std/encoding/csv.ts

// Ported from Go:
// https://github.com/golang/go/blob/go1.12.5/src/encoding/csv/
// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.

import { BufReader, EOF } from "../io/bufio.ts";
import { TextProtoReader } from "../textproto/mod.ts";

const INVALID_RUNE = ["\r", "\n", '"'];

export class ParseError extends Error {
  StartLine: number;
  Line: number;
  constructor(start: number, line: number, message: string) {
    super(message);
    this.StartLine = start;
    this.Line = line;
  }
}

export interface ParseOptions {
  comma: string;
  comment?: string;
  trimLeadingSpace: boolean;
  lazyQuotes?: boolean;
  fieldsPerRecord?: number;
}

function chkOptions(opt: ParseOptions): void {
  if (
    INVALID_RUNE.includes(opt.comma) ||
    (opt.comment && INVALID_RUNE.includes(opt.comment)) ||
    opt.comma === opt.comment
  ) {
    throw new Error("Invalid Delimiter");
  }
}

export async function read(
  Startline: number,
  reader: BufReader,
  opt: ParseOptions = { comma: ",", comment: "#", trimLeadingSpace: false }
): Promise<string[] | EOF> {
  const tp = new TextProtoReader(reader);
  let line: string;
  let result: string[] = [];
  let lineIndex = Startline;

  const r = await tp.readLine();
  if (r === EOF) return EOF;
  line = r;
  // Normalize \r\n to \n on all input lines.
  if (
    line.length >= 2 &&
    line[line.length - 2] === "\r" &&
    line[line.length - 1] === "\n"
  ) {
    line = line.substring(0, line.length - 2);
    line = line + "\n";
  }

  const trimmedLine = line.trimLeft();
  if (trimmedLine.length === 0) {
    return [];
  }

  // line starting with comment character is ignored
  if (opt.comment && trimmedLine[0] === opt.comment) {
    return [];
  }

  result = line.split(opt.comma);

  let quoteError = false;
  result = result.map(
    (r): string => {
      if (opt.trimLeadingSpace) {
        r = r.trimLeft();
      }
      if (r[0] === '"' && r[r.length - 1] === '"') {
        r = r.substring(1, r.length - 1);
      } else if (r[0] === '"') {
        r = r.substring(1, r.length);
      }

      if (!opt.lazyQuotes) {
        if (r[0] !== '"' && r.indexOf('"') !== -1) {
          quoteError = true;
        }
      }
      return r;
    }
  );
  if (quoteError) {
    throw new ParseError(Startline, lineIndex, 'bare " in non-quoted-field');
  }
  return result;
}

export async function readAll(
  reader: BufReader,
  opt: ParseOptions = {
    comma: ",",
    trimLeadingSpace: false,
    lazyQuotes: false
  }
): Promise<string[][]> {
  const result: string[][] = [];
  let _nbFields: number;
  let lineResult: string[];
  let first = true;
  let lineIndex = 0;
  chkOptions(opt);

  for (;;) {
    const r = await read(lineIndex, reader, opt);
    if (r === EOF) break;
    lineResult = r;
    lineIndex++;
    // If fieldsPerRecord is 0, Read sets it to
    // the number of fields in the first record
    if (first) {
      first = false;
      if (opt.fieldsPerRecord !== undefined) {
        if (opt.fieldsPerRecord === 0) {
          _nbFields = lineResult.length;
        } else {
          _nbFields = opt.fieldsPerRecord;
        }
      }
    }

    if (lineResult.length > 0) {
      if (_nbFields! && _nbFields! !== lineResult.length) {
        throw new ParseError(lineIndex, lineIndex, "wrong number of fields");
      }
      result.push(lineResult);
    }
  }
  return result;
}