package rushlink

import (
	"fmt"
	"log"
	"net/http"
	"net/url"
	"runtime/debug"
	"strconv"
	"time"

	"gitea.hashru.nl/dsprenkels/rushlink/internal/db"
	"github.com/gorilla/mux"
	"github.com/pkg/errors"
)

const staticFilenameExpr = "[A-Za-z0-9-_.]+"
const urlKeyExpr = "{key:[A-Za-z0-9-_]{4,}}"
const urlKeyWithExtExpr = urlKeyExpr + "{ext:\\.[A-Za-z0-9-_]+}"

type rushlink struct {
	db      *db.Database
	fs      *db.FileStore
	rootURL *url.URL
}

func (rl *rushlink) RootURL() *url.URL {
	return rl.rootURL
}

func (rl *rushlink) recoveryMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		logRequestInfo := func() {
			log.Printf("in request: %v - %v %q %v", r.RemoteAddr, r.Method, r.RequestURI, r.Proto)
		}
		defer func() {
			defer func() {
				if err := recover(); err != nil {
					w.WriteHeader(500)
					log.Printf("error: panic while recovering from another panic: %v\n", err)
					logRequestInfo()
					debug.PrintStack()
					fmt.Fprintf(w, "internal server error: %v\n", err)
				}
			}()

			if err := recover(); err != nil {
				w.WriteHeader(500)
				log.Printf("error: %v\n", err)
				logRequestInfo()
				debug.PrintStack()
				rl.renderInternalServerError(w, r, err)
			}
		}()
		next.ServeHTTP(w, r)
	})
}

func (rl *rushlink) metricsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tick := time.Now()
		srw := statusResponseWriter{Inner: w}
		next.ServeHTTP(&srw, r)
		tock := time.Now()

		status := strconv.Itoa(srw.StatusCode)
		labels := map[string]string{"code": status, "method": r.Method}
		// Update requests counter metric
		metricRequestsTotalCounter.With(labels).Inc()
		// Update request latency metric
		elapsed := tock.Sub(tick)
		metricRequestsLatencyNanoSeconds.With(labels).Observe(elapsed.Seconds())
	})
}

type statusResponseWriter struct {
	Inner      http.ResponseWriter
	StatusCode int
}

func (w *statusResponseWriter) Header() http.Header {
	return w.Inner.Header()
}

func (w *statusResponseWriter) Write(buf []byte) (int, error) {
	if w.StatusCode == 0 {
		w.WriteHeader(http.StatusOK)
	}
	return w.Inner.Write(buf)
}

func (w *statusResponseWriter) WriteHeader(statusCode int) {
	w.StatusCode = statusCode
	w.Inner.WriteHeader(statusCode)
}

// InitMainRouter creates the main Gorilla router for the application.
//
// This function will not populate the  router with an error-recovery and
// metrics-reporting middleware. If these middleware are required, then the
// caller should encapsulate this router inside of another router and register
// the middlewares on the encapsulating router.
func InitMainRouter(r *mux.Router, rl *rushlink) {
	r.HandleFunc("/{path:img/"+staticFilenameExpr+"}", rl.staticGetHandler).Methods("GET", "HEAD")
	r.HandleFunc("/{path:css/"+staticFilenameExpr+"}", rl.staticGetHandler).Methods("GET", "HEAD")
	r.HandleFunc("/{path:js/"+staticFilenameExpr+"}", rl.staticGetHandler).Methods("GET", "HEAD")
	r.HandleFunc("/", rl.indexGetHandler).Methods("GET", "HEAD")
	r.HandleFunc("/", rl.newPasteHandler).Methods("POST")
	r.HandleFunc("/users", rl.createUserHandler).Methods("POST")
	r.HandleFunc("/users/{user}", rl.changeUserHandler).Methods("POST")
	r.HandleFunc("/users/{user}", rl.deleteUserHandler).Methods("DELETE")
	r.HandleFunc("/"+urlKeyExpr, rl.viewPasteHandler).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyWithExtExpr, rl.viewPasteHandler).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyExpr+"/nr", rl.viewPasteHandlerNoRedirect).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyWithExtExpr+"/nr", rl.viewPasteHandlerNoRedirect).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyExpr+"/meta", rl.viewPasteHandlerMeta).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyWithExtExpr+"/meta", rl.viewPasteHandlerMeta).Methods("GET", "HEAD")
	r.HandleFunc("/"+urlKeyExpr, rl.deletePasteHandler).Methods("DELETE")
	r.HandleFunc("/"+urlKeyWithExtExpr, rl.deletePasteHandler).Methods("DELETE")
	r.HandleFunc("/"+urlKeyExpr+"/delete", rl.deletePasteHandler).Methods("POST")
	r.HandleFunc("/"+urlKeyWithExtExpr+"/delete", rl.deletePasteHandler).Methods("POST")
}

// StartMainServer starts the main http server listening on addr.
func StartMainServer(addr string, db *db.Database, fs *db.FileStore, rawRootURL string) {
	var rootURL *url.URL
	if rawRootURL != "" {
		var err error
		rootURL, err = url.Parse(rawRootURL)
		if err != nil {
			log.Fatalln(errors.Wrap(err, "could not parse rootURL flag"))
		}
	}
	rl := rushlink{
		db:      db,
		fs:      fs,
		rootURL: rootURL,
	}

	router := mux.NewRouter()
	router.Use(rl.metricsMiddleware)
	router.Use(rl.recoveryMiddleware)
	InitMainRouter(router, &rl)

	srv := &http.Server{
		Handler:      router,
		Addr:         addr,
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}
	log.Fatal(srv.ListenAndServe())
}