//
//  MPTokenStream.m
//  MathPad
//
//  Created by Kim Wittenburg on 20.09.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPTokenStream.h"

@implementation MPTokenStream {
    NSUInteger currentTokenIndex;
    NSUInteger eofLocation;
}

- (instancetype)initWithTokens:(NSArray *)tokens
{
    self = [super init];
    if (self) {
        self.tokens = tokens;
        self.ignoringWhitespaceTokens  = YES;
        if (tokens.count > 0) {
            eofLocation = NSMaxRange([tokens.lastObject range]);
        }
        [self reset];
    }
    return self;
}

- (void)skipWhitespaces
{
    if (!self.isIgnoringWhitespaceTokens) {
        return;
    }
    while (currentTokenIndex < self.tokens.count) {
        MPToken *token = self.tokens[currentTokenIndex];
        if (token.tokenType != MPWhitespaceToken) {
            return;
        }
        self.currentLocation = NSMaxRange(token.range);
        ++currentTokenIndex;
    }
}

- (void)reset
{
    currentTokenIndex = 0;
    self.currentLocation = 0;
    [self skipWhitespaces];
}

- (BOOL)hasMoreTokens
{
    [self skipWhitespaces];
    return currentTokenIndex < self.tokens.count;
}

- (MPToken *)nextToken
{
    [self skipWhitespaces];
    if (currentTokenIndex >= self.tokens.count) {
        return [[MPToken alloc] initEOFTokenAtLocation:eofLocation];
    } else {
        MPToken *token = self.tokens[currentTokenIndex++];
        self.currentLocation = NSMaxRange(token.range);
        return token;
    }
}

- (MPToken *)nextTokenOfType:(MPTokenType)type
{
    [self skipWhitespaces];
    if (currentTokenIndex >= self.tokens.count) {
        return nil;
    } else {
        MPToken *token = self.tokens[currentTokenIndex];
        if (token.tokenType != type) {
            return nil;
        }
        ++currentTokenIndex;
        self.currentLocation = NSMaxRange(token.range);
        return token;
    }
}

@end