feat: code for a decent csv parser

src/csvParser.ts

@@ -0,0 +1,80 @@
+function unwrapDq(item: string): string {
+  const s = item.at(0);
+  const e = item.at(-1);
+  if (s === '"' && e === '"') {
+    return item.slice(1, -1);
+  }
+
+  return item;
+}
+
+function splitCsvBlock(text: string): string[] {
+  if (!text.endsWith('\r\n')) {
+    text += '\r\n';
+  }
+  const lines = [];
+  let line = '';
+  let inDq = false;
+
+  for (let i = 0; i <= text.length; i++) {
+    const c = text[i];
+
+    if (
+      c === '"' &&
+      ((c[i + 1] === '"' && c[i + 2] === '"') || c[i + 1] !== '"')
+    ) {
+      inDq = !inDq;
+    }
+
+    if (!inDq && c === '\r' && text[i + 1] === '\n') {
+      lines.push(line);
+      line = '';
+      i = i + 1;
+      continue;
+    }
+
+    line += c;
+  }
+
+  return lines;
+}
+
+function splitCsvLine(line: string): string[] {
+  if (line.at(-1) !== ',') {
+    // if conforming to spec, it should not end with ','
+    line += ',';
+  }
+
+  const items = [];
+  let item = '';
+  let inDq = false;
+
+  for (let i = 0; i < line.length; i++) {
+    const c = line[i];
+
+    if (
+      c === '"' &&
+      ((c[i + 1] === '"' && c[i + 2] === '"') || c[i + 1] !== '"')
+    ) {
+      inDq = !inDq;
+    }
+
+    if (!inDq && c === ',') {
+      item = unwrapDq(item);
+      item = item.replaceAll('""', '"');
+      items.push(item);
+      item = '';
+      continue;
+    }
+
+    item += c;
+  }
+
+  return items;
+}
+
+export function parseCSV(text: string): string[][] {
+  //  Works on RFC 4180
+  const rows = splitCsvBlock(text);
+  return rows.map(splitCsvLine);
+}