@masala/parser/src/lib/stream/parserstream.js

Masala Parser

/*
 * Parsec
 * https://github.com/d-plaindoux/parsec
 *
 * Copyright (c) 2016 Didier Plaindoux
 * Licensed under the LGPL2 license.
 */

import Stream from './stream';
import option from '../data/option';

/**
 * ParserStream stream class
 * Compared to StringStream, it is NOT a RandomAccess.
 * You must use a substream before making an access to a unreached point.
 */
class ParserStream extends Stream {
    constructor(parser, lowerStream) {
        super();
        //TODO: why the parser is called source ?
        this.source = parser;
        this.input = lowerStream;
        this.offsets = [0];
    }

    getOffset(index) {
        if ( index < this.offsets.length) {
            // TODO logger console.log('found offset', this.offsets[index]);
            return option.some(this.offsets[index]);
        }
        return option.none();

    }


    // Stream 'a => number -> number
    location(index) {
        if (index === 0) {
            return 0;
        }
        const option = this.getOffset(index)
        if (option.isPresent()) {
            // TODO: check the +1 ; the -1 has disappeared
            return this.input.location(option.get());
        } else {
            // TODO logger
            throw 'No location has been found yet for index '+index;
            // TODO: What is the use case ?
            // return this.input.location(this.getOffset(index - 1) + 1);
        }

    }

    // ParserStream 'a => unit -> boolean
    endOfStream(index) {
        const option = this.getOffset(index);
        if (option.isPresent()) {
            return this.input.endOfStream(option.get());
        } else {
            // If last was the last befor end of stream, then yes
            const last = this.offsets[this.offsets.length - 1];
            return this.input.endOfStream(last +1);
        }

    }

    // ParserStream 'a => number -> 'a <+> error
    /**
     * index is the token index ; It uses getOffset(index) to retrieve the location
     * in the stringStream
     * @param index  token index
     */
    unsafeGet(index) {
        // the wrapped parser parses the StringStream
        let sourceIndex;
        let option = this.getOffset(index);
        if (option.isPresent()){
            // we have already read it. Should be caught by the bufferedStream
            sourceIndex = option.get();
        }else{
            // TODO logger
            throw new Error();
        }
        const result = this.source.parse(this.input, sourceIndex);

        if (result.isAccepted()) {
            // Why index+1 ? Because we succeeded, and the source is at result.offset
            this.offsets.push(result.offset);
            return result.value;
        } else {
            // TODO logger
            throw new Error();
        }
    }
}

function factory(parser, lowerStream) {
    return new ParserStream(parser, lowerStream);
}

export default factory;