// TINYGO: The following is copied and modified from Go 1.26.2 official implementation.

// TINYGO: Omit DualStack support
// TINYGO: Omit Fast Fallback support
// TINYGO: Don't allow alternate resolver
// TINYGO: Omit DialTimeout
// TINYGO: Omit Multipath TCP

// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package net

import (
	"context"
	"errors"
	"fmt"
	"internal/bytealg"
	"syscall"
	"time"
)

const (
	// defaultTCPKeepAlive is a default constant value for TCPKeepAlive times
	// See go.dev/issue/31510
	defaultTCPKeepAlive = 15 * time.Second
)

// mptcpStatus is a tristate for Multipath TCP, see go.dev/issue/56539
type mptcpStatus uint8

// TINYGO: mptcpStatusListen stub for ListenConfig compatibility
type mptcpStatusListen uint8

// A Dialer contains options for connecting to an address.
//
// The zero value for each field is equivalent to dialing
// without that option. Dialing with the zero value of Dialer
// is therefore equivalent to just calling the [Dial] function.
//
// It is safe to call Dialer's methods concurrently.
type Dialer struct {
	// Timeout is the maximum amount of time a dial will wait for
	// a connect to complete. If Deadline is also set, it may fail
	// earlier.
	//
	// The default is no timeout.
	//
	// When using TCP and dialing a host name with multiple IP
	// addresses, the timeout may be divided between them.
	//
	// With or without a timeout, the operating system may impose
	// its own earlier timeout. For instance, TCP timeouts are
	// often around 3 minutes.
	Timeout time.Duration

	// Deadline is the absolute point in time after which dials
	// will fail. If Timeout is set, it may fail earlier.
	// Zero means no deadline, or dependent on the operating system
	// as with the Timeout option.
	Deadline time.Time

	// LocalAddr is the local address to use when dialing an
	// address. The address must be of a compatible type for the
	// network being dialed.
	// If nil, a local address is automatically chosen.
	LocalAddr Addr

	// KeepAlive specifies the interval between keep-alive
	// probes for an active network connection.
	//
	// KeepAlive is ignored if KeepAliveConfig.Enable is true.
	//
	// If zero, keep-alive probes are sent with a default value
	// (currently 15 seconds), if supported by the protocol and operating
	// system. Network protocols or operating systems that do
	// not support keep-alive ignore this field.
	// If negative, keep-alive probes are disabled.
	KeepAlive time.Duration

	// KeepAliveConfig specifies the keep-alive probe configuration
	// for an active network connection, when supported by the
	// protocol and operating system.
	//
	// If KeepAliveConfig.Enable is true, keep-alive probes are enabled.
	// If KeepAliveConfig.Enable is false and KeepAlive is negative,
	// keep-alive probes are disabled.
	KeepAliveConfig KeepAliveConfig

	// Resolver optionally specifies an alternate resolver to use.
	//
	// TINYGO: present for API compatibility; DialContext resolves via the
	// netdev-backed ResolveTCPAddr/ResolveUDPAddr and does not consult this
	// field.
	Resolver *Resolver
}

// Dial connects to the address on the named network.
//
// See Go "net" package Dial() for more information.
//
// Note: Tinygo Dial supports a subset of networks supported by Go Dial,
// specifically: "tcp", "tcp4", "udp", and "udp4".  IP and unix networks are
// not supported.
func Dial(network, address string) (Conn, error) {
	var d Dialer
	return d.Dial(network, address)
}

// DialTimeout acts like [Dial] but takes a timeout.
//
// The timeout includes name resolution, if required.
// When using TCP, and the host in the address parameter resolves to
// multiple IP addresses, the timeout is spread over each consecutive
// dial, such that each is given an appropriate fraction of the time
// to connect.
//
// See func Dial for a description of the network and address
// parameters.
func DialTimeout(network, address string, timeout time.Duration) (Conn, error) {
	d := Dialer{Timeout: timeout}
	return d.Dial(network, address)
}

// Dial connects to the address on the named network.
//
// See func Dial for a description of the network and address
// parameters.
//
// Dial uses [context.Background] internally; to specify the context, use
// [Dialer.DialContext].
func (d *Dialer) Dial(network, address string) (Conn, error) {
	return d.DialContext(context.Background(), network, address)
}

// DialContext connects to the address on the named network using
// the provided context.
//
// The provided Context must be non-nil. If the context expires before
// the connection is complete, an error is returned. Once successfully
// connected, any expiration of the context will not affect the
// connection.
//
// When using TCP, and the host in the address parameter resolves to multiple
// network addresses, any dial timeout (from d.Timeout or ctx) is spread
// over each consecutive dial, such that each is given an appropriate
// fraction of the time to connect.
// For example, if a host has 4 IP addresses and the timeout is 1 minute,
// the connect to each single address will be given 15 seconds to complete
// before trying the next one.
//
// See func [Dial] for a description of the network and address
// parameters.
func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {

