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

#import "MPVariable.h"
#import "MPEvaluationContext.h"

@implementation MPVariable {
    NSRange _range;
}

- (instancetype)init
{
    self = [super init];
    if (self) {
    }
    return self;
}

- (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
{
    self = [self init];
    if (self) {
        [tokenStream beginIgnoringWhitespaceTokens];
        MPToken *token = tokenStream.currentToken;
        if (token.tokenType == MPVariableToken) {
            self.variableName = token.stringValue;
            _range = token.range;
        } else {
            @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:@"Expected Variable" userInfo:nil];
        }
        [tokenStream currentTokenConsumed];
        [tokenStream endIgnoringOrAcceptingWhitespaceTokens];
    }
    return self;
}

- (NSRange)range
{
    return _range;
}

- (BOOL)validate:(MPParseError *__autoreleasing *)error
{
    if (![[MPEvaluationContext sharedContext] isVariableDefined:self.variableName]) {
        if (error) {
            *error = MPParseError(self.range, @"Undefined Variable");
        }
        return NO;
    }
    return YES;
}

- (NSDecimalNumber *)evaluate
{
    return [[MPEvaluationContext sharedContext] valueForVariable:self.variableName];
}

- (NSArray *)expressionElements
{
    return @[self.variableName];
}

@end