(function(){

	'use strict';

var
/** @const */ FormatOptions = [
	'decimals',
	'thousand',
	'mark',
	'prefix',
	'postfix',
	'encoder',
	'decoder',
	'negativeBefore',
	'negative',
	'edit',
	'undo'
];

// General

	// Reverse a string
	function strReverse ( a ) {
		return a.split('').reverse().join('');
	}

	// Check if a string starts with a specified prefix.
	function strStartsWith ( input, match ) {
		return input.substring(0, match.length) === match;
	}

	// Check is a string ends in a specified postfix.
	function strEndsWith ( input, match ) {
		return input.slice(-1 * match.length) === match;
	}

	// Throw an error if formatting options are incompatible.
	function throwEqualError( F, a, b ) {
		if ( (F[a] || F[b]) && (F[a] === F[b]) ) {
			throw new Error(a);
		}
	}

	// Check if a number is finite and not NaN
	function isValidNumber ( input ) {
		return typeof input === 'number' && isFinite( input );
	}

	// Provide rounding-accurate toFixed method.
	function toFixed ( value, decimals ) {
		var scale = Math.pow(10, decimals);
		return ( Math.round(value * scale) / scale).toFixed( decimals );
	}


// Formatting

	// Accept a number as input, output formatted string.
	function formatTo ( decimals, thousand, mark, prefix, postfix, encoder, decoder, negativeBefore, negative, edit, undo, input ) {

		var originalInput = input, inputIsNegative, inputPieces, inputBase, inputDecimals = '', output = '';

		// Apply user encoder to the input.
		// Expected outcome: number.
		if ( encoder ) {
			input = encoder(input);
		}

		// Stop if no valid number was provided, the number is infinite or NaN.
		if ( !isValidNumber(input) ) {
			return false;
		}

		// Rounding away decimals might cause a value of -0
		// when using very small ranges. Remove those cases.
		if ( decimals !== false && parseFloat(input.toFixed(decimals)) === 0 ) {
			input = 0;
		}

		// Formatting is done on absolute numbers,
		// decorated by an optional negative symbol.
		if ( input < 0 ) {
			inputIsNegative = true;
			input = Math.abs(input);
		}

		// Reduce the number of decimals to the specified option.
		if ( decimals !== false ) {
			input = toFixed( input, decimals );
		}

		// Transform the number into a string, so it can be split.
		input = input.toString();

		// Break the number on the decimal separator.
		if ( input.indexOf('.') !== -1 ) {
			inputPieces = input.split('.');

			inputBase = inputPieces[0];

			if ( mark ) {
				inputDecimals = mark + inputPieces[1];
			}

		} else {

		// If it isn't split, the entire number will do.
			inputBase = input;
		}

		// Group numbers in sets of three.
		if ( thousand ) {
			inputBase = strReverse(inputBase).match(/.{1,3}/g);
			inputBase = strReverse(inputBase.join( strReverse( thousand ) ));
		}

		// If the number is negative, prefix with negation symbol.
		if ( inputIsNegative && negativeBefore ) {
			output += negativeBefore;
		}

		// Prefix the number
		if ( prefix ) {
			output += prefix;
		}

		// Normal negative option comes after the prefix. Defaults to '-'.
		if ( inputIsNegative && negative ) {
			output += negative;
		}

		// Append the actual number.
		output += inputBase;
		output += inputDecimals;

		// Apply the postfix.
		if ( postfix ) {
			output += postfix;
		}

		// Run the output through a user-specified post-formatter.
		if ( edit ) {
			output = edit ( output, originalInput );
		}

		// All done.
		return output;
	}

	// Accept a sting as input, output decoded number.
	function formatFrom ( decimals, thousand, mark, prefix, postfix, encoder, decoder, negativeBefore, negative, edit, undo, input ) {

		var originalInput = input, inputIsNegative, output = '';

		// User defined pre-decoder. Result must be a non empty string.
		if ( undo ) {
			input = undo(input);
		}

		// Test the input. Can't be empty.
		if ( !input || typeof input !== 'string' ) {
			return false;
		}

		// If the string starts with the negativeBefore value: remove it.
		// Remember is was there, the number is negative.
		if ( negativeBefore && strStartsWith(input, negativeBefore) ) {
			input = input.replace(negativeBefore, '');
			inputIsNegative = true;
		}

