/*
Copyright 2014 Google Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package kubelet

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/httplog"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/types"
	"github.com/golang/glog"
	"github.com/google/cadvisor/info"
)

// Server is a http.Handler which exposes kubelet functionality over HTTP.
type Server struct {
	host HostInterface
	mux  *http.ServeMux
}

// ListenAndServeKubeletServer initializes a server to respond to HTTP network requests on the Kubelet.
func ListenAndServeKubeletServer(host HostInterface, address net.IP, port uint, enableDebuggingHandlers bool) {
	glog.V(1).Infof("Starting to listen on %s:%d", address, port)
	handler := NewServer(host, enableDebuggingHandlers)
	s := &http.Server{
		Addr:           net.JoinHostPort(address.String(), strconv.FormatUint(uint64(port), 10)),
		Handler:        &handler,
		ReadTimeout:    5 * time.Minute,
		WriteTimeout:   5 * time.Minute,
		MaxHeaderBytes: 1 << 20,
	}
	glog.Fatal(s.ListenAndServe())
}

// HostInterface contains all the kubelet methods required by the server.
// For testablitiy.
type HostInterface interface {
	GetContainerInfo(podFullName string, uid types.UID, containerName string, req *info.ContainerInfoRequest) (*info.ContainerInfo, error)
	GetRootInfo(req *info.ContainerInfoRequest) (*info.ContainerInfo, error)
	GetDockerVersion() ([]uint, error)
	GetMachineInfo() (*info.MachineInfo, error)
	GetBoundPods() ([]api.BoundPod, error)
	GetPodByName(namespace, name string) (*api.BoundPod, bool)
	GetPodStatus(name string, uid types.UID) (api.PodStatus, error)
	RunInContainer(name string, uid types.UID, container string, cmd []string) ([]byte, error)
	GetKubeletContainerLogs(podFullName, containerName, tail string, follow bool, stdout, stderr io.Writer) error
	ServeLogs(w http.ResponseWriter, req *http.Request)
}

// NewServer initializes and configures a kubelet.Server object to handle HTTP requests.
func NewServer(host HostInterface, enableDebuggingHandlers bool) Server {
	server := Server{
		host: host,
		mux:  http.NewServeMux(),
	}
	server.InstallDefaultHandlers()
	if enableDebuggingHandlers {
		server.InstallDebuggingHandlers()
	}
	return server
}

// InstallDefaultHandlers registers the default set of supported HTTP request patterns with the mux.
func (s *Server) InstallDefaultHandlers() {
	s.mux.HandleFunc("/healthz", s.handleHealthz)
	s.mux.HandleFunc("/podInfo", s.handlePodInfoOld)
	s.mux.HandleFunc("/api/v1beta1/podInfo", s.handlePodInfoVersioned)
	s.mux.HandleFunc("/boundPods", s.handleBoundPods)
	s.mux.HandleFunc("/stats/", s.handleStats)
	s.mux.HandleFunc("/spec/", s.handleSpec)
}

// InstallDeguggingHandlers registers the HTTP request patterns that serve logs or run commands/containers
func (s *Server) InstallDebuggingHandlers() {
	s.mux.HandleFunc("/run/", s.handleRun)

	s.mux.HandleFunc("/logs/", s.handleLogs)
	s.mux.HandleFunc("/containerLogs/", s.handleContainerLogs)
}

// error serializes an error object into an HTTP response.
func (s *Server) error(w http.ResponseWriter, err error) {
	http.Error(w, fmt.Sprintf("Internal Error: %v", err), http.StatusInternalServerError)
}

func isValidDockerVersion(ver []uint) (bool, string) {
	minAllowedVersion := []uint{1, 15}
	for i := 0; i < len(ver) && i < len(minAllowedVersion); i++ {
		if ver[i] != minAllowedVersion[i] {
			if ver[i] < minAllowedVersion[i] {
				versions := make([]string, len(ver))
				for i, v := range ver {
					versions[i] = fmt.Sprint(v)
				}
				return false, strings.Join(versions, ".")
			}
			return true, ""
		}
	}
	return true, ""
}

// handleHealthz handles /healthz request and checks Docker version
func (s *Server) handleHealthz(w http.ResponseWriter, req *http.Request) {
	versions, err := s.host.GetDockerVersion()
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("unknown Docker version"))
		return
	}
	valid, version := isValidDockerVersion(versions)
	if !valid {
		w.WriteHeader(http.StatusInternalServerError)
		msg := "Docker version is too old (" + version + ")"
		w.Write([]byte(msg))
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Write([]byte("ok"))
}

