//
//  MPPowerFunction.m
//  MathPad
//
//  Created by Kim Wittenburg on 30.09.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPPowerFunction.h"

#import "MPExpression.h"
#import "MPExpressionTree.h"

#import "MPValueGroup.h"

@implementation MPPowerFunction

MPFunctionAccessorImplementation(ExponentExpression, _exponentExpression)

- (NSArray *)childrenAccessors
{
    return @[@"exponentExpression"];
}

- (BOOL)validate:(NSError *__autoreleasing *)error
{
    if (!self.baseValue) {
        if (error) {
            *error = MPParseError(11,
                                  NSLocalizedString(@"No Base For Power.", @"Error message. This is displayed when a power does not have a base value."),
                                  nil);
        }
        return NO;
    }
    return [self.baseValue validate:error] && [[self.exponentExpression parse] validate:error];
}

- (NSDecimalNumber *)evaluate
{
    NSDecimalNumber *base = [self.baseValue evaluate];
    NSDecimalNumber *exponent = [[self.exponentExpression parse] evaluate];
    if ([base isEqualToNumber:@(0)] && [exponent isEqualToNumber:@(0)]) {
        // The C pow function returns 1 for pow(0, 0). Mathematically this should be undefined.
        return [NSDecimalNumber notANumber];
    }
    return [[NSDecimalNumber alloc] initWithDouble:pow(base.doubleValue, exponent.doubleValue)];
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"^%@", self.exponentExpression.description];
}

@end