const FRACTION_DELIMITER  = ' per ';
const SYSTEMS = ['imperial', 'metric'];
// This table should mirror that of the units.php file and application_inventory_footprint view
const UNITS = {
    // LIQUID (Base is Fluid Oz}
    'Fluid Oz'         : {'base' : 1.0,   'type' : 'liquid', 'system' : 'imperial', 'display': 'Fl Oz'},
    'Gallons'          : {'base' : 128.0, 'type' : 'liquid', 'system' : 'imperial', 'sprayer' : true, 'display': 'Gal'},
    'Pints'            : {'base' : 16.0,  'type' : 'liquid', 'system' : 'imperial', 'display': 'Pt'},
    'Quarts'           : {'base' : 32.0,  'type' : 'liquid', 'system' : 'imperial', 'display': 'Qt'},
    'Liters'           : {'base' : 33.814, 'type' : 'liquid', 'system' : 'metric', 'sprayer' : true, 'display': 'L'},
    'Milliliters'      : {'base' : 0.03381402265,   'type' : 'liquid', 'system' : 'metric', 'display': 'mL'},
    // SOLID  (Base is Oz}
    'Oz'               : {'base' : 1.0,  'type' : 'solid',  'system' : 'imperial', 'display': 'Oz'},
    'Lbs'              : {'base' : 16.0, 'type' : 'solid',  'system' : 'imperial', 'display': 'Lbs'},
    'Grams'            : {'base' : 0.03527399072,   'type' : 'solid',  'system' : 'metric', 'display': 'g'},
    'Kilograms'        : {'base' : 35.2739907226, 'type' : 'solid',  'system' : 'metric', 'display': 'kg'},
    // AREA   (Base is Acre}
    'Acre'             : {'base' : 1.0,         'type' : 'area',   'system' : 'imperial', 'course_area' : true},
    '1000 Square Feet' : {'base' : 0.022956841138659, 'type' : 'area',   'system' : 'imperial'},
    'Hectare'          : {'base' : 2.47105,      'type' : 'area',   'system' : 'metric', 'course_area' : true},
    '100 Square Meters': {'base' : 0.0247105163, 'type' : 'area',   'system' : 'metric'},
    'Square Feet'      : {'base' : 0.0000229568, 'type' : 'hidden_area',   'system' : 'imperial', 'course_area' : true},
    'Square Meters'    : {'base' : 0.000247105,  'type' : 'hidden_area',   'system' : 'metric', 'course_area' : true},
    // TEMPERATURE
    'F' : {'base' : temperature_handler, 'type' : 'temperature', 'system' : 'imperial'},
    'C' : {'base' : temperature_handler, 'type' : 'temperature', 'system' : 'metric'},
    // SPEED
    'MPH' : {'base' : 1.0, 'type' : 'speed', 'system' : 'imperial'},
    'KPH' : {'base' : 0.621371, 'type' : 'speed', 'system' : 'metric'},
    // PSI
    'Lbs per Square Inch' : {'base' : 1.0, 'type' : 'psi', 'system' : 'imperial'},
    'Bar' : {'base' : 0.0689476, 'type' : 'psi', 'system' : 'metric'},
};

class Unit {
    static is(unitName, typeOrSys) {
        if (!UNITS.hasOwnProperty(unitName)) {
            console.error(`ERROR: ${unitName} not in unit list`);
            return false
        } else {
            return UNITS[unitName].type === typeOrSys || UNITS[unitName].system === typeOrSys
        }
    }

    /*
    static function get(numeratorOpts = array(), denominatorOpts = FALSE, all = FALSE) {
        pref = self::preference('pref_general_units');
        numerators = array();
        foreach (UNITS as numeratorUnit => numeratorMeta) {
            addUnit = all || in_array(numeratorMeta['system'], pref) || numeratorMeta['system'] == 'both';
            foreach (numeratorOpts as field => filter) {
                if (numeratorMeta[field] !== filter) {
                    addUnit = FALSE;
                }
            }
            if (addUnit) {
                numerators[] = numeratorUnit;
            }
        }
        if (denominatorOpts !== FALSE) {
            denominators = self::get(denominatorOpts);
            fractions = array();
            foreach (numerators as numerator) {
                foreach (denominators as denominator) {
                    // If nominator and denominator are from the same system
                    if (UNITS[numerator]['system'] === UNITS[denominator]['system']) {
                        fractions[] = units::fraction(numerator, denominator);
                    }
                }
            }

            sort(fractions);
            return fractions;
        }
        sort(numerators);
        return numerators;
    }
    */

