import Foundation

enum CSV {
    static func parse(_ text: String) -> [[String]] {
        var rows: [[String]] = []
        var row: [String] = []
        var field = ""
        var inQuotes = false

        let scalars = Array(text.unicodeScalars)
        var index = 0

        while index < scalars.count {
            let scalar = scalars[index]

            if inQuotes {
                if scalar == "\"" {
                    if index + 1 < scalars.count && scalars[index + 1] == "\"" {
                        field.unicodeScalars.append("\"")
                        index += 2
                    } else {
                        inQuotes = false
                        index += 1
                    }
                } else {
                    field.unicodeScalars.append(scalar)
                    index += 1
                }
                continue
            }

            switch scalar {
            case "\"":
                inQuotes = true
                index += 1
            case ",":
                row.append(field)
                field = ""
                index += 1
            case "\r", "\n":
                row.append(field)
                field = ""
                rows.append(row)
                row = []
                if scalar == "\r", index + 1 < scalars.count, scalars[index + 1] == "\n" {
                    index += 2
                } else {
                    index += 1
                }
            default:
                field.unicodeScalars.append(scalar)
                index += 1
            }
        }

        if !field.isEmpty || !row.isEmpty {
            row.append(field)
            rows.append(row)
        }

        return rows
    }
}