//
//  MPProduct.m
//  MathPad
//
//  Created by Kim Wittenburg on 09.10.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPProduct.h"

#import "MPFactor.h"
#import "MPValueGroup.h"

#import "MPTokenStream.h"
#import "MPToken.h"

#import "MPExpression.h"

@implementation MPProduct {
    NSMutableArray *_factors;
}

- (id)init
{
    self = [super init];
    if (self) {
        _factors = [[NSMutableArray alloc] init];
    }
    return self;
}

- (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
{
    self = [self init];
    if (self) {
        [tokenStream beginIgnoringWhitespaceTokens];
        
        while ([tokenStream hasMoreTokens] && tokenStream.currentToken.tokenType != MPOperatorListToken) {
            [_factors addObject:[[MPFactor alloc] initWithTokenStream:tokenStream]];
        }
        [tokenStream endIgnoringOrAcceptingWhitespaceTokens];
    }
    return self;
}

- (NSArray *)factors
{
    return _factors;
}

- (BOOL)validate:(NSError *__autoreleasing *)error
{
    if (_factors.count == 0) {
        if (error) {
            *error = MPParseError(5,
                                  NSLocalizedString(@"Expected A Value.", @"Error message. Displayed when a value was expected in an expression but none was found."),
                                  nil);
        }
        return NO;
    }
    MPFactor *factor = _factors[0];
    if (factor.hasMultiplicationSymbol) {
        if (error) {
            *error = MPParseError(6,
                                  NSLocalizedString(@"Unexpected Symbol.", @"Error message. Displayed when or inappropriate symbol was encountered during parsing."),
                                  nil);
        }
        return NO;
    }
    if (![factor.value validate:error]) {
        return NO;
    }
    for (NSUInteger index = 1; index < _factors.count; index++) {
        factor = _factors[index];
        if (![factor validate:error]) {
            return NO;
        }
    }
    return YES;
}

- (NSDecimalNumber *)evaluate
{
    NSDecimalNumber *value = [NSDecimalNumber one];
    for (MPFactor *factor in _factors) {
        NSDecimalNumber *currentValue = [factor evaluate];
        if ([currentValue isEqualToNumber:[NSDecimalNumber notANumber]]) {
            value = currentValue;
            break;
        }
        value = [value decimalNumberByMultiplyingBy:currentValue];
        if ([value compare:@(0)] == NSOrderedSame) {
            break;
        }
    }
    return value;
}

@end