// Copyright (C) 2019 Marius Schellenberger

package main

import (
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"reflect"
	"regexp"
	"time"
	//corev1 "k8s.io/api/core/v1"

	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
)

var debug = false

const (
	prAction           = "X-Interceptor-Pr-Action"
	pushRef            = "X-Interceptor-Push-Ref"
	commentHeader      = "X-Interceptor-Comment"
	commentAction      = "X-Interceptor-Comment-Action"
	labelHeader        = "X-Interceptor-Label"
	removeLabelsHeader = "X-Interceptor-Remove-Labels"

	githubEvent = "X-GitHub-Event"
	giteaEvent  = "X-Gitea-Event"

	issueHeader  = "Issue"
	commitHeader = "Commit"
)

func init() {
	log.SetFlags(log.Flags() | log.Lshortfile)
}

type Handler struct {
	git *Git
}

func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	event := r.Header.Get(githubEvent)
	switch event {
	case "pull_request":
		h.prHandler(w, r)
	case "push":
		h.pushHandler(w, r)
	case "issue_comment":
		h.commentHandler(w, r)
	default:
		h.dumpHandler(w, r)
	}
	status := int(reflect.Indirect(reflect.ValueOf(w)).FieldByName("status").Int())
	log.Printf("%s %s %s event:%s status:%d", r.RemoteAddr, r.Method, r.URL, event, status)
}

func (h *Handler) prHandler(w http.ResponseWriter, r *http.Request) {
	var prb PullRequestBody
	body, err := readBody(r.Body, &prb)
	if err != nil {
		logError(w, err.Error())
		return
	}

	if contains(r.Header[prAction], prb.Action) {
		if l := r.Header.Get(labelHeader); l != "" {
			label, _ := getLabel(l)
			var labels []string
			for _, l := range prb.PullRequest.Labels {
				labels = append(labels, l.Name)
			}

			if !contains(labels, label) {
				w.WriteHeader(http.StatusBadRequest)
				return
			}
		}
		h := w.Header()
		h.Set(issueHeader, itoa(prb.Number))
		h.Set(commitHeader, prb.PullRequest.Head.SHA)
		w.Write(body)
		return
	}
	w.WriteHeader(http.StatusBadRequest)
}

func (h *Handler) pushHandler(w http.ResponseWriter, r *http.Request) {
	var pb PushBody
	body, err := readBody(r.Body, &pb)
	if err != nil {
		logError(w, err.Error())
		return
	}
	push := r.Header.Get(pushRef)
	//if contains(r.Header[pushAction], pb.Ref) {
	if push != "" && push == pb.Ref {
		h := w.Header()
		h.Set(commitHeader, pb.After)
		w.Write(body)
		return
	}
	w.WriteHeader(http.StatusBadRequest)
}

func (h *Handler) commentHandler(w http.ResponseWriter, r *http.Request) {
	var cb CommentBody
	body, err := readBody(r.Body, &cb)
	if err != nil {
		logError(w, err.Error())
		return
	}

	if !contains(r.Header[commentAction], cb.Action) {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	//if contains(r.Header[commentAction], cb.Comment.Body) {
	comment := r.Header.Get(commentHeader)
	if comment == "" {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	m, err := regexp.MatchString("(?m)^"+comment+"$", cb.Comment.Body)
	if err != nil {
		logError(w, err.Error())
		return
	}
	if m {
		issue := itoa(cb.Issue.Number)
		api := detectAPI(r)
		if api == "" {
			logError(w, "unable to detect git provider API")
			return
		}
		if l := r.Header.Get(labelHeader); l != "" {
			label, color := getLabel(l)
			var labels []string
			for _, l := range cb.Issue.Labels {
				labels = append(labels, l.Name)
			}
			if !contains(labels, label) {
				err := h.git.setLabel(cb.Repository, api, issue, label, color, r.Header[removeLabelsHeader])
				if err != nil {
					logError(w, err.Error())
					return
				}
			}
		}

		pr, err := h.git.getPullRequest(cb.Repository, api, issue)
		if err != nil {
			logError(w, err.Error())
			return
		}

		h := w.Header()
		h.Set(issueHeader, issue)
		h.Set(commitHeader, pr.Head.SHA)
		w.Write(body)
		return
	}
	w.WriteHeader(http.StatusBadRequest)
}

func (h *Handler) dumpHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	if debug {
		body, err := ioutil.ReadAll(r.Body)
		if err != nil {
			logError(w, err.Error())
			return
		}
		log.Printf("debug headers: %#v", r.Header)
		log.Printf("debug: %s", string(body))
	}
	w.WriteHeader(http.StatusBadRequest)
}

func main() {
	cfg, err := rest.InClusterConfig()
	if err != nil {
		log.Fatalf("error configuring kube client: %s\n", err)
	}
	cl, err := kubernetes.NewForConfig(cfg)
	if err != nil {
		log.Fatalf("error creating new kube client: %s\n", err)
	}
	ns, err := getNS()
	if err != nil {
		log.Fatalf("error getting current namespace %s\n", err)
	}
	h := &Handler{
		&Git{
			sec: cl.CoreV1().Secrets(ns),
			cl: &http.Client{Transport: &http.Transport{
				DialContext: (&net.Dialer{
					Timeout: 30 * time.Second,
				}).DialContext,
			}},
		},
	}

	http.Handle("/", h)
	s := &http.Server{
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  120 * time.Second,
		Addr:         ":8080",
	}
	log.Println("started webhook listener")
	log.Fatal(s.ListenAndServe())
}