url-parser-2.type

export type function parseURL = (text) => ^{
    if (parseProtocol<text> extends [infer protocol, infer rest]) {
        return {
            protocol,
            ...parseAuthority<rest>
        }
    } else {
        return never
    }
}

type function parseProtocol = (text) => ^{
    if(text extends `${infer protocol}://${infer rest}`) {
        return [
            protocol,
            rest
        ]
    } else {
        return never
    }
}

type function parseUserInfo = (text) => ^{
    if(text extends `${infer username}:${infer password}`) {
        return { username, password }
    } else {
        return { username: text }
    }
}

type function parseAuthority = (text) => ^{
    if(text extends `${infer authority}@${infer rest}`) {
        return {
            authority: parseUserInfo<authority>,
            ...parseHost<rest>
        }
    } else { 
        return {
            authority: null,
            rest: text
        }
    }
}

type function parseHost = (text) => ^{
    if(text extends `${infer name}:${infer port}`) {
        return ^{
            if(parsePort<port> extends never) {
                return never
            } else {
                return { name, port }
            }
        }
    } else {
        return { name: text }
    }
}

type function parsePort = (text) => ^{
    if(isNumberString<text> extends true) {
        return text
    } else {
        return never
    }
}

type function isNumberString = (text) => ^{
    if(text extends "") {
        return never
    } else {
        return _isNumberString<text>
    }
}

type function _isNumberString = (text) => ^{
    /* the end of recursion: each char of text is digit, no more chars to inspect */
    if(text extends "") {
        return true
    } else if(text extends `${infer digit}${infer rest}`) {
        return ^{
            if(digit extends Digit) {
                return _isNumberString<rest>
            } else {
                return false
            }
        }
    } else {
        return false
    }
}

type Digit = union ["0" , "1" , "2" , "3" , "4" , "5" , "6" , "7" , "8" , "9"]