package usermanager

import (
	"WWWShop/wwwshop/model/user"
	"database/sql"
	"fmt"
	"golang.org/x/crypto/bcrypt"
	"strings"
    "errors"
)

type UserManager struct {
	db *sql.DB
}

func New(db *sql.DB) UserManager {
	return UserManager{db}
}

func (self UserManager) Add(username string, password_hash string) (*user.User, error) {
	var id int64

	result := self.db.QueryRow("INSERT INTO users(username, password) VALUES ($1, $2) RETURNING id", username, password_hash)
	err := result.Scan(&id)
	if err != nil {
		return nil, err
	}
	user := user.New(id, username, password_hash)
	return &user, nil
}

func (self UserManager) AddWithPlainPassword(username string, password string) (*user.User, error) {
	password_hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return nil, err
	}
	user, err := self.Add(username, string(password_hash))
	return user, err
}

type QueryParameter interface{}

func (self UserManager) GenerateWhere(cur_key *int64, ids []int64, usernames []string) string {
    where_string := "WHERE true "
    if usernames != nil && len(usernames) > 0 {
        where_string = strings.Join([]string{where_string, "AND ( false"}, "")
        for range usernames {
            where_string = strings.Join([]string{where_string, fmt.Sprintf(" OR username = $%d", *cur_key)}, "")
            (*cur_key)++
        }
        where_string = strings.Join([]string{where_string, " ) "}, "")
    }
    if ids != nil && len(ids) > 0 {
        where_string = strings.Join([]string{where_string, "AND ( false"}, "")
        for range ids {
            where_string = strings.Join([]string{where_string, fmt.Sprintf(" OR id = $%d", *cur_key)}, "")
            (*cur_key)++
        }
        where_string = strings.Join([]string{where_string, " ) "}, "")
    }
    return where_string
}

func (self UserManager) Delete(ids []int64, usernames []string) ([]string, error) {
    var where bool
    var cur_key int64
    var where_string string
    cur_key = 1

    if ids != nil && len(ids) > 0 {
        where = true
    }
    if usernames != nil && len(usernames) > 0 {
        where = true
    }

    if where {
        where_string = self.GenerateWhere(&cur_key, ids, usernames)
    } else {
        return nil, errors.New("Cannot delete without a clause")
    }

	query_parameters := make([]interface{}, 0)
	for _, username := range usernames {
		query_parameters = append(query_parameters, username)
	}
	for _, id := range ids {
		query_parameters = append(query_parameters, id)
	}
    query_string := fmt.Sprintf("DELETE FROM users %s RETURNING username", where_string)
	result, err := self.db.Query(
		query_string,
		query_parameters...,
	)
    if err != nil {
        return nil, err
    }
    defer result.Close()
    var deleted_users []string
    for result.Next() {
        var username string
        err := result.Scan(&username)
        if err != nil {
            return nil, err
        }
        deleted_users = append(deleted_users, username)
    }
    if deleted_users == nil {
        deleted_users = make([]string, 0)
    }
    return deleted_users, nil
}

func (self UserManager) Retrieve(page int64, ids []int64, usernames []string) ([]user.User, error) {
	var where bool
    var cur_key int64

	if ids != nil && len(ids) > 0 {
		where = true
	}
	if usernames != nil && len(usernames) > 0 {
		where = true
	}
	cur_key = 1
	where_string := ""
	if where {
        where_string = self.GenerateWhere(&cur_key, ids, usernames)
	}
    page = (10 * page)
	page_string := fmt.Sprintf("LIMIT 10 OFFSET %d", page)
	query_parameters := make([]interface{}, 0)
	for _, username := range usernames {
		query_parameters = append(query_parameters, username)
	}
	for _, id := range ids {
		query_parameters = append(query_parameters, id)
	}
	query_string := fmt.Sprintf("SELECT id, username, password from users %s %s;", where_string, page_string)
	result, err := self.db.Query(
		query_string,
		query_parameters...,
	)
	if err != nil {
		return nil, err
	}
	defer result.Close()
	var users []user.User
	for result.Next() {
		var (
			id_user       int64
			username_user string
			password_user string
		)
		err := result.Scan(&id_user, &username_user, &password_user)
		if err != nil {
			return nil, err
		}
		u := user.New(id_user, username_user, password_user)
		users = append(users, u)
	}
    if users == nil {
        users = make([]user.User, 0)
    }
	return users, nil
}