//
//  MPExpressionEvaluator.m
//  MathPad
//
//  Created by Kim Wittenburg on 31.08.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPExpressionEvaluator.h"
#import "MPExpression.h"

#import "MPParsedElement.h"
#import "MPMath.h"

@implementation MPExpressionEvaluator {
    NSMutableDictionary *_variableBindings;
}
- (id)initWithExpression:(MPExpression *)expression
{
    self = [super init];
    if (self) {
        _expression = expression;
        _variableBindings = [[NSMutableDictionary alloc] init];
    }
    return self;
}

#pragma mark Lexing
- (MPParsedElement *)structuredRepresentationOfElementAtIndex:(NSUInteger)index
{
    NSString *string = (NSString *)[self.expression elementAtIndex:index];
    YY_BUFFER_STATE buffer = yy_scan_string(string.UTF8String);
    yyparse();
    yy_delete_buffer(buffer);
    return [parseResult copy];
}

#pragma mark Evaluating Expressions
- (NSDictionary *)variableBindings
{
    return [_variableBindings copy];
}

- (void)bindValue:(double)value toVariableName:(NSString *)name
{
    [_variableBindings setObject:@(value)
                          forKey:name];
}

- (double)evaluateWithError:(NSError *__autoreleasing *)error
{
    MPParsedElement *element = [self structuredRepresentationOfElementAtIndex:0];
    return element.standaloneValue;
}

@end