package srv

import (
	"fmt"
	"html/template"
	"net/http"
	"path"
	"path/filepath"
	"time"

	"github.com/julienschmidt/httprouter"
	pb "github.com/linkerd/linkerd2/controller/gen/public"
	"github.com/linkerd/linkerd2/pkg/filesonly"
	"github.com/linkerd/linkerd2/pkg/prometheus"
	log "github.com/sirupsen/logrus"
)

const (
	timeout = 10 * time.Second
)

type (
	// Server encapsulates the Linkerd control plane's web dashboard server.
	Server struct {
		templateDir     string
		staticDir       string
		reload          bool
		templateContext templateContext
		templates       map[string]*template.Template
		router          *httprouter.Router
	}

	templateContext struct {
		WebpackDevServer string
	}
	templatePayload struct {
		Context  templateContext
		Contents interface{}
	}
	appParams struct {
		Data                pb.VersionInfo
		UUID                string
		ControllerNamespace string
		SingleNamespace     bool
		Error               bool
		ErrorMessage        string
		PathPrefix          string
	}
)

// this is called by the HTTP server to actually respond to a request
func (s *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	s.router.ServeHTTP(w, req)
}

// NewServer returns an initialized `http.Server`, configured to listen on an
// address, render templates, and serve static assets, for a given Linkerd
// control plane.
func NewServer(
	addr string,
	grafanaAddr string,
	templateDir string,
	staticDir string,
	uuid string,
	controllerNamespace string,
	singleNamespace bool,
	webpackDevServer string,
	reload bool,
	apiClient pb.ApiClient,
) *http.Server {
	server := &Server{
		templateDir:     templateDir,
		staticDir:       staticDir,
		templateContext: templateContext{webpackDevServer},
		reload:          reload,
	}

	server.router = &httprouter.Router{
		RedirectTrailingSlash:  true,
		RedirectFixedPath:      true,
		HandleMethodNotAllowed: false, // disable 405s
	}

	wrappedServer := prometheus.WithTelemetry(server)
	handler := &handler{
		apiClient:           apiClient,
		render:              server.RenderTemplate,
		serveFile:           server.serveFile,
		uuid:                uuid,
		controllerNamespace: controllerNamespace,
		singleNamespace:     singleNamespace,
		grafanaProxy:        newGrafanaProxy(grafanaAddr),
	}

	httpServer := &http.Server{
		Addr:         addr,
		ReadTimeout:  timeout,
		WriteTimeout: timeout,
		Handler:      wrappedServer,
	}

	// webapp routes
	server.router.GET("/", handler.handleIndex)
	server.router.GET("/overview", handler.handleIndex)
	server.router.GET("/servicemesh", handler.handleIndex)
	server.router.GET("/namespaces", handler.handleIndex)
	server.router.GET("/namespaces/:namespace", handler.handleIndex)
	server.router.GET("/deployments", handler.handleIndex)
	server.router.GET("/replicationcontrollers", handler.handleIndex)
	server.router.GET("/pods", handler.handleIndex)
	server.router.GET("/authorities", handler.handleIndex)
	server.router.GET("/namespaces/:namespace/pods/:pod", handler.handleIndex)
	server.router.GET("/namespaces/:namespace/deployments/:deployment", handler.handleIndex)
	server.router.GET("/namespaces/:namespace/replicationcontrollers/:replicationcontroller", handler.handleIndex)
	server.router.GET("/tap", handler.handleIndex)
	server.router.GET("/top", handler.handleIndex)
	server.router.GET("/routes", handler.handleIndex)
	server.router.GET("/profiles/new", handler.handleProfileDownload)
	server.router.ServeFiles(
		"/dist/*filepath", // add catch-all parameter to match all files in dir
		filesonly.FileSystem(server.staticDir))

	// webapp api routes
	server.router.GET("/api/version", handler.handleAPIVersion)
	// Traffic Performance Summary.  This route used to be called /api/stat
	// but was renamed to avoid triggering ad blockers.
	// See: https://github.com/linkerd/linkerd2/issues/970
	server.router.GET("/api/tps-reports", handler.handleAPIStat)
	server.router.GET("/api/pods", handler.handleAPIPods)
	server.router.GET("/api/services", handler.handleAPIServices)
	server.router.GET("/api/tap", handler.handleAPITap)
	server.router.GET("/api/routes", handler.handleAPITopRoutes)

	// grafana proxy
	server.router.DELETE("/grafana/*grafanapath", handler.handleGrafana)
	server.router.GET("/grafana/*grafanapath", handler.handleGrafana)
	server.router.HEAD("/grafana/*grafanapath", handler.handleGrafana)
	server.router.OPTIONS("/grafana/*grafanapath", handler.handleGrafana)
	server.router.PATCH("/grafana/*grafanapath", handler.handleGrafana)
	server.router.POST("/grafana/*grafanapath", handler.handleGrafana)
	server.router.PUT("/grafana/*grafanapath", handler.handleGrafana)

	return httpServer
}

// RenderTemplate writes a rendered template into a buffer, given an HTTP
// request and template information.
func (s *Server) RenderTemplate(w http.ResponseWriter, templateFile, templateName string, args interface{}) error {
	log.Debugf("emitting template %s", templateFile)
	template, err := s.loadTemplate(templateFile)

	if err != nil {
		log.Error(err.Error())
		http.Error(w, "internal server error", http.StatusInternalServerError)
		return nil
	}

	w.Header().Set("Content-Type", "text/html")
	if templateName == "" {
		return template.Execute(w, args)
	}

	return template.ExecuteTemplate(w, templateName, templatePayload{Context: s.templateContext, Contents: args})
}

func (s *Server) loadTemplate(templateFile string) (template *template.Template, err error) {
	// load template from disk if necessary
	template = s.templates[templateFile]

	if template == nil || s.reload {
		templatePath := safelyJoinPath(s.templateDir, templateFile)
		includes, err := filepath.Glob(filepath.Join(s.templateDir, "includes", "*.tmpl.html"))
		if err != nil {
			return nil, err
		}
		// for cases where you're not calling a named template, the passed-in path needs to be first
		templateFiles := append([]string{templatePath}, includes...)
		log.Debugf("loading templates from %v", templateFiles)
		template, err = template.ParseFiles(templateFiles...)
		if err == nil && !s.reload {
			s.templates[templateFile] = template
		}
	}
	return template, err
}

func safelyJoinPath(rootPath, userPath string) string {
	return filepath.Join(rootPath, path.Clean("/"+userPath))
}

func (s *Server) serveFile(w http.ResponseWriter, fileName string, templateName string, args interface{}) error {
	dispositionHeaderVal := fmt.Sprintf("attachment; filename='%s'", fileName)

	w.Header().Set("Content-Type", "text/yaml")
	w.Header().Set("Content-Disposition", dispositionHeaderVal)

	template, err := s.loadTemplate(templateName)
	if err != nil {
		return err
	}

	template.Execute(w, args)
	return nil
}