package db

import (
	"golang.org/x/crypto/argon2"
	"crypto/rand"
	"encoding/base64"
	"database/sql"
)


func getNextUserId(db *sql.DB) (int, error) {
	row := db.QueryRow("select coalesce(max(userid), 0) from users;")
	if row.Err() != nil {
		return -1, row.Err()
	}

	var id int
	err := row.Scan(&id)
	if err != nil {
		return -1, err
	}
	return id+1, nil
}


func hashPassword(password string, salt []byte) []byte {
	return argon2.IDKey([]byte(password), salt, 1, 64*1024, 4, 32)
}


func (p *Phlox) CreateUser(username, password string) (User, error) {
	user := User{}

	userId, err := getNextUserId(p.db)
	if err != nil {
		return user, err
	}

	salt := make([]byte, 10)
	_, err = rand.Read(salt)
	if err != nil {
		return user, err
	}

	hash := hashPassword(password, salt)

	hash64 := base64.StdEncoding.EncodeToString(hash)
	salt64 := base64.StdEncoding.EncodeToString(salt)

	_, err = p.db.Exec("insert into users (userid, username, passwordhash, salt) values (?, ?, ?, ?)", userId, username, hash64, salt64)
	if err != nil {
		return user, err
	}

	user.Id = userId
	user.Name = username
	user.PasswordHash = hash
	user.Salt = salt

	return user, nil
}



func (p *Phlox) DeleteUser(user User) error {
	_, err := p.db.Exec("delete from users where userid=?;", user.Id)
	return err
}



func (p *Phlox) SetPassword(user User, password string) error {
	hash := hashPassword(password, user.Salt)
	hash64 := base64.StdEncoding.EncodeToString(hash)

	_, err := p.db.Exec("update users set passwordhash=? where userid=?;", hash64, user.Id)
	return err
}



func extractUser(s Scanner) (User, error) {
	var userid int
	var username string
	var hash64 string
	var salt64 string
	err := s.Scan(&userid, &username, &hash64, &salt64)
	if err != nil {
		return User{}, err
	}

	hash, err := base64.StdEncoding.DecodeString(hash64)
	if err != nil {
		return User{}, err
	}
	salt, err := base64.StdEncoding.DecodeString(salt64)
	if err != nil {
		return User{}, err
	}

	user := User{
		Id: userid,
		Name: username,
		PasswordHash: hash,
		Salt: salt,
	}

	return user, nil
}


func (p *Phlox) AuthenticateUser(username, password string) (bool, User, error) {
	row := p.db.QueryRow("select * from users where username = ?;", username)
	user, err := extractUser(row)
	if err != nil {
		return false, User{}, err
	}

	hash := hashPassword(password, user.Salt)
	for i, v := range user.PasswordHash {
		if v != hash[i] { return false, user, nil; }
	}
	return true, user, nil
}


func (p *Phlox) GetByUsername(username string) (User, error) {
	row := p.db.QueryRow("select * from users where username = ?;", username)
	user, err := extractUser(row)
	if err != nil {
		return User{}, err
	}
	return user, nil
}


func (p *Phlox) GetById(id int) (User, error) {
	row := p.db.QueryRow("select * from users where userid = ?;", id)
	user, err := extractUser(row)
	if err != nil {
		return User{}, err
	}

	return user, nil
}


func (p *Phlox) AllUsers() ([]User, error) {
	users := make([]User, 0)
	rows, err := p.db.Query("select * from users;")
	if err != nil {
		return users, err
	}
	defer rows.Close()

	for rows.Next() {
		user, err := extractUser(rows)
		if err != nil {
			return users, err
		}
		users = append(users, user)
	}

	return users, nil
}