// handleContainerLogs handles containerLogs request against the Kubelet
func (s *Server) handleContainerLogs(w http.ResponseWriter, req *http.Request) {
	defer req.Body.Close()
	u, err := url.ParseRequestURI(req.RequestURI)
	if err != nil {
		s.error(w, err)
		return
	}
	parts := strings.Split(u.Path, "/")

	// req URI: /containerLogs/<podNamespace>/<podID>/<containerName>
	var podNamespace, podID, containerName string
	if len(parts) == 5 {
		podNamespace = parts[2]
		podID = parts[3]
		containerName = parts[4]
	} else {
		http.Error(w, "Unexpected path for command running", http.StatusBadRequest)
		return
	}

	if len(podID) == 0 {
		http.Error(w, `{"message": "Missing podID."}`, http.StatusBadRequest)
		return
	}
	if len(containerName) == 0 {
		http.Error(w, `{"message": "Missing container name."}`, http.StatusBadRequest)
		return
	}
	if len(podNamespace) == 0 {
		http.Error(w, `{"message": "Missing podNamespace."}`, http.StatusBadRequest)
		return
	}

	uriValues := u.Query()
	follow, _ := strconv.ParseBool(uriValues.Get("follow"))
	tail := uriValues.Get("tail")

	pod, ok := s.host.GetPodByName(podNamespace, podID)
	if !ok {
		http.Error(w, fmt.Sprintf("Pod %q does not exist", podID), http.StatusNotFound)
		return
	}
	// Check if containerName is valid.
	containerExists := false
	for _, container := range pod.Spec.Containers {
		if container.Name == containerName {
			containerExists = true
		}
	}
	if !containerExists {
		http.Error(w, fmt.Sprintf("Container %q not found in Pod %q", containerName, podID), http.StatusNotFound)
		return
	}

	fw := FlushWriter{writer: w}
	if flusher, ok := fw.writer.(http.Flusher); ok {
		fw.flusher = flusher
	} else {
		s.error(w, fmt.Errorf("unable to convert %v into http.Flusher", fw))
	}
	w.Header().Set("Transfer-Encoding", "chunked")
	w.WriteHeader(http.StatusOK)
	err = s.host.GetKubeletContainerLogs(GetPodFullName(pod), containerName, tail, follow, &fw, &fw)
	if err != nil {
		s.error(w, err)
		return
	}
}

// handleBoundPods returns a list of pod bound to the Kubelet and their spec
func (s *Server) handleBoundPods(w http.ResponseWriter, req *http.Request) {
	pods, err := s.host.GetBoundPods()
	if err != nil {
		s.error(w, err)
		return
	}
	boundPods := &api.BoundPods{
		Items: pods,
	}
	data, err := latest.Codec.Encode(boundPods)
	if err != nil {
		s.error(w, err)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Header().Add("Content-type", "application/json")
	w.Write(data)
}

func (s *Server) handlePodInfoOld(w http.ResponseWriter, req *http.Request) {
	s.handlePodStatus(w, req, false)
}

func (s *Server) handlePodInfoVersioned(w http.ResponseWriter, req *http.Request) {
	s.handlePodStatus(w, req, true)
}

// handlePodStatus handles podInfo requests against the Kubelet
func (s *Server) handlePodStatus(w http.ResponseWriter, req *http.Request, versioned bool) {
	u, err := url.ParseRequestURI(req.RequestURI)
	if err != nil {
		s.error(w, err)
		return
	}
	podID := u.Query().Get("podID")
	podUID := types.UID(u.Query().Get("UUID"))
	podNamespace := u.Query().Get("podNamespace")
	if len(podID) == 0 {
		w.WriteHeader(http.StatusBadRequest)
		http.Error(w, "Missing 'podID=' query entry.", http.StatusBadRequest)
		return
	}
	if len(podNamespace) == 0 {
		w.WriteHeader(http.StatusBadRequest)
		http.Error(w, "Missing 'podNamespace=' query entry.", http.StatusBadRequest)
		return
	}
	pod, ok := s.host.GetPodByName(podNamespace, podID)
	if !ok {
		http.Error(w, "Pod does not exist", http.StatusNotFound)
		return
	}
	status, err := s.host.GetPodStatus(GetPodFullName(pod), podUID)
	if err != nil {
		s.error(w, err)
		return
	}
	data, err := exportPodStatus(status, versioned)
	if err != nil {
		s.error(w, err)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Header().Add("Content-type", "application/json")
	w.Write(data)
}

// handleStats handles stats requests against the Kubelet.
func (s *Server) handleStats(w http.ResponseWriter, req *http.Request) {
	s.serveStats(w, req)
}

