```typescript
export function parseCsvLine(line: string): string[] {
  if (typeof line !== 'string') {
    throw new Error('Input is not a string');
  }

  const fields: string[] = [];
  let currentField = '';
  let inQuote = false;

  for (let i = 0; i < line.length; i++) {
    const char = line[i];

    if (char === '"') {
      inQuote = !inQuote;
    } else if (char === ',' && !inQuote) {
      fields.push(currentField.trim());
      currentField = '';
    } else {
      currentField += char;
    }
  }

  // Handle trailing field
  fields.push(currentField.trim());

  // Close any unclosed quotes
  if (inQuote) {
    throw new Error('Quoted field is never closed');
  }

  return fields;
}
```