    static convert(from, fromUnit, toUnit) {
        var to = parseFloat(from);
        var fromUnit = Unit.fraction(fromUnit);
        var toUnit = Unit.fraction(toUnit);

        if (fromUnit['numerator'] !== '1' && toUnit['numerator'] !== '1') {
            var fromBase = Unit.getBaseConversion(fromUnit['numerator']);
            var toBase = Unit.getBaseConversion(toUnit['numerator']);
            if (typeof fromBase === "function") {
                to = fromBase(from, fromUnit['numerator'], toUnit['numerator']);
            } else {
                to = to * fromBase;
                to = to / toBase;          //  NUMERATOR
            }
        } // -----------------------------------------------------------------------------------
        if (fromUnit['denominator'] !== '1' && toUnit['denominator'] !== '1') { // DENOMINATOR
            var fromBase = Unit.getBaseConversion(fromUnit['denominator']);
            var toBase = Unit.getBaseConversion(toUnit['denominator']);
            if (typeof fromBase === "function") {
                to = to / fromBase(to, fromUnit['denominator'], toUnit['denominator']);
            } else {
                to = to / fromBase;
                to = to * toBase;
            }
        }
        return to;
    }

    static fraction(nominatorOrUnit, denominator = false) {
        if (denominator !== false) {
            return `${nominatorOrUnit}${FRACTION_DELIMITER}${denominator}`;
        }
        var fraction = nominatorOrUnit.split(FRACTION_DELIMITER);
        var numerator = fraction[0];
        var denominator = fraction.length > 1 ? fraction[1] : '1';
        return {
            'numerator': numerator, 'denominator': denominator,
            0:  numerator, 1: denominator
        };
    }

    /**
     * Converts given quantity to its display form
     * @param {float} from quantity being converted
     * @param {string} fromUnit original unit of quantity being converted
     */
    static getDisplayUnits(from, fromUnit) {
        // Verify we are working with a valid unit
        if(!UNITS.hasOwnProperty(fromUnit)) {
            console.error(`${fromUnit} not in units table`);
            return '';
        }

        var majorUnit, minorUnit;
        fromUnit = UNITS[fromUnit];
        if(fromUnit['system'] == 'imperial' && fromUnit['type'] == 'liquid') {
            majorUnit = UNITS['Gallons'];
            minorUnit = UNITS['Fluid Oz'];
        } else if(fromUnit['system'] == 'metric' && fromUnit['type'] == 'liquid') {
            majorUnit = UNITS['Liters'];
            minorUnit = UNITS['Milliliters'];
        } else if(fromUnit['system'] == 'imperial' && fromUnit['type'] == 'solid') {
            majorUnit = UNITS['Lbs'];
            minorUnit = UNITS['Oz'];
        } else if(fromUnit['system'] == 'metric' && fromUnit['type'] == 'solid') {
            majorUnit = UNITS['Kilograms'];
            minorUnit = UNITS['Grams'];
        } else {
            console.error("Display format not defined");
            return `${from}`;
        }

        var fromBase = from * fromUnit['base'];
        var major = Math.trunc(fromBase / majorUnit['base']);
        if (minor >= 1) {
            var minor = Math.round((fromBase - major * majorUnit['base']) / minorUnit['base']);
        } else {
            var minor = Math.round(((fromBase - major * majorUnit['base']) / minorUnit['base']) * 100) / 100;
        }

        if(minorUnit == UNITS['Fluid Oz']){
            if(minor == 128){
                minor = 0;
                major += 1;
            }
        } else if(minorUnit == UNITS['Milliliters']){
            if(minor == 1000){
                minor = 0;
                major += 1;
            }
        } else if(minorUnit == UNITS['Oz']){
            if(minor == 16){
                minor = 0;
                major += 1;
            }
        } else if(minorUnit == UNITS['Grams']){
            if(minor == 1000){
                minor = 0;
                major += 1;
            }
        }

        return major ? `${major} ${majorUnit['display']}, ${minor} ${minorUnit['display']}` : `${minor} ${minorUnit['display']}`;
    }

    static getBaseConversion(fromUnit) {
        return UNITS.hasOwnProperty(fromUnit) ? UNITS[fromUnit].base : 1.0;
    }
}

function temperature_handler(from, fromUnit, toUnit) {
    if (fromUnit == toUnit) {
        return from;
    }
    if (fromUnit == 'C' && toUnit == 'F') {
        return (from * 9 / 5) + 32;
    }
    if (fromUnit == 'F' && toUnit == 'C') {
        return (from - 32) / (9 / 5);
    }
}