package org.shedlang.compiler.tokeniser;

import org.zwobble.sourcetext.SourcePosition;

import java.util.List;

public class TokenIterator<TTokenType> {
    private final InfinitelyPaddedIterator<Token<TTokenType>> tokens;

    public TokenIterator(List<Token<TTokenType>> tokens, Token<TTokenType> end) {
        this.tokens = new InfinitelyPaddedIterator<>(tokens, end);
    }

    public void skip(TTokenType tokenType) {
        nextValue(tokenType);
    }

    public Token<TTokenType> next(TTokenType tokenType) {
        var token = tokens.get();
        if (token.tokenType().equals(tokenType)) {
            tokens.moveNext();
            return token;
        } else {
            throw new UnexpectedTokenException(
                tokenType.toString(),
                token
            );
        }
    }

    public String nextValue(TTokenType tokenType) {
        return this.next(tokenType).value().toString();
    }

    public boolean isNext(TTokenType tokenType) {
        return tokens.get().tokenType().equals(tokenType);
    }

    public boolean isNext(TTokenType tokenType1, TTokenType tokenType2) {
        return tokens.get().tokenType().equals(tokenType1) &&
            tokens.get(1).tokenType().equals(tokenType2);
    }

    public boolean trySkip(TTokenType tokenType) {
        if (isNext(tokenType)) {
            tokens.moveNext();
            return true;
        } else {
            return false;
        }
    }

    public Token<TTokenType> peek() {
        return tokens.get();
    }

    public Token<TTokenType> peek(int offset) {
        return tokens.get(offset);
    }

    public SourcePosition startPosition() {
        return tokens.get().sourceRange().start();
    }

    public SourcePosition endPosition() {
        if (tokens.isAtStart()) {
            return startPosition();
        } else {
            return tokens.get(-1).sourceRange().end();
        }
    }
}