// Command rekopub-web runs the converter behind the form on
// rekopub.monoexp.com. It listens on 127.0.0.1 only, behind nginx, and runs
// the rekopub command for each conversion.
//
// Settings come from the environment:
//
//	PORT               port to listen on (required)
//	REKOPUB            the rekopub command (default: rekopub next to this program)
//	DATA_DIR           writable folder; books are kept in DATA_DIR/books (default: data)
//	KEEP_HOURS         hours a book is kept and its link works (default: 24)
//	LIMIT              conversions for all visitors together... (default: 50)
//	LIMIT_PER_VISITOR  ...and per visitor... (default: 10)
//	LIMIT_MINUTES      ...within this many minutes (default: 15)
//	MAX_RUNNING        conversions running at once (default: 2)
//	MAX_STORAGE_MB     disk used by kept books before conversions pause (default: 2048)
package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strconv"
	"syscall"
	"time"

	"git.monoexp.com/bajdev/rekopub/internal/web"
)

func main() {
	log.SetFlags(0) // the journal adds timestamps
	port, cfg, err := config()
	if err != nil {
		log.Fatal(err)
	}
	srv, err := web.New(cfg)
	if err != nil {
		log.Fatal(err)
	}

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	go srv.CleanEvery(ctx, 10*time.Minute)

	hs := &http.Server{
		Addr:              "127.0.0.1:" + port,
		Handler:           srv.Handler(),
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       30 * time.Second,
		IdleTimeout:       60 * time.Second,
		// No WriteTimeout: a conversion can take minutes. Each run of the
		// command has its own time limit instead.
	}
	go func() {
		<-ctx.Done()
		shutdown, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		hs.Shutdown(shutdown)
	}()
	log.Printf("rekopub-web listening on %s, running %s", hs.Addr, cfg.CLI)
	if err := hs.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

func config() (string, web.Config, error) {
	var cfg web.Config
	port := os.Getenv("PORT")
	if _, err := strconv.ParseUint(port, 10, 16); err != nil {
		return "", cfg, fmt.Errorf("PORT %q: must be a port number", port)
	}
	cfg.CLI = os.Getenv("REKOPUB")
	if cfg.CLI == "" {
		exe, err := os.Executable()
		if err != nil {
			return "", cfg, err
		}
		cfg.CLI = filepath.Join(filepath.Dir(exe), "rekopub")
	}
	if _, err := os.Stat(cfg.CLI); err != nil {
		return "", cfg, fmt.Errorf("REKOPUB: %w", err)
	}
	data := os.Getenv("DATA_DIR")
	if data == "" {
		data = "data"
	}
	cfg.Dir = filepath.Join(data, "books")

	var err error
	num := func(name string) int {
		v := os.Getenv(name)
		if v == "" || err != nil {
			return 0 // the default
		}
		n, perr := strconv.Atoi(v)
		if perr != nil || n <= 0 {
			err = fmt.Errorf("%s %q: must be a whole number above 0", name, v)
		}
		return n
	}
	cfg.Keep = time.Duration(num("KEEP_HOURS")) * time.Hour
	cfg.Limit = num("LIMIT")
	cfg.PerVisitor = num("LIMIT_PER_VISITOR")
	cfg.Window = time.Duration(num("LIMIT_MINUTES")) * time.Minute
	cfg.MaxRunning = num("MAX_RUNNING")
	cfg.MaxStorage = int64(num("MAX_STORAGE_MB")) << 20
	return port, cfg, err
}