package web

import (
	"fmt"
	"io/fs"
	"math/rand"
	"net/http"
	"os"

	"golang.org/x/net/context"
)

func imageHandler() http.Handler {
	fs := http.FS(os.DirFS(config.imageDir))
	hfs := http.FileServer(fs)
	return hfs
}

func chooseRandomFile(ctx context.Context, imageDir string) (filepath string, err error) {
	validEntries := make([]string, 0)
	log := config.logger.With("imageDir", imageDir)
	err = fs.WalkDir(
		os.DirFS(imageDir), ".", func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				log.Error("Error walking directory", "err", err)
				return err
			}
			if ctxErr := ctx.Err(); ctxErr != nil {
				log.Error("Context closed while walking directory", "err", ctxErr)
				return ctxErr
			}
			if d.Type().IsRegular() {
				filename := fmt.Sprintf("%s%c%s", imageDir, os.PathSeparator, d.Name())
				log.Debug("file scan", filename, "filename")
				validEntries = append(validEntries, filename)
			}
			return nil
		})
	if err != nil {
		return
	}
	if ctxErr := ctx.Err(); ctxErr != nil {
		err = ctxErr
		return
	}
	chosen := rand.Intn(len(validEntries))
	filepath = validEntries[chosen]
	return
}

func randomImageFunc(w http.ResponseWriter, r *http.Request) {
	log := config.logger
	path, err := chooseRandomFile(r.Context(), config.imageDir)
	if err != nil {
		log.Error("Couldn't choose a random file", "err", err)
		w.WriteHeader(http.StatusInternalServerError)
		return
	}
	log.Info("random image served", "imagefile", path)
	http.ServeFile(w, r, path)
}