package controller

import (
	"bytes"
	"compress/gzip"
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/TwinProduction/gatus/config"
	"github.com/TwinProduction/gatus/security"
	"github.com/TwinProduction/gatus/watchdog"
	"github.com/TwinProduction/gocache"
	"github.com/TwinProduction/health"
	"github.com/gorilla/mux"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

const (
	cacheTTL = 10 * time.Second
)

var (
	cache = gocache.NewCache().WithMaxSize(100).WithEvictionPolicy(gocache.LeastRecentlyUsed)

	// staticFolder is the path to the location of the static folder from the root path of the project
	// The only reason this is exposed is to allow running tests from a different path than the root path of the project
	staticFolder = "./web/static"

	// server is the http.Server created by Handle.
	// The only reason it exists is for testing purposes.
	server *http.Server
)

func init() {
	if err := cache.StartJanitor(); err != nil {
		log.Fatal("[controller][init] Failed to start cache janitor:", err.Error())
	}
}

// Handle creates the router and starts the server
func Handle() {
	cfg := config.Get()
	var router http.Handler = CreateRouter(cfg)
	if os.Getenv("ENVIRONMENT") == "dev" {
		router = developmentCorsHandler(router)
	}
	server = &http.Server{
		Addr:         fmt.Sprintf("%s:%d", cfg.Web.Address, cfg.Web.Port),
		Handler:      router,
		ReadTimeout:  15 * time.Second,
		WriteTimeout: 15 * time.Second,
		IdleTimeout:  15 * time.Second,
	}
	log.Println("[controller][Handle] Listening on " + cfg.Web.SocketAddress())
	if os.Getenv("ROUTER_TEST") == "true" {
		return
	}
	log.Println("[controller][Handle]", server.ListenAndServe())
}

// Shutdown stops the server
func Shutdown() {
	if server != nil {
		_ = server.Shutdown(context.TODO())
		server = nil
	}
}

// CreateRouter creates the router for the http server
func CreateRouter(cfg *config.Config) *mux.Router {
	router := mux.NewRouter()
	if cfg.Metrics {
		router.Handle("/metrics", promhttp.Handler()).Methods("GET")
	}
	router.Handle("/health", health.Handler().WithJSON(true)).Methods("GET")
	router.HandleFunc("/favicon.ico", favIconHandler).Methods("GET")
	router.HandleFunc("/api/v1/statuses", secureIfNecessary(cfg, serviceStatusesHandler)).Methods("GET") // No GzipHandler for this one, because we cache the content
	router.HandleFunc("/api/v1/statuses/{key}", secureIfNecessary(cfg, GzipHandlerFunc(serviceStatusHandler))).Methods("GET")
	router.HandleFunc("/api/v1/badges/uptime/{duration}/{identifier}", badgeHandler).Methods("GET")
	// SPA
	router.HandleFunc("/services/{service}", spaHandler).Methods("GET")
	// Everything else falls back on static content
	router.PathPrefix("/").Handler(GzipHandler(http.FileServer(http.Dir(staticFolder))))
	return router
}

func secureIfNecessary(cfg *config.Config, handler http.HandlerFunc) http.HandlerFunc {
	if cfg.Security != nil && cfg.Security.IsValid() {
		return security.Handler(handler, cfg.Security)
	}
	return handler
}

// serviceStatusesHandler handles requests to retrieve all service statuses
// Due to the size of the response, this function leverages a cache.
// Must not be wrapped by GzipHandler
func serviceStatusesHandler(writer http.ResponseWriter, r *http.Request) {
	gzipped := strings.Contains(r.Header.Get("Accept-Encoding"), "gzip")
	var exists bool
	var value interface{}
	if gzipped {
		writer.Header().Set("Content-Encoding", "gzip")
		value, exists = cache.Get("service-status-gzipped")
	} else {
		value, exists = cache.Get("service-status")
	}
	var data []byte
	if !exists {
		var err error
		buffer := &bytes.Buffer{}
		gzipWriter := gzip.NewWriter(buffer)
		data, err = watchdog.GetServiceStatusesAsJSON()
		if err != nil {
			log.Printf("[controller][serviceStatusesHandler] Unable to marshal object to JSON: %s", err.Error())
			writer.WriteHeader(http.StatusInternalServerError)
			_, _ = writer.Write([]byte("Unable to marshal object to JSON"))
			return
		}
		_, _ = gzipWriter.Write(data)
		_ = gzipWriter.Close()
		gzippedData := buffer.Bytes()
		cache.SetWithTTL("service-status", data, cacheTTL)
		cache.SetWithTTL("service-status-gzipped", gzippedData, cacheTTL)
		if gzipped {
			data = gzippedData
		}
	} else {
		data = value.([]byte)
	}
	writer.Header().Add("Content-Type", "application/json")
	writer.WriteHeader(http.StatusOK)
	_, _ = writer.Write(data)
}

// serviceStatusHandler retrieves a single ServiceStatus by group name and service name
func serviceStatusHandler(writer http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	serviceStatus := watchdog.GetServiceStatusByKey(vars["key"])
	if serviceStatus == nil {
		log.Printf("[controller][serviceStatusHandler] Service with key=%s not found", vars["key"])
		writer.WriteHeader(http.StatusNotFound)
		_, _ = writer.Write([]byte("not found"))
		return
	}
	data := map[string]interface{}{
		"serviceStatus": serviceStatus,
		// The following fields, while present on core.ServiceStatus, are annotated to remain hidden so that we can
		// expose only the necessary data on /api/v1/statuses.
		// Since the /api/v1/statuses/{key} endpoint does need this data, however, we explicitly expose it here
		"events": serviceStatus.Events,
		"uptime": serviceStatus.Uptime,
	}
	output, err := json.Marshal(data)
	if err != nil {
		log.Printf("[controller][serviceStatusHandler] Unable to marshal object to JSON: %s", err.Error())
		writer.WriteHeader(http.StatusInternalServerError)
		_, _ = writer.Write([]byte("Unable to marshal object to JSON"))
		return
	}
	writer.Header().Add("Content-Type", "application/json")
	writer.WriteHeader(http.StatusOK)
	_, _ = writer.Write(output)
}

// favIconHandler handles requests for /favicon.ico
func favIconHandler(writer http.ResponseWriter, request *http.Request) {
	http.ServeFile(writer, request, staticFolder+"/favicon.ico")
}

// spaHandler handles requests for /favicon.ico
func spaHandler(writer http.ResponseWriter, request *http.Request) {
	http.ServeFile(writer, request, staticFolder+"/index.html")
}