// handleLogs handles logs requests against the Kubelet.
func (s *Server) handleLogs(w http.ResponseWriter, req *http.Request) {
	s.host.ServeLogs(w, req)
}

// handleSpec handles spec requests against the Kubelet.
func (s *Server) handleSpec(w http.ResponseWriter, req *http.Request) {
	info, err := s.host.GetMachineInfo()
	if err != nil {
		s.error(w, err)
		return
	}
	data, err := json.Marshal(info)
	if err != nil {
		s.error(w, err)
		return
	}
	w.Header().Add("Content-type", "application/json")
	w.Write(data)

}

// handleRun handles requests to run a command inside a container.
func (s *Server) handleRun(w http.ResponseWriter, req *http.Request) {
	u, err := url.ParseRequestURI(req.RequestURI)
	if err != nil {
		s.error(w, err)
		return
	}
	parts := strings.Split(u.Path, "/")
	var podNamespace, podID, container string
	var uid types.UID
	if len(parts) == 5 {
		podNamespace = parts[2]
		podID = parts[3]
		container = parts[4]
	} else if len(parts) == 6 {
		podNamespace = parts[2]
		podID = parts[3]
		uid = types.UID(parts[4])
		container = parts[5]
	} else {
		http.Error(w, "Unexpected path for command running", http.StatusBadRequest)
		return
	}
	pod, ok := s.host.GetPodByName(podNamespace, podID)
	if !ok {
		http.Error(w, "Pod does not exist", http.StatusNotFound)
		return
	}
	command := strings.Split(u.Query().Get("cmd"), " ")
	data, err := s.host.RunInContainer(GetPodFullName(pod), uid, container, command)
	if err != nil {
		s.error(w, err)
		return
	}
	w.Header().Add("Content-type", "text/plain")
	w.Write(data)
}

// ServeHTTP responds to HTTP requests on the Kubelet.
func (s *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	defer httplog.NewLogged(req, &w).StacktraceWhen(
		httplog.StatusIsNot(
			http.StatusOK,
			http.StatusMovedPermanently,
			http.StatusTemporaryRedirect,
			http.StatusNotFound,
		),
	).Log()
	s.mux.ServeHTTP(w, req)
}

// serveStats implements stats logic.
func (s *Server) serveStats(w http.ResponseWriter, req *http.Request) {
	// /stats/<podfullname>/<containerName> or /stats/<namespace>/<podfullname>/<uid>/<containerName>
	components := strings.Split(strings.TrimPrefix(path.Clean(req.URL.Path), "/"), "/")
	var stats *info.ContainerInfo
	var err error
	var query info.ContainerInfoRequest
	err = json.NewDecoder(req.Body).Decode(&query)
	if err != nil && err != io.EOF {
		s.error(w, err)
		return
	}
	switch len(components) {
	case 1:
		// Machine stats
		stats, err = s.host.GetRootInfo(&query)
	case 2:
		// pod stats
		// TODO(monnand) Implement this
		errors.New("pod level status currently unimplemented")
	case 3:
		// Backward compatibility without uid information, does not support namespace
		pod, ok := s.host.GetPodByName(api.NamespaceDefault, components[1])
		if !ok {
			http.Error(w, "Pod does not exist", http.StatusNotFound)
			return
		}
		stats, err = s.host.GetContainerInfo(GetPodFullName(pod), "", components[2], &query)
	case 5:
		pod, ok := s.host.GetPodByName(components[1], components[2])
		if !ok {
			http.Error(w, "Pod does not exist", http.StatusNotFound)
			return
		}
		stats, err = s.host.GetContainerInfo(GetPodFullName(pod), types.UID(components[3]), components[4], &query)
	default:
		http.Error(w, "unknown resource.", http.StatusNotFound)
		return
	}
	if err != nil {
		s.error(w, err)
		return
	}
	if stats == nil {
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, "{}")
		return
	}
	data, err := json.Marshal(stats)
	if err != nil {
		s.error(w, err)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Header().Add("Content-type", "application/json")
	w.Write(data)
	return
}

func exportPodStatus(status api.PodStatus, versioned bool) ([]byte, error) {
	if versioned {
		// TODO: support arbitrary versions here
		codec, err := findCodec("v1beta1")
		if err != nil {
			return nil, err
		}
		return codec.Encode(&api.PodStatusResult{Status: status})
	}
	return json.Marshal(status)
}

func findCodec(version string) (runtime.Codec, error) {
	versions, err := latest.InterfacesFor(version)
	if err != nil {
		return nil, err
	}
	return versions.Codec, nil
}