getaddrinfo

import Foundation

public final class addrinfo {
    fileprivate(set) public var ai_flags: Int32
    fileprivate(set) public var ai_family: Int32
    fileprivate(set) public var ai_socktype: Int32
    fileprivate(set) public var ai_protocol: Int32
    fileprivate(set) public var ai_addrlen: socklen_t
    fileprivate(set) public var ai_canonname: String?
    fileprivate(set) public var ai_addr: sockaddr_storage?
    fileprivate(set) public var ai_next: addrinfo?

    fileprivate init(
        ai_flags: Int32,
        ai_family: Int32,
        ai_socktype: Int32,
        ai_protocol: Int32,
        ai_addrlen: socklen_t,
        ai_canonname: String?,
        ai_addr: sockaddr_storage?,
        ai_next: addrinfo?)
    {
        self.ai_flags = ai_flags
        self.ai_family = ai_family
        self.ai_socktype = ai_socktype
        self.ai_protocol = ai_protocol
        self.ai_addrlen = ai_addrlen
        self.ai_canonname = ai_canonname
        self.ai_addr = ai_addr
        self.ai_next = ai_next
    }

    public convenience init(ai_flags: Int32, ai_family: Int32, ai_socktype: Int32, ai_protocol: Int32) {
        self.init(
            ai_flags: ai_flags,
            ai_family: ai_family,
            ai_socktype: ai_socktype,
            ai_protocol: ai_protocol,
            ai_addrlen: 0,
            ai_canonname: nil,
            ai_addr: nil,
            ai_next: nil)
    }
}

public func getaddrinfo(_ node: String?, _ service: String?, _ hints: addrinfo?) throws -> addrinfo? {
    if let hints = hints {
        precondition(hints.ai_addrlen == 0)
        precondition(hints.ai_canonname == nil)
        precondition(hints.ai_addr == nil)
        precondition(hints.ai_next == nil)
    }

    let err: Int32
    var res: UnsafeMutablePointer<Foundation.addrinfo>?
    if let hints = hints {
        var hints = Foundation.addrinfo(
            ai_flags: hints.ai_flags,
            ai_family: hints.ai_family,
            ai_socktype: hints.ai_socktype,
            ai_protocol: hints.ai_protocol,
            ai_addrlen: 0,
            ai_canonname: nil,
            ai_addr: nil,
            ai_next: nil)
        if let node = node {
            if let service = service {
                err = Foundation.getaddrinfo(node, service, &hints, &res)
            } else {
                err = Foundation.getaddrinfo(node, nil, &hints, &res)
            }
        } else {
            if let service = service {
                err = Foundation.getaddrinfo(nil, service, &hints, &res)
            } else {
                err = Foundation.getaddrinfo(nil, nil, &hints, &res)
            }
        }
    } else {
        if let node = node {
            if let service = service {
                err = Foundation.getaddrinfo(node, service, nil, &res)
            } else {
                err = Foundation.getaddrinfo(node, nil, nil, &res)
            }
        } else {
            if let service = service {
                err = Foundation.getaddrinfo(nil, service, nil, &res)
            } else {
                err = Foundation.getaddrinfo(nil, nil, nil, &res)
            }
        }
    }
    if err == EAI_SYSTEM {
        throw SystemError.getaddrinfo(err, errno)
    }
    if err != 0 {
        throw SystemError.getaddrinfo(err, nil)
    }
    defer {
        freeaddrinfo(res)
    }

    var result: addrinfo? = nil
    var ai_last: addrinfo? = nil
    if let res = res {
        for res in sequence(first: res.pointee, next: { $0.ai_next?.pointee }) {
            var ai_addr: sockaddr_storage?
            if res.ai_addr != nil {
                ai_addr = sockaddr_storage()
                assert(Int(res.ai_addrlen) <= MemoryLayout.size(ofValue: ai_addr))
                memcpy(&ai_addr, res.ai_addr!, Int(res.ai_addrlen))
            }
            let ai = addrinfo(
                ai_flags: res.ai_flags,
                ai_family: res.ai_family,
                ai_socktype: res.ai_socktype,
                ai_protocol: res.ai_protocol,
                ai_addrlen: res.ai_addrlen,
                ai_canonname: res.ai_canonname == nil ? nil : String(cString: res.ai_canonname!),
                ai_addr: ai_addr,
                ai_next: nil)

            result = result ?? ai
            ai_last?.ai_next = ai
            ai_last = ai
        }
    }
    return result
}