package main

import (
	"compress/gzip"
	"context"
	"flag"
	"fmt"
	"log/slog"
	"net/http"
	"nonsense-time/api"
	"os"
	"strings"
	"time"
)

var logger *slog.Logger

// Middleware to timeout requests after a given duration
func timeoutMiddleware(next http.Handler, duration time.Duration) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx, cancel := context.WithTimeout(r.Context(), duration)
		defer cancel()

		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

type gzipResponseWriter struct {
	gzip.Writer
	http.ResponseWriter
}

func newGzipResponseWriter(w http.ResponseWriter) *gzipResponseWriter {
	gzrw := new(gzipResponseWriter)
	gzrw.Writer = *gzip.NewWriter(w)
	gzrw.ResponseWriter = w

	return gzrw
}

func (gzrw *gzipResponseWriter) Close() error {
	return gzrw.Writer.Close()
}

func (gzrw *gzipResponseWriter) Header() http.Header {
	return gzrw.ResponseWriter.Header()
}

func (gzrw *gzipResponseWriter) Write(p []byte) (int, error) {
	n, err := gzrw.Writer.Write(p)
	return n, err
}

func (gzrw *gzipResponseWriter) WriteHeader(statuscode int) {
	gzrw.ResponseWriter.WriteHeader(statuscode)
}

// Middleware to conditionally gzip a response
func gzipMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		acceptedEncodings := r.Header.Get("Accept-Encoding")

		if !strings.Contains(acceptedEncodings, "gzip") {
			logger.DebugContext(r.Context(), "Using gzip middleware but client does not support gzip encoding")
			next.ServeHTTP(w, r)
			return
		}

		w.Header().Add("Content-Encoding", "gzip")
		gzrw := newGzipResponseWriter(w)
		defer gzrw.Close()

		next.ServeHTTP(gzrw, r)
	})
}

func main() {

	port := flag.Int("p", 8080, "the port to listen on")
	bindAddr := flag.String("b", "", "the adress to bind to (leave empty for all interfaces)")
	waitTime := flag.Duration("w", 2*time.Second, "the maximum  time for a request, unit defaults to ns")
	logLevel := flag.String("l", "info", "log level (debug, info, warn, error)")

	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s [options]\n", os.Args[0])
		fmt.Fprintln(os.Stderr, "Options:")
		flag.PrintDefaults()
	}

	flag.Parse()

	mux := http.NewServeMux()
	loggerOpts := new(slog.HandlerOptions)

	switch *logLevel {
	case "debug":
		loggerOpts.Level = slog.LevelDebug
		loggerOpts.AddSource = true
	case "info":
		loggerOpts.Level = slog.LevelInfo
	case "warn":
		loggerOpts.Level = slog.LevelDebug
	case "error":
		loggerOpts.Level = slog.LevelError
	default:
		panic(fmt.Sprintf("Unkown log level %s", *logLevel))
	}

	addr := fmt.Sprintf("%s:%d", *bindAddr, *port)
	logger = slog.New(slog.NewTextHandler(os.Stdout, loggerOpts))

	api.Logger = logger

	vtt := timeoutMiddleware(http.HandlerFunc(api.VttOnline), *waitTime)
	vttLogs := gzipMiddleware(http.HandlerFunc(api.VttLogs))

	mux.Handle("GET /vtt/status", vtt)
	mux.HandleFunc("GET /vtt", api.VttRedirect)
	mux.Handle("GET /vtt/logs", vttLogs)

	logger.Info(fmt.Sprint("Listening on ", addr))
	logger.Info(http.ListenAndServe(addr, mux).Error())
}