Jison Custom Scanner

custom_parser.js

import {Parser} from 'jison'

// tokens
const EOL = 'EOL'           // End of line
const EOR = 'EOR'           // End of record
const LEFT = 'x'
const TOP = 'y'
const WIDTH = 'c'
const HEIGHT = 'r'
const INVALID = 'INVALID'
const NUMBER = 'NUMBER'

// regex
const rxDigit = /[0-9]/
const rxSpace = /\s/
const rxLeft = /[xX]/
const rxTop = /[yY]/
const rxWidth = /[cC]/
const rxHeight = /[rR]/
const rxEOR = /,/

class LayoutScanner {
    constructor() {
        this._text = ''
        this.yytext = ''
        this.yylloc = this.yyloc = {
            first_column: 0, // eslint-disable-line camelcase
            first_line  : 1, // eslint-disable-line camelcase
            last_line   : 1, // eslint-disable-line camelcase
            last_column : 0, // eslint-disable-line camelcase
        }
    }

    setInput(text) {
        this._text = text
    }

    lex() {
        if (this._text === '') {
            return EOL
        }

        // Consume a single character and increment our column numbers.
        let c = this._text.charAt(0)
        this._text = this._text.substring(1)

        // Ignore any whitespace
        while (rxSpace.test(c)) {
            if (this._text === '') {
                return EOL
            }

            c = this._text.charAt(0)
            this._text = this._text.substring(1)
        }

        this.yytext = c
        this.yyloc.first_column++
        this.yyloc.last_column++

        // Numbers
        if (rxDigit.test(c)) {
            c = this._text.charAt(0)
            while (rxDigit.test(c)) {
                this._text = this._text.substring(1)
                this.yytext += c
                this.yyloc.last_column++
                c = this._text.charAt(0)
            }
            return NUMBER
        }

        if (rxLeft.test(c)) {
            return LEFT
        }

        if (rxTop.test(c)) {
            return TOP
        }

        if (rxWidth.test(c)) {
            return WIDTH
        }

        if (rxHeight.test(c)) {
            return HEIGHT
        }

        if (rxEOR.test(c)) {
            return EOR
        }

        console.log(`Error at ${this.yyloc.first_column}`)
        return INVALID
    }
}

const grammar = String.raw`
%%

expressions
    : DISPLAY_LIST EOL
        {return $1;}
    ;

DISPLAY_LIST
    : DISPLAY
        {$$ = [$1];}
    | DISPLAY_LIST EOR DISPLAY
        {$1.push($3); $$ = $1;}
    ;

DISPLAY
    : x NUMBER y NUMBER c NUMBER r NUMBER
        {$$ = {x: $2, y: $4, c: $6, r: $8};}
    | x NUMBER y NUMBER c NUMBER
        {$$ = {x: $2, y: $4, c: $6, r: 1};}
    | x NUMBER y NUMBER r NUMBER
        {$$ = {x: $2, y: $4, c: 1, r: $6};}
    | x NUMBER y NUMBER
        {$$ = {x: $2, y: $4, c: 1, r: 1};}
    ;
`

const parser = new Parser(grammar)
parser.lexer = new LayoutScanner()
try {
    const displays = parser.parse('x 1 y 1 c 2 r 2 , x3y1, x3y2, x1y1, x1y2, x1y3')
    console.log(JSON.stringify(displays))
} catch (e) {
    console.log(e)
}