package main

import (
	"fmt"
	"net/http"
	"encoding/json"
	"crypto/rand"
	"reflect"
	"log"
	"os"

	// muxer and form parser
	"github.com/gorilla/mux"
	"github.com/gorilla/handlers"
	"github.com/gorilla/schema"

	// error returns for HandlerFunc
	"github.com/creack/ehttp"

	// JWT stuff
	"github.com/auth0/go-jwt-middleware"
	"github.com/dgrijalva/jwt-go"

	// form validation
	"github.com/asaskevich/govalidator"

	// database backend
	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/sqlite"

	// password hashing
	"golang.org/x/crypto/scrypt"
)

type User struct {
	gorm.Model

	Name	string	`valid:"alphanum,required" sql:"unique"`
	Pass	string	`valid:"runelength(8|999),required"`
	Salt	string	`valid:"optional"`
	Email	string	`valid:"email,required" sql:"unique"`
	Lists	[]List
}

type List struct {
	gorm.Model
	UserID		uint	`gorm:"unique_index:idx_userid_name"`

	Name		string	`valid:"alphanum,required" gorm:"unique_index:idx_userid_name"`
	Icon		string	`valid:"alphanum,optional"`
	Items		[]Item
}

type Item struct {
	gorm.Model
	ListID	uint

	Name	string	`valid:"alphanum,required"`
	Amount	float64	`valid:"optional"`
	Bought	bool	`valid:"required"`
	Unit	Unit
	UnitID	uint
}

type Unit struct {
	gorm.Model

	Name	string `valid:"alphanum,required"`
}

var db *gorm.DB

func getToken(w http.ResponseWriter, r *http.Request) error {
	var userInput User
	var userRecord User
	var err error
	decoder := schema.NewDecoder()

	// Parse form data
	err = r.ParseForm()
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not parse form", err)
	}

	// Decode to struct
	err = decoder.Decode(&userInput, r.Form)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not decode user from form", err)
	}

	// Find user in DB
	db.First(&userRecord)
	if db.Error != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "database lookup error", err)
	}

	// Check hashed PW
	hash, err := scrypt.Key([]byte(userInput.Pass), []byte(userRecord.Salt), 16384, 8, 1, 32)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "cannot hash pass", err)
	}
	if userRecord.Name == userInput.Name && reflect.DeepEqual(hash, []byte(userRecord.Pass)) {
		// Generate JWT-token
		token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
			"name":userRecord.Name,
		})
		tokenString, err := token.SignedString([]byte("TODO"))
		if err != nil {
			return ehttp.NewErrorf(http.StatusForbidden, "could not construct token", err)
		}

		// Reply with token
		jsonOut, _ := json.Marshal(map[string]string{"token": tokenString})
		fmt.Fprint(w, string(jsonOut))
		return nil
	}

	// User was not found
	return ehttp.NewErrorf(http.StatusForbidden, "Could not find user/pass")
}

func register(w http.ResponseWriter, r *http.Request) error {
	decoder := schema.NewDecoder()

	// Parse http request to request-struct
	err := r.ParseForm()
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not parse form", err)
	}

	// Decode request into struct
	var input User
	err = decoder.Decode(&input, r.PostForm)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not decode user", err)
	}

	// Validate struct
	res, err := govalidator.ValidateStruct(input)
	if err != nil || res != true {
		return ehttp.NewErrorf(http.StatusBadRequest, "could not validate your data", err)
	}

	// Check if users already exists
	/*countName := 0; countEmail := 0
	db.Model(&User{}).Where("name = ?", input.Name).Count(&countName)
	db.Model(&User{}).Where("email = ?", input.Email).Count(&countEmail)
	if countName != 0 || countEmail != 0{
		return ehttp.NewErrorf(http.StatusConflict, "username or email already exists")
	}*/

	// Generate salt
	salt := make([]byte, 64)
	_, err = rand.Read(salt)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not generate salt", err)
	}
	input.Salt = string(salt)

	// Generate scrypt hash of pass
	hash, err := scrypt.Key([]byte(input.Pass), salt, 16384, 8, 1, 32)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not hash pass", err)
	}
	input.Pass = string(hash)

	// add to database
	db.NewRecord(input)
	retCreate := db.Create(&input)
	if retCreate.Error != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not create user", err)
	}
	log.Println("registered user", input.Name)

	return nil
}

func createList(w http.ResponseWriter, r *http.Request) error {
	decoder := schema.NewDecoder()
	decoder.IgnoreUnknownKeys(true)

