/*
Package corehttp provides utilities for the webui, gateways, and other
high-level HTTP interfaces to IPFS.
*/
package corehttp

import (
	"net/http"
	"time"

	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
	core "github.com/ipfs/go-ipfs/core"
	eventlog "github.com/ipfs/go-ipfs/thirdparty/eventlog"
)

var log = eventlog.Logger("core/server")

// ServeOption registers any HTTP handlers it provides on the given mux.
// It returns the mux to expose to future options, which may be a new mux if it
// is interested in mediating requests to future options, or the same mux
// initially passed in if not.
type ServeOption func(*core.IpfsNode, *http.ServeMux) (*http.ServeMux, error)

// makeHandler turns a list of ServeOptions into a http.Handler that implements
// all of the given options, in order.
func makeHandler(n *core.IpfsNode, options ...ServeOption) (http.Handler, error) {
	topMux := http.NewServeMux()
	mux := topMux
	for _, option := range options {
		var err error
		mux, err = option(n, mux)
		if err != nil {
			return nil, err
		}
	}
	return topMux, nil
}

// ListenAndServe runs an HTTP server listening at |listeningMultiAddr| with
// the given serve options. The address must be provided in multiaddr format.
//
// TODO intelligently parse address strings in other formats so long as they
// unambiguously map to a valid multiaddr. e.g. for convenience, ":8080" should
// map to "/ip4/0.0.0.0/tcp/8080".
func ListenAndServe(n *core.IpfsNode, listeningMultiAddr string, options ...ServeOption) error {
	addr, err := ma.NewMultiaddr(listeningMultiAddr)
	if err != nil {
		return err
	}
	handler, err := makeHandler(n, options...)
	if err != nil {
		return err
	}
	return listenAndServe(n, addr, handler)
}

func listenAndServe(node *core.IpfsNode, addr ma.Multiaddr, handler http.Handler) error {
	_, host, err := manet.DialArgs(addr)
	if err != nil {
		return err
	}

	server := &http.Server{Addr: host, Handler: handler}

	// if the server exits beforehand
	var serverError error
	serverExited := make(chan struct{})

	node.Children().Add(1)
	defer node.Children().Done()

	go func() {
		serverError = server.ListenAndServe()
		close(serverExited)
	}()

	// wait for server to exit.
	select {
	case <-serverExited:

	// if node being closed before server exits, close server
	case <-node.Closing():
		log.Infof("server at %s terminating...", addr)

		// make sure keep-alive connections do not keep the server running
		server.SetKeepAlivesEnabled(false)

	outer:
		for {
			// wait until server exits
			select {
			case <-serverExited:
				break outer
			case <-time.After(5 * time.Second):
				log.Infof("waiting for server at %s to terminate...", addr)
			}
		}
	}

	log.Infof("server at %s terminated", addr)
	return serverError
}
