import type { ParsedCsvData } from '../../types/auto-group'

function parseCSVLine(line: string, delimiter: string = ','): string[] {
  const result: string[] = []
  let current = ''
  let inQuotes = false
  for (let i = 0; i < line.length; i++) {
    const char = line[i]
    if (char === '"') {
      if (inQuotes && line[i + 1] === '"') {
        current += '"'
        i++
      } else {
        inQuotes = !inQuotes
      }
    } else if (char === delimiter && !inQuotes) {
      result.push(current.trim())
      current = ''
    } else {
      current += char
    }
  }
  result.push(current.trim())
  return result
}

export function parseCSV(text: string): ParsedCsvData {
  const lines = text.trim().split('\n')
  if (lines.length < 2) throw new Error('CSV must have at least a header and one data row')
  const firstLine = lines[0]
  const csvDelimiter = firstLine.includes('\t') ? '\t' : ','
  const headers = parseCSVLine(firstLine, csvDelimiter)
  const rows: Record<string, string>[] = []
  for (let i = 1; i < lines.length; i++) {
    const values = parseCSVLine(lines[i], csvDelimiter)
    if (values.length !== headers.length) continue
    const row: Record<string, string> = {}
    headers.forEach((h, idx) => { row[h] = values[idx] })
    rows.push(row)
  }
  const sampleKeywords = ['sample', 'name', 'id', 'sample_name', 'samplename', 'file name', 'filename', 'file_name']
  const sampleColumn = headers.find(h => sampleKeywords.includes(h.toLowerCase())) ?? headers[0]
  return { columns: headers, rows, sampleColumn, delimiter: csvDelimiter }
}