parse_url.kt

// http_URL = "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]]
//  
// Usage:
// ----------------------------------------------
//    val url = URL("http://abc.com:80/smith/home.html?key=value&key2=value2")
//    println("${url.protocol} -- ${url.host} -- ${url.port} -- ${url.path} -- ${url.query}")
// ---------------------------------------------

class URL(url: String){
    var protocol = ""
    var host = ""
    var port = ""
    var path = ""
    var query = ""

    var slashCount = 0
    var colonCount = 0
    var qustionCount = 0
    init {
        for (i in url.indices) {

            val char = url[i]
            val decimal = char.decimal

            when (decimal) {
                47 /* / */ -> slashCount++
                58 /* : */ -> colonCount++
                63 /* ? */ -> qustionCount++
            }

            when {
                slashCount==0 && colonCount==0 && qustionCount==0 -> if (decimal.isText) protocol+=char
                slashCount==2 && colonCount==1 && qustionCount==0 -> if (decimal.isAllowed(Type.HOST)) host+=char
                slashCount==2 && colonCount==2 && qustionCount==0 -> if (decimal.isAllowed(Type.PORT)) port+=char
                slashCount>2 && qustionCount==0 -> if (decimal.isAllowed(Type.PATH)) path+=char
                slashCount>2 && qustionCount==1 -> if (decimal.isAllowed(Type.QUERY)) query+=char
            }
        }
    }

    enum class Type { HOST, PORT, PATH, QUERY }

    val Char.decimal get() = this - '0' + 48

    fun Int.isAllowed(type: Type): Boolean {
        return when (type) {
            Type.HOST -> (this.isText|| this==46)
            Type.PORT -> this.isNumber
            Type.PATH -> (this.isText || this.isNumber || this==46 || this==47 || this==95)
            Type.QUERY -> (this.isText || this.isNumber || this==61 || this==38)
        }
    }

    val Int.isText get() = this in 97..122 || this in 65..90
    val Int.isNumber get() = this in 48..57
}