	// Parse http request to request-struct
	err := r.ParseForm()
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not parse form", err)
	}

	// Decode request into struct
	var input List
	err = decoder.Decode(&input, r.PostForm)
	if err != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "could not decode ", err)
	}

	// Validate struct
	res, err := govalidator.ValidateStruct(input)
	if err != nil || res != true {
		return ehttp.NewErrorf(http.StatusBadRequest, "could not validate your data", err)
	}

	// Find request-corresponding user
	// TODO: push into middleware?
	userName := r.Context().Value("user").(*jwt.Token).Claims.(jwt.MapClaims)["name"].(string)
	user := User{Name: userName}
	db.Where(&user).First(&user)
	if user.ID == 0 { // TODO: ugly way to check for user-not-found
		return ehttp.NewErrorf(http.StatusForbidden, "cannot find claimed user")
	}

	// create the new list
	db.NewRecord(&input)
	ret := db.Create(&input)
	if ret.Error != nil {
		return ehttp.NewErrorf(http.StatusInternalServerError, "cannot create list in db")
	}

	return nil
}

func main() {
	var err error

	// TODO: maybe move to init()?
	db, err = gorm.Open("sqlite3", "test.db")
	if err != nil {
		log.Fatalln("cannot open db", err)
	}
	db.LogMode(false)

	jwt := jwtmiddleware.New(jwtmiddleware.Options{
		Extractor: func(r *http.Request) (string,error) {
			r.ParseForm()
			return r.Form["token"][0], nil
		},
		ValidationKeyGetter: func(token *jwt.Token) (interface{}, error) {
			return []byte("TODO"), nil
	}})
	var jHdlr = jwt.Handler // make an alias so routes will be more readable

	// Create or update schemas …
	db.AutoMigrate(&User{})
	db.AutoMigrate(&List{})
	db.AutoMigrate(&Item{})
	db.AutoMigrate(&Unit{})
	db.Model(&User{}).Related(&List{})
	db.Model(&List{}).Related(&Item{})
	db.Model(&Item{}).Related(&Unit{})
	defer db.Close()


	// define URL handlers
	r := mux.NewRouter()

	// User Management
	r.Handle("/users", ehttp.HandlerFunc(register)).Methods("POST") // Make new user
	r.Handle("/users", ehttp.HandlerFunc(getToken)).Methods("GET") // Get user „info“(=token)
	// TODO: delete, modify

	// List Management
	r.Handle("/lists", jHdlr(ehttp.HandlerFunc(createList))).Methods("POST") // Make a new list
	r.Handle("/lists", jHdlr(ehttp.HandlerFunc(nil))).Methods("GET") // Get list of lists
	r.Handle("/lists/{name}", jHdlr(ehttp.HandlerFunc(nil))).Methods("PUT") // Update list (name, icon, …)
	r.Handle("/lists/{name}", jHdlr(ehttp.HandlerFunc(nil))).Methods("DELETE") // Delete a list
	r.Handle("/lists/{name}", jHdlr(ehttp.HandlerFunc(nil))).Methods("GET") // Get list content (i.e., items)
	// List sharing
	r.Handle("/lists/{name}/sharers", jHdlr(ehttp.HandlerFunc(nil))).Methods("POST") // Add new sharer
	r.Handle("/lists/{name}/sharers", jHdlr(ehttp.HandlerFunc(nil))).Methods("GET") // Get list of sharers
	r.Handle("/lists/{name}/sharers/{user}", jHdlr(ehttp.HandlerFunc(nil))).Methods("DELETE") // Remove sharer

	r.Handle("/lists/{name}/items", jHdlr(ehttp.HandlerFunc(nil))).Methods("PUT") // Add new item
	r.Handle("/lists/{name}/items/{item}", jHdlr(ehttp.HandlerFunc(nil))).Methods("DELETE") // Delete item
	r.Handle("/lists/{name}/items/{item}", jHdlr(ehttp.HandlerFunc(nil))).Methods("POST") // Update item

	// Unit-history (unit is a ever-growing list only used for auto-completion)
	r.Handle("/units", jHdlr(ehttp.HandlerFunc(nil))).Methods("POST") // Make a new unit
	r.Handle("/units", jHdlr(ehttp.HandlerFunc(nil))).Methods("GET") // Get list of units

	loggedRouter := handlers.LoggingHandler(os.Stdout, r)
	http.Handle("/", loggedRouter)
	http.ListenAndServe(":8000", nil)
}