CSV Parser

README.md

https://www.jdoodle.com/execute-nodejs-online/

main.js

const fs = require("fs");
const stdin = fs.readFileSync("/dev/stdin", "utf-8");

class Reader {
    location = {l: 0, c:0};
    i = 0;
    constructor(stdin) {
        this.stdin = stdin;
        this.current = this.stdin.length > 0 ? this.stdin[0] : undefined;
    }
    
    // current() {
    //     return 
    // }
    next() {
        if (this.i < this.stdin.length) {
            this.i++;this.location.c++;
            this.current = this.stdin[this.i];
            if (this.current == '\n') {
                this.location.l++;
                this.location.c = 0;
            }
        } else {
            this.current = undefined;
        }
        return this.current;
    }
    substring(start, end) {
        return this.stdin.substring(start, end);
    }
    
    readUntil(chars) {
        console.log(`Reader.readUntil: start (${this.location.l},${this.location.c})`);
        let start = 0;
        while (this.current !== undefined && !chars.includes(this.current)) {
            this.next();
        }
        return this.substring(start, this.i);
    }
    
    readSpaces() {
        console.log(`Reader.readSpaces: start (${this.location.l},${this.location.c})`);
        let start = this.i;
        let next = this.current();
        while (this.current === ' ') {
            next = this.next();
        }
        return this.substring(start, this.i);
    }
    
    readValue() {
        console.log(`Reader.readValue: start (${this.location.l},${this.location.c})`);
        const enclosed = this.current === '"';
        if (enclosed) {
            this.next(); // Passed '"'
            let string = '';
            let finished = false;
            let start = this.i;
            while (!finished) {
                let substring = this.readUntil('"');
                string += substring;
                this.next(); // Passed '"'
                if (this.current === '"') {
                    string += this.current;
                    this.next();  // Passed '"'
                    start = this.i;
                } else {
                    finished = true;
                }
            }
            console.log(`Reader.readValue: end (${this.location.l},${this.location.c}: ${string})`);
            return string;
        } else {
            let string = this.readUntil([',', '\n']);
            console.log(`Reader.readValue: end (${this.location.l},${this.location.c}: ${string})`);
            return string;
        }
    }
    
    readRow() {
        console.log(`Reader.readRow: start (${this.location.l},${this.location.c})`);
        let row = [];
        let finished = false;
        while (!finished) {
            let value = this.readValue();
            row.push(value);
            switch (this.current) {
                case ',':
                    // Go next value
                    this.next();
                    break;
                case '\n':
                    this.next();
                    finished = true;
                    break;
                default:
                    // Error
                    throw `Invalid character (${this.current}) at (${this.location.l},${this.location.c}}): expected value separator (',') or end of line ('\n')`;
            }
        }
        return row;
    }
    
    readAll() {
        console.log(`Reader.readAll: start (${this.location.l},${this.location.c})`);
        let rows = [];
        let finished = false;
        while (!finished) {
            let row = this.readRow();
            rows.push(row);
            finished = this.current === undefined;
        }
        return rows;
    }
}

// function readString(stdin, start) {
//     let string = "";
//     if (stdin[start] != '"') throw `Invalid character start: ${stdin[start]} (position: ${start})`;
//     let finished = false;
//     let next = start+1;
//     while (!finished) {
//         const indexOf = stdin.indexOf('"', next);
//         if (indexOf < 0) {
//             throw `Unexpected EOF: Data starting at ${start} is incomplete`;
//         }
//         string += stdin.substring(next, indexOf);
//         if ((indexOf+1) < stdin.length && stdin[indexOf+1] == '"') {
//             next = indexOf+2;
//         } else {
//             next = indexOf+1;
//             finished = true;
//         }
//     }
//     return {string,next};
// }

// function readRow(stdin, start) {
//     let finished = false;
//     let row = [];
//     let next = start;
//     while (!finished) {
//         let read = readString(stdin, next);
//         row.push(read.string);
//         if (read.next >= stdin.length) {
//             next = read.next;
//             finished = true;
//         } else {
//             switch (stdin[read.next]) {
//                 case ',':
//                     next = read.next + 1;
//                     break;
//                 case '\n':
//                     next = read.next + 1;
//                     finished = true;
//                     break;
//                 default:
//                     throw `Unexpected character between cell values: ${stdin[read.next]} (position: ${read.next})`;
//             }
//         }
//     }
//     return {row,next};
// }

// function readData(stdin) {
//     let finished = false;
//     let next = 0;
//     let data = [];
//     while (!finished) {
//         let spaces = readSpaces(stdin, next);
//         if (spaces.next >= stdin.length) {
//             finished = true;
//         } else {
//             let read = readRow(stdin, spaces.next);
//             data.push(read.row);
//             finished = read.next >= stdin.length;
//             next = read.next;
//         }
//     }
//     return {data,next};
// }

console.log(JSON.stringify(new Reader(stdin).readAll(), undefined, 2));