package main

import (
	"encoding/json"
	"io/fs"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"countrygame/web"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}

	// Used by the compose healthcheck: the distroless image has no curl.
	if len(os.Args) > 1 && os.Args[1] == "-healthcheck" {
		resp, err := http.Get("http://127.0.0.1:" + port + "/healthz")
		if err != nil || resp.StatusCode != http.StatusOK {
			os.Exit(1)
		}
		os.Exit(0)
	}

	// Background music: .mp3 files read live from this folder, so adding a track needs no rebuild.
	musicDir := os.Getenv("MUSIC_DIR")
	if musicDir == "" {
		musicDir = "music"
	}

	root, err := fs.Sub(web.Files, ".")
	if err != nil {
		log.Fatal(err)
	}

	log.Printf("country game listening on :%s (music folder %q)", port, musicDir)
	log.Fatal(http.ListenAndServe(":"+port, newMux(root, musicDir)))
}

// newMux serves the embedded game, /healthz, and the music folder under /music/.
func newMux(root fs.FS, musicDir string) *http.ServeMux {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("ok"))
	})
	mux.HandleFunc("/music/index.json", musicIndex(musicDir))
	mux.Handle("/music/", http.StripPrefix("/music/", noCache(http.FileServer(noListing{http.Dir(musicDir)}))))
	mux.Handle("/", noCache(http.FileServer(http.FS(root))))
	return mux
}

// noCache keeps iteration simple: data and scripts are always revalidated.
func noCache(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "no-cache")
		next.ServeHTTP(w, r)
	})
}

// noListing hides directory listings and dot files: only the tracks themselves are served.
type noListing struct{ fs http.FileSystem }

func (n noListing) Open(name string) (http.File, error) {
	if strings.Contains(filepath.Base(name), "..") || strings.HasPrefix(filepath.Base(name), ".") {
		return nil, os.ErrNotExist
	}
	f, err := n.fs.Open(name)
	if err != nil {
		return nil, err
	}
	if info, err := f.Stat(); err != nil || info.IsDir() {
		f.Close()
		return nil, os.ErrNotExist
	}
	return f, nil
}

// musicIndex lists the playable tracks: non-empty .mp3 files (the empty placeholder is skipped), sorted by name.
// A missing folder is not an error: the game simply shows an empty tape deck.
func musicIndex(dir string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		tracks := []string{}
		entries, _ := os.ReadDir(dir)
		for _, e := range entries {
			name := e.Name()
			if e.IsDir() || strings.HasPrefix(name, ".") || !strings.EqualFold(filepath.Ext(name), ".mp3") {
				continue
			}
			if info, err := e.Info(); err == nil && info.Size() > 0 {
				tracks = append(tracks, name)
			}
		}
		sort.Strings(tracks)
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Cache-Control", "no-store")
		json.NewEncoder(w).Encode(map[string]any{"tracks": tracks})
	}
}