#import "MYCalculator.h"

@implementation MYCalculator

- (id) init {
    self = [super init];
    if (self) {
        operator = 0;
        currentVal = [[NSMutableString stringWithString: @"0"] retain];
        previousVal = [[NSMutableString stringWithString: @"0"] retain];
    }
    return self;
}

- (IBAction)butDigit:(id)sender {
    NSMutableString * str = (NSMutableString *)[sender currentTitle];
    if ([currentVal isEqualToString:@"0"])
    {
        currentVal = str;
    }
    else {
        currentVal = [currentVal stringByAppendingString:str];
    }
    [txtViewer setText:currentVal];
}

- (IBAction)butOperator:(id)sender {
    NSString *tmpStr = [currentVal substringFromIndex:([currentVal length] - 1)];
    if ([tmpStr isEqualToString:@"."]) {
        currentVal = (NSMutableString *)[currentVal substringToIndex:([currentVal length] - 1)];
        [txtViewer setText:currentVal];
    }
    NSMutableString* str = (NSMutableString *)[sender currentTitle];
    if (operator >= 1 && operator <= 4) {
        [self doEquals];
    }
    if (operator != 5) {
        previousVal = [currentVal copy];
        currentVal = @"0";
    }
    if ([str isEqualToString:@"+"]) {
        operator = 1;
    } else if ([str isEqualToString:@"-"]) {
        operator = 2;
    } else if ([str isEqualToString:@"x"]) {
        operator = 3;
    } else if ([str isEqualToString:@"/"]) {
        operator = 4;
    }
}

- (IBAction)butEquals:(id)sender {
    [self doEquals];
}

- (void)doEquals {
    if (operator >= 1 && operator <= 4) {
        NSDecimalNumber* num1 = 0;
        num1 = [NSDecimalNumber decimalNumberWithString:previousVal];
        NSDecimalNumber* num2 = 0;
        num2 = [NSDecimalNumber decimalNumberWithString:currentVal];
        if (operator == 1){
            num1 = [num1 decimalNumberByAdding:num2];
            currentVal = [NSMutableString stringWithString:[num1 stringValue]];
        } else if (operator == 2){
            num1 = [num1 decimalNumberBySubtracting:num2];
            currentVal = [NSMutableString stringWithString:[num1 stringValue]];
        } else if (operator == 3){
            num1 = [num1 decimalNumberByMultiplyingBy:num2];
            currentVal = [NSMutableString stringWithString:[num1 stringValue]];
        } else if (operator == 4){
            if (![currentVal isEqualToString:@"0"]) {
                num1 = [num1 decimalNumberByDividingBy:num2];
                currentVal = [NSMutableString stringWithString:[num1 stringValue]];
            }
        }
        [txtViewer setText:currentVal];
        previousVal = [currentVal copy];
        currentVal = @"0";
        operator = 5;
    }
}

- (IBAction)butDecimal:(id)sender {
    NSRange range = [currentVal rangeOfString:@"." options:(NSCaseInsensitiveSearch)];
    if (range.location == NSNotFound) {
        currentVal = [currentVal stringByAppendingString:@"."];
    }
    [txtViewer setText:currentVal];
}

- (IBAction)butClear:(id)sender {
    currentVal = @"0";
    previousVal = @"0";
    operator = 0;
    [txtViewer setText:currentVal];
}

- (IBAction)butAbout:(id)sender {
    //Show Alert
    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"About iCalculator"
                          message:@"iCalculator version 1.0\nAuthor Pasha L. Topchiyev"
                          delegate:self
                          cancelButtonTitle:@"OK"
                          otherButtonTitles: nil];
    [alert show];
    [alert release];
}

@end