package proxy

import (
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/rancher/wrangler/pkg/kubeconfig"
	utilnet "k8s.io/apimachinery/pkg/util/net"
	"k8s.io/apimachinery/pkg/util/proxy"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/transport"
)

// Mostly copied from "kubectl proxy" code
func HandlerFromConfig(prefix, kubeConfig string) (http.Handler, error) {
	loader := kubeconfig.GetInteractiveClientConfig(kubeConfig)
	cfg, err := loader.ClientConfig()
	if err != nil {
		return nil, err
	}

	return Handler(prefix, cfg)
}

// Mostly copied from "kubectl proxy" code
func Handler(prefix string, cfg *rest.Config) (http.Handler, error) {
	host := cfg.Host
	if !strings.HasSuffix(host, "/") {
		host = host + "/"
	}
	target, err := url.Parse(host)
	if err != nil {
		return nil, err
	}

	transport, err := rest.TransportFor(cfg)
	if err != nil {
		return nil, err
	}
	upgradeTransport, err := makeUpgradeTransport(cfg, 0)
	if err != nil {
		return nil, err
	}

	proxy := proxy.NewUpgradeAwareHandler(target, transport, false, false, er)
	proxy.UpgradeTransport = upgradeTransport
	proxy.UseRequestLocation = true

	handler := setHost(target.Host, proxy)

	if len(target.Path) > 1 {
		handler = prependPath(target.Path[:len(target.Path)-1], handler)
	}

	if len(prefix) > 2 {
		return stripLeaveSlash(prefix, handler), nil
	}

	return handler, nil
}

func setHost(host string, h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		req.Host = host
		h.ServeHTTP(w, req)
	})
}

func prependPath(prefix string, h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		if len(req.URL.Path) > 1 {
			req.URL.Path = prefix + req.URL.Path
		} else {
			req.URL.Path = prefix
		}
		h.ServeHTTP(w, req)
	})
}

// like http.StripPrefix, but always leaves an initial slash. (so that our
// regexps will work.)
func stripLeaveSlash(prefix string, h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		p := strings.TrimPrefix(req.URL.Path, prefix)
		if len(p) >= len(req.URL.Path) {
			http.NotFound(w, req)
			return
		}
		if len(p) > 0 && p[:1] != "/" {
			p = "/" + p
		}
		req.URL.Path = p
		h.ServeHTTP(w, req)
	})
}

func makeUpgradeTransport(config *rest.Config, keepalive time.Duration) (proxy.UpgradeRequestRoundTripper, error) {
	transportConfig, err := config.TransportConfig()
	if err != nil {
		return nil, err
	}
	tlsConfig, err := transport.TLSConfigFor(transportConfig)
	if err != nil {
		return nil, err
	}
	rt := utilnet.SetOldTransportDefaults(&http.Transport{
		TLSClientConfig: tlsConfig,
		DialContext: (&net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: keepalive,
		}).DialContext,
	})

	upgrader, err := transport.HTTPWrappersForConfig(transportConfig, proxy.MirrorRequest)
	if err != nil {
		return nil, err
	}

	return proxy.NewUpgradeRequestRoundTripper(rt, upgrader), nil
}