import Foundation

// Quoting matches spreadsheets: tabs/newlines/quotes round-trip as cell content.
enum TSV {
  static func encode(_ rows: [[String]]) -> String {
    rows.map {
      $0.map { text in
        text.contains(where: {
          $0 == "\t" || $0 == "\r" || $0 == "\n" || $0 == "\r\n" || $0 == "\""
        }) ? "\"" + text.replacingOccurrences(of: "\"", with: "\"\"") + "\"" : text
      }.joined(separator: "\t")
    }.joined(separator: "\n")
  }
  static func decode(_ text: String) -> [[String]] {
    let chars = Array(text)
    var rows: [[String]] = []
    var row: [String] = []
    var cell = ""
    var quoted = false
    var i = 0
    while i < chars.count {
      let ch = chars[i]
      if ch == "\"" {
        if quoted && i + 1 < chars.count && chars[i + 1] == "\"" {
          cell.append(ch)
          i += 1
        } else if quoted || cell.isEmpty {
          quoted.toggle()
        } else {
          cell.append(ch)
        }
      } else if !quoted && ch == "\t" {
        row.append(cell)
        cell = ""
      } else if !quoted && (ch == "\n" || ch == "\r\n" || ch == "\r") {
        row.append(cell)
        rows.append(row)
        row = []
        cell = ""
      } else {
        cell.append(ch)
      }
      i += 1
    }
    row.append(cell)
    rows.append(row)
    if rows.last == [""] && (text.last == "\n" || text.last == "\r\n" || text.last == "\r") {
      rows.removeLast()
    }
    return rows
  }
}