	// TINYGO: Ignoring context

	switch network {
	case "tcp", "tcp4":
		raddr, err := ResolveTCPAddr(network, address)
		if err != nil {
			return nil, err
		}
		return DialTCP(network, nil, raddr)
	case "udp", "udp4":
		raddr, err := ResolveUDPAddr(network, address)
		if err != nil {
			return nil, err
		}
		return DialUDP(network, nil, raddr)
	}

	return nil, fmt.Errorf("Network %s not supported", network)
}

// ListenConfig contains options for listening to an address.
type ListenConfig struct {
	// If Control is not nil, it is called after creating the network
	// connection but before binding it to the operating system.
	//
	// Network and address parameters passed to Control function are not
	// necessarily the ones passed to Listen. Calling Listen with TCP networks
	// will cause the Control function to be called with "tcp4" or "tcp6",
	// UDP networks become "udp4" or "udp6", IP networks become "ip4" or "ip6",
	// and other known networks are passed as-is.
	Control func(network, address string, c syscall.RawConn) error

	// KeepAlive specifies the keep-alive period for network
	// connections accepted by this listener.
	//
	// KeepAlive is ignored if KeepAliveConfig.Enable is true.
	//
	// If zero, keep-alive are enabled if supported by the protocol
	// and operating system. Network protocols or operating systems
	// that do not support keep-alive ignore this field.
	// If negative, keep-alive are disabled.
	KeepAlive time.Duration

	// KeepAliveConfig specifies the keep-alive probe configuration
	// for an active network connection, when supported by the
	// protocol and operating system.
	//
	// If KeepAliveConfig.Enable is true, keep-alive probes are enabled.
	// If KeepAliveConfig.Enable is false and KeepAlive is negative,
	// keep-alive probes are disabled.
	KeepAliveConfig KeepAliveConfig

	// If mptcpStatus is set to a value allowing Multipath TCP (MPTCP) to be
	// used, any call to Listen with "tcp(4|6)" as network will use MPTCP if
	// supported by the operating system.
	mptcpStatus mptcpStatusListen
}

// Listen announces on the local network address.
//
// See func Listen for a description of the network and address
// parameters.
//
// The ctx argument is used while resolving the address on which to listen;
// it does not affect the returned Listener.
func (lc *ListenConfig) Listen(ctx context.Context, network, address string) (Listener, error) {
	return nil, errors.New("dial:ListenConfig:Listen not implemented")
}

// ListenPacket announces on the local network address.
//
// See func ListenPacket for a description of the network and address
// parameters.
//
// The ctx argument is used while resolving the address on which to listen;
// it does not affect the returned PacketConn.
func (lc *ListenConfig) ListenPacket(ctx context.Context, network, address string) (PacketConn, error) {
	return nil, errors.New("dial:ListenConfig:ListenPacket not implemented")
}

func parseNetwork(ctx context.Context, network string, needsProto bool) (afnet string, proto int, err error) {
	i := bytealg.LastIndexByteString(network, ':')
	if i < 0 { // no colon
		switch network {
		case "tcp", "tcp4", "tcp6":
		case "udp", "udp4", "udp6":
		case "ip", "ip4", "ip6":
			if needsProto {
				return "", 0, UnknownNetworkError(network)
			}
		case "unix", "unixgram", "unixpacket":
		default:
			return "", 0, UnknownNetworkError(network)
		}
		return network, 0, nil
	}
	afnet = network[:i]
	switch afnet {
	case "ip", "ip4", "ip6":
		protostr := network[i+1:]
		proto, i, ok := dtoi(protostr)
		if !ok || i != len(protostr) {
			proto, err = lookupProtocol(ctx, protostr)
			if err != nil {
				return "", 0, err
			}
		}
		return afnet, proto, nil
	}
	return "", 0, UnknownNetworkError(network)
}

// Listen announces on the local network address.
//
// See Go "net" package Listen() for more information.
//
// Note: Tinygo Listen supports a subset of networks supported by Go Listen,
// specifically: "tcp", "tcp4".  "tcp6" and unix networks are not supported.
func Listen(network, address string) (Listener, error) {

	//	println("Listen", address)
	switch network {
	case "tcp", "tcp4":
	default:
		return nil, fmt.Errorf("Network %s not supported", network)
	}

	laddr, err := ResolveTCPAddr(network, address)
	if err != nil {
		return nil, err
	}

	return listenTCP(laddr)
}

// ListenPacket announces on the local network address.
//
// TINYGO: only UDP networks are supported, backed by ListenUDP; the
// returned PacketConn is a *UDPConn.
func ListenPacket(network, address string) (PacketConn, error) {
	switch network {
	case "udp", "udp4":
	default:
		return nil, fmt.Errorf("Network %s not supported", network)
	}

	laddr, err := ResolveUDPAddr(network, address)
	if err != nil {
		return nil, err
	}

	return ListenUDP(network, laddr)
}