// Command lsf provides functions to use the lsf with the commandline.
package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path"
	"strings"
	"syscall"

	"git.marceltransier.de/lsf"
	cli "github.com/jawher/mow.cli"
	"github.com/pkg/errors"
	"golang.org/x/crypto/ssh/terminal"
)

var (
	sessionCacheDir *string
	username        *string
)

var s *lsf.Session

func main() {
	cacheDir, err := os.UserCacheDir()
	if err != nil {
		log.Fatal(err)
	}
	defaultSessionCacheDir := path.Join(cacheDir, "go-lsf/sessions")

	app := cli.App("lsf", "LSF Shutthe Fuckup")

	sessionCacheDir = app.StringOpt("c session-cache-dir", defaultSessionCacheDir, "path to where the session tokens are cached")
	username = app.StringOpt("u username", "", "username to login with")

	app.Command("grades", "view your grades", cmdGrades)
	//app.Command("events", "show your personalized events", cmdEvents)
	//app.Command("reports", "download reports", cmdReports)
	//app.Command("courses", "show courses", cmdCourses)

	app.Run(os.Args)
}

func cmdGrades(cmd *cli.Cmd) {
	cmd.Before = sessionNeeded
	cmd.Action = func() {
		grades, err := s.Grades()
		if err != nil {
			log.Fatal(err)
		}
		grades.Print()
	}
}

func sessionNeeded() {
	err := os.MkdirAll(*sessionCacheDir, os.ModePerm)
	if err != nil {
		log.Fatal(err)
	}
	if len(*username) == 0 {
		var err error
		*username, err = readUsername()
		if err != nil {
			log.Fatal(err)
		}
	}
	s, err = session(*username)
	if err != nil {
		log.Fatal(err)
	}
}

func readUsername() (string, error) {
	var username string
	fmt.Fprint(os.Stderr, "Username: ")
	_, err := fmt.Scanf("%s", &username)
	if err != nil {
		return "", errors.Wrap(err, "could not read username")
	}
	return username, nil
}

func readPassword() (string, error) {
	var password string
	fmt.Fprint(os.Stderr, "Password: ")
	b, err := terminal.ReadPassword(int(syscall.Stdin))
	if err != nil {
		return "", err
	}
	fmt.Fprint(os.Stderr, "\n")
	password = string(b)
	return password, nil
}

func session(username string) (*lsf.Session, error) {

	sessionPath := path.Join(*sessionCacheDir, username)
	sessionFile, err := os.Open(sessionPath)
	if err != nil {
		pErr, ok := err.(*os.PathError)
		if !ok {
			return nil, err
		}
		errno, ok := pErr.Unwrap().(syscall.Errno)
		if !ok {
			return nil, err
		}
		if errno != syscall.ENOENT {
			log.Fatal(err)
		}
		log.Printf("no session for %s cached\n", username)
		return login(username)
	}
	defer sessionFile.Close()

	b, err := ioutil.ReadAll(sessionFile)
	if err != nil {
		return nil, errors.Wrapf(err, "could not read session file %s", sessionPath)
	}
	sid := strings.TrimSuffix(string(b), "\n")
	s, err := lsf.NewSessionBySID(sid)
	if err == lsf.ErrInvalSID {
		log.Println("session is not valid")
		err := os.Remove(sessionPath)
		if err != nil {
			log.Println(errors.Wrap(err, "could not remove invalid session file"))
		}
		return login(username)
	} else if err != nil {
		return nil, errors.Wrap(err, "could not get session by existing sid")
	}
	return s, nil
}

func login(username string) (*lsf.Session, error) {
	password, err := readPassword()
	if err != nil {
		return nil, errors.Wrap(err, "could not read password")
	}
	s, err := lsf.Login(username, password)
	if err != nil {
		return nil, err
	}
	sessionPath := path.Join(*sessionCacheDir, username)
	err = ioutil.WriteFile(sessionPath, []byte(s.SID), 0666)
	if err != nil {
		log.Println(errors.Wrap(err, "could not cache session id"))
	}
	return s, nil
}