		// Repeat the same procedure for the prefix.
		if ( prefix && strStartsWith(input, prefix) ) {
			input = input.replace(prefix, '');
		}

		// And again for negative.
		if ( negative && strStartsWith(input, negative) ) {
			input = input.replace(negative, '');
			inputIsNegative = true;
		}

		// Remove the postfix.
		// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice
		if ( postfix && strEndsWith(input, postfix) ) {
			input = input.slice(0, -1 * postfix.length);
		}

		// Remove the thousand grouping.
		if ( thousand ) {
			input = input.split(thousand).join('');
		}

		// Set the decimal separator back to period.
		if ( mark ) {
			input = input.replace(mark, '.');
		}

		// Prepend the negative symbol.
		if ( inputIsNegative ) {
			output += '-';
		}

		// Add the number
		output += input;

		// Trim all non-numeric characters (allow '.' and '-');
		output = output.replace(/[^0-9\.\-.]/g, '');

		// The value contains no parse-able number.
		if ( output === '' ) {
			return false;
		}

		// Covert to number.
		output = Number(output);

		// Run the user-specified post-decoder.
		if ( decoder ) {
			output = decoder(output);
		}

		// Check is the output is valid, otherwise: return false.
		if ( !isValidNumber(output) ) {
			return false;
		}

		return output;
	}


// Framework

	// Validate formatting options
	function validate ( inputOptions ) {

		var i, optionName, optionValue,
			filteredOptions = {};

		for ( i = 0; i < FormatOptions.length; i+=1 ) {

			optionName = FormatOptions[i];
			optionValue = inputOptions[optionName];

			if ( optionValue === undefined ) {

				// Only default if negativeBefore isn't set.
				if ( optionName === 'negative' && !filteredOptions.negativeBefore ) {
					filteredOptions[optionName] = '-';
				// Don't set a default for mark when 'thousand' is set.
				} else if ( optionName === 'mark' && filteredOptions.thousand !== '.' ) {
					filteredOptions[optionName] = '.';
				} else {
					filteredOptions[optionName] = false;
				}

			// Floating points in JS are stable up to 7 decimals.
			} else if ( optionName === 'decimals' ) {
				if ( optionValue >= 0 && optionValue < 8 ) {
					filteredOptions[optionName] = optionValue;
				} else {
					throw new Error(optionName);
				}

			// These options, when provided, must be functions.
			} else if ( optionName === 'encoder' || optionName === 'decoder' || optionName === 'edit' || optionName === 'undo' ) {
				if ( typeof optionValue === 'function' ) {
					filteredOptions[optionName] = optionValue;
				} else {
					throw new Error(optionName);
				}

			// Other options are strings.
			} else {

				if ( typeof optionValue === 'string' ) {
					filteredOptions[optionName] = optionValue;
				} else {
					throw new Error(optionName);
				}
			}
		}

		// Some values can't be extracted from a
		// string if certain combinations are present.
		throwEqualError(filteredOptions, 'mark', 'thousand');
		throwEqualError(filteredOptions, 'prefix', 'negative');
		throwEqualError(filteredOptions, 'prefix', 'negativeBefore');

		return filteredOptions;
	}

	// Pass all options as function arguments
	function passAll ( options, method, input ) {
		var i, args = [];

		// Add all options in order of FormatOptions
		for ( i = 0; i < FormatOptions.length; i+=1 ) {
			args.push(options[FormatOptions[i]]);
		}

		// Append the input, then call the method, presenting all
		// options as arguments.
		args.push(input);
		return method.apply('', args);
	}

	/** @constructor */
	function wNumb ( options ) {

		if ( !(this instanceof wNumb) ) {
			return new wNumb ( options );
		}

		if ( typeof options !== "object" ) {
			return;
		}

		options = validate(options);

		// Call 'formatTo' with proper arguments.
		this.to = function ( input ) {
			return passAll(options, formatTo, input);
		};

		// Call 'formatFrom' with proper arguments.
		this.from = function ( input ) {
			return passAll(options, formatFrom, input);
		};
	}

	/** @export */
	window.wNumb = wNumb;

}());