) per character
	 */
	this.arrBuf2BinStr = function(buf) {
		var b = new Uint8Array(buf);
		var str = '';
		
		for(var i = 0; i < b.byteLength; i++){
			str += String.fromCharCode(b[i]);
		}
		
		return str;
	};
	
	/**
	 * Converts a UInt8Array to a binary String.
	 * @param buf [UInt8Array]
	 * @return [String] a binary string with integer values (0..255) per character
	 */
	this.uint8Arr2BinStr = function(buf) {
		var str = '';
		
		for(var i = 0; i < buf.byteLength; i++){
			str += String.fromCharCode(buf[i]);
		}
		
		return str;
